Grundfos pump making unusual sound/boiler not coming on

[Stephen JW]

First post so greetings to all!

We have a problem with our elderly Potterton boiler and its Grundfos pump as follows:

• Boiler started behaving erratically, switching on & off at short intervals
• Within days boiler stopped coming on at all
• Noticed that Grundfos pump was making an unusual sound as though struggling to function
• Tried method shown here without success:

Am I correct in assuming that the boiler is not working due to loss of pressure because the pump is not circulating the water through the system?

• NOTE that when the programmer was replaced a couple of years ago with a Drayton Lp112 the person installing it wired it incorrectly so that the heating and hot water could not be controlled separately. It has been like it ever since.

We would appreciate advice as to how to best tackle this problem, bearing in mind the following:

• We are looking for a short term affordable solution as we will be moving house in the next 12-18 months
• We do not have the funds for a full system replacement at this time

Many thanks!

Stephen

 

[Stephen JW]

What was the old pump like eg in the outlets of the pump any blockage or was it clean and around 15mm dia ?

What was the old pump like eg in the outlets of the pump any blockage or was it clean and around 15mm dia ?

What is the boiler power and is it a modulating boiler?

How many rads?.

IF the UPS3 is working properly then CCII is more powerful than CC3 was on your old 5M selectric.
The UPS3 on CCII will maintain +5M up to a demand of 1.1 m3/hr, 18.3LPM.
Also, there should be little or no delay in pump startup after changing settings.
Is the system clean as very dirty systems can build up magnetite on these pump rotors which can slow them down or stop them, the pump head can be removed for cleaning.

Hi John. Thanks for all the information you have provided. This is a steep learning curve for me as I am a complete layman and unfamiliar with the terminology and power ratings etc. But this is what I do know:

Boiler is Potterton Netaheat 50e which Google tells me is max. 14.65kw output

We have 10 radiators in all, smallest 72cm, largest 180cm

4 radiators + heated towel rail upstairs

3 long + 2 short radiators downstairs

The engineer drained, refilled and added inhibitor and fitted new valves with the new pump and 3-port valve.

When we put the pump back into CCIII after everything switched off on CCII last night the pump was ‘throbbing’ and making a ‘thrum-thrum-thrum’ sound as it was running. We left it for a few minutes to see if it would return to normal. It didn’t so we turned it off. This morning there was a lot of gurgling and ‘ticking’ but it is now running on CCIII as before. All radiators are hot. The resonating noise is back.

Many thanks again.

Stephen

 

[John.g]

Looks definitely like a pump problem there IMO, there were a few "dud" UPS3s sold, I would inform your engineer as a new pump should be supplied without question, under warranty, except that your system was/is filthy.
You can yourself just ensure that the pump isol valves are fully open and just recheck that the pump is orientated correctly, ie, if on the boiler flow side, pumping away from the boiler and if on the boiler return, pumping into it.

 

[Stephen JW]

Looks definitely like a pump problem there IMO, there were a few "dud" UPS3s sold, I would inform your engineer as a new pump should be supplied without question, under warranty, except that your system was/is filthy.
You can yourself just ensure that the pump isol valves are fully open and just recheck that the pump is orientated correctly, ie, if on the boiler flow side, pumping away from the boiler and if on the boiler return, pumping into it.

Thanks John. Sadly I don't know how to check these things. The pump itself is physically mounted upside down, presumably as if it were the 'correct' way up the mains cable and its mounting would prevent the airing cupboard door from closing. I have attached a few photos. A couple of further things to mention that may or may not be relevant.

1. Our system has no wall-mounted thermostat. We have old Servowarm thermostatic radiator valves on each rad.
2. We usually run the boiler on setting 3-4 on the control dial (range 1-5/max).

Thanks again!

 

[John.g]

There is an arrow on the pump body, see if its pointing up or down, then follow the pipe (up or down) and see where its attached to the diverter valve and we can soon figure it out.

The pump valves, just turn each one clockwise until shut then anticlockwise until fully open, it should take ~ 3 to 5 full turns each way to fully close/open them.

 

[John.g]

Didn't notice attachments before.......if the arrow on the pump body is pointing downwards then the pump is installed correctly.

