Heating Controls Explained | Weather Compensation v OpenTherm NGCFE

#NGCFE #Plumber Historically, heating controls have been antiquated on/off type programmers and thermostats. While this has served the heating industry well as they are simple to understand and install, they have led to significant efficiency and comfort issues that needed to be addressed by the industry.
The problem with basic on/off controls is that the control they have over the heat source (outside of switching it on and off) is non-existent. What this meant was that boilers would operate at maximum output and chuck masses of heat around the radiators which would transfer heat to the rooms until the room thermostat switched off the boiler when the room achieved its target temperature. The issue here is that the temperature of the radiators / system would continue transferring the heat to the room until the radiators cooled down. This excess heat being transferred into the room would result in the room getting hotter than desired, usually by a couple of degrees. The same situation would apply to the room undershooting the room temperature as the room began to cool down and the heating control would not turn the boiler on until the set temperature was lost. The boiler would turn back on, but there would be a delay in getting the radiators hot enough to heat the room adequately again. This again may be a couple of degrees below the room set temperature.
This process of the room fluctuating in temperature and the boiler constantly turning on and off is known as cycling. Cycling really isn’t great for heating systems and can reduce the life expectancy of the heat source. It can also lead to increased maintenance costs due to components becoming worn quicker. Not to mention a reduction in comfort for customers.
Opentherm is a protocol developed by Honeywell a while back whereby heating manufacturer’s products can all communicate using the same ‘language’. The idea is that if we can get appliances and controls to constantly communicate with each other then we can achieve a much more efficient system. We can do this by utilising technology like load compensation and weather compensation.
Load compensation is a process whereby the control monitors the difference between the actual room temperature and the room set temperature and tells the boiler to give more or less heat depending on how much further the room needs to be heated. The result is that a well-designed load compensation system will ensure that the boiler operates at a lower output for longer periods of time. While this is more efficient in the majority of cases, its also much gentler on the boiler components as there is far less cycling.
Weather compensation is another process whereby the boilers output is controlled by external controls. In the case of weather compensation, The output of the boiler is controlled by an NTC sensor on the outside of the property (ideally on a north facing wall). Depending on the temperature of the outside atmosphere, the boiler will adjust its flow temperature to put either more or less heat energy into the property. While the temperature of the radiators will fluctuate depending on the outside temperature, the room temperature and comfort levels should be maintained if designed correctly.
As always, should you want to learn more about controls and opentherm, please contact us at the
National Gas Centre for Excellence on 01924973260 or visit www.ngcfe.co.uk .

[@danb.7529]

A very nice, clear presentation and explanation. Thanks. I chuckled, though, when the presenter blithely suggested that with weather comp. heating curves it’s simply a matter of a little post-installation education of the customer and the occasional subsequent revisit to tweak the curve for them. Back in early 2010 my excellent heating engineer and I decided to install a Viessmann Vitodens 200 combi with weather compensation in my house in N.E. England (where it gets chilly in the winter). We also researched Opentherm in it’s early days. But back in 2010 Viessmann resolutely refused to offer an Opentherm option. I’ve never regretted installing the Viessmann, and it’s still going strong in autumn 2022. However, regarding the heating curves - and I have exactly the same set of curves to choose from as that feature in this video - my experience has been that it is just a wee bit more complicated than the Presenter suggests in order to arrive at the optimum curve. I am a retired university science Professor, and while it was simple enough to make a good initial guess at a workable choice of heating curve, it took me several successive heating seasons worth of trial and error with a clipboard and regular noting of external and internal temperatures to optimise it. I can imagine what most installers’ response would be to customers’ repeated requests to “could you just please pop back again and tweak my heating curve”! Maybe in Germany it is the norm, though. One other thing, at least in my case zoning seems to work well with weather comp. It’s a largish detached house, and we simply divided it into 3 zones: the sitting room/lounge; my study (at the time I was still in harness, so it wasn’t used most days); and the upstairs (bedrooms and bathrooms). Thanks to the layout of the plumbing, the downstairs hall and the kitchen are “permanently live” and heated whenever any any zone is. For control we installed underfloor Honeywell 2-port zoning valves that are themselves controlled by Honeywell programmable roomstats (one per zone) with RF wireless communication. However, this is perforce a bit of a hybrid design, necessitated by the weather comp, since we deliberately did NOT install a roomstat receiver connected so as to control the boiler. In other words, the boiler operates purely in response to its weather comp, while the zoning valves do their own thing in response to the roomstats. Not elegant, and maybe not optimally efficient, but practical and effective, and it’s worked very well for 12 years now. I am led to believe that the new(ish) Drayton Wiser Smart Thermostat system, if connected in Opentherm mode and set to access local area weather information by WiFi, can effect an adequate version of weather comp (although less accurate than with a Viessmann box on your own wall) and, what’s more, manage over a period of time (approx. a month) automatically to calculate the optimum heating curve and then keep on refining it subsequently. If true, that would really take the pain out of implementing weather comp. and presumably make it a more attractive proposition for householders. Several times over the years, I have thought of writing to Viessmann to ask whether they could help the householder by designing some way of automatically calculating heat loss from a room. For example, possibly by comparing the external temperature (which is always indicated on the boiler if in weather comp mode) against the temperature of a room containing an electronic thermometer in communication with the boiler (e.g. a roomstat, which I believe Viessmann also offer), and applying some clever programming algorithm (which would also need some manual input as to the probable U-value of the wall), and then automatically applying the value obtained to select the optimum heating curve. But my early interactions with Viessmann indicated that it would be pointless, since Viessmann’s attitude to its domestic customers in the UK seemed to be along the lines of “our designs are tried and tested and the best on the market” (which they possibly indeed are) “and we’re not much interested in modifying them” (which is a shame, because whilst making for reliable apparatus, leaves them almost inevitably hostage to being overtaken by new developments).

