Underfloor heating control system teardown (with schematic)

This is a set of fairly common Polypipe controllers that interface an underfloor heating system to an existing heating boiler. There are two modules - the main one and then optional slave modules that allow extra thermostats and manifold valves to be used with multiple zones.
It's a very simple and neat arrangement that literally just plugs end to end to build up the desired number of channels. It also has a DIN rail mounting facility for use in panels.
There's a story behind this. Some elderly friends asked if I could check out their heating system as they had an issue with it. The issue turned out to be that while renovating a cupboard they had mistaken the manifold and wiring for their new underfloor heating system as being part of the old and obsolete heating system.
They laid into it with wire cutters (while it was live) stuffing the chopped wires back into the plasterboard they were sticking out from and also pushing them down under the floorboards (while still live).
The original controller in that section - the master unit shown here, was then thrown in the bin.
It was one of those "wish I hadn't got involved" moments. Their original heating engineer who installed the system was no longer living on the island and other heating maintenance companies had declined to get involved.
I had to identify the control system from the modules in use on other parts of the system, download the manual, work out what component was missing and replace the chopped cables.
Initially I just reconnected the boiler control line so that the rest of the system could control the boiler, then when the replacement module arrived I used the handy existing mounting holes to fit it, and reinstated their system to its original form.
During the research on the system I bought a few cheap modules from eBay. It seems to be a common thing that people enthusiastically buy complete kits for installing underfloor heating and then subsequently realise it's not just a case of banging down pipes and hooking up a few wires. They then sell the unwanted components on eBay at a greatly reduced price.
One of the notable design features is the use of a standard 230V AC relay with a capacitor across its coil to allow it to be actuated by multiple circuits via diodes. That effectively saved the use of a relay per channel. The rest is fundamentally a wire marshalling box with diagnostic indicators.
The terminals are reassuringly good quality rising clamp modules with a generous cable capacity.
I also got some of the thermal manifold actuators, so I'll take one apart in a video at some point.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies, miscellaneous heating components and random gadgets for disassembly at:-
www.bigclive.com/coffee.htm
This also keeps the channel independent of KZbin's advertising algorithms allowing it to be a bit more dangerous and naughty.

[@Rok_Satanas]

Big Clive: They say to not open these, they have a powerful spring and they are dangerous. Also Big Clive's next sentence: Maybe I will open one for a future video...

[@Chrisamic]

Sometimes the warnings really do mean something. The Detroit diff locker I put in my Hilux has a spring loaded setup (for the dog clutch) that has reportedly removed fingers from DIYers. These things can have hidden treachery if you don't know the correct assembly or disassembly procedures. I hope Clive takes care. I can't imagine something that small having a great potential for bloody chaos, but sometimes that's the trap. ETA: now that I've had a look the spring in these waxtuators it probably isn't that bad. You probably just need to make sure the cap doesn't fly off and hit you in the eye.

[@Dreddy72]

i think this is more a case of "the springs ae quite powerful for their size, and its gonna make it a pita to put it back together" more than poses an actual risk to a person

[@William_Hada]

It's amazing that a person like that managed to live so long.

[@stridermt2k]

I like getting the HVAC stuff in small doses like this. The insight is absolutely invaluable!

[@I_am_Allan]

Search "HVACR Videos" ... he shows you industrial repairs.

[@noakeswalker]

Your story of the aged gent cutting through all the cables and throwing the controller out just made me go "noooooooooooo" out loud. Haha. Nightmare for you Clive.

[@johncrunk8038]

DIY indeed.

[@oliverer3]

I'm not sure that I would have been able to keep myself from politely explaining that this was the stupidest thing I'd ever experienced in that situation.

[@bluephreakr]

@@johncrunk8038 r/diwhy

[@FoxDren]

@@oliverer3 I'd have stuggled with the politely part

[@PurityVendetta]

@@oliverer3 Seriously? I'm with Einstein on the hypothesis that the universe has limits while human stupidity does not. I guess at least this story ended with no one dying. I have far darker stories involving qualified electricians and the smell of burning flesh 🤨

[@DahVoozel]

"So... do you want me to rip out your floor or your ceiling?"

[@reggiedixon2]

I have the exact same underfloor heating system (Polypipe) upstairs and downstairs. I was initially sceptical but it is brilliant. Your tale of what the elderly chap did to it had me double facepalming.

[@millomweb]

Do you run it 24/7 for the simple reason it takes ages to respond to demand ?

[@reggiedixon2]

@@millomweb I never touch it as the thermostats mean it only comes on occasionally for most of the year. The house is new so is very well insulated. I have never once thought a room was cold and needs a sudden blast of heat like previous houses I have lived in. So yes to your question but no in the sense that most of the time it appears to do nothing.

[@millomweb]

@@reggiedixon2 My aunt moved into a new bungalow - it has rads all over. I've never lived in a new house ! My flat is reasonably well insulated but is brick. Rads heating system takes about 4 hours each morning to reheat the bricks ! So I leave it on overnight - usually does a heat top up a couple of times through the night and not for very long !

[@davidhale5304]

What a brilliant video and description.A lot of time and effort went into this .Many thanks for the clear ,concise and eloquent description.It has increased my understanding of these units and the systems they control.There are hundreds of the actuators you describe on this development (5 or 6 per property ) each one capable of blowing the local fuse or CB.We may be seeing more UFH systems being installed in the future as they are ideal for Heat Pumps .

[@SigEpBlue]

2:49 Holy Hell, good on ya for stickin' with it. I don't think I could've finished with that kind of start! Sounds like there's a Manx version of Florida Man.

