Water Underfloor Heating - Zone 2

[Michael CC]

I have a question regarding my water UFH and wondered if anyone could help.

In my UFH setup I have 2 zones; both have individual room stats, when Zone 1 stat requests heat it opens actuators, opens motorised valve, starts UFH pump and boiler fires.   

When Zone 2 stat requests heat it only opens actuators and turns on UFH pump (not the motorised valve or boiler) The only way for Zone 2 to get heat is to have Zone 1 requesting heat at the same time.

 

Is there a straightforward way to rewire this up so that it can work independently, I have attached a photo from wiring centre.

Note – this is how the system was commissioned by the electrician when UFH was installed approx 10 years ago and I was told that the kitchen zone (Zone 1) would need to be on for the second zone to work as would be complicated to have both working independently.

 

I live in Northants, I’m a keen DIYer and quite happy to have a go at most things.

 

Any suggestions would be great.

 

Thanks

Mike

 

[ProDave]

No you should not need to have zone 2 on to get zone 1 to work.

 

the zone 1 wiring looks odd, it has a brown wire to the "call for heat" input (right facing arrow) but it does not have a connection to the L terminal above it which is live out to feed the thermostat.

 

Can you take the cover off the zone 1 thermostat (be careful, some designs of thermostat have poorly shrouded terminals so a shock hazard may exist with the cover off) and post a picture of the connections inside the thermostat please.

 

EDIT: looking again, that brown wire I am seeing into zone 1 call for heat, looks to be just a link to a L supply inside the box.  Is there in fact a thermostat for zone 1?

[Michael CC]

Hi ProDave, 

Thanks for reply, attached photo of Zone1 Stat:

[Michael CC]

13 minutes ago, ProDave said:

No you should not need to have zone 2 on to get zone 1 to work.

 

the zone 1 wiring looks odd, it has a brown wire to the "call for heat" input (right facing arrow) but it does not have a connection to the L terminal above it which is live out to feed the thermostat.

 

Can you take the cover off the zone 1 thermostat (be careful, some designs of thermostat have poorly shrouded terminals so a shock hazard may exist with the cover off) and post a picture of the connections inside the thermostat please.

 

EDIT: looking again, that brown wire I am seeing into zone 1 call for heat, looks to be just a link to a L supply inside the box.  Is there in fact a thermostat for zone 1?

Yes attached photo, although there is also another wiring box where the white flex cables go into from wiring center shall I send a picture ?

[Michael CC]

37 minutes ago, Michael CC said:

Yes attached photo, although there is also another wiring box where the white flex cables go into from wiring center shall I send a picture ?

 

[ProDave]

Okay, pretty sure the thermostat wiring is okay.  He has used (in controller speak) zone 1 and zone 2 on the controller for what you refer to as zone 1, and zone 3 on the controller for what you call zone 2.  He did not need to do that but nothing wrong with it.

 

Where he has gone wrong, is he has not used the boiler call for heat terminals.  They are the 2 empty terminals bottom right, just to the left of the manifold pump terminals.  These currently unused terminals are what should energise the motorised valve, and then the feedback contact in the motorised valve calls for heat from the boiler.

 

I suspect he has connected the motorised valve somehow directly to one of the thermostats.

 

To complete the picture can we have a photo of the inside of the other thermostat, and the inside of the other junction box you mention please?

[Michael CC]

See attached wiring box and Stat2. Thank you.

Edited November 14, 2022 by Michael CC

[Michael CC]

[Michael CC]

The close up of the wiring box, I lifted the wiring wall cover so you can see the UFH motorised valve black cable entering from the bottom.

[ProDave]

This is the normal wiring configuration for that junction box

 

 

I would expect terminals 2 and 3 (shown here as "room thermostat" should connect to those 2 call for heat terminals in the manifold control box.  That would then energise the motorised valve when anything calls for heat.

 

It would be interesting to carefully follow the the wires coming out of terminals 2 and 3 and tell us where they go.

[Michael CC]

I carefully followed wires 2 and 3 (brown and black) and from what I can see these go to one of the thermostat grey cables which enter box from the bottom right hand side.

[ProDave]

I think I see what he has done.  One of the thermostats goes via this box (there is no reason for them to) and he has connected that to the "room thermostat" input.  I take it that is the grey wires into a separate terminal block wrapped in white tape?

 

If you want to try correcting it (turn the power off first!!!!!!!)

 

Disconnect the 2 wires from terminals 2 and 3 and park them individually in 2 spare terminal blocks.

 

connect a new bit of 2 core flex to terminals 2 and 3, (brown to 3 and blue to 2) and connect the other end of that bit of 2 core flex to those currently unused terminal blocks bottom right of the manifold control box, brown to the left hand one, blue to the right hand one.

