Heating Wiring Problem - cylinder thermostat not working

[dfreitag]

Hi there,

I've had 4 plumbers & 1 electrician look at my problem (seemingly without dedicating too much time unfortunately), spending more than £1000 already , but none of them has found the issue to my problem - that's why I'm reaching out to you!


I have the below set up

• 1x gas system boiler (Vaillant ecoTEC plus 624 R1) New Pump and New PCB installed rather recently
• 1x UNICYL HE indirect unvented 150L Cylinder
• 1x Cylinder Thermostat (ESI ESCTDEB ESCTDEB Electronic dual cylinder thermostat - https://www.esicontrols.co.uk/esctdeb.html)
• 1x Nest Thermostat (the "learning" type)
• traditional radiators

The Nest controls (or tries to) both heating & hot water.


At the moment the cylinder thermostat is not working - it just doesn't switch on anymore... (it used to only switch on when setting the Nest to boost hot water)

Thinking it was faulty I ordered an identical replacement, and replaced it myself.

By doing so I found the wiring to be rather odd - I have no prior experience at all with these things, so could obviously be wrong..


I am suspecting that someone messed up the wiring at one point.. Can you please have a look?


Many thanks!!


Central Wiring

Cylinder Stat Wiring

Cylinder Stat Wiring Instructions

 

[SparkyChick]

Can you be more specific about where you are in the UK? A local member may be able to help.

 

[SparkyChick]

On reading the thermostat installation instructions, it states quite clearly it requires a permanent power supply. As best as I can tell, yours is only being powered when the Nest is requesting hot water. Given the thermostat has some automation (the weekly legionella killing cycle for example), it could be the constant power cycling is affecting it's operation.

 

[dfreitag]

On reading the thermostat installation instructions, it states quite clearly it requires a permanent power supply. As best as I can tell, yours is only being powered when the Nest is requesting hot water. Given the thermostat has some automation (the weekly legionella killing cycle for example), it could be the constant power cycling is affecting it's operation.

Hi, and thanks for the input!

I thought this was the case..

Is it at all possible to show me how to wire the cylinder stat correctly so that it has permanent power supply, or is this too complicated?
I can't afford to spend even more money on this, so I'd love to avoid a call-out fee for switching just a couple of wires around..

Many thanks!

 

[dfreitag]

Also, to clarify - the way it's wired rightnow the cylinder stat NEVER goes on - not even when the Nest tells it to..

 

[SparkyChick]

Also, to clarify - the way it's wired rightnow the cylinder stat NEVER goes on - not even when the Nest tells it to..

So that suggests the wiring in the Nest is also bad. A photo of the Nest connections may help.

 

[brianmoooore]

Is the black from the 'stat taped off at the wiring box? If so, the 'stat isn't getting a neutral.
There are a few things that need addressing with this installation - not least that the cable clamps for the wiring box haven't been broken off from their resting place and used to actually secure the cables.

 

[SparkyChick]

Is the black from the 'stat taped off at the wiring box? If so, the 'stat isn't getting a neutral.
There are a few things that need addressing with this installation - not least that the cable clamps for the wiring box haven't been broken off from their resting place and used to actually secure the cables.

Good spot... missed that

 

[dfreitag]

Is the black from the 'stat taped off at the wiring box? If so, the 'stat isn't getting a neutral.
There are a few things that need addressing with this installation - not least that the cable clamps for the wiring box haven't been broken off from their resting place and used to actually secure the cables.

Many thanks for the feedback

Exactly!! The black one is connected to the stat and it goes nowhere in the wiring box..!

Excuse my ignorance, but which cable clamps do you mean - and how can I correct this?

Also, sending a photo of the wiring at the Nest

 

[dfreitag]

Can you be more specific about where you are in the UK? A local member may be able to help.

sure, London E5

 

[brianmoooore]

Excuse my ignorance, but which cable clamps do you mean - and how can I correct this?