 

[Stephen JW]

Didn't notice attachments before.......if the arrow on the pump body is pointing downwards then the pump is installed correctly.

Thanks John. Valves seem to be fully open. Can't see an arrow on the pump body. Where should I be looking?
Does the setting on our boiler that I mentioned have any bearing (3-4 on range 1-5/max) on things?. Likewise the thermostatic radiator valves?

 

[John.g]

Settings on boiler and TRVs are fine.

The pump arrow is on the pump body directly behind o the plug socket and is pointing upwards, probably downwards in your installation (on right hand side).


Can you also get a close up photo of the arrowed area in attachment.

And also around the pipework runs from the mid position valve to the cylinder coil flow and return etc.

 

[Stephen JW]

Settings on boiler and TRVs are fine.

The pump arrow is on the pump body directly behind o the plug socket and is pointing upwards, probably downwards in your installation (on right hand side).


Can you also get a close up photo of the arrowed area in attachment.

And also around the pipework runs from the mid position valve to the cylinder coil flow and return etc.

View attachment 65156

Arrow on pump was quite difficult to access and take snap of but have attached the best I could get. It is pointing down.

Also attached close up arrowed.

Many thanks

 

[John.g]

So pump is correct, the arrowed item is a mini ball valve by pass which is partially opened, can't see any reason why CCII shouldn't give perfectly acceptable flow rates compared to CCIII, it should give ~ 90%. so still points to pump problems IMO.
Its a bit surprising that your engineer didn't try out any other modes as most would settle traditionally for CCII even if they knew nothing about the other modes.

Also point out to him that the UPS3 CCII is more powerful than the Selectric CCIII.

Did your engineer make any other changes apart from the new pump & mid position valve?.

So, Stephen, If it were my installation, I would contact him and inform him of results, can't offer any other words of wisdom I'm afraid.

 

[Stephen JW]

So pump is correct, the arrowed item is a mini ball valve by pass which is partially opened, can't see any reason why CCII shouldn't give perfectly acceptable flow rates compared to CCIII, it should give ~ 90%. so still points to pump problems IMO.
Its a bit surprising that your engineer didn't try out any other modes as most would settle traditionally for CCII even if they knew nothing about the other modes.

Also point out to him that the UPS3 CCII is more powerful than the Selectric CCIII.

Did your engineer make any other changes apart from the new pump & mid position valve?.

So, Stephen, If it were my installation, I would contact him and inform him of results, can't offer any other words of wisdom I'm afraid.

Hi John. Firstly thank you so much for all your words of wisdom. You really have gone above and beyond to help and it is very much appreciated. It makes a huge difference to us to be able to call the engineer back knowing what it is reasonable to expect from the UPS3 in general and particularly, as you say, that UPS3 CCII is more powerful than our old pump - which supplied the system perfectly well for many years.

We are not aware of any other changes he made apart from fitting the Grundfos pump (and new pump valves), Drayton mid position valve and rewiring the (previously incorrectly wired) existing Drayton controller. He also drained and refilled the system.

Can I just ask couple more things before signing off?

The engineer initially quoted for a Honeywell mid position valve but actually supplied a Drayton. We didn't query this as the controller is a Drayton. Is this likely to have any bearing on the issue?

I only noticed after our last exchange of messages that, after I tried different pump settings and returned it to CCIII, one radiator that had previously been hot was lukewarm and one had not come on at all (both downstairs). I turned the boiler controller to 5 and both radiators came on. Any implications there?

And finally a (probably) really stupid question... should the circulating pump be constantly running when only hot water is selected on the controller?

Once again, many thanks for all your help John, you have been brilliant!

 

[John.g]

Mid position valve make should make no difference.

Don't think changing the boiler flow temperature should have any effect on the pump operation.

Pump should be constantly running with HW only selected as long as the cylinder stat is requesting heat.

Let us know how you get on.

 

[Stephen JW]

Mid position valve make should make no difference.

Don't think changing the boiler flow temperature should have any effect on the pump operation.

Pump should be constantly running with HW only selected as long as the cylinder stat is requesting heat.

Let us know how you get on.

