Pump staying on at night. Faulty PCB relay or HPA2 m/switch - or ?

[Dmitri]

Glowworm Ultimate 50FF + 2x Danfoss HPA2 valves for CH and HW.
Pressurised system. No frost stat and wiring (S-plan – I think) has been OKd by two separate engineers.

At the end of the day, the pump is not switching off when boiler/CH/HW shut down.
After the 6-7 minute pump overrun, the levers on the HPA2 are in the closed position but the pump remains on for hours. This tends to happen more when the whole system is hot and has been running all day.

If I switch off the pump via mains power at bedtime, and switch it back on in the morning the pump comes on even though the boiler cabinet is cold and the controller (Honeywell ST699) is not calling for heat. The boiler fires up when I switch the CH on.

If I then let the boiler run for about 1 minute – or an hour, and then switch off the CH, the boiler shuts down, the pump overrun occurs and the pump stops as normal.

The boiler ia 20 years old, has had several HPA2s and 3 (4?) PCBs. It had a new stat and PCB two years ago and a new top fan a month ago.

Could my problem be a faulty micro-switch on the CH (or HW) motorized valve after a prolonged period of heating or – as has been suggested - a faulty relay on the PCB? (but there are no noises coming from the control box). Or something else?

Any advice would be much appreciated

 

[AMGasServices]

I don’t think it’s your PCB. It’s possibly one of your valves or programmer.

 

[DGT plumbing]

Is your pump controlled by your boiler or is it directly wired into the control wiring centre. If it's your boiler there could be an internal problem with that. If it's into the wiring centre you need to test your switch lives from your control valves to see if either of them are calling when they are off. Hard to say definitively without seeing it in the flesh. So many options to go wrong.

 

[Murdoch]

Contributing as a spark ....... I would doubt its the valve as this should send the signal to run the boiler .............. not just to the pump to run

Is the pump internal or external to the boiler?

 

[Dmitri]

Thanks for these two replies. Not sure of answer to 'is pump wired to control centre of boiler'. Looking at the wiring diagram in the Glowworm manual, the pump live is connected to one end of a fuse on the PCB so I possibly need to test the switch lives. Wouldn't harm to check this anyway.

 

[Dmitri]

Thanks Murdoch - pump is external to boiler. Pretty sure its just the pump that runs and not the boiler as well.

 

[Murdoch]

Thanks Murdoch - pump is external to boiler. Pretty sure its just the pump that runs and not the boiler as well.

Where is the pump wiring going to / from? The boiler or wiring centre?

What test equipment do you have?

 

[DGT plumbing]

If the boiler is controlling the pump then it's going to be something internal to the boiler that's telling it to run so your going to need to get yourself a gas safe engineer.

 

[Steve weightman]

Had several from experience it's the pcb otherwise the boiler would fire up It's a motorised valve

 

[Harvest Fields]

Please pm @Harvest Fields @ShaunCorbs or @Riley your gas safe number please @Steve weightman

 

[Steve weightman]

Please pm @Harvest Fields @ShaunCorbs or @Riley your gas safe number please @Steve weightman

Sorry post message where please

 

[Steve weightman]

Sorry post message where please

And how thanks

 

[Harvest Fields]

Click on one of the 3 names and start conversation

 

[garygvl]

Contributing as a spark ... I would doubt its the valve as this should send the signal to run the boiler ... not just to the pump to run

Is the pump internal or external to the boiler?

pump external but overrun controlled by pcb

 

[Dmitri]

Where is the pump wiring going to / from? The boiler or wiring centre?

What test equipment do you have?

 

[Dmitri]

Thanks Murdoch. Pic attached - hope it gets thro' OK. I have a multimeter.

 

[Dmitri]

If the boiler is controlling the pump then it's going to be something internal to the boiler that's telling it to run so your going to need to get yourself a gas safe engineer.

Thanks DGT. Msg rec'd & understood

 

[Dmitri]

Had several from experience it's the pcb otherwise the boiler would fire up It's a motorised valve

Please.... so is it the PCB or the motzed valve that's at fault?

 

[Riley]

You won’t get the answer you’re looking for as we will not give advice potentially leading to diy gas work. Please see forum rules

 

[ShaunCorbs]

If just the pump is running frost stat / pipe stat more than likely

 

[Dmitri]

You won’t get the answer you’re looking for as we will not give advice potentially leading to diy gas work. Please see forum rules

Not planning on any DIY. Having just spent £400+ on boiler, just wanting to know likely cost to correct the pump problem. A new PCB is a much bigger expense than a new HPA2 valve.

 

[Dmitri]

If just the pump is running frost stat / pipe stat more than likely

Don't have a frost stat - thanks anyway

 

[Riley]

If you’ve already spent £400 I’d look at getting shot mate

 

[Harvest Fields]

If you’ve already spent £400 I’d look at getting shot mate

Your joking. It’s an investment now😛😛😛

 

[Dmitri]

Your joking. It’s an investment now😛😛😛

Tend to agree Harvest. Another £50 for a valve (if this is the problem) versus £2.5k-£3k for a new boiler (say Worcester Bosch?) would be worth it. That's why I asked the Q in the first place. 🙂

 

[Riley]

But if it’s not just a valve then the boiler becomes uneconomical.

 

[Harvest Fields]

So they need an engineer to diagnose properly. Then they go from there.

 

[Dmitri]

So they need an engineer to diagnose properly. Then they go from there.

Roger that Harvest. At least it was worth trying to get a diagnosis via the Forum. Thanks everybody for chipping in.