[@dantronics1682]

Hi Is this AJ from cs?

[@johnburns4017]

A few points to add on weather compensation: *1)* They are _feed forward_ controllers, *not* _feedback,_ as say a room thermostat is. That is, they *anticipate the coming heat loss or heat gain to a building.* Weather compensation will say, turn up the boiler flow temperature, because the outside temperature has dropped, even though the desired room temperature has been reached, as heat is being lost from the building. It prevents that cold spot when a room cools before a boiler is switched on to reheat to get back to setpoint. Also no overshooting of setpoint. *2)* They *inject the correct level of heat into a building,* corresponding to its heat loss. *3)* They *keep the temperature of the boiler as low as possible.* In on-off controls, a boiler say will be full on, say 80C, then it is switched off as the room has reached set point. With weather compensation. If the boiler temperature wanted is 50C, weather compensation maintains 50C, no more - usually by reducing the boiler fan speed reducing the kW output of the boiler. So the boiler is not operating at needless inefficient higher temperatures. Also low boiler temperatures promote boiler longevity. *4) Boilers operate more efficiently when a boiler modulates down to a low kW, especially when using weather compensation control.* The lower the kW modulation rate of the boiler the more efficient. Weather compensation can modulate the boiler down to its lowest kW automatically, keeping the boiler just humming for most of the day. Inefficient boiler cycling will be vastly reduced. So choose a boiler that modulates down very low, especially when having underfloor heating. So always get the lowest kW modulation you can get.

[@CommercialGasEngineerVideos]

John Burns you're a clever lad. Thanks for your input.

[@bimiuk4051]

Now, can u use opentherm and weather compensation both at same time?

[@johnburns4017]

@@bimiuk4051 Yes. With some boilers. OpenTherm will lower the boiler temperature as setpoint is neared then off when reached. But the OpenTherm stat is only in one location in the building. Best use the stat as a high limit, as the weather compensation does the real work.

[@bimiuk4051]

@@johnburns4017 thanks. One plumber advised that weather comp is bad because mu front door is not facing right way … confused the boiler rtc etc. should I insist for it? Also OpenTherm is it not the smartThermoneter (Nest)??

[@johnburns4017]

@@bimiuk4051 Plumbers should stick to drains - heating control is out of their league. The outside sensor should _ideally_ be facing north. But it can OK be facing east or west - need to adjust the compensation curve to suit. The effect is lessened but still works by adjustment. If facing south it should be shaded from the sun. Some use unobtrusive bell wire run outside to get an outside sensor on the north wall, with the wire coloured to the brickwork (not white on red brick), run in the cement seams. An OpenTherm stat directly modulates the burner when it nears the setpoint. Before nearing the setpoint it will be on _full._ Smart phone stats/timers are not necessarily OpenTherm, although some later versions are. I believe the latest Nest is (needs checking). Earlier models clearly were not, being just on-off. I am no fan of Nest. They have a clumsy user interface and are expensive for what they are. Come across a few failures as well. They are not cheap. EPH sell a version which is I believe OpenTherm, but a lot cheaper.

