Evohome, DHW priority and x-plan

[lloyd]

On the Intergas x-plan wiring diagram, there is a cylinder ntc sensor. Does anyone know what part this plays when there is also a cylinder sensor for Evohome?

[bruce_miranda]

My guess is based on the Vaillant but it will be similar. The Intergas Cylinder NTC will tell the boiler what the temperature of the water in the Cylinder is. There must be some HW settings on the boiler. But when you use Evohome, the boiler doesn't need to know what the temperature of the water is, Evohome does. So use only the Evohome NTC sensor. You still need to keep the Cylinder's main cut out sensor in place as a fail safe. So check if the Intergas NTC is not actually that. I can't see it being that though.

[mtmcgavock]

I have a Main and have an X plan.

Evohome does differentiate between HW & CH. When my Opentherm requests HW reheat, it demands an 80oc flow temp. On CH it modulates to what it likes, which is usually 30oc. At which point I get a bit of cycling, however I did realise this would happen and it was a trade off. However it works fine and really lowered my gas consumption. I just use the Evohome NTC sensor.

[bruce_miranda]

I have a Main and have an X plan.

Evohome does differentiate between HW & CH. When my Opentherm requests HW reheat, it demands an 80oc flow temp. On CH it modulates to what it likes, which is usually 30oc. At which point I get a bit of cycling, however I did realise this would happen and it was a trade off. However it works fine and really lowered my gas consumption. I just use the Evohome NTC sensor.

Evohome will use a 90C flow temp on 100% heat demand, whether that demand is from HW or CH. Hence why I say it doesn't differentiate between HW and CH. HW will only ever go from 0% to 100% heat demand. CH on the other day can have a Heat Demand between 0% and 100% and that is when you will see the lower Flow temperatures.
What OT and Evohome could have done is used the fact that it knows if the demand is from HW or CH and used a different desired max flow temperature.