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london1a1

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Hi all (new here),

I recently had a boiler service and they mentioned that the wiring looks wrong. Boiler otherwise in good condition. I've seen similar threads and not sure my case matches so here goes. Previous owner installation so not sure who did the job.

System setup:
Myson controller for UFH and a Center controller for rads and HW. Valliant ecoTec plus 630 boiler. The rads upstairs do not have a stat and seem to be only controlled by programmer.

Symptoms:
Seems system is constantly calling for heat as boiler rad icon always displayed. During the night in particular the boiler turns on/off constantly.

Now, I've tried removing the 24v link from the boiler PCB and the UFH works fine, however the Center controller for Rads/HW no longer manages to call for heat (despite programmer on).

Looking at the wiring, it does seem like the switched line from the programmers to the boiler are connected together.

Attached pics of boiler PCB and setup. Happy to provide more details at request a d and help hugely appreciated.

Thanks
Jeff
 

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Adding PCB wiring as don't think it uploaded
 

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Can you post a picture of the whole PCB showing the mains and 230v RT connections
 
Thanks for taking a look. Hopefully this is better? Tried separating the cables a bit
 

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Valliant ecoTec plus wiring advice EF Boiler - EletriciansForums.net

Is this a T&E with the earth sleeved brown going into the connector block?. This would be a definite no no
 
View attachment 102650

Is this a T&E with the earth sleeved brown going into the connector block?. This would be a definite no no
Yeah looks like it. Took out the tape to check. Hard to confirm at the programmer end of this use of earth line continues. Any thoughts on heating issue other than bad practice wiring from installer
 

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Yeah looks like it. Took out the tape to check. Hard to confirm at the programmer end of this use of earth line continues. Any thoughts on heating issue other than bad practice wiring from installer

That made me take a closer look at the setup, this is what I found, hopefully useful:

1. HW call from programmer only goes to immersion tank and valve. Does not go to boiler

2. That connector block you highlighted goes live with CH or UFH call for heat, however, RT 230v on the boiler only goes live with UFH call and not with CH call. This is without the 24v link in. Seems time that it should be this cable going to RT rather than the existing one. Any reason for just UFH to be calling for heat in my setup? I was surprised that HW doesn't so maybe also reason for CH not going 🤷‍♂️


3. Also noticed this odd link on the PCB itself which I have no clue why it's in
 

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Last edited:
Yeah looks like it. Took out the tape to check. Hard to confirm at the programmer end of this use of earth line continues. Any thoughts on heating issue other than bad practice wiring from installer
As you can probably understand I'm trying to work out how this is wired from afar it is not helped when someones bad wiring and misuse of T&E is involved
That made me take a closer look at the setup, this is what I found, hopefully useful:

1. HW call from programmer only goes to immersion tank and valve. Does not go to boiler
It will be going to the tank stat which controls the water temperature by regulating the boiler
2. That connector block you highlighted goes live with CH or UFH call for heat, however, RT 230v on the boiler only goes live with UFH call and not with CH call. This is without the 24v link in
I have no idea why you would make that connection/ joint in the boiler when the boiler operation is controlled by the RT 230v terminal. The 24v link should be in this is for low volage control of the boiler

For info taken from the boiler installation manual
Valliant ecoTec plus wiring advice 1665836184397 - EletriciansForums.net
3. Also noticed this odd link on the PCB itself which I have no clue why it's in
The PCB is possibly used in other Vaillant boilers ie combi's and these terminals may have specific uses / control functions that are not used in a system boiler so are linked out

I'm thinking that all of the heating controls need checking as it looks like the UFH was installed after the rest of the system and it's controls were cobbled into the existing system given that you have 2 programmers rather than one multi channel one

So the next question is how many and what type (2 or 3 port) of motorised valves do you have on this system
 
As you can probably understand I'm trying to work out how this is wired from afar it is not helped when someones bad wiring and misuse of T&E is involved

It will be going to the tank stat which controls the water temperature by regulating the boiler

I have no idea why you would make that connection/ joint in the boiler when the boiler operation is controlled by the RT 230v terminal. The 24v link should be in this is for low volage control of the boiler

For info taken from the boiler installation manual
View attachment 102660

The PCB is possibly used in other Vaillant boilers ie combi's and these terminals may have specific uses / control functions that are not used in a system boiler so are linked out

I'm thinking that all of the heating controls need checking as it looks like the UFH was installed after the rest of the system and it's controls were cobbled into the existing system given that you have 2 programmers rather than one multi channel one

So the next question is how many and what type (2 or 3 port) of motorised valves do you have on this system

Thanks again. Unfortunately, I inherited the setup from previous owner. I wasn't sure from your response if you are saying the 24v link should be in? It was originally in but the controllers are 230V. It seems to me that the wire into that block is what should be in the RT port and not the existing one.