[@1ralton1]

Thanks for this, I recently came across this model for the first time so I found it was very relevant. Your tear down proves they're a lot simpler than I cared to believe. Which is nice. Simple = reliable. I guess the low voltage models make things a bit more complicated but a lot safer. My experience with Under Floor Heating has shown me that it often suffers two common problems; the valve pins on the manifolds leaking and the thermal actuator heads shattering due to the plastics becoming brittle and the pressure from the spring blowing the outer shell to pieces. On the Extra low voltage designs this is not such a problem with respect to safety but the 230V design is a bit more iffy!

[@DocNo27]

I love underfloor heating - it's amazing and sucks it's not more prevalent here in the US. We rented a condo when I went on a high school ski trip and it was the most comfortable house I have ever been in. What was really fun was walking across the floor after getting off the slopes when you are soaking wet, leaving footprints on the floor and then watching them fast evaporate. Our dog didn't want to get in the car when it was time to leave!

[@Mike_5]

Love the way you add (with schematic) to these videos

[@soyeonaddict8693]

Schematics are porn to us.

[@bdagle]

Clive, Thank you for the inside look into this control system. I found it very interesting! Especially that they use 220 volts for the control circuit. Here is America, HVAC control circuits are for the most part low voltage (24 volts). And relays are used to control the higher voltages.

[@bigclivedotcom]

I noticed that. In a way it's good for safety of the people working on the systems.

[@ollylewin]

Commerical HVAC is all 24v control voltage here and in Europe. It's standard. I've always thought the reason the US uses 24v on domestic is due to the high use of AC systems which have routes in the commercial sector. Makes perfect sense to unify it all.

[@spokehedz]

I'm always amazed at how other countries manage the 'basics' of a household.

[@miniwarrior7]

Over here we basically can't get a ice maker to connect to water without leaking 😂

[@johndododoe1411]

@@miniwarrior7 Around here, ice making is a delicate use of open containers filled to the point of overflowing.

[@fonkbadonk2957]

Floor heating, here in Germany, usually has a rep of being slightly posh, not basic. Most homes use radiators, most often mounted in the areas below windows. Some people even prefer radiators, often because floor heating is usually rather slow to regulate. It takes ~1-2h to get warm, but even longer to go down to comfy levels if you've overshot to quick-heat. All that cement has quite some heat capacity! That also means that floor heating isn't the most economical solution if you're only home in the evenings and weekend, because you basically have to let it simmer on a constant level even if no one is home. Talking from experience =)

[@ZaphodHarkonnen]

The colour coded diagram was really useful for understanding how it all hooks together. Highly recommend doing that in the future where it makes sense.

[@bigclivedotcom]

It did help. The original sketch was a bit too cluttered.

[@COBARHORSE1]

A dashed line (colored) to show which relay coil goes to which relay contacts would be welcome too.

[@mor4y]

I helped fit a similar system recently, the company who supplied it had the loops all equal length (50 or 75 metres dependent on pipe diameter), and they supplied a handy floor plan to show us how to place the loops out. A 11x5m room took 4 50m loops to fully cover, and other odds and sods took up the 2x75m loops. It would have been a bit of a nightmare without that floor plan, hopefully we use that place again if we do any more underfloor heating!

[@YagiChanDan]

Ufh loops have maximum lengths, so can only cover a certain amount of floor. Hence you often have 3 or 4 loops per zone. My ground floor has something like 12 individual loops.

[@nmsspacedude1793]

I've just subbed. I'm totally clueless about this stuff... I think I can recognise a screwdriver if necessary. However, a reader in the Telegraph just responded about smart meters and added your teardown link re them. I've been watching your vids, engrossed, for the last hour! I recognise an artist when I see one!

[@twotone3070]

You should see the ones his brother does on whisky, but then he's a different type of artist.

[@paulfinglas1305]

What a brilliantly simplified video god knows how many takes it took you to make this video but believe me from my point of view it was worth it if you are not a college teacher/ lecturer you should consider it well done and thank you 👍

[@bigclivedotcom]

Usually a single take. No need to teach in college. More people can view it here.

[@sharpvamp]

You just saved me so much time! Thanks

[@tlangdon12]

The thermal actuators can be fitted to Thermostatic Radiator Valves (TRVs) and so you can use these "Underfloor Heating" control centre to achieve that nirvana of domestic heating where every room has a thermostat for the radiator and every room is its own zone. So whereas TRVs can only stop a room getting too warm, the UFH control centre can turn the radiator, boiler and pump on if any room gets too cold.

[@tlangdon12]

The Wavin Hep2O AHC 9000 is a great system for this as the thermostats are cheap, simple, reasonably attractive and you can add floor sensors to them if you want to control underfloor heating. The controller can use wired (24v) and wireless thermostats, it has an integrated receiver and the facility to connect an external aerial if any wirelss stats have trouble connecting. It will also control a zone valve for DHW using a temperature sensor (thermocouple) on the cylinder. If we could just have the Salus auto-balancing actuators with a variable Delta T, this would make a brilliant setup for most UK homes to give full control over the temperature in each room.

[@crimsonhalo13]

As a Canadian, this video carries a huge novelty factor for me because our underfloor heating systems are electric and use thin resistance pads. The current-gen stuff is basically a roll of plastic with the wiring printed on it. If you end up doing a video on UK boiler systems at some point in the future, I'd definitely want to see that.

[@edc1569]

Difference between being in a nation with lots of mountains to dam up, or one that discovered a mega ton of natural gas 50 years ago.

