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Evohome and Vaillent

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Discuss Evohome and Vaillent in the Central Heating Forum area at Plumbers Forums

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1animal1

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Hi, having fitted a full evohome system before using opentherm and underfloor, having moved into a new build recently, I've decided to fit it again, despite not being able to use OT.

I have a Valiant ecotec boiler which is quite far away from the cylinder. The set up is a 2 zone plus HW, so 3 zone valves. My plan is to remove the upstairs zone stat and fit the evohome controller in the position of the down stairs zone stat. I will be following the Y plan wiring schematic.

Couple of questions...

The Vaillant boiler I understand has a pump live feed, so in the wiring I'll connect the pump live to that.

The boiler also has the full mains plus an RT connection, which I presume is the switched live for the above circuit? The main live fitted as permanent.

Also, I presume I'm fine wiring the two heating zone valves together.

Thanks

Tim
 
1666523566027322380794135208677.jpg
 
I think you mean s plan

Rt is switch yes and yes perm live as you have pump overrun
 
ShaunCorbs said:
I think you mean s plan

Rt is switch yes and yes perm live as you have pump overrun
Click to expand...
Thanks! Yes sorry, S plan...

So the boiler switch in the diagram in my switched live, and I just add in a permanent.

Next question...

Does the high limit stat need wiring into the HW zone valve or the boiler live? Picture below of high limit and control star wiring...
 
Always run the hot water stat before the zone valve eg live to stat live out of stat to brown on zone
 
ShaunCorbs said:
Always run the hot water stat before the zone valve eg live to stat live out of stat to brown on zone
Click to expand...
So on the schematic above, does the stat go between the brown wire on the HW valve. I found the attached for the same stat... Presume common is the main live, and the 1/2 on the right is linking between the valve brown?

Sorry if I've misunderstood you

Screenshot_20221023_142452.jpg
 
Last edited:
Common live from timer / hot water on
Load brown 2 port
Don’t need sat
 
EvilDrPorkChop said:
Should be on your HW BDR91,

Perm Live to A
B on the Relay to C on the High Limit Stat. (Remove link between 2 High limit and C on Temp Stat)
2 on the High Limit Stat to Brown on the HW motorised valve.
Click to expand...
Fantastic, thanks.

I had an old BDR which only gave the wiring for direct boiler control.


The above confirms what Shaun was saying and of course pulls the adjustable stat out of the loop... I didn't know if that was needed or not, so thanks for simplifying further 👍😁
 
I would say leave the running stat eg leave the link in else you will be running on the safety which I think is set to 90dc
 
ShaunCorbs said:
I would say leave the running stat eg leave the link in else you will be running on the safety which I think is set to 90dc
Click to expand...
I've no paperwork for it, so that makes sense keeping the adjustable in.

What's the word on the likes of opentherm nowadays, I thought it would be much more mainstream by now. I did check with a Vaillent rep I know, and he mentioned that they'd gone down the route of their own BUS method. I did take a look at their smart controls, but didn't fancy a second mortgage
 
EvilDrPorkChop said:
Disagree really, why isn't it? It still has a Dual Stat. A temperature stat via Evohome and then a High Limit Stat wired in. Don't see how it doesn't comply.
Click to expand...

Your altering the controls on an unvented i
Don’t get why you can’t leave it in and just set the running stat higher eg 65 set the evo for 60

The evo will turn off the cylinder and the running is there for any reason if the ntc fails
 
ShaunCorbs said:
Your altering the controls on an unvented i
Don’t get why you can’t leave it in and just set the running stat higher eg 65 set the evo for 60

The evo will turn off the cylinder and the running is there for any reason if the ntc fails
Click to expand...
Because EvoHome can run on HW priority. Someone could easily turn the HW stat down to 45. If the panel is set at 60 for instance then the Manual stat will click in before Evohome and cause the rest of the house not to heat.

Regs say Dual Stat is needed, and IMO that meets the criteria still. High Limit is still functional, and theres a stat for temp control.
 
EvilDrPorkChop said:
Because EvoHome can run on HW priority. Someone could easily turn the HW stat down to 45. If the panel is set at 60 for instance then the Manual stat will click in before Evohome and cause the rest of the house not to heat.

Regs say Dual Stat is needed, and IMO that meets the criteria still. High Limit is still functional, and theres a stat for temp control.
Click to expand...

Removed the adjustable dial sorted no one can adjust it then
 

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