[@phillipware6179]

Brilliant video and contents as a new engineer is very helpful and informative

[@brendanfisher2528]

I heard you was down duftons last week allen? My mates works there 'dean' he called me up asking me to go down but I couldn't make it! I was hoping to come down.. hopefully another time... keep the quality videos coming mate!

[@jockster5525]

Astounding work lads .very much appreciated. thanks for your efforts ❤️

[@AllenHart999]

Hi Jock, Thank you, Let us know what other videos would help you. Thanks.

[@CommercialGasEngineerVideos]

@@AllenHart999 good content Allen, you're on the money. Making the right videos.

[@CommercialGasEngineerVideos]

What an excellent teacher.

[@scobeno1911]

Best explanation I’ve heard yet👍👍

[@AllenHart999]

Thank You.

[@nindes]

Great content very calm and clearly explained, top job!

[@nindes]

Keep em coming!

[@AllenHart999]

What type of videos would help you? Thanks.

[@johntaylor6845]

Could you post a link to the site that lists Boiler/WeatherCompensation Control compatibility.

[@dannywashington2056]

If you fit a nest [ with weather comp ] can you turn that off and fit an actual weather compensator, and just use the nests load optimisation? Or will the nests weather comp fight against the external weather stat? Thanks.

[@RichardABW]

Hello, I have updated my wiring so that my S-Plan Ideal Vogue Gen2 S32 has now got an outside weather sensor (plumber didn't bother) and also Opentherm with Nest (yes you can do this with S-Plan, I just set my HW schedule to occur when my CH turns off, again plumber didn't bother/couldn't work it out). However, in order to maintain (for example) a 40 degree flow temp, my boiler now cycles on/off around every 30 seconds while the flow oscillates from 35 to 45 degrees. Is this ok? Does it indicate that my boiler is actually too big and I should have bought the S26 or even S18? Thank you!

[@chriswhitehead6095]

So I have a Baxi 836 and a bad choice of thermostat being the Hive. Would you recommend adding outside temp compensation or an Opentherm thermostat?

[@rodgerq]

Does anyone know if Tado controls use OT to control power output from the boiler?

[@b.saravanakumarsaravanan7797]

Hi Allen, Is it possible to use Opentherm for Conventional boiler/system boilers where they are having separate boiler setup.. Please help me to understand

[@markwhittam8744]

Viessmann don’t allow the use of weather comp and opentherm from a Nest at the same time. They prefer you to use weather comp and a 240 switched live - at least for the new 050 that is…

[@45graham45]

can a nest thermostat use it's external temperature info (from weather stations etc) as weather compensation?

[@handle1196]

Can you have zoned rooms with different temperatures with weather comp? Ie: How do you keep rooms warm in winter without making a kitchen too hot where you cook?

[@leeevans369]

Great video really informative 👌

[@AllenHart999]

Thank you

[@marlonw5429]

Very sensible you are heading in this direction, gas boilers are on the wane in terms of new installs except where no other option is possible. On commercial sites temperature compensation has been standard part of plant room design for a long time now, these things are now seeping into public domain. The BMS programmes used to modulate temperatures are now on the market in a simplified format, not requiring specialist BMS engineers. I’m seriously considering expanding my domestic operations in renewables as it presents an interesting opportunity!

[@edrobens5145]

Agree with you about commercial systems. The boiler provided a primary circuit for the DHW and the compensated heating was delivered via a secondary circuit using a three port mixing valve and secondary pump to regulate flow temp. This could also provide an early morning boost, delivered on a sliding scale dependent on the outdoor ambient. This aspect of the control system often had self learning capacity to gradually improve efficiency.

[@stephendoherty8291]

I rang Bosch who said weather compensation is not needed in a modern reasonably insulated home. That was bosch themselves saying this.