[@wdavem]

Yeah that's an interesting one. Inaccessible pipes embedded in concrete don't seem like a good idea unless you like demolishing houses. My Grandparents had a 1950's floor heating system but sold the house when I was a kid. But I remember the warm concrete floor and the boiler room I wasn't allowed to go into. It was an oil fuel system, possibly only one zone (single floor house). I remember something about them having to convert the heating into another system just before they sold it because of problems with the pipes in the house foundation.

[@RambozoClown]

But did you remember to remove the insulation from his snips, so he knows when he cuts live wires in the future?

[@askjacob]

high copper content plasti-dip

[@totherarf]

Underfloor heating used to be a staple of multi story flats! Gas was not allowed so they would put a heating wire threaded throughout the rooms and connect it to an economy 7 meter (or one of the 4 arm time switches dependent on the tariff ) There was obviously no insulation so if you had an empty flat above you it could get cold but if it was occupied you got a heated ceiling too! Tenants would complain of sore feet with this method of heating and it went out of fashion in favor of Electric Storage Heaters. In the early 80's they came up with a predictable controller for those too. It had an outside temp sensor and a strange controller inside with a simple dial on it, min to max with no other markings. This did not last long as every 7 min it would click a loud relay off and on which annoyed everyone (10 PM to 7 AM cant think why people would not like that one ;0))!

[@strehlow]

This is good timing as I'm zoning my radiator system. Hopefully I'll procure all the bits and tear into it within the week.

[@edc1569]

I stuck 24V valves, as shown here, on each radiator, lot of wiring but worth it.

[@HELLHAMMERHANDHIX]

Used to fiddle the "leccy" in my flat...warmest flat in "castle vale" !!!

[@DaveCooper-td2ue]

Brilliant - thanks for uploading

[@bigjd2k]

It’s great but that carbon interconnect is asking for trouble long-term, they could have used proper right-angle PCB plugs & sockets.

[@edc1569]

the terminals are designed to cut into the copper, they work, I've shipped thousands of a product with a similar interface without issues, though they are typically only rated for 5 connections, after that you've mangled up the receiving PCB too much, fine for some applications. Ideal as you don't have to burden the basic product with the cost (of the connector) of an optional extended configuration.

[@jkbrown5496]

I bought a spare defrost board for my heat pump after one went out, or so they say, with the thermistors used for adaptive demand defrost. Mass of resistors and such which slowly revealed themselves. Mostly clipper circuits to condition the 24v ac signals for the PIC chip pins. Along with a discrete diode rectifier for the 24v dc relays and a zener for the 5v dc chip power, transistor control and thermistor circuits. Not as complex as it first seemed and interesting.

[@SeanBZA]

Graphite coat used to both provide corrosion protection and lubrication during the insertion cycle. Cheaper to apply the 3 spots both sides of the board than to order the boards with an ENIG coat that is thick enough to not scrape off the first few cycles of use. The coating is very cheap, as the ink used is incredibly cheap, used in every remote control to make the pads, so it is hard wearing. When mated resistance likely is in the sub ohm range as the metal contact presses down on the graphite and almost gets metal to metal contact.

[@lImbus924]

I think they provide the possibility to connect multiple of those valves to one zone because you could use this for radiators as well, and you might end up having more than one radiator per room (/zone)

[@millomweb]

You can run more than one rad through one TRV when the rads are in the same room. Plumbers aren't generally intelligent enough to do engineering. I find many places with multiple thermostats in a room - clearly indicating the installers were clueless. You end up with the rads red hot and the air con working flat out.

[@bdf2718]

That "connector" for chaining the master to the slave scares me. I doubt its reliability.

[@bigclivedotcom]

It doesn't inspire confidence. Fortunately it's low current.

[@jonbob2]

@@bigclivedotcom It doesn't need to withstand being disconnected and reconnected more than a few times. Because the paint is relatively soft the metal side of the connector can bed in for a better connection than you would get if you had to worry about fatigue. I'd still prefer something I could screw down.

[@plageran]

@@jonbob2 in networking terms: it's looking for a shit storm, Piggyback \ Daisychain is never a good thing.

[@edc1569]

@@jonbob2 exactly, it'll be rated at five connections, I've shipped a product in the thousands with a similar connection method, no issues. Carbon is there as I guess they went for a cheap PCB finish and didn't want to have corroded connections.

[@grafnemilligun9183]

You can have multiple pipe loops on a single thermostat. That's why it let's you connect multiple valves to one control point.

[@johnmorgan1629]

What did he say when you told him what he'd done; Oops!

[@bigclivedotcom]

I didn't rub it in too much. He was clearly a bit agitated.

[@johnmorgan1629]

@@bigclivedotcom No matter how experienced, or the intention we all make mistakes, often the worst punishment is how bad you feel yourself when you do **** up.

[@bigclivedotcom]

@@Okurka. She smouldered quietly.

[@millomweb]

@@bigclivedotcom But not enough to still need heating, obviously.

[@gary_rumain_you_peons]

@@Okurka. She gave him the cold shoulder.

[@b3j8]

My parents had in-the-floor heat. Even in the garage. Worked pretty well tho in bitter cold weather it was very expensive!

[@Bollen2]

Great video

[@johnjordan3126]

I'm thinking the valve actuator may be a wax motor.

[@bigclivedotcom]

It might be. I'm going to open one.

[@YagiChanDan]

@@bigclivedotcom they are.

[@samuelfellows6923]

Similar to the little ones used to silently open the automatic shutters/flaps on extractor fans when switched on. 😉

[@tuttocrafting]

Yes, they are. And they have strong springs. On my holiday house I have like 20 of those after 15 years the plastic started to degrading and springs was breaking the enclosure. After that also the valve collector started to fail. And we had to "rewire" that part of the heating system.(not native English here) rewire for plumbing word is missing on my vocabulary...

