Suspected pump failed in combi boiler.

mordzy · 5 Nov 2019

Came back off holiday and my hot water works fine but heating doesn't. Heating pipe gets red hot and after a few hours the first rad gets warm. Possibly by convection/conduction. So I suspected the pump which a recall was making some odd clicking noises before I went away.

Ive listened to the pump through a screwdriver on the bleed screw and it sounds like it's running. So I've drained the system to inspect it and it looks ok. Ive ordered a replacement anyway.

The replacement is a different model.

Old - Grundfos UPR15-70
New - Grundfos UPS015-60

Plumbers merchants said it would be ok.

My question is regarding the wiring. The old one has a Neutral, Live and Earth feed to the spring loaded terminals and also a live (pin 6) and neutral (pin1) to the capacitor terminal. Im not sure why. Perhaps its a boiler controlled dual speed pump as it has no switch wheres the new pump has a switch with 3 settings.

Any help would be great.

ianmcd · 5 Nov 2019

mordzy said:
Grundfos UPS015-70

are you sure it is a 15-70 ? and what is the make and model of the boiler, if the HW is working it is more likely a diverter valve or external control problem than the pump

muggles · 5 Nov 2019

mordzy said:
Any help would be great.

Help us to help you - what's the make and model of your boiler? Are you sure the old pump wasn't a UPM 15-70, not a UPS? Either way I agree with Ian that the pump is unlikely to be the fault

mordzy · 5 Nov 2019

Sorry I got the pumps wrong, Pump is UPR15-70. New is UPS0-15-60 (corrected on orig post)

Boiler - Remeha 35c.

About a meter from the boiler on the CH flow is a Honeywell 2 port actuator valve that isolates the rads from the extensions UFH. Ive manually moved this valve which makes no difference. I can hear it actuating its self when the thermostat calls. The valve is less than 6 months old, while I know this doesn't mean its not faulty, I would assume manual switch would actuate the valve and open it. The pipe before the valve is red hot to the touch, as it is after. Following the pipes along to the first rad the heat slowly dissipates till it's just Luke warm. following the pipe to the UFH manifold which is 'T' off before the valve is the same. after an hour or so of the boiler running the first rad is Luke warm all over.

attached is a picture of the current pump

Gasguru · 5 Nov 2019

That's a 2 speed pump.
The idiots behind the counter at merchants know nothing about boilers/heating systems.
Not only have they tried to palm you off with a standard pump they have given you a pump with insufficient performance...the 60 and 70 refer to maximum head pressure generated (6 and 7 meters).

If it's faulty you need an identical pump.

Since the hot water appears to work ok then the pump is almost certainly working ok on it's high speed setting.

However, the factory settings will run the heating on the low speed setting. Perhaps this low speed setting has failed or the relay on the main boiler pcb controlling it has failed.
If you look in the manual you could try adjusting P21 parameter to run the pump at high speed (on heating) to confirm whether this is the issue.

With a heating demand 240V will operate the motor within the zone valve. The motor opens the valve and when nearly fully open a microswitch operates telling the boiler there's a demand.

muggles · 5 Nov 2019

mordzy said:
Sorry I got the pumps wrong, Pump is UPR15-70. New is UPS0-15-60 (corrected on orig post)

No it isn't, it's still a 15-70, the merchants have tried to sell you an incorrect item. I suspect they've sold you the pump for the 24kW boiler, your 35kW boiler has a different pump which is this one https://www.wolseley.co.uk/product/broag-s62747-pump-15-70-for-35---39/

The 24 and 28kW boilers use the 15-60, the 35 and 39kW boilers use the 15-70 because the 15-60 isn't powerful enough.

If it's a diverter valve issue, then that's nothing to do with your zone valve near the boiler - the diverter valve is a component inside the boiler.

mordzy · 5 Nov 2019

Thanks, Ill take the pump back. Is there a way to diagnose the diverter valve other than running the hot water - which works fine.

Ill run the existing pump out of the system tonight and see if it runs ok. If it does I won't bother replacing it.

mordzy · 5 Nov 2019

Got home, wired up the old pump to a 3pin plug and switched it on. It doesn’t rotate, flicked it and nothing. Just hums.

out of curiosity, I’ve done the same with the new one supplied and that does the same. I must be really unlucky

muggles · 5 Nov 2019

Pretty sure it needs the control wires to be connected or it won't do anything at all.

Put the old one back in the boiler, put a cloth under it and remove the big silver central screw. Turn on a hot tap and look inside the pump through the hole created by the screw you removed to see if it's spinning

mordzy · 6 Nov 2019

muggles said:
Pretty sure it needs the control wires to be connected or it won't do anything at all.

Put the old one back in the boiler, put a cloth under it and remove the big silver central screw. Turn on a hot tap and look inside the pump through the hole created by the screw you removed to see if it's spinning

I take it I need to re fill the system to do that. Is the screw ok being out on a pressurised system?

muggles · 6 Nov 2019

Yes and yes

Gasguru · 6 Nov 2019

Jeez we're going round in circles on this one.
It's a multispeed pump....all the wires must be connected in a particular way in order to obtain the 2 speeds.
IN DHW the pump runs at maximum speed and it's likely it works ok since you have DHW.
Run the boiler in heating mode to check the minimum speed is working.

mordzy · 6 Nov 2019

Gasguru said:
Jeez we're going round in circles on this one.
It's a multispeed pump....all the wires must be connected in a particular way in order to obtain the 2 speeds.
IN DHW the pump runs at maximum speed and it's likely it works ok since you have DHW.
Run the boiler in heating mode to check the minimum speed is working.

Well not really Gasguru, I took the pump back as per your recommendation not being a two speed this morning and picked up a recon 15-70 on my way back just in case mine is shot. My updates just wanted information on why the old pump wont run outside the boiler? Running a 240v input to the main terminals just makes it hum. the additional two imputs are just live and neutral to energise more windings in the motor for the faster speed?. so the primary input should make it spin.

Can anyone clarify as to why it wouldn't? just so I understand.

Gasguru · 6 Nov 2019

There is no such thing as a recon pump...it's just an old secondhand pump of unknown quality and performance, I hope you didn't pay more than a fiver for it.
Domestic heating pumps can't be reconditioned....

The 3 motor windings and capacitor are connected in quite complicated ways to achieve the 2 speeds...you can't just apply 240 V to the other 2 wires.
You'll find a speed control relay on the boiler pcb...reverse engineer the connections to find the exact configuration.

The old Keston combi 3 speed pumps have 2 relays on their pcbs...just for speed control.

There will always be a further relay just for main pump switch on.

Not quite so simple

That's why I suggested changing the pump speed parameter to force the pump to run at high speed (in heating mode) which we suspect is ok since your DHW works fine. If you want to test the low speed you need to run the boiler in heating mode only. Now of course there may be variants of Remehas but AFAIR the low speed was only used when in the heating mode.

ianmcd · 6 Nov 2019

https://www.ebay.co.uk/itm/NEW-BAXI...160798&hash=item23c469d2ca:g:5~MAAOSwjkhc~rsp

That is the correct pump for your boiler and no it wont work by simply putting 3 wires LNE to it, still dont think it is your pump if you have HW

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