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Discuss Evohome boiler interlock in the Central Heating Systems area at ElectriciansForums.net

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I have an Honeywell evohome sytsem at my house.

I have 6 valve TRV's installed on the radiators and 2 radiators that currently do not have any valves until i change them.

The relay box has been installed attached to the boiler and can be turned on and off via my phone and the evotouch box.

The problem is, the boiler is firing and heating up the other radiators that don't have the valves on, even when the command is not being sent by the relay box to turn the radiators on as there is not a demand for heat. Is there anyway to stop this as it is kind of defeating the object of having the system if the boiler is turning on to heat non valved radiators?

Does the evohome need a boiler interlock wired in or should that be part of the installation of the relay box?

Kind Regards
Sounds like the existing room stat is still calling for heat and heating the 2 rads without evohome valves. Evohome working correctly does have boiler interlock via the rad valves and relay box. I'd guess the relay box is connected in parallel to old room stat. Try turning down room stat and it should stop. But ideally need to fit evo valves to remaining rads for it to be fully functional.


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An automatic bypass valve may need to be fitted if all the radiators are having evo valves fitted.
Hi Which type of boiler is it? Ie combi, heat only etc?
If it’s conventional, what valves are in the system?
You normally lock the heating zone valve open so perhaps the boiler is running on the pump over run stat and circulating heat without demand.
There shouldn’t be a room stat in play or it’s wired/set up wrong.
The room stats are built into controller and rad valves
It set for domestic hot water as well, it can fire up to prevent legionnaires, theory on my system is if pump does not run then central heating will not work, in practice it does.

I use Nest not EvoHome but realised the upper floor in naturally warmer than lower floors so used cheap (£15) programmable TRV heads for the upper floors, as said by-pass valve is required with all TRV control, but often that is built into the boiler.

I would guess there is an error with wiring, but can't help as to what error, leaving old thermostat in place normally means it will stop heating if turned down, not fire up if turned up.
boiler doesnt fire up by its own so i would get a pro in to check the wiring eg gas safe engy

Are there enough independent certification companies?

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