View attachment 99982

Cable clamps are at the back of the wiring box, right at the top, partly hidden by the terminal numbers. Screws to secure them in place where originally packed in a small plastic bag with the orange wire links, but presumably are now lost.
There are strange connections in the nest pic! The four core flex appears to have an earth connection to terminal 6, and the two core flex has an unused terminal marked with an earth symbol next to where it connects.
Going back to the wiring box, there are two four core flexes where the black wire has been used as a neutral. This should be the grey wire by convention, and it should be marked with a short length of blue sleeving.
Similarly, the blacks should have been used for 'lives', and identified with a short length of brown sleeving.

 

[dfreitag]

Cable clamps are at the back of the wiring box, right at the top, partly hidden by the terminal numbers. Screws to secure them in place where originally packed in a small plastic bag with the orange wire links, but presumably are now lost.
There are strange connections in the nest pic! The four core flex appears to have an earth connection to terminal 6, and the two core flex has an unused terminal marked with an earth symbol next to where it connects.
Going back to the wiring box, there are two four core flexes where the black wire has been used as a neutral. This should be the grey wire by convention, and it should be marked with a short length of blue sleeving.
Similarly, the blacks should have been used for 'lives', and identified with a short length of brown sleeving.

Hi Brian

Thanks for your feedback!


Cable clamps - that's good to know. Saying that, I guess there's not much I can do at this point, right?

Wiring Box + Cylinder Stat - At the moment this is the real priority to me, just trying to get the Cyl Stat working at this point.. so I was hoping you maybe have some advice for me there?
I'm suspecting it's just a "simple" mistake someone did, so even little old me could solve it..

Nest Wiring - do you think I should connect the earth from the four-core (and remove it from T6) and/or connect the earth from the two-core (where it's just cut off)?

Wiring Box - so you're saying they've used wrong colours and markings (which is not encouraging). But regardless of the colours, are they connected correctly?


Many thanks for your help - much much appreciated!!
D

 

[dfreitag]

By the way, I'd be happy for a professional in the area to reach out who could fix all this..
and get my hot water & heating back!!

 

[brianmoooore]

cable clamps: The clamps can still be broken free from where they are, and fitted where they should be, but you'll need to find four suitable self tapping screws.
This really needs to be done, with these flexibles looping unsecured to various parts of the airing cupboard.

Cylinder stat: I've already answered this one. The neutral supply to the stat appears to be floating free and not connected to anything at the wiring box end. It's never going to work without power.

Nest wiring: The green/yellow appears to have been used for 'hot water on', since it's connected to 10 at the wiring box. Wires can be used for purposes other than that indicated by their colour if a short identifying sleeve is fitted over the wire at each end, BUT this does not apply to a green/yellow wire. This can only be used for earth and for no other purpose.
The cable used appears to be only 4 core, so should be replaced by 5 core, with the green/yellow used for the earth connection to the nest, and the grey (with brown sleeves at each end) used for 'hot water on'.

Wiring box: The wires that are connected appear to be connected properly, but, as I've already written, the neutral for the 'stat isn't connected, and I suspect theirs also a green/yellow in that cable that has just been cut short.

 

[davesparks]

Wiring Box + Cylinder Stat - At the moment this is the real priority to me, just trying to get the Cyl Stat working at this point.. so I was hoping you maybe have some advice for me there?
I'm suspecting it's just a "simple" mistake someone did, so even little old me could solve it..

Nest Wiring - do you think I should connect the earth from the four-core (and remove it from T6) and/or connect the earth from the two-core (where it's just cut off)?

I've studied the pictures in detail but it looks like the cable from the wiring centre to the cylinder stat doesn't have enough cores in it. It should have a 5 core flex in order to connect it up in the traditional manner, how hard would it be to replace that cable?

That cylinder stat is unusual as it requires a permanent live and neutral supply whereas most don't so I suspect that is where this problem has arisen from.

No, don't go moving that green/yellow wire, it won't work at all if you do that. Whilst it is not right, it is not causing the problem.
Connecting the green/yellow of the two core flex to that earth terminal is unlikely to achieve anything either as the other end of that cable won't be connected to earth as it goes to the nest thermostat.