[@pulesjet]

Crazy simple cheap to make and does the job.

[@umxrr8677]

7:05 you could've just put the slave board on and then measure from the connected terminal

[@johndododoe1411]

You mean the Student board. Comparing equipment to the plight of trafficked humans is unpopular with the language politicians.

[@templebrown7179]

@@johndododoe1411 Next you lot will complain about the word robot because of its etymology. Also, daughter board would be a lot more accurate than student board.

[@johndododoe1411]

@@templebrown7179 A daughter board is attached to a motherboard in a notably different way. As for master/slave terminology, there are rumors that it has been formally banned in some places, making me search for alternative words that preserve the actual labeling of products and circuits. Servant is historically neutral but may upset the same political forces as Slave. Apprentice or Assistant would work logically but not match single letter markings. Student is vaguely similar but more flattering and works with existing M/S markings.

[@templebrown7179]

@@johndododoe1411 I heartily disagree that a daughter board must attach in a certain manner. I have worked with many different automation systems for electronic locker systems, computerized vending, ATMs, and self-checkout and in all these cases, boards that expand off of the main control unit are referred to as daughter boards in practice and by convention. Being that the manufacturer was the first to make most of these technologies possible, I must cede to their priority on the naming convention.

[@Lachlant1984]

In Australia, systems like this in residential installations are not common, though I have seen them in a school. I've seen a few installations like this, but in these systems they've had wall radiators filled with heated water.

[@stevetobias4890]

Sometimes friends are a learning experience on their own. Some of the things they do have you dumbfounded wondering what happened to common sense.

[@tlangdon12]

Salus have a very interesting microprocessor-controlled auto-balancing actuator that will adjust the temperature difference (Delta T) on the flow and return pipes to the floor (or radiator) to maintain the optimal temperature for UFH. They have a very fast acting motor, that is not wax. I'm just waiting for them to release a switchable version that can also maintains the correct Delta T for radiators - please Salus, you might only sell ten of them, all to me, but I will love them and cherish them! They might also make an interesting teardown for Bigclive as he now knows more about UFH than he wanted or needed to.

[@sirusalpha8605]

I am not familiar with them, but I asume you want the head to screw onto the radiator valve. You could, if there is enough room, cut in a valve body to the radiators feed pipe.

[@tlangdon12]

Me too! I wanted a version for radiators as soon as I heard about them. They potentially have a use in fan coil units as well.

[@justsayen2024]

I am an HVAC Tech with almost 40 years of experience. And that was the most spectacular screw up I've heard of (that was done by a homeowner.) If it was a contractor that would be predictable and of course when confronted the contractor would claim ignorance🤷‍♂️..

[@stephenbell9257]

The purpose of the DC supply to the control relay is to facilitate independent control of the relay from the extension units. With the DC supply the diodes in the extension units form a very simple OR gate which can be easily extended. Doing the the same function with an AC supply to the relay would be more complex.

[@bigclivedotcom]

It would pretty much need a relay per channel.

[@AntonioClaudioMichael]

Nice work @BigCliveDotCom

[@khaitomretro]

No pump overrun if you wire it from that control panel? For some boilers you'll need to let the boiler control the main circulation pump and have an automatic bypass to bridge the heating flow/return pipes when the valves are closed (sometimes a bathroom towel rail was plumbed to be the bypass meaning it was also on if either heating or how water were running). The live for the pump could also be used to signal the panel to light the pump LED. That way the pump LED will actually show when the pump is running. Could have a removable link on the board in place for systems with no pump overrun. In the water circuit as drawn the mixer for the underfloor heating may act as a bypass. Some do some don't. If they can be plumbed in series then they do but on the drawing it's in parallel with other zones.

[@compactc9]

I've been in a house where they used the radiant floors for cooling too.

[@movax20h]

Weird to not see microcontrollers in this day and age. I guess that is often good, makes it probably more reliable, easier to troubleshoot, etc. I am pretty sure there are microcontroller and network enabled ones, with extra smart functions, diagnostic, control, and monitoring.

[@SB-vb8ch]

I thought the water valve on the thermo controlled valve is normally closed (pin fully out) & then opens as the pin is pressed in against the spring in the valve? That way if you remove a waxstat then the valve is off? Might be wrong, has been a while since i messed with one.

[@prjndigo]

The graphite contact may have a couple ohms resistance to a pinpoint contact, but what is the wide-pad resistance under ohm's law?

[@mihumono]

those electric valve actuators are great for hooking regular radiators into Your home automation system ;)

[@sparkyprojects]

larger rooms often have more than one zone, often there's a zone just inside a patio door Strong spring ?, i once opened a landis and gyr steam control vale (spring return), it was more like a coil spring from a small car suspension :D

[@johndododoe1411]

@Razorback73 For heating thermostats, the main spring pushing against the regulation is actually the steam pressure.

[@DaimonWalker]

Hi Big Clive! Love your teardowns and 'subtle' approach to gentle prying things apart. Aside from that, very informative and interesting. I have a question for you and the community here - how would I be able to work out the correct resistor value (for want of a better phrase)? I'll explain - I plugged the wrong charger into my hair trimmer and fried a resistor. It's so burnt that I can't see any values/markings on the outside of the resistor (oops). So, where would one go to find information or how would one work out the information on the resistor? Note: I've not been able to find the PCB schematic online. Thanks all in advance!

[@aaa000777]

I am guessing that the reason they show multiple valves is so that wall radiators can be controlled as well as floor heating. The same valve system is used to control the water into wall radiators. There might be multiple radiators in one room / zone, therefore the ability to wire in multiple valves.

