Ideal Logic Combi 30 - pump only keeps activating for 4 mins.

[SteveE63]

Hi,

As per the thread title, I have an Ideal Logic Combi 30 and I am having a problem with the pump, which keeps activating without any DHW/DCH.

When the pump activates, it runs for exactly 4 minutes each time and this can happen as frequently as something like 5 times an hour or as infrequently as once an hour, so it's pretty inconsistent. These episodes only occur with the boiler set to Winter Mode (HW & CH) and not when set to Summer Mode (HW only).


When these pump run episodes occur:

The burner does not ignite,

I can hear water running through the radiators, which remain cold,

The display shows 0 and is free of codes,

Zero HW and CH demand,

Hot water preheat is also switched off,

DHW & DCH working fine when actually commanded.


The Grundfos pump failed early last year and it was replaced with a generic replacement as it was a mid-winter emergency and it's all the engineer had to hand on a Friday evening. I did wonder if this generic pump could be at fault as I don't recall this issue prior to replacement but I believe the pump can only operate if commanded by the boiler PCB.

The boiler is located in the house and thus doesn't have an external frost stat, although I beleive the Ideal Logic uses the return flow thermistor for frost protection in the absence of an external stat. I also believe a faulty thermistor would give a code if faulty or fire up the burner if it thought frost was a potential issue, and it's not firing the burner, just running the pump.

The only other change since the pump was replaced is the addition of a Honeywell R8810 Opentherm relay as I already had Evohome running with a BDR91. Opentherm works fine plus I can't imagine this would be running the pump without firing the burner if faulty.

Any ideas as I'm at a loss as to where to go with this - the only thing I can think of is a faulty PCB as the PCB fuse had to be replaced when the pump failed and blew it? I'm just a home owner with little knowledge, so fingers crossed the more knowledgeable of you might have an idea what's going on.

Thanks in advance for any help.

 

[AshAsh]

Our Logic Combi also runs for a couple of minutes a night. I think it may be some kind of preheat or frost protection. Strangely, ours has only started doing it since it was serviced. I have known other boilers to do this too and it is most annoying if the boiler is next to a bedroom.

 

[SteveE63]

Our Logic Combi also runs for a couple of minutes a night. I think it may be some kind of preheat or frost protection. Strangely, ours has only started doing it since it was serviced. I have known other boilers to do this too and it is most annoying if the boiler is next to a bedroom.

Thanks for your reply.

I believe these boilers run a brief anti-seize cycle every 24 hours but this might only apply if the boiler hasn't operated in a 24 hour period. I'm guessing this is what yours is doing when it runs for a couple of minutes.

I could live with once every 24 hours but the pump on my boiler runs for exactly 4 minutes and this can happen as frequently as 5 or 6 times an hour or as infrequently as once every several hours or so.

I have resorted to switching the boiler to Summer mode when the heating is off but this means I can't schedule the heating to come on unless I first switch it to Winter mode, which is very inconvenient at 6am on a Sunday morning.