Combi Boiler 2 Heating Zones Volt Free - 24V and Others

Wiring for a combination boiler with two central heating zones, each zone controlled by its own thermostat.
This shows two methods of switching the boiler using volt free contacts and is intended for boilers that do NOT have a 230V switched input, and use some other voltage such as 24V. 230V switching is covered in the previous episode here: • Combi Boiler with Two ...
The arrangements in this video could be used for 230V switching, but there is very little point in doing so.
Suitable for use with almost any thermostat including Nest, Hive and other smart devices. Also applies to wireless, wired, mains powered and battery thermostats.
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[@alanrother8477]

Great video. Have just rewired my heating centre with this method and added a hive thermostat. Was a bit confused before but this made it so clear to understand. Thanks John.

[@Skeletoncrew46and2]

Thanks john. As usual an excellent video and made so easy to understand. Very informative!

[@mikearthur2586]

Once again. a brilliant breakdown. thanks.

[@samwhite6734]

As usual very clear and precise explanations 👍

[@leaturk11]

Nicely explained.

[@mianasifgujar]

Excellent Mr J W

[@gurdturd7763]

Brilliant , Thanks John. Can i add a cylinder stat to this wiring by using an extra terminal for zone 3 then connecting cylinder stat to 1 and 4 terminals of hive multi zone/thermostat?

[@garethjones6887]

Keep these videos coming.. what spec of relays would I need to ask for ? And would I piggy back the low voltage side of the relays into the boiler thanks

[@gorillagamerimm396]

Awesome Thanks

[@brotherjohnno]

Hi John, enjoying your wiring videos. Do you have a video covering the installation of relays on S plan systems. I have a problem where I have a back feed from my UFH zone bringing live to my pump for my other zones. Any information would be greatly appreciated. Thanks

[@martinuk1001]

Hello John, another great video. Are the relays usually supplied with boilers where non-230v to A & B terminals? Or if not can you suggest one please?

[@jwflame]

Relay won't be supplied with the boiler, if one is needed you will have to obtain it yourself. For the diagram in this video, it would need a 230V AC coil and at least one normally open contact.

[@Chris-js4yq]

Hi mate would a and b be the terminals in a baxi for this diagram?

[@Itsyaboycameron]

Hi John videos are very informative, in this example of a zone to a volt free combi, how could I also add a 240v pump to the wiring for an underfloor heating zone? Thanks

[@jwflame]

If it's a single UF zone with only a pump, then the pump connects to the switched output of the thermostat in the same way that the valve motor does. Pump N&E connects to 3&5. For zone 1 in the diagram, pump L connects to 7 For zone 2 in the diagram, pump L connects to 8

[@millomweb]

John, guessing, what proportion of UK boilers don't use 230V SL ? I'd be sorely tempted to permanently link A-B in the boiler and have the zone valves just power up the boiler ! My boiler doesn't have a permanent live - so not an issue. I believe many systems in the USA are 24VAC control systems - so zone valve motors are 24V.

[@PeteyPeteee]

Hi John, can you make a video about installing a nest or hive? Also can you include the required components for a minimum configuration that will operate a combination boiler. Thanks for the great videos :)

[@jwflame]

Hive & Nest: kzbin.info/www/bejne/qne3YnSAqMeAnNE Combi boiler thermostat: kzbin.info/www/bejne/nn7IpotpaNKHd6c The rest of the heating videos: kzbin.info/aero/PLVsHvs2Suqmr5HtxgbInR4bXmH0kLseWc

[@PeteyPeteee]

John Ward thanks. That is my evening watching sorted 👍🏼

[@michaelyounge5743]

Mike Younge Another informative video. In the drawing is show that Thermostat terminal 3 is linked to wiring Centre 7. In the Tado Thermostat it can be linked directly to the boiler A&B . This would leave the brown zone wire free (7) where would this be linked to operate the zone motor to trigger 9&10?

[@jwflame]

Any thermostat with volt free contacts can be linked directly to the boiler, but that is only usable for a single heating zone, where there are no zone valves.

[@andyhiggins1144]

Hi John, I’ve come across your videos and have found them extremely helpful. I have just bought a new build property with a dual zone combi boiler and want to install hive but I’m struggling to identify which type of system I have. Could I share a picture of the wiring centre and ask for your help identifying it?

[@daleprosser350]

Hi, this is a great video for learning! 2 questions if you don’t mind: 1) On the boilers with a 24v input, how is that 24v generated? Does the permanent 240v live to the boiler branch off and get reduced down through the circuit board? 2) Where can you see what I put a particular boiler requires? Thank you!

[@JasperJanssen]

In this boiler’s case, one of the two terminals is outputting 24v and the other is detecting its presence. Hence the voltage is not very important, what it’s detecting is merely presence or not of a dead short between those two pins.

[@huyongquan6554]

Very impressive. How about add nest gen3 diagram to demonstrate how to connect the OT1 OT2 of Boilers and nests through Valve grey and orange. That the Opentherm function can be achieve.

[@Matt.ffgmatHexPulseChain]

Hi Have you sorted out the problem with nest ? I am now in this situation. Thanks for any help.