[@jordandavies2528]

You have multiple actuators to cover multiple pipe loops on the same zone (thermostat) you have a maximum area of around 20m² depending on the underfloor heating style used per loop of pipe, so it common to have multiple loops per room. This is why you have multiple slots for actuators :)

[@jerenable]

Are you going to take a look at the newish IKEA usb c pd power supply in the future?

[@jerenable]

@@Okurka. I have both, only 30w max on the usb c port tho so no powering laptops.

[@twocvbloke]

I wonder what the fella felt like when he realised what he'd done with his DIY improvement exploits? Gravity must have felt quite strong that day for him... :P

[@darmontie]

Suppose I had a single zone with 2/3 circuits controlled by 1 room stat would there be any need for a "control system" and actuators as discussed here? The UFH would be one zone and the radiators in the rest of the house would be another zone controlled by a different room stat. The controller/programmer (Drayton Wiser) has 2 independently controllable CH channels and 1 HW channel. Would it be acceptable to wire the UFH zone valve and pump into the boiler and programmer in the same way that the current radiators have been done? Currently the heating system is wired as an S-plan. Thanks

[@itslenny]

Hi Clive. I have the exact same system. When I monitor the control circuit (the top connector) it shows a 5v demand signal from slave to main, not 240v? I'm attempting to make a smart addition to my ufh, and need the demand control signal to activate from a smart zone valve controller, so wanted to validate what I have seen before I setup.

[@viperidaenz1]

I assume the diodes for the relay control are for safety and I assume the diode is on the "C" line side for the slave units. That would mean no power could flow from live to the thermostats if they were shorted to earth or neutral

[@TheEmbeddedHobbyist]

Just looking at the circuit? How does the boiler keep the pump running while it's cooling down. All the CHHW systems i've had always have the pump controlled by the boiler as when demand is removed the boiler keeps the pump running for a min or 2 until the heat exchanger has cooled down. Just stopping the pump will cause the temperature in the exchanger to rise and it could overheat.

[@YagiChanDan]

Ufh has its own pump. The boiler has its own pump and bypass circuit

[@TheEmbeddedHobbyist]

@@YagiChanDan Thanks, only thing under my floors is concrete. Also due to the thermal mass of the floor do you get a long lag from demand to the room warming. a bit like storage heaters?

[@YagiChanDan]

@@TheEmbeddedHobbyist there are insulated overlay systems for retrofit. New builds and new floors extensions etc) you would have a flat sub floor, sharp sand, 100mm of celotex insulation (or the equivalent), then a damp proof membrane. On top of that you then lay down your pipes. Then pour a screed between 50 and 90mm thick. Overlay is quick to respond but slightly less thermally efficient. Pipe in slab is longer to respond, but has less heat loss down. In all cases smart controls that can predict heating and cooling times are essential. Then they predict the on off times accordingly. What is rare but available are PWM actuators as well as self balancing actuators. The latter use ^T° to modulate the actuators to get the correct heatloss from the pipes to the floor.

[@TheEmbeddedHobbyist]

@@YagiChanDan thanks.

[@tyhuffman5447]

Clive, in your water diagram you may have forgot to complete the loop unless the "mixer valve" completes the loop. As it is, when the boiler pump kicks on to keep the loop warm it would be dead headed. A very minor gaff, if a gaff at all, I could be mistaken, I've been mistaken before.

[@bigclivedotcom]

I believe the mixer either allows the water in or bypasses it so it circulates back to the boiler.

[@AntonioClaudioMichael]

Very neet video Clive very intriguing @BigCliveDotCom

[@pyk_]

That's funny how in the slave module one of the banks of four screw terminals is replaced by two banks of two. I wonder if these are hand assembled and they ran out of four banks? Or maybe they just ran out of reels of four banks in the pick and place machine so they used the 2 banks that were already loaded in. Actually... now I'm curious if a pick and place machine could even place those terminal blocks since they link together.

[@trondhansen9896]

i think the waterpump is on the water return side,i might be wrong but to me it sounds logical to have the pump run cooler and possibly last for a longer time.

[@bigclivedotcom]

It is. I screwed up.

[@icarossavvides2641]

Could the 'graphite" coating be just for corrosion protection? On your slave board schematic, does the series diode on the 'C 'terminal actually exist as I can't see it on the PCB photo, it wouldn't function as required if included as all you're trying to accomplish is an 'OR' function? The 'pump' relay with the capacitor is probably used because it should be an AC relay but they're much more expensive?

[@bigclivedotcom]

The use of a DC relay allows simple OR logic to be done with diodes.

[@icarossavvides2641]

@@bigclivedotcom As this is the 'pump relay' it's not part of the OR logic, whenever heat is called for the 'pump relay' must be energised. What about the 'rogue' diode?😁

[@William_Hada]

Maybe the graphite pads are more resistant to corrosion than copper metal and cheaper than good or silver contacts? Plus you will not get the galvanic corrosion you do using dissimilar metal contacts.

[@kennybiel9688]

Mains voltage in a thermostat is strange to me. In North America most residential HVAC control uses 24V.

[@greentjmtl]

Central heating yes, baseboard heaters run 120/240v directly through thermostats.

[@cambridgemart2075]

Our thermostats are double insulated so safe for 240V; it also means the switched current is much lower which improves reliability.

[@kennybiel9688]

@@cambridgemart2075 I don't know what the purpose of stepping down to 24V does for us. I suspect it's just an old standard as our wired door bells also use 24V and I would guess the door bells were more common before central HVAC thermostats. In any case, it's become ridiculous that any modern system still requires it when we could use digital control systems these days. In my home I had to use an "add a wire" system for a 2nd thermostat b/c of this old standard.

