24 Dec - update - Grundfos pump still runs constantly

[Littlemiss21]

Dear Friends
Please, please, please could somebody point me in the right direction? Moved into this house (house is approx 10 years old) in September. Fully sealed system, HE Tribune cylinder, S Plan, drayton actuator on the heating side, honeywell valve on water side, grundfos red pump next to cylinder. The water is on timed and the heating on constant - drayton RTS2 thermstat in hall
(as elderly father has a health condition and needs a warm enviroment).

The grundfos pump would not switch off and ran constantly for nearly 48 hours (no call for heat from thermostat and kept firing the boiler up too - radiators cols). Called British Gas out and they replaced the Drayton actuator (and a new brass spindle section on the water pipe too) on 31 October.

All ran fine and we also had a new Vaillant boiler installed on 21 November (straight swap keeping existing controls). all good. But then on Friday 7 December, AGAIN the grundfos pump ran and ran and ran until I switched it off at the main fuse spur. British Gas came out and replaced the Drayton actuator again.

Sunday 9 December - same issue again - pump constantly running - called BG again who came out checked both valves using their multimeter, checked the junction box in the airing cupboard, the thermostat and the programmer wires - cant find the fault. All working fine - BUT AGAIN woke up this morning to the pump constantly running again. I switched the heating off at the myson programmer, but the pump still ran. Switched the boiler off at the fuse spur and the pump stopped - switched the mains on again 10 mins later and the pump is STILL running. BG been out again - 4th time for the same issue and again unable to find what is wrong. All is running fine again - the BG job is still open and the engineer will be coming back on Thursday 11 December. So, this intermittent fault was present with the old boiler and again with the new boiler. Almost feel like asking BG to contribute towards the new boiler, as had we known that this fault would still be here we wouldnt have had a new boiler fitted. The boiler is in the kitchen, so no frost stat issue. Please help, Im almost sucidal now !!! Could it be a faulty progammer? There is some live feed somewhere that is making the pump stay on and not swtich off when the room stat is satisfed. The BG engineer also checked for sticky microswtiches in both valves this morning.

Any suggestions would be greatly welcome, so I am armed with info when BG arrive on Thursday!! Thanking everybody in advance. PS Im un Huddersfield, if any engineers can diagnose and repair the fault - happy to pay!

 

[picasso]

double post.

 

[picasso]

Ask the bg engineer to check the 24v link has been removed from the boiler pcb.

 

[Littlemiss21]

Dear Picasso
Thank you for your kind response. Apologies if I have posted twice - I’m trying to work out how to use this site. Yes, I will ask the BG to check the PCB - although we had the exact same issue with our old boiler (Potterton HE Plus) and now again with the Vaillant Ecotec Plus 418 installed 3 weeks.

 

[picasso]

I double posted not you there is only a couple of things that can make the boiler run without demand, one is sticky microswitches which bg seem to have covered and the link left in the boiler which is easily done, has the Honeywell valve been changed or just the drayton?

 

[Littlemiss21]

Thank you again. The Drayton one has been changed twice now - first on 31 October and again on 7 December. BG stripped open the Honeywell one this morning and tested it all - all the motor etc appeared to be working fine.

 

[breadnbutter]

the boiler will have an integral frost setting in its software, normally reads of the temp sensor,it might be faulty..

 

[ianmcd]

Thank you again. The Drayton one has been changed twice now - first on 31 October and again on 7 December. BG stripped open the Honeywell one this morning and tested it all - all the motor etc appeared to be working fine.

The end switches can stick intermittently and you can only really test them if the pump is running at the time of the visit

 

[jeff the gasman]

Is there a frost stat hiding somewhere?

 

[Littlemiss21]

Hi - thank you for your responses. The end switches were tested as the pump was constantly running when BG arrived this morning I’ve just put the heating on timed to see if the pump behaves and comes on and off as per the timer - just trying to rule out the programmer - totally desperate to get it sorted now.

 

[Littlemiss21]

Hi Jeff. Thank you for your message. The boiler is in the kitchen. We had this exact same issue with the old boiler and again with this new boiler. Would a frost stat cause this issue intermittently? As this issue started in October, when we weren’t using the heating at all - if I think back, they very first time it happened was when I put the water on constant but the pump didn’t switch off for a good few hours, so I turned the water to timed and it was fine. The darn pump only goes onto constant mode intermittently when we have the heating on constant. Thank you again.

 

[Gasguru]

Without a heating and hot water demand get them to check the voltage on the boiler switched Live terminal....it may be a problem with induced voltage being sufficient to turn on the boiler even without the motorised valves switching.

 

[dilalio]

As above, also check that any flex (cable) to the boiler isn't supplying both 240v and 24v (or other low voltage) in the one, shared flex. This can sometimes cause induced voltage on the other cores within the insulated sheathing.

 

[Littlemiss21]

Thank you Dilalio - will get that checked too.

 

[Mottie]

As Picasso said above, check the 24v link has been removed. I had exactly the same symptoms when I had a Vaillant Ecotec plus 418 boiler fitted three months ago by a Vaillant approved installer. According to Vaillant, it is very, very common.

 

[Littlemiss21]

Thank you Motman and to everyone who has kindly replied to my dilemma - it is greatly appreciated