As for your question on valves, there are 3 (one for rads, another for UFH and another for HW into the cylinder). They are all like in the attached photo but not sure how many ports.
 

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  • Valliant ecoTec plus wiring advice 36CFF5EF-9744-4416-AF81-88ACB6788A09 - EletriciansForums.net
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Thanks again. Unfortunately, I inherited the setup from previous owner. I wasn't sure from your response if you are saying the 24v link should be in? It was originally in but the controllers are 230V. It seems to me that the wire into that block is what should be in the RT port and not the existing one.
As you can see from this wiring diagram it shows X100, the 24v=RT connector linked out
Valliant ecoTec plus wiring advice 1665842898187 - EletriciansForums.net
As for your question on valves, there are 3 (one for rads, another for UFH and another for HW into the cylinder). They are all like in the attached photo but not sure how many ports.
So you have have 2 port valves

In an ideal world this is how you system should be wired (closest diagram I can find online) your boiler has an internal pump so only the SL line to the 230v RT terminal on the boiler is needed
Valliant ecoTec plus wiring advice 1665843959477 - EletriciansForums.net
This diagram uses a 3 channel programmer but could be adapted to use 2 programmers as you have got

From your pictures I'm not sure if you have a wiring centre for the heating controls but for an upgrade of the programmers and simplification of the wiring I would suggest https://www.draytoncontrols.co.uk/product/wiser-thermostat-kit-3-0
Valliant ecoTec plus wiring advice 1665844706435 - EletriciansForums.net
 
As you can see from this wiring diagram it shows X100, the 24v=RT connector linked out
View attachment 102665

So you have have 2 port valves

In an ideal world this is how you system should be wired (closest diagram I can find online) your boiler has an internal pump so only the SL line to the 230v RT terminal on the boiler is needed
View attachment 102668
This diagram uses a 3 channel programmer but could be adapted to use 2 programmers as you have got

From your pictures I'm not sure if you have a wiring centre for the heating controls but for an upgrade of the programmers and simplification of the wiring I would suggest https://www.draytoncontrols.co.uk/product/wiser-thermostat-kit-3-0
View attachment 102671

My plan was to get a Tado system installed but wanted to sort out the issue where the heating in on call constantly. I've read posts from other people saying the 24v link shouldn't be in (and the Valliant serviceman was also saying the same). I need an electrician to come in and check the wiring over. It still seems odd that the SL from the CH controller does not make it to the RT230V and is wired into that block you originally highlighted.
 
My plan was to get a Tado system installed but wanted to sort out the issue where the heating in on call constantly.
Good luck with that, Just had a look at the Tado site and as an installer it doesn't impress me couldn't even find a wiring diagram although I did lose interest after 2 minutes
I only suggested the Wiser system set up as it would very easily integrate into your system and does most if not all that the Tado system does
I've read posts from other people saying the 24v link shouldn't be in (and the Valliant serviceman was also saying the same). I need an electrician to come in and check the wiring over. It still seems odd that the SL from the CH controller does not make it to the RT230V and is wired into that block you originally highlighted.
I'm only going on the boiler wiring diagram I have very little hands on with Vaillant boilers as I generally walk away from jobs where they are fitted, having recently spoken to an ex Vaillant guy he didn't rate their service engineers and some of the products they produce
 
Getting an electrician in (unfortunately in a couple of weeks only) will post what he finds. Not set on Tado but have a friend who swears by his and I wanted to increase the zones upstairs and control them separately. But the change in controller is secondary to this issue. Appreciate your time and input.