[@ollylewin]

In commercial HVAC 24v DC/AC is a standard control voltage in the UK and Europe. I'm going to guess that your domestic HVAC uses it due to AC being common place which whilst domestic in nature, will have routes back to commercial systems. It makes sense to work to a standard control voltage.

[@DrGreenGiant]

Why are there breaks in the solder that's added to the tracks for increased current carrying?

[@henryokeeffe5835]

It seems the whole removal of the soldermask over the trace is done a bit of an afterthought. I would have traced out the whole trace on the soldermask layer, rather than just the middle portion and wouldn't have included breaks. As solder has such a high resistance compared to copper, and the additional solder is so thin (due to the wave soldering process they used), it's not really doing much at all anyway.

[@stephenbell9257]

Probably because PCB layout designer had seen it done somewhere else and they just copied it. The PCB designer obviously has very little knowledge of electrical circuit theory otherwise they would have realised that the effect the small amount of additional solder applied to the wider tracks would have been absolutely minimal.

[@I_am_Allan]

They also have 'wire' in floor heating.

[@rolfs2165]

I assume the initial explanation only applies to that particular system? Both houses I lived in so far that had underfloor heating that the pump on a timer (usually run early in the morning and again in the afternoon) and the valves for the zones were manual to control water flow and thus how much heat the room got (more flow -> more heat). No mixer and circulating pump inside the zones.

[@falsemcnuggethope]

That's not a control system.

[@reecemellor8955]

Have you got a video of wiring with multiple zones?

[@frankowalker4662]

just a thought, could you run chilled water through under-floor heating system in summer to cool the place down ? (I don't know how you would chill it though.)

[@hrenes]

Franko Walker when you could, you would have condensation, making tiles very slippery and bringing mold to carpets

[@frankowalker4662]

@@hrenes LOL. Never thought of that.

[@TheGodpharma]

Actually you can, with modern air-source heat pumps. It is relatively straightforward to run them 'in reverse' and supply cool water instead of hot, although you'd pay a bit more for such a model. I don't think the water is cool enough for condensation to be a problem, at least not here in the UK where it isn't normally very humid.

[@robincotgrove6256]

I have one of these in my UFH install and recently the UFH has stopped working. Nothing was changed. Just stopped working. Fuse is intact, Green lights come for Thermostats but Red LEDs for Boiler/Pump lights do not come on. Tested pump independently works fine. I have changed both Power Relays & the Capacitor. Diodes & Resistors test OK. Still does not work. I'm lost as to what's gone wrong and how to fix. Any ideas?

[@johncrunk8038]

Good for a "set and forget" system, but today I would definitely hack together an IOT box so as to have a way to monitor it. How times have changed.

[@R0T3]

When did you get so modern in the UK? ;)

[@brondesvillas2123]

Thanks for the excellent video. I now know the fault with my UF heating is related to the heating control. Heating is turning on itself. The control (not the slave) feels hot and has a slight burn smell. Would I need a new Control ?

[@leebithell8653]

Id be interested in your take on the nest thermostat..... you said a bit on honeywell and now UFH 😁

[@ollylewin]

They work as long as its not a big house (the range is weak). Pretty solid and reliable otherwise. They do a little bit of PWM for underfloor too which is nice.

[@poellot]

So for diagnostic, if a valve goes bad it would be simple to tell because the valve light will be on but the pump light will not, correct? So activating valves one at a time and simply watching lights you can find where the faulty valve is. Thats a nice simple setup.

[@bigclivedotcom]

In the case of the manifold actuators the light would be lit on the unit, but the red flag in the actuator wouldn't retract. In the case of the main motorised valve, if valve was lit but the pump/boiler wasn't it would suggest that the valve had not activated its end of travel switch.

[@YagiChanDan]

The ufh valves have physical indicators to show they have lifted.

[@martinsparks6410]

very instructional video, I have a problem with this system, it was installed about 13 years ago and has in the main given great service until now! the problem I have is for some reason the controller will not activate the pump or send a signal to light my boiler, the mains is ok and the valve light is lit, no light on the pump or boiler, having researched a little I ordered a new controller thinking this would sort the problem, after connecting it was like for like and a quick job, I still have the same conclusion ? the boiler , hot water and another part of the heating system ( radiators ) is working as it should. If you have any suggestions I would be grateful . A friend of mine who is a plumber is going to take a look but this could be a while as christmas etc !!

[@bigclivedotcom]

It's something that would need a bit of knowledge and a suitable tester to trace.

[@neddyladdy]

How may people have a boiler in the house ?. Boiler complete with turbine ? Are they to power the weather vane on the roof ?

[@robincotgrove6256]

I have one of these in my UFH install and recently the controller has stopped working. The thermostats call for heat but the relay circuit does not switch on. I have replaced both of the power relays on the PCB and yet the problem still persists. Would my symptoms be explained by the failure of the capacitor. It doesn’t physically look blown????? TIA

[@bigclivedotcom]

Are LEDs lighting? Is the fuse intact?

[@user-gg2wj7op6c]

Hi, I have one of these systems and the other day the main boiler fuse blew. I've managed to establish its a fault with 1 of the zones and at first thought It was likely the zone actuator. However this appears to measure the same resistance as the others (1.2k) and also that that particular zone is outputting 38v on the thermostat contacts and 160v on the actuator contacts with both devices disconnected so no demand. Am I right in thinking my fault is due to the above conditions and the board needs replaced? Great videos and any advice would be greatly appreciated 👍🏻

[@bigclivedotcom]

One of the most common failures is the zone valve actuation heaters. They may read normal with a meter. but may flash-over with the full mains voltage. If the replacement fuses blow very quickly then it may be worth taking a zone actuator out of circuit and seeing if the fuse blows. Or disconnect them all and add them back one at a time until the fuse blows again. If there aren't that many actuators it might be an idea to just replace them.

