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

Discuss Pump staying on at night. Faulty PCB relay or HPA2 m/switch - or ? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Dmitri

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11
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
 
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.
 
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.
 
Murdoch said:
Where is the pump wiring going to / from? The boiler or wiring centre?

What test equipment do you have?
Click to expand...

Wiring.JPG
 
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
 
If just the pump is running frost stat / pipe stat more than likely
 
Riley said:
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
Click to expand...
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.
 

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