 

Let us know if that works.

 

This is typical of heating engineers / plumbers / electricians who just don't understand under floor heating. they are used to a gas boiler where typically you have just one room thermostat.

 

With under floor heating it is common to have a thermostat per room  and these all go to the manifold control box, and the manifold control box created it's own "call for heat" when any zone is wanting heat, and it is that which goes to the "room thermostat" connection on conventional boiler wiring.

 

He probably scratched his head how to do it before coming up with this bodge and making the excuse that is how it should be.

[Michael CC]

Thanks very much for this information.  I can also confirm that the wires 2 and 3 (brown and black) which i traced are in fact for the radiator thermostat (I totally formgot to mention this 3rd stat). I was able to confirm this by doing a continuity test with the thermostat when requesting heat. Does this alter your recomendation?

Edited November 14, 2022 by Michael CC

[ProDave]

3 minutes ago, Michael CC said:

Thanks very much for this information.  I can also confirm that the wires 2 and 3 (brown and black) which i traced are in fact for the radiator thermostat (I totally formgot to mention this 3rd stat). I was able to confirm this by doing a continuity test with the thermostat when requesting heat. Does this alter your recomendation?

Potentially yes.

 

I would modify that to leave the existing wires in terminals 2 and 3, and connect your new bit of flex into 2 and 3  with them,  and the other end still into the unused pair on the manifold control box.  then the boiler will fire up if either the radiator thermostat click in or either of the UFH zones.

[Michael CC]

Sorry for the basic questions and thanks very much for your help.  I will have a go and will confirm if it has worked.👍

 

[Michael CC]

Will this then also open the UFH motorised valve?

[ProDave]

This is the trouble trying to work it out remotely.

 

So are there THREE motorised valves, one for DHW, one for UFH and one for radiators?

 

It's how the UFH and radiator motorised valves are linked (or not) that is the issue.

 

confirm there are three before I go further?

[Michael CC]

47 minutes ago, ProDave said:

This is the trouble trying to work it out remotely.

 

So are there THREE motorised valves, one for DHW, one for UFH and one for radiators?

 

It's how the UFH and radiator motorised valves are linked (or not) that is the issue.

 

confirm there are three before I go further?

Hi yes, there are three motorised valves, one for hot water, one for UFH and one for radiators.

The UFH valve only opens when Zone 1 is requesting heat, the second zone doesnt open the valve when requesting heat.

 

[ProDave]

1 minute ago, Michael CC said:

Hi yes, there are three motorised valves, one for hot water, one for UFH and one for radiators.

The UFH valve only opens when Zone 1 is requesting heat, the second zone doesnt open the valve when requesting heat.

 

So when I was looking at the wiring centre just now, was the "heating motorised valve" connected to that, the UFH  one or the radiator one?

 

The UFH zone valve should be the one that is connected to that currently unused pair of terminals in the UFH control box.  I would expect it to be the radiator UFH valve connected to the wiring centre.

 

Then there will need to be a link somewhere to connect the feedback contacts from all 3 motorised valves together so any one fires up the boiler,

[Michael CC]

9 minutes ago, ProDave said:

So when I was looking at the wiring centre just now, was the "heating motorised valve" connected to that, the UFH  one or the radiator one?

 

The UFH zone valve should be the one that is connected to that currently unused pair of terminals in the UFH control box.  I would expect it to be the radiator UFH valve connected to the wiring centre.

 

Then there will need to be a link somewhere to connect the feedback contacts from all 3 motorised valves together so any one fires up the boiler,

Will have a look and confirm.  Thanks for your help

[Michael CC]

/

Edited November 15, 2022 by Michael CC

[Michael CC]

18 hours ago, Michael CC said:

Will have a look and confirm.  Thanks for your help

Good morning ProDAve,

 

I had a look in the wiring centre and I can see:

- UFH valve = Orange goes into 12 and Grey into 7

- Radiator Valve = Orange goes into 6 and Grey into 7

- HotWater Valve = Orange into 6 and Grey into 7

 

Does that help? hope I'm not being a nuisance 😞

[ProDave]

Where does the Brown and Blue of the UFH valve go to?

 

Orange and grey seem correct.

[Michael CC]

7 minutes ago, ProDave said:

Where does the Brown and Blue of the UFH valve go to?

 

Orange and grey seem correct.

Hi

 

Brown into 5 and Blue into Neutral block. 

 

What I cant undertsnad is that with this wiring as it is in the wiring centre the UFH works fine for one zone1 its only the other Zone on the other room stat that doesnt open the valve. 

[ProDave]

24 minutes ago, Michael CC said:

Brown into 5 and Blue into Neutral block. 

Now follow the black also in 5 and tell me where that goes please?  (this could take a while)