 

[dfreitag]

Hi again, and THANKS SO MUCH for your time and for bearing with my being an amateur!

Cylinder stat: I've already answered this one. The neutral supply to the stat appears to be floating free and not connected to anything at the wiring box end. It's never going to work without power.

Gotcha! This was 100% working before the last wave of "professionals".. meaning one of them did this.. anyway..
(Just looking at this again, I've just noticed that both black cables from cable (2) on the right and from the CylStat bear the same (clumsy) black isolation tape - were they maybe connected before? )

Where should I connect it to at the wiring box to make sure it gets power again?

Also, is there anything you think I should change on the actual CylStat wiring, or should I leave this as is?

(I'm uploading a new marked up version of the previous photo for easy reference to each point of the wiring box.)

Nest wiring: The green/yellow appears to have been used for 'hot water on', since it's connected to 10 at the wiring box. Wires can be used for purposes other than that indicated by their colour if a short identifying sleeve is fitted over the wire at each end, BUT this does not apply to a green/yellow wire. This can only be used for earth and for no other purpose.
The cable used appears to be only 4 core, so should be replaced by 5 core, with the green/yellow used for the earth connection to the nest, and the grey (with brown sleeves at each end) used for 'hot water on'.

I'll get a 5-core and try to do as suggested.

Wiring box: The wires that are connected appear to be connected properly, but, as I've already written, the neutral for the 'stat isn't connected, and I suspect theirs also a green/yellow in that cable that has just been cut short.

Thanks for your feedback on proper connection at Wiring Box. At least that's ok!

Someone has definitely cut the earth on both sides of that cable. (This CylStat cable is actually a 4-core, but you can only see 3.)

I'll take it out again on both sides.

Can you please guide me as to where to connect the earth to properly (on both wiring box and CylStat)?


Many thanks!!

 

[dfreitag]

I've studied the pictures in detail but it looks like the cable from the wiring centre to the cylinder stat doesn't have enough cores in it. It should have a 5 core flex in order to connect it up in the traditional manner, how hard would it be to replace that cable?

That cylinder stat is unusual as it requires a permanent live and neutral supply whereas most don't so I suspect that is where this problem has arisen from.

No, don't go moving that green/yellow wire, it won't work at all if you do that. Whilst it is not right, it is not causing the problem.
Connecting the green/yellow of the two core flex to that earth terminal is unlikely to achieve anything either as the other end of that cable won't be connected to earth as it goes to the nest thermostat.

Thanks for your help davesparks.

brianmoooore already suggested I get a 5-core for the Nest, too, so I'll jusst get some more to replace the CylStat cable, too (and leave the earth as is for now..)

 

[brianmoooore]

Any wire or flex that contains an earth wire should have that wire connected at the wiring box end, whether or not that earth wire is connected to anything at the other end. The earth connection points at the wiring box are the lower three of the vertical connector strip, provided that the little wire links that connect the three together are in place. (E, F, G)
The disconnected black wire to the 'stat should be connected to any of the neutral terminals in the wiring box. These are the next three terminals up in the vertical connector strip, again assuming the wire links are in place. (B, C, D).

 

[dfreitag]

Any wire or flex that contains an earth wire should have that wire connected at the wiring box end, whether or not that earth wire is connected to anything at the other end. The earth connection points at the wiring box are the lower three of the vertical connector strip, provided that the little wire links that connect the three together are in place. (E, F, G)
The disconnected black wire to the 'stat should be connected to any of the neutral terminals in the wiring box. These are the next three terminals up in the vertical connector strip, again assuming the wire links are in place. (B, C, D).

Thank you - again!

Very clear. I'll give it a go now.

Earths to EFG

Black to BCD

Should I also connect the black one from cable (2) to BCD? (what is cable (2)?)

I'll report back after trying this..

 

[brianmoooore]

I wouldn't advice connecting the other black without knowing if or where the other end is connected.