Would you know what other 'system' would need to know about the SL? The reason why I ask is that that block you originally called out feeds straight back into the wall behind the boiler and does not make sense to me. So the:

SL = CHon + UFHon (this brown 'earth' wire feeds in to the block you highlighted and goes back into the wall)

And the other wire feeding into the RT 230v is only UFHon.
 
Getting an electrician in (unfortunately in a couple of weeks only) will post what he finds. Not set on Tado but have a friend who swears by his and I wanted to increase the zones upstairs and control them separately. But the change in controller is secondary to this issue. Appreciate your time and input.

Would you know what other 'system' would need to know about the SL? The reason why I ask is that that block you originally called out feeds straight back into the wall behind the boiler and does not make sense to me. So the:

SL = CHon + UFHon (this brown 'earth' wire feeds in to the block you highlighted and goes back into the wall)

And the other wire feeding into the RT 230v is only UFHon.
If you look back at post #10 I posted the S plan wiring diagram and the bottom right of that diagram shows the boiler connections the SL connection is switched by the motorised 2 port valves so as the CH, UFH or HW call for heat the motorised valve for the particular zone opens and also switches the SL feed to the boiler so it fires
Your 2 programmers could be wired in tandem and do the same as 1 multi channel programmer
The Tado is just one of many smart heating controls and they all have their good points for the end user but the end user does not generally consider or look at the engineering needed to install them
From an installation point of view my preferred choice is the Drayton Wiser set up having previously installed some other systems that were a compromise.
Having looked at the Tado website it is a lot more complicated than it needs to be and it is not easy, no it appears impossible to find any wiring schematics which would save on the pages and pages of nothing they have up on their site, even something as simple as turning the hot water on is difficult. I'm assuming your friend has a combi boiler to which it seems a Tado system is better suited although even that is difficult confirm from the Tado site the only thing that is easy to confirm is it's expensive

With regard to smart controls do your own research what suits one person and their heating system may or may not suit another person and their heating system
 
If you look back at post #10 I posted the S plan wiring diagram and the bottom right of that diagram shows the boiler connections the SL connection is switched by the motorised 2 port valves so as the CH, UFH or HW call for heat the motorised valve for the particular zone opens and also switches the SL feed to the boiler so it fires
Your 2 programmers could be wired in tandem and do the same as 1 multi channel programmer
The Tado is just one of many smart heating controls and they all have their good points for the end user but the end user does not generally consider or look at the engineering needed to install them
From an installation point of view my preferred choice is the Drayton Wiser set up having previously installed some other systems that were a compromise.
Having looked at the Tado website it is a lot more complicated than it needs to be and it is not easy, no it appears impossible to find any wiring schematics which would save on the pages and pages of nothing they have up on their site, even something as simple as turning the hot water on is difficult. I'm assuming your friend has a combi boiler to which it seems a Tado system is better suited although even that is difficult confirm from the Tado site the only thing that is easy to confirm is it's expensive

With regard to smart controls do your own research what suits one person and their heating system may or may not suit another person and their heating system

Maybe I am missing something but I've tested the SL that goes into the RT230V port and that only fires with UFH.

The wire going into the block fires with CH and UFH. HW does not fire the boiler at all just turns on the immersion tank and valve.

All the actuators seem to fire directly from the wiring center or junction box near the controllers.
 

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Maybe I am missing something but I've tested the SL that goes into the RT230V port and that only fires with UFH.

The wire going into the block fires with CH and UFH. HW does not fire the boiler at all just turns on the immersion tank and valve.
The only thing you are missing is the correct system wiring for your heating system for it to operate correctly, the SL connection should become live when the CH, UFH or HW calls for heat

Ignore what you currently have as it is wrong, it would probably take less than an hour to wire it as the S plan diagram I posted earlier so it works as it should. The only likely problem that may delay that is if they have used the earth in T&E's elsewhere in the wiring as that would have to be rewired and I think that it is possible from what you have found in the boiler although that may be avoided if an alternative heating control is used
All the actuators seem to fire directly from the wiring center or junction box near the controllers.
The wiring centre is exactly what it is all the motorised valves, thermostats and the programmer is wired through it and if you look at the the S plan diagram it is the motorised valves that call the boiler for heat on the SL connection and as the system cannot pump against closed valves when the programmer and stat call for heat the valve opens and the switch closes to fire the boiler and pump
 

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