Thanks so much John. Will do.

 

[Stephen JW]

Mid position valve make should make no difference.

Don't think changing the boiler flow temperature should have any effect on the pump operation.

Pump should be constantly running with HW only selected as long as the cylinder stat is requesting heat.

Let us know how you get on.

Good morning John

Not the response I imagine either of us expected me to post I’m afraid…

Apologies for the length of this post but as succinctly as possible…

• Engineer returned and suggested that running the pump on CCIII continuously was fine
• We said CCIII was noisy & resonating and that CCII was more powerful than our old pump
• Engineer said he would balance the radiators (but only adjusted 4-5 rads)
• Ran quietly on CCII for a couple of hours after he left but 2 upstairs radiators soon cooled
• Following morning successfully ran on CCII for an hour on water only – water very hot in < 1 hour
• Switched to heat (CCII) - only 3 upstairs rads fully hot, 5 downstairs warm only and 2 upstairs cold
• Within an hour boiler was mostly off and all rads cooling

We are waiting for the engineer to return but in the meantime we have tried various combos of heat only/water only/heat+water in both CCIII and CCII and have concluded the following:

• Since engineer ‘balanced’ the radiators 2 upstairs rads do not heat (1 cold/1 lukewarm) even in CCIII
• Pump and system is still noisy on CCIII (vibration can be felt through feet on floor outside airing cupboard)
• On CCIII in heat only mode the 8 radiators that do work get very hot
• Boiler continues to repeatedly fire up after the 8 working radiators have reached full heat
• On CCIII in water only mode water in the tank is fully hot (from cold) within 30mins
• On CCIII in heat+water mode 2 downstairs rads failed to reach full heat & water took 60mins to get hot
• Running heat+water seems to result in air getting into the system and the pump pulsing
• On CCII in water only mode system successfully fully heated the tank in < 1 hour
• On CCII in heat only mode system will run for an hour or so but ONLY AFTER rads have fully heated on CCIII first then switched to CCII
• Running on CCII after system had cooled for an hour (after running heat+water on CCIII) the downstairs rads failed to reach full heat after 90mins, pump started pulsing and the rads started to cool
• 2nd attempt to run heat only on CCII after the system had fully cooled resulted in pulsing after only 20-25 mins see attached video
• Switching on heat in CCII mode the morning after the above resulted in spluttering from the pump and the sound of rushing water see attached video

Summary:

We can run in CCIII in either heat only or water only but if we try to run heat+water together in CCIII or run other than water only in CCII we get problems that seem to be related to air getting into the system.

Could this be caused by a problem with the mid-position valve?

 

[John.g]

Its most likely that the air is a result in running in CCIII which is 6.4M, CCII should definitely be more than enough but obviously isn't. If we assume that the pump isn't faulty then I would shut that by pass fully, (see closeup.jpg post 38) put a mark opposite the slot ends and then either use a screwdriver or a allen key to turn the slot fully horizontallly and see if pump still noisy, even if it is retry it on CCII.

If you have 2 cold water storage tanks in your attic, check that the smaller of the two has water in it, you didn't say I think that you had this small tank but did say you didn't have a pressure gauge.

 

[Stephen JW]

Its most likely that the air is a result in running in CCIII which is 6.4M, CCII should definitely be more than enough but obviously isn't. If we assume that the pump isn't faulty then I would shut that by pass fully, (see closeup.jpg post 38) put a mark opposite the slot ends and then either use a screwdriver or a allen key to turn the slot fully horizontallly and see if pump still noisy, even if it is retry it on CCII.

If you have 2 cold water storage tanks in your attic, check that the smaller of the two has water in it, you didn't say I think that you had this small tank but did say you didn't have a pressure gauge.

Thanks John

Yes small tank is full & we don't have a pressure gauge. Just to be 100% sure I am adjusting the correct thing - we are talking about the attached valve, correct?

Interesting that you say that the air is a result of running in CCIII. I spoke to someone from Grundfos who told me to run it in CCIII to vent the air after it started pulsing in CCII.

Do you think that the pulsing and spluttering in the previously attached videos is indeed air in the system? Could the pump actually be faulty?

Thank you so much again!