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Heating controller and thermostat change


James94

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There are a few spurs but none that isolate that I can see. The one round the corner looks like it goes up to a plug that’s connected to the  immersion heater which is turned off.

C70DD833-46DE-4BAC-A492-DF064DDCDD46.jpeg

Edited by James94
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I suggest the next step is get an electrician (one who understands heating systems, check that point first) to come and check the system over.  He will find the isolator or if none fitted will fit one and check it all out and advise what is needed.

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I’d like to thank you all for your time and great advice, I’ll let them know what’s been discussed. I’m sure they can carry on using it as they have been for a while longer.I might keep googling and watching videos to enable me to sort it myself, ill see how it goes.

Regards. James

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1 hour ago, James94 said:

There are a few spurs but none that isolate that I can see. The one round the corner looks like it goes up to a plug that’s connected to the  immersion heater which is turned off.

C70DD833-46DE-4BAC-A492-DF064DDCDD46.jpeg


 

behind the grey lagging at the same height as the wiring centre

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Turn that switched spur in the above picture off.  Does the programmer downstairs go off?  that's all you need to know at the moment.  If so remove the programmer from it's connector plate on the wall, turn on again and do that test with the two motorised valves above.  Or let us know id the boiler is running continuously.

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@ProDave @TonyT

As soon as I go back I’ll try isolating the wiring centre with that fused spur and see what goes off.

I did try that test which you said,not sure if anything was wrong. I’ll have to look at the wires and try following some cables to see what goes where and to what.

 

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4 hours ago, James94 said:

@TonyT

Oh just got a picture of that could be it, I’m back at work now so when I get back there I’ll isolate it and see where it goes in wiring centre and test it.

Regards. James

69DC141B-5D58-4CF8-B6AC-CAF0C63BFE57.jpeg

 

This is a good candidate as someone has sensibly written 3A fuse fitted on top.

 

The behaviour of the programmer does indicate a problem there, but looking at the wiring centre, it's difficult to establish from the photos exactly what is going where as several of the wires are hidden behind others, and some seem to disappear behind it. From looking at the labelling, it hasn't been wired up according to the labelling either- which doesn't help.

 

As @ProDave has said, I think you really need to have the system looked at either by an electrician who understands heating systems or a heating engineer that understands heating system wiring to ensure all the components are working correctly.

 

If you are competent using a multimeter, then it's possible to work through the system methodically and trace any problem backwards. For this you need an S-plan wiring diagram and then to understand the various switched lives within the system. I'm afraid I simply don't have the time right now to go through the steps I'd take to figure it all out, but here's my partial take on the current wiring situation on the wiring centre (based purely on the photo so worth what you've paid for it 😉).

 

T3 - this is your switched live from room thermostat to 2 port motorised valve for heating system - bridged to T9 with yellow

T5 - white from Honeywell valve - ignore

T6 - Switched live from both heating and hot water valves. This goes live (orange from each valve) when either/both the valves are open. This turns on your pump and boiler. If you're having a problem with boiler running constantly then look here with multimeter and check each orange. The red from T6 looks like it connects to T12 & T13 which are what look like the supplies for pump and boiler

T7 - permanent live to motorized valves (grey) coming from red originating at T11 which appears to be permanent live either from programmer or other supply.

T8 - brown to hot water valve coming from blue at T14 which should be your cylinder stat

T9 - bridged to T3 - presume yellow from room stat e.g. heating from programmer via stat

T10 - bridged to T15 - should be swiched live from programmer for hot water but I can't determine where the connected blue comes from

T11 - permanent live bridged to T7

T12 - bridged switched live from T6????? - to pump or boiler

T13 - bridged swtich live from T12 and T6 ?????? - to pump or boiler

T14 - switched live from cylinder stat bridged to T8

T15 - switched from programmer for hot water????? - bridged to T10 which may go to cylinder stat?????

 

Some of these clearly have some big question marks but hopefully help in some beneficial direction.

 

Online videos for s-plan are plenty. On Youtube plumberparts and Allen Hart have videos on the topic.

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My point about get someone in is if you find the right person you will get a resolution and understanding for a fair price.  Don't always assume things have been wired properly.  I did one recently where clearly the motorised valves were not working, and were that plastic type where you could not swap the actuator heads.  It was the microswitch in the heating valve was stuck and the motor in the HW valve that was also stuck.  Both replaced by robbing parts from the new head the owner had bought hoping to swap the entire head.  All seemed to work fine turning on from cold.  Next day they called me back, no heating, there was demand from the programmer but the heating valve was not energised.  It turned out it was wired wrong and the heating valve was connected via the hot water tank thermostat.  I can't imagine how it ever worked, but I was clearly the first person to check the wiring through and find the error.

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2 hours ago, ProDave said:

My point about get someone in is if you find the right person you will get a resolution and understanding for a fair price.  Don't always assume things have been wired properly.  I did one recently where clearly the motorised valves were not working, and were that plastic type where you could not swap the actuator heads.  It was the microswitch in the heating valve was stuck and the motor in the HW valve that was also stuck.  Both replaced by robbing parts from the new head the owner had bought hoping to swap the entire head.  All seemed to work fine turning on from cold.  Next day they called me back, no heating, there was demand from the programmer but the heating valve was not energised.  It turned out it was wired wrong and the heating valve was connected via the hot water tank thermostat.  I can't imagine how it ever worked, but I was clearly the first person to check the wiring through and find the error.

