Nest/Boiler issues

[ianmcd]

your wiring diagram is wrong, shouldnt be anything in SL2 and the Outside sensor is wired into the terminal on the RHS installer panel marked weather compensation page 36 of the manual, HW off and HW satisfied are not used.

https://idealboilers.com/uploads/documents/logic-heat-h-installation-and-servicing.pdf

 

[ianmcd]

your wiring diagram is wrong, shouldnt be anything in SL2 and the Outside sensor is wired into the terminal on the RHS installer panel marked weather compensation page 36 of the manual, HW off and HW satisfied are not used.

https://idealboilers.com/uploads/documents/logic-heat-h-installation-and-servicing.pdf

 

[Mpw7826]

Thanks for the reply. Yeah that’s the S-plan with no weather compensator. https://idealboilers.com/uploads/documents/spec-sheet-weather-compensation-kit.pdf Shows SL2 wired and I’ve looked inside the boiler and it has SL2 and the comp wired as in the diagram.

 

[Deleted member 267285]

I wonder if it’s an wiring diagram error by Ideal boilers? @shambolic?

 

[Mpw7826]

I spoke to an Ideal Technical and she suggested it’s correct, the boiler uses the HWOFF signal to differentiate for the weather comp I’m told.

 

[shambolic]

SL2 should be wired from cyl stat and hw off on timer so that weather comp kicks in after HW is satisfied, otherwise the cyl may not get to temp if warmer outside.

 

[shambolic]

you dont use HW off on an S plan only a Y plan system

We do to control when the weather comp works.

 

[shambolic]

Again DHW off and DHW satisfied are only wired in on Y Plan, not on S plan, weather compensation or not

Wrong we do use it.

 

[shambolic]

The software in the pcb is a pain. So bear with me. Even if there is no demand from end switches on SL1 the boiler will run on open therm if it doesn’t have 240v down SL2 when hw satisfied.
That will be your problem. The Lack of 240v in SL2 makes the boiler run at 80deg to heat the cyl.
as I said I feel that the software shouldn’t use that if there is no demand on SL1 from end switches. Cause exactly as you described happens. Boiler fires up at 80deg but valves are shut and pump has no demand.
it’s a bit back to front but it’s to do with low voltage opentherm side being ignored until cyl up to temp. It overrides everything and brings boiler on at 80deg even if no SL1

 

[shambolic]

Hope that makes sense. I’m pretty crap at explaining it but I know how it should be done.

 

[Mpw7826]

Thanks shambolic. So the connector which had two wires going into it on the tank (I’m assuming this is cyclinder off and hw off) now only has one as the nest isn’t hooked up to send the hw off.
Am I correct in saying I have two options here, get the hw off connected or remove the SL2 and weather comp? Is there any issue that the cyclinder off is still wired up if SL2 is disconnected?
I’m not using opentherm.

 

[shambolic]

Easiest remedy is to remove weather comp and remove SL2. Turn boiler off at spur for 10 minutes so boiler forgets weather comp.

 

[Mpw7826]

Thanks shambolic, that’s what I thought, thanks for confirming. Is there any issues with me leaving the cyclinder off wired into the HW OFF slot or can I just leave that?

 

[shambolic]

Thanks shambolic, that’s what I thought, thanks for confirming. Is there any issues with me leaving the cyclinder off wired into the HW OFF slot or can I just leave that?

You can’t as it will also keep the boiler on 24hrs if no weather comp fitted. So both must be removed. Just snip it and leave safe in a bit of terminal strip inside boiler if too difficult to trace and remove at wiring centre.

 

[Mpw7826]

Sorry I mean, I’ll remove SL2 in the boiler but in the tank junction box can I just leave the cyclinder off wired? That’s what thermostat HW OFF went into before. I assume it makes no difference if SL2 is disconnected at the boiler?