[@Oldgamingfart]

OpenTherm with Vaillant is a bit of a strange one, as you have to get the VR33 module installed, which isn't available in the UK (European import), and thus not officially supported by Vaillant UK. On the plus-side, their own controls are generally quite good, and naturally the best match with the boiler. I believe Tado also support eBus..

[@jaganadenmauri8706]

Hi Allen nice video as always He did mention a website, but I couldn't get it right can you please put a link of the website he did mention please many thanks

[@timhancock6626]

The Ideal weather compensation kit I fitted to my Logic 18 heat ( Y plan) is a simple fit and not costly and the instructions offer three curve profiles controlled by having the boiler stat at minimum, mid position or maximum. This confused me for a bit as I thought the adjustment would be linear. It also includes a relay that locks out the weather comp when the hot water cylinder circuit is engaged. Unfortunately the system would need complex repiping to incorporate Open Therm, so it is possible on Heat Only boilers, though possibly not practical in many cases to make the necessary alterations .

[@my_carp_life3424]

I've also got a logic plus h18 did you take the wire out of the open therm screws or leave it in when fitting the weather compensation sensor?

[@stephendoherty8291]

Yet Bosch doesn't support opentherm in the UK

[@sheriefgerges7789]

Great video, what is the name of the website he mentioned about third Controls and boiler work together. Thank you

[@AllenHart999]

www.theheatinghub.co.uk/

[@philpkhouse1097]

Great explanatory video but I have a few questions regarding Google Nest for heat only systems. I'm on the brink of buying but am unsure of the open them connectivity. The confusion comes from the fact that I have an Ideal Logic+ Heat 24 on Y plan. The boiler has Open Therm connections available. When installing a Nest, do I ignore/disconnect the switched live 1 in favour of OT1 & OT2? Also, as the boiler needs to know the valve is in position, SL1 comes through the valve, out on orange to power the pump and boiler, etc, so how would I get around this? My main reasoning for getting a Nest is Open Therm and its Load Compensating feature Many thanks in anticipation that you may be able to help me out.

[@scottk2765]

Wouldn't you be better off using Ideal's Halo controller. This is open therm and load compensating ready

[@philpkhouse1097]

@@scottk2765 Thank you Scott. Yes, the Ideal Halo was my preferred option but I had heard that the Nest was better. I have since purchased the Halo which also comes with its own dedicated wiring centre to get over the valve positioning, etc, problems. Thanks again for your help and instructional videos.

[@marksmith6989]

So when a boiler is setup would I add both an Opentherm Controller and a Weather Comp Controller, or just one of them?

[@AllenHart999]

one or the other. thanks.

[@Swwils]

It's absolutely ridiculous that in 2020 and beyond we still have boilers being installed for 80C flow temps.

[@AllenHart999]

👍👍👍👍

[@bimiuk4051]

Yes, I just got a new boiler Ideal Vogue Max s18 and requested PDHW with Opentherm but both plumber and electrician cannot get it installed. Boiler is installed and he said "we always set it to max degree" and OT makes no sense to create two seperate flow temps. So, got a new boiler but not a working thermostat. I am just fuming. Apparently u can't get OT work on a S PLAN

[@slurmdogmillionaire4969]

@@bimiuk4051 kzbin.info/www/bejne/Y2bTeWuferepsLc

[@ma40]

@@bimiuk4051 That’s just poor training. Find a different heating engineer and swap from S-plan to hot water priority using the second switched live. You can then easily run either weather compensation or OpenTherm controls.

[@bimiuk4051]

@@ma40 does that depend on the smart controller how many connectors it got? For example NEST has got lot of connectors in the back but TADO EU model has one RELAY: COM NC NO and then Digital + -

[@rmthomas749]

I recently had a viessmann combi installed with weather comp and EPH room stat controller connected to open therm. Veissmann are saying you can't use both together as it will confuse the boiler, my boiler was fitted my Viessmann installer, so I'm confused now, 😕, anyone advise on this?

[@AllenHart999]

I would listen to what Viessmann say. Thanks.

[@cagcos]

Can we use weather comp and opentherm at the same time? Thanks

[@phoenixxavier9615]

Baxi told my engineer that their weather compensation sensor isn't compatible with OT, so that explained why it was impossible to change the boiler temp whilst the sensor was fitted. So you can either have your OT thermostat working, or the weather sensor. Not both together. They do not advertise this IMPORTANT fact.

