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

 

[Deleted member 120897]

Greetings Stephen, I’m confused, has the boiler lost pressure and now not functioning, or is it the pump noise or both? Which potterton boiler? are you bothered for now about fixing the programmer?

 

[steadyon]

1. If the pump spindle is not turning when the pump is on, then it has a fault.
2. If water is not circulating fast enough, the boiler will overheat and turn itself off. Its not a pressure issue, more a flow one.
3. Not sure about your boiler, but some will detect whether pump is running or not, and if not will not turn on.
4. I suspect you are going to need a new pump. As you have a system boiler with the pump inside you are probably forced to buy one at Vaillant prices and pay to have it fitted by a Gas Safe registered person.
5. There is a possibility that a circuit board fault, or other boiler internal fault, is causing the pump not to start, but given that it was making unusual noises, this seems unlikely.
6. I think your first port of call should be a boiler repair person, preferably one with Vaillant experience. Some manufacturers do a "fixed price" fault repair service. Worth finding out if Vaillant do this if you can't find someone locally.

 

[Stephen JW]

Greetings Stephen, I’m confused, has the boiler lost pressure and now not functioning, or is it the pump noise or both? Which potterton boiler? are you bothered for now about fixing the programmer?

Hi there

Many thanks for the fast response! And thanks in advance for any advice you may be able to give me.

I'm confused too, which was the reason I posted my query here. The extent of my understanding of the problem(s) was listed in the bullet points of my first post.

The boiler is a Potterton Netaheat Profile of indeterminate age. It has no external pressure gauge so (as a lay person) I have no way of telling whether it has lost pressure. My question was as to whether the pump (Grindfos Selectric UPS 15-50) malfunctioning would cause loss of pressure that would prevent the boiler from coming on at all. Or to put it another way, whether I have one problem here or two separate problems that have coincided. Note that the pump body gets hot when the system is switched on but the pipework around it does not.

Its not essential to have the programmer correctly rewired at the present time, but if the overall solution to the immediate problem was the replacement of the pump only, it would be preferable if it could be done at the same time.

Many thanks again!

 

[Deleted member 120897]

Ok, so you have tanks in the loft then - not a pressure gauge. So a lack of water in the system, a sticking pump or faulty capacitor (but like a starter motor) could cause this issue. I suspect the pump isn’t circulating as you have kind of describe, so follow the video you posted and try and turn the pump/circulator shaft. If the pump sounds like it’s trying to kick in, but just a slight humming noise, then i suspect the capacitor. If the heating system worked recently, but has stopped I suspect the water in the system is fine.

 

[Stephen JW]

1. If the pump spindle is not turning when the pump is on, then it has a fault.
2. If water is not circulating fast enough, the boiler will overheat and turn itself off. Its not a pressure issue, more a flow one.
3. Not sure about your boiler, but some will detect whether pump is running or not, and if not will not turn on.
4. I suspect you are going to need a new pump. As you have a system boiler with the pump inside you are probably forced to buy one at Vaillant prices and pay to have it fitted by a Gas Safe registered person.
5. There is a possibility that a circuit board fault, or other boiler internal fault, is causing the pump not to start, but given that it was making unusual noises, this seems unlikely.
6. I think your first port of call should be a boiler repair person, preferably one with Vaillant experience. Some manufacturers do a "fixed price" fault repair service. Worth finding out if Vaillant do this if you can't find someone locally.

Thanks for your helpful reply. Just to clarify the boiler is a Potterton Netaheat Profile and the Grundfos Selectric UPS 15-50 pump is in the airing cupboard.

 

[Deleted member 120897]

1. If the pump spindle is not turning when the pump is on, then it has a fault.
2. If water is not circulating fast enough, the boiler will overheat and turn itself off. Its not a pressure issue, more a flow one.
3. Not sure about your boiler, but some will detect whether pump is running or not, and if not will not turn on.
4. I suspect you are going to need a new pump. As you have a system boiler with the pump inside you are probably forced to buy one at Vaillant prices and pay to have it fitted by a Gas Safe registered person.
5. There is a possibility that a circuit board fault, or other boiler internal fault, is causing the pump not to start, but given that it was making unusual noises, this seems unlikely.
6. I think your first port of call should be a boiler repair person, preferably one with Vaillant experience. Some manufacturers do a "fixed price" fault repair service. Worth finding out if Vaillant do this if you can't find someone locally.

OP has Potterton boiler, the video is just a link to YouTube, using a Vaillant pump, obviously causing the confusion.

 

[Stephen JW]

Ok, so you have tanks in the loft then - not a pressure gauge. So a lack of water in the system, a sticking pump or faulty capacitor (but like a starter motor) could cause this issue. I suspect the pump isn’t circulating as you have kind of describe, so follow the video you posted and try and turn the pump/circulator shaft. If the pump sounds like it’s trying to kick in, but just a slight humming noise, then i suspect the capacitor. If the heating system worked recently, but has stopped I suspect the water in the system is fine.

Ah that's great as you seem to have eliminated two out of three of those possibilities. I did try the method shown in the video and the pump impeller was turning freely. I have also checked the small tank in the loft and it is full. Which seems to leave just the capacitor. I should mention that the fault actually occurred a few weeks ago but we have been managing for hot water with the electric immersion heater. Would you anticipate having left the system idle for this length of time causing any additional problems? Many thanks again.

 

[Deleted member 120897]

Would you anticipate having left the system idle for this length of time causing any additional problems? Many thanks again

No I wouldn’t. When you spun the impeller, was there a demand on, eg heating or hot water?

 

[Stephen JW]

No I wouldn’t. When you spun the impeller, was there a demand on, eg heating or hot water?

Thanks again for all your replies. Apologies if I am misunderstanding your question but the boiler and programmer were both off when I spun the impeller with a screwdriver. I thought this was correct.