[@aryonllewellyn]

Hi Clive. Would you check out a Hive Heating System, as I have always wondered how it works?

[@gorak9000]

The bees eat the honey, and their metabolic heat output keeps the hive warm!

[@edc1569]

Comes with two parts the thermostat and the receiver, the receiver is wired to the boiler/valves and the thermostat is paired to the receiver, the system is then connected to your wifi.

[@ollylewin]

The Nest is the same principle but more refined. They just look and feel better. And they do PWM (to a degree) for undefloor.

[@CarlosFandandgo]

I have this single zone box controlling our main living area UFH, but it's had some issues recently. Firstly the zone valve actuator motor went and wouldn't open or close. We didn't really need this as the room with the UFH was in sync with the rest of the house in terms of temperature. So I removed the valve actuator, and left the valve itself open. This meant the UFH just came on with the rest of the house and worked fine. But just this week it stopped working. The green light was on, but the red lights weren't and the pump wasn't working. I stripped the pump wires out and tested the pump using a simple plug and the pump is fine so that's not the issue. I cant see any problems on the PCB but I'm guessing it might be the relays that have gone. Is there any way to test the relays?

[@bigclivedotcom]

If you measure across the relay coils you should get a resistance. If they are open circuit they may have failed. But I don't think it's a common failure. You should also hear the relays click quietly when energised by a thermostat. Are the stats working?

[@CarlosFandandgo]

@@bigclivedotcom Thank you, you’ve indirectly helped me to fix it. 😍 I had a thermostat on the old heating, plus a stat on the new system. I assumed I could get rid of the new stat and just use the old one but having reinstated everything tonight it’s all working again. I’ll have to have a rethink on it now, but at least it’s working so thanks again. 👍🏻

[@nicholasviney5975]

Relays in those things fail all the time they are not man enough for most larger external system components, I have had several wiring terminals fail as well if you are lucky you catch those before the board gets crispy you can re-solder them.

[@electroniquepassion]

👍

[@maxmerton]

Perhaps it would be better to measure the resistance across the graphite junction *after* the slave unit is connected, using the probe on the metal instead of the graphite pad?

[@djsmokinj]

Hi I have the same ufh system and the green power light has gone off but there is 240 volts going to the master. Would this indicate that the master has become defective?. All the rooms thermostats still have the displays working and show the flame icon when it calls for heat. Thanks

[@bigclivedotcom]

If the unit still works then it may be a faulty solder connection or light.

[@1234Raddy]

Hi Big Clive..a bit of advice please..I have the same polypipe control unit..yesterday I noticed my room thermostats had blank screens and my fused had tripped..I've narrowed it down to the 240v feed to the unit..once connected it blows the 3amp fuse..I've disconnected the thermostats and it still trips...could it be the pump off the manifold or a faulty control unit..really unusual as my heating was switched off when it happened..only DHW was on. Please please can you advise me. Kind regards Radcliffe

[@bigclivedotcom]

A common failure seems to be the electrical actuated valves if any are used with your system. They can arc over internally and pop the fuse

[@1234Raddy]

Thanks Big Clive..the fuse Only blows when I connect the 240v feed on the polypipe single zone master..I've also disconnected the zone thermostats just in case they were the problem..the only thing connected is the pump..but the heating is off

[@bigclivedotcom]

@@1234Raddy There's a possibility that your unit and the heating are on different circuits and that the unit may be trying to backfeed the heating. It might be worth disconnecting the heating control wires, but treat everything as possibly being live. Heating engineers aren't the best at electrics.

[@alanwadsworth1735]

I know this video is a couple of years old now but i have this exact system and it's just stopped working. I think i have traced it to a faulty relay as the thermostats are registering calling for heat but the valve and pump and boiler don't turn on. Before i try to replace with a new one do you have any other guesses? How reliable are the relays in these things? Thanks

[@bigclivedotcom]

Does the relay click when the thermostat tries to turn it on?

[@alanwadsworth1735]

@@bigclivedotcom No there is nothing. It's like everything in the system is calling for the boiler and pump to activate but nothing happens, the valve doesn't open either.

[@itslenny]

@@alanwadsworth1735 I had a similar problem with this exact setup. It turned out to be a faulty motorised valve. If that doesn't open and send the signal back, nothing kicked in to life. I was still seeing the led for the thermostat/actuator led light up.

[@alanwadsworth1735]

@@itslenny Your were right, replaced the motorised valve and bingo all back to normal, thanks for the help

[@stesmif19]

@@itslenny Just a note of thanks. This video and these replies just saved me many £100's figuring out the exact same problem. Themostat was calling for heat, all seemed ok fine but no signal to trigger the boiler. I saw this and checked the motorised valve - bingo! I am a complete amature and would never have though of that otherwise. Thank you all.

[@imadsayyed8354]

There are two types of these valves 1 normally open 2 normally closed

[@pulesjet]

I found light pipes interesting and amazing when I was little kid. LOL No idea why.

[@millomweb]

I thought car dash boards should use optical fibre running to all the lights to indicate each bulb is working.

[@pulesjet]

@@millomweb I know right ? The make damn dash boards IMPOSSIBLE to clean.