[@45graham45]

how do you enable weather compensation in a Baxi?

[@phoenixxavier9615]

If it's wired into your boiler, it should work without you doing anything & then allow you to adjust the flow temp so that it takes into account the external temp & adjust itself automatically thereafter. However, if you have an opentherm thermostat, then the weather compensation sensor will not work as it will confuse the system & you will not be able to adjust the flow temp. So you can either have OT or weather compensation, not both. Baxi don't advertise this.

[@joncoke8208]

Great video alan although I thought you couldnt wire open therm Into worcesters

[@timhancock6626]

Worcester produce their own proprietary version of Open Therm. They call it Easy Control. However if you want to fit it to their system boilers you have to buy their diverter control pack as well. I know this as a friend has just had a WB 8000 system fitted as a replacement and the extra work needed to repipe put him off the idea of Easy Control, so they have stuck a Hive in instead. Easy Control is fine on the combis of course.

[@salam238]

Hi Allen Can EPH Combipack4 fullfil the requirement of Boiler Plus? Regards

[@AllenHart999]

Yes.

[@salam238]

@@AllenHart999 Without any control from mobile or Tablet?

[@AllenHart999]

@@salam238 yes.

[@salam238]

@@AllenHart999 Thanks for your reply. I was a bit confused after attending Baxi training. 😉 Have a good day.

[@AllenHart999]

@@salam238 It says boiler plus on the box I believe ? Thanks.

[@jorkirasalas2726]

He mentions Nest, which is an Opentherm controller, and then Hive which is not OT. At the end he mentions OT can be applied to system boilers, which is true, but if the system boiler has a hot water storage cylinder then that cylinder needs its own OT thermostat to ensure the boiler heats the domestic hot water at high temperature to reach 55 to 60C to avoid legionella risk. Might then need to implement Priority HW to avoid that high temp output feeding the radiators! Viessman say their Cylinder Demand box accessory is needed to convert a standard cylinder stat to a feed into their vitodens 100-W system boiler to achieve OT HW control. EPH have an OT cylinder stat & Allen says in his OT multizone video (m.kzbin.info/www/bejne/qZeriaF5a5yercU) that an S plan can be made OT that way. ESi apparently have an OT cylinder stat but not sure if this is available yet. Cant get any info on the Nest to see if it can control HW via OT.

[@AllenHart999]

You would be best to contact EPH for any advice on this and what products you need to buy. Thanks.

[@gavinbiard3745]

How soon do you think gas will be phased out?

[@AllenHart999]

I have my gas meter turned off at the moment. not sure if it will ever be phased out though.

[@johnburns4017]

Gas for electricity generation will be phased out first. We use quite a lot of gas for that. Of all the fossil fuels, gas is by far the cleanest. Gas usage will reduce, relatively, as new builds do not have gas installed. It is difficult to remove gas from apartment buildings and terraced houses, replacing with noisy heat pumps.

[@bimiuk4051]

One of plumber said that Weather compensation is not good as it can confuse the boiler!!! 🤭

[@Allegedly2right]

Move it back at £140 call out fee they are all at it snake oil salesmen no one will tell it as it is.Gas fire too hot turn it down too cold turn it up job done.Good video well presented.

[@uknokianut]

Commercial have been using weather compensation for the last 60 years.

[@user-cc6kd5ye9y]

I'm told by all installers that load comp smart thermostats re opentherm and weather compensators are not needed for home gas boiler heating installers or the cost saving is very marginal for homes not occupied e.g during weekday when occupants not at home. Are gas boilers installers just all unskilled. Climate is northern England

[@Moose185]

Basically when it’s 10 degrees outside and 22 on my thermostat my heating doesn’t go on at all. My heating is completely pointless now. I need to get rid of weather compensator. I should be able to control my heating how I want. Don’t like these new designs there terrible. I like my home very warm.

[@AllenHart999]

Thank You

[@johnhunter4181]

How can Viessmaan justify charging £115 for their outside sensor - a cheap plastic box with a 30p NTC in it? They're stealing money from unsuspecting loyal customers.

[@MrKlawUK]

how do load comp and weather comp compare? if you have load compensation with eg Tado, should you still set a max flow temp to avoid too high temperatures being selected - eg 60c in your example (assuming you’ve measured your radiators to be ok with that)?