 

I completely agree, I've recently had to re-wire 3 systems that were wired up incorrectly. One which was running constantly with no thermostatic control, despite the thermostat working, another new installation where the electrician had wired it all up using wagos and then shoved it all into the smallest backbox and screw it all down tight - no hot water and when I took the wires out, several live wires just fell out of the connectors. This was was even wired up incorrectly within the boiler itself. I'm just about to completely re-wire a system with combined UFD and rads where heating switched live was permanently live thanks to a dodgy 2 port valve, but when that was fixed I still had 85v at the boiler switched live together with rads heating when they shouldn't and random function of the 4 ufh zones. Weirdly all of these jobs came about because people had just bought and moved into the properties and thought things weren't quite right.

 

I think there really should be a proper boiler/heating system training/certification coz the problems seem to be rampant out there.

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4 hours ago, SimonD said:

I think there really should be a proper boiler/heating system training/certification coz the problems seem to be rampant out there

Even easier would be a standard control system. Similar to car pedals. It is really for the manufacturers to make a common standard, and stick to it.

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5 hours ago, SimonD said:

 

I completely agree, I've recently had to re-wire 3 systems that were wired up incorrectly. One which was running constantly with no thermostatic control, despite the thermostat working, another new installation where the electrician had wired it all up using wagos and then shoved it all into the smallest backbox and screw it all down tight - no hot water and when I took the wires out, several live wires just fell out of the connectors. This was was even wired up incorrectly within the boiler itself. I'm just about to completely re-wire a system with combined UFD and rads where heating switched live was permanently live thanks to a dodgy 2 port valve, but when that was fixed I still had 85v at the boiler switched live together with rads heating when they shouldn't and random function of the 4 ufh zones. Weirdly all of these jobs came about because people had just bought and moved into the properties and thought things weren't quite right.

 

I think there really should be a proper boiler/heating system training/certification coz the problems seem to be rampant out there.


 

fully agree, just completed my EV installation course, so a heating controls course would be good for the industry 

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3 hours ago, SteamyTea said:

Even easier would be a standard control system. Similar to car pedals. It is really for the manufacturers to make a common standard, and stick to it.

There is for standard gas or oil boilers.  That does not of course mean everyone actually understands it.  I am convinced a lot of installers just connect the wires into the wiring centre according to their colour, actually completely ignorant of how it actually works, and are completely stumped when it does not work (or may not even notice it is not working properly)

 

We just need heat pump manufacturers to bang their heads together and agree a standard. Or have one imposed on them?

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Thanks for the time you’ve all taken and there is some excellent advice. When I do get back there I’ll trace some of the wiring and do some testing, check out that fused spur too. This system has been working for years and I’m hoping it’s just the programmer but could be anything, is there anyway to test it?

I’ve been looking at some of the YouTube videos you’ve recommended and I’ll keep watching, some great advice and they do simplify it when the system is stripped down to each component.

It would make things simple if all wiring centres were wired the same.

Regards. James

 

 

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Well assuming you work safe of course 

you could power the circuit down, remove the programmer and join terminal 3 to the live conductor and apply power, this will energise part of the system. To let you see if everything opens/fires up.

 

power off, reinstate terminal 3 and then do the same with terminal 4.

 

 

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  • 6 months later...
On 12/04/2023 at 09:31, James94 said:

@SimonD@temp

Just removed the thermostat casing and taken a picture, if I choose not to or struggle tracing wires back to wiring centre. Is it just the case of a wago the live and yellow together that’s in three?

what do I need to do with neutral and earth wires?

Regards. James

C08BAECB-3167-4E9A-8A36-252E46C83D3D.jpeg

 

I am also trying to wire up a Hive system, although the existing system was working fine.

 

Have been renovating my brother's flat and he asked for a new app controlled heating system. The old controls had turned yellow with age.

 

I have connected up the Hive Receiver and it is working. I can use it to turn the hot water on and it was working to turn on the heating when the original Potterton PRT2 thermostat was in place.

 

I then tried to bridge the old thermostat by connecting the red and yellow cables together here and isolating the blue one. That isn't working. I did think it might not work as the Neutral was previously connected to thermostat also.

 

Can anyone tell me the right way to bridge the thermostat please.

 

 

IMG_2199.JPG

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The neutral connection to an old type mechanical thermostat is just to power a tiny "accelerator heater" to eliminate the hysteresis between turn on and turn off point.  So leaving that not connected won't be why it does not work.

 

If you are just replacing a thermostat, there is probably a programmer somewhere that needs bypassing if you want it all to be controlled by the app.

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I have already replaced the programmer with the Hive Receiver. This seems to be working fine.

 

The receiver has manual switches to turn on the heating and hot water. I tested it with the original PRT2 thermostat in place and it worked fine. When I hit the hot water button the light goes green and the boiler fires up. When I hit the heating button it turns green but the boiler does not fire up.

 

Now with the thermostat taken out of the circuit, I thought I could bridge it by connecting the red and yellow wires there, but the boiler is not firing up as I am guessing it is acting like the thermostat is not calling for heat.

 

The wireless thermostat is connected to the Receiver and calling for heat, so I am wondering if it is how I have bridged the old thermostat.

 

 

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Typically a thermostat in a heating system will energise a motorised valve (either 2 port or 3 port) and the feedback switch in the motorised valve will call for heat from the boiler.  So the boiler may not fire up for a few seconds after the thermostat closes.

 

Are you SURE it was 100% working before you changed the thermostats?

 

Yes normally linking the red and the yellow would be the same as turning the thermostat up.

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