[@pineappleroad]

Unfortunately it’s not possible to use opentherm with multi zone heating (opentherm is a digital connection which doesn’t support multiple heating zones)

[@marioz.3022]

Great video John!!! I just want to ask is it posible to add more zones in this system and how many relays i would need ?

[@jwflame]

You can add as many zones as you want. Each zone needs a valve and thermostat, thermostat output connected to the valve brown wire. All other wires connect as in the diagram. No relays required.

[@Matt.ffgmatHexPulseChain]

Great video. I have one question, how to do it with nest thermostat with don’t have 230v ?? Boiler is directly connected to the nest by the OpenTherm . How to send signal to zone valve?? I am trying to find some solution.. Thank you for any suggestions.

[@jwflame]

You will need to use the other terminals on the Nest to switch 230V for the valve motors. Opentherm is only control for the boiler.

[@nagarajahnavaneethan6634]

Very helpful. How could I accommodate a pump to this diagram please? I would like it to come on after the 2 port valve has fully opened. Thank you

[@jwflame]

Combination boilers have the pump inside the boiler, it's not a separately controlled component.

[@nneethan5]

Hi John, my apologies i should have been a bit clearer as to what pump i was referring to , the pump i am quoting here is the ufh manifold pump which is connected to one of the two zone valves in my setup. i think i will need to use the 230V switching diagram for this, any advise will be much appreciated. thanks

[@jwflame]

@@nneethan5 Yes, it's the 230V version. If it's a single UFH zone with only 1 thermostat, the pump connects to the switched output of the thermostat, which is also where the brown valve wire connects. Pump will run for a short time before the valve opens but this doesn't matter as it only circulates water via the manifold and UFH, not through the valve. For more than one UFH zone, the pump, thermostats and zone actuators are wired to a UFH controller, with the switched output from the controller connected directly to the valve brown wire.

[@robertmccully2792]

Zones are great but not very efficient. Heat on first floor rises to second floor, and second floor heat get combined with first floor heat that has risen . The first floor is usual to cold and the second to hot. For this to really work correctly there needs to be a zones in every room upstairs . For that to work you need electrical dampers/valves to each room and a cold air/ water return in every room. Interesting theory on paper.

[@millomweb]

Your floors aren't very efficient ! Here, heat on downstairs and upstairs rooms are very cold ! I have 5 zones: House, hot water, 3 bedrooms.

[@arinb12]

What if my UFH controller has volt free output switching for the boiler, but my boiler wants. 240v live return to turn on?

[@jwflame]

Connect 240V to one of the output terminals, the other connects to the boiler. 'Volt free' is just a switch with nothing connected to it, you can use it for any voltage you want.

[@saidhissoufi277]

Hi Mr John what is the best route to become a qualified electrician, knowing that I am 39 years old? Thank you

[@jwflame]

www.electricalcareers.co.uk/joining-the-industry/training-routes/

[@asifk159786]

Can A & B be connected in any order to the orange and grey

[@jwflame]

Yes. They are just connected together when heat is required, so makes no difference.

[@asifk159786]

@jwflame would I still require the link from L to 1. I assume your using hive in this set up.

[@jwflame]

​@@asifk159786NO, as the title states, this is for volt free switching. If you connect L to any part of a volt free boiler input, it will destroy the boiler circuit board. If the boiler has 230V switching, use the 230V wiring as described here: kzbin.info/www/bejne/b2nPi6mEbtZqqNk

[@asifk159786]

@jwflame thanks. Boiler in question is ideal vogue which I belive isn't low voltage. The boiler has 2 outputs room stat and time. Similar A&b so I think the low voltage video should be fine.

[@JohnnyB6969]

Hello Dear HOPEFULLY someone knows 😊 where is SL In my glow worm energy 25c. on the left side where is mains I have L N E RT and on the right side of PCB have B OFF(burner) RT (24v )BUS (+-) At the moment I have salus room thermostat connected to RT 24v My diagram required SL Thank you guys 😊

[@jwflame]

If you are using 24V switching, it's the two 24V RT terminals where the thermostat is connected. The L and RT terminals are the equivalent if using 230V switching. These must NOT be connected in any way to the 24V terminals, doing so will cause damage.

[@robswingler]

Only problem here is you would have a 5 core flex going into the 2 port valve with single insulated cables inside the outer sheath with both 230v and 24v when really they would need double insulation atleast to keep the 230v away from the 24v.

[@alhughes9698]

Think you have misread the diagram as the only 24 volt connections are from the relay terminals 1 and 2 on to the boiler terminals A and B. All conductors to the 2 port valves in this instance have mains 230 voltage on them.

[@robswingler]

Al Hughes no I think you’ve misread its terminals A & B which clearly go upto the 2 port valve which has 240v at it too.

[@alhughes9698]

@@robswingler i see whats happening now, i am looking at the second diagram with the relay in not the first diagram which is what you are on about :P

[@JasperJanssen]

A better option than a relay so you can do most of the work in 230V would be using the other kind of zone valve, with a 24v motor. There’s no real reason to do this all by switching non touch safe voltages, afaict.