[@edc1569]

@@millomweb the first variable speed cameras on the M25 had a fibre optic running from each lamp on the speed limit display, this would then get exposed into the photo of you speeding, so they could demonstrate that the display was working correctly. I imagine there's a digital equivalent now.

[@edc1569]

I was always fascinated by optical TOSlink cables as a kid, use to spend hours pointing it at things and seeing the colour projected to the far end.

[@millomweb]

@@edc1569 And why not ! Maybe now they use digital images with 'average speed' cameras instead.

[@cunning-stunt]

AVE striped a thermal actuator a while back if you are interested?

[@millomweb]

As for your friend, you could have advised them to get a heating engineer out to it.

[@bigclivedotcom]

The one who installed the system has left the island, and the companies they approached checked out the job and then didn't get back in touch.

[@millomweb]

@@bigclivedotcom And we know why !

[@twotone3070]

Great sense of satisfaction from fixing it for them though.

[@millomweb]

@@twotone3070 You don't always get that ! If i's a pig of a job it becomes an ordeal and you're just glad it's over at the end !

[@twotone3070]

@@millomweb I suppose it's more to do with my constant need for re-affirmation.

[@scottgray6276]

I read about one that uses the water heater, as the boiler! I'm thinking that when this furnace goes tits-up, l might retrofit the house. (One level with a crawl space.)

[@ramigrafx]

Hi Clive. Very fortunate that I came accross this video. I have to repair my controller which is very similar to the one that you were working on. Mine is a master with 4 zones and an attached slave with four zones. The leds on 3 of the zones are out and so they will not work the activators. Looks like very basic electronics 100k resistors diodes and leds. Did you make a note of the value of the diodes so that I can make sure that I have them before I take the unit off the wall. Thanks, Richard

[@tuttocrafting]

They are trying to make a cheap board and than there is me that does the same with a logo 8 plc and it's expansions from siemens... So I can remap the logic... This has been handy due to the fact the circuit has been changed due to lack of a replacement. My old valves didn't had callback when fully open. So timer logic was needed. New ones have. So I just updated the program I wrote.

[@chrismooney1549]

Does the master unit have an internal fuse at all? I’ve got live power going in but nothing is working!

[@bigclivedotcom]

Yes. I think it was a 5Amp type T 20mm fuse in this one. If it has failed it may be because of a faulty valve actuator.

[@chrismooney1549]

@@bigclivedotcomI will check the fuse first . Is the valve actuator the motorised valve? A small metal box?

[@bigclivedotcom]

@@chrismooney1549 The metal box valve actuators tend to fail open circuit. The ones on underfloor heating manifolds are more prone to flashing over inside.

[@TechItOut]

True story for you Clive. A brand new hospital was built here with underfloor heating. Unfortunately to maintain the room and hall temps it was too hot to walk on in bare feet and so had to be replaced with a standard wet system at immense cost. The previous hospital built on the first occasion it rained it was discovered had porous roof tiles. I kid you not. news.bbc.co.uk/1/hi/wales/8045202.stm

[@tbelding]

I guess they didn't understand that the whole purpose of floor heating is to make the _floor_ warm? Not to use it to heat _everything_? It was an up and coming thing from Japan in the early 1980's, and featured in a book called "What will they think of next?" (also inkjet printing) The point was to make it comfortable for people that go barefoot or with slippers, as well as sleep and sit on the floor. By heating the floor, it required less energy to keep them warm rather than heat the entire house.

[@edc1569]

@@tbelding plenty of homes are heated entirely by underfloor heating, you have to install it correctly though, can't have too long lengths and the pipe runs are critical - software packages design these for you nowadays to get uniform heating across the room.

[@tbelding]

@@edc1569 - Just because it _works_ for heating the whole room doesn't mean that it was invented for that. That's my point. Personally, I'd rather have floors I don't have to worry about leaking/catching on fire/exploding, and just used a forced air system that complements the air conditioning I already have. We need A/C far more than heating, anyway.

[@yuqingshi6913]

Hi thanks for the video! Both of these two units for my underfloor heating stopped working for some reason. The engineer said that there is no electric current detected anywhere within these two units. Does it mean that I have to replace both of them? Thanks!

[@bigclivedotcom]

A common failure is an electrically operated valve shorting out and blowing tracks. Check for a fuse. If both seem dead then it hints at either the main PCB failing or external power to it failing. The engineer should have detected an incoming supply on the terminals regardless. Keep in mind that many heating engineers are not very good with electrical matters. It might be worth getting a second opinion from a technically competent friend.

[@jimkershaw1966]

thanks for the video. mine has started blowing fuses after 12 years. would you swap out the controller or try and test the unit? thanks Jim

[@bigclivedotcom]

@@jimkershaw1966 One of the most common failures seems to be one of the electrically operated valve actuators failing internally and popping the fuse in the controller.

[@jimkershaw1966]

@@bigclivedotcom thanks so much for your quick reply. you are correct, I have already replaced two as we have two controllers! wd40 has freed it up for now but I'll probably need a 3rd. Anyway great upload, thanks again, Jim

[@bigclivedotcom]

@@jimkershaw1966 The way the actuators fail is that the little heater block inside starts arcing across and pops the fuse.

[@phonotical]

pump and boiler led should be seperated, it might help determine if the pump has failed

[@YagiChanDan]

Easier more reliable ways to do that.

[@phonotical]

@@YagiChanDan how? it could still be implimented as an option.

[@YagiChanDan]

@@phonotical modern (decent) pumps have their own indicators and sounds. Old ones... Check for power, check for heat circulation. All an led tells you is if there is power. What if the crappy led or resistor has gone? On these it's the same relay doing the work, so if the boiler is on/receiving demand, then the pump should be running.