UK Problem with Grundfos UPS 3 pump?

View the thread, titled "Problem with Grundfos UPS 3 pump?" which is posted in Central Heating Forum on UK Plumbers Forums.

UK
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garyevans

I previously posted a couple of years ago - Thread 'Help please! Issues with Central heating & Hot water' Help please! Issues with Central heating & Hot water | Central Heating Forum | Plumbers Forums - https://www.plumberstalk.net/threads/help-please-issues-with-central-heating-hot-water.128693/


2 years later and I am back. To cut a very long story short, it all sorted itself after the above thread. However, back in November it started to play up again. The heating would come on and the pump would be silent (on PP1) but a few hours in it then started to make a noise like a whirring sound in the pump. If I hear that noise I know the boiler stops. The heating cools. Just before Xmas I managed to sort it. Valve 1 fully closed and valve 2 just open (see photo). Heating worked fine for 4 weeks on PP1 but when the Hot Water came on the timer there would be a banging in the pipe every 90 seconds which was a pain in the middle of the night. A week ago I changed to CP1 and it was fine with both hot water silent and heating great but in the last 2 days that whirring noise starts after a few hours of the heating being on and the boiler stops. One of the videos I have attached shows you the noise while the other video shows it when it is almost silent and everything works. Sometime I can press the button and put the pump on CC1 and then repress so it goes to CP1 and the noise stops but not anymore. Any ideas? When the pump is quiet the heating works perfectly. All rads across the house nice and hot. All rads are balanced and have been bled. It seems that the whirring noise starts more often than not when the boiler restarts when the temp is below thermostat temp. It restarts and the noise begins. It can also happend the second the heating comes on. At that point, I switch it off, put the hot water on and if the pump is silent I can then switch the heating back on and it will be fine. Until the whirring starts and the boiler stops. It is doing my head in.
 

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  • PXL_20250126_183136384.mp4
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Sounds like the pump is cavitating eg not pumping

Valve 2 should be open 1/2 way
 
garyevans said:
I previously posted a couple of years ago - Thread 'Help please! Issues with Central heating & Hot water' Help please! Issues with Central heating & Hot water | Central Heating Forum | Plumbers Forums - https://www.plumberstalk.net/threads/help-please-issues-with-central-heating-hot-water.128693/


2 years later and I am back. To cut a very long story short, it all sorted itself after the above thread. However, back in November it started to play up again. The heating would come on and the pump would be silent (on PP1) but a few hours in it then started to make a noise like a whirring sound in the pump. If I hear that noise I know the boiler stops. The heating cools. Just before Xmas I managed to sort it. Valve 1 fully closed and valve 2 just open (see photo). Heating worked fine for 4 weeks on PP1 but when the Hot Water came on the timer there would be a banging in the pipe every 90 seconds which was a pain in the middle of the night. A week ago I changed to CP1 and it was fine with both hot water silent and heating great but in the last 2 days that whirring noise starts after a few hours of the heating being on and the boiler stops. One of the videos I have attached shows you the noise while the other video shows it when it is almost silent and everything works. Sometime I can press the button and put the pump on CC1 and then repress so it goes to CP1 and the noise stops but not anymore. Any ideas? When the pump is quiet the heating works perfectly. All rads across the house nice and hot. All rads are balanced and have been bled. It seems that the whirring noise starts more often than not when the boiler restarts when the temp is below thermostat temp. It restarts and the noise begins. It can also happend the second the heating comes on. At that point, I switch it off, put the hot water on and if the pump is silent I can then switch the heating back on and it will be fine. Until the whirring starts and the boiler stops. It is doing my head in.
Click to expand...
These UPS3 pumps have had more than their fair share of failures, some just don't install them anymore.
It might be worth investing in a plug in energy monitor for £15/£20, these are very accurate and the flowrates/pump performance can then easily be derived from the pump curves, just disconnect the pump cable in the JB, connect in a bit of cable to the pump terminals in the JB with a trailing socket on the other end, plug the energy monitor into the socket, connect a plug to the pump cable end and plug this into the energy monitor.
 

Attachments

ShaunCorbs said:
Half way from fully to closed
Click to expand...
Thanks Shaun. I sorted that last night and it worked a treat. Hot water and heating have been great all day today but about half an hour before the timer was set to go off for the heating I could heat that noise again. Is there anything else I can do to prevent it? Is CP1 the right setting on the pump? Do I need to set the thermometer at a certain temperature? Thanks in advance.
 
It is hard to say but I think the the heating has just switched off as the thermometer temp had been reached. However, this morning the hot water and heating worked fine as usual.
 
Hi Shaun. This worked perfectly. Until last night. Every day we had a quiet pump and hot water and central heating worked great. Last night, I was upstairs when I heard the heating come back on and the pump was making that noise again. I turned the heating off, put it back on and tried CC3 to vent the system but nothing would make that noise disappear. Decided to turn heating off and wait til this morning. Same issue. What I can't work out is why it would be great for a full week and then just stop. You mentioned cavitation. What causes this and how do I avoid it? I am not a plumber by the way. Thanks.
 
I'm curious and I may have missed it in a previous message and the photo's are just blank grey squares, but have you bled the pump? Apologies if this has already been asked.
 
Rtplumb said:
I'm curious and I may have missed it in a previous message and the photo's are just blank grey squares, but have you bled the pump? Apologies if this has already been asked.
Click to expand...
How do you bleed a pump? The Grundfos UPS3 has no bleed screw. I have had it on Cc3 which vents the pump according to the manual. I have reattached photo of pump and valves etc
 

Attachments

The Grundfos UPS3 does not have a bleed screw as the pump is self venting. You can aid in the ventilation process by following the steps below:

• Step One: Set the Pump to Speed III: Find the button on the pump’s operating panel and set it to Speed III, which is the highest setting.
• Step Two: Run the Pump for at Least 30 Minutes: This helps the pump push any trapped air out of the system. How fast the pump vents depends on the size and design of your system, but 30 minutes is a minimum.
• Step Three: Listen: The system should now be running quietly. A low hum is normal but loud banging, whirring or clanking could mean air is still trapped or another issue is at play.

When venting is complete, adjust the pump back to the recommended speed setting for regular operation.

After venting, let the pump run for a few minutes to ensure it’s operating quietly and smoothly. Regular venting isn’t usually needed, as the UPS3 self-vents over time. However, if you hear unusual noises, repeating this process should help. Noise on starting is normal and will cease as the pump clears.

If you are still experiencing noise every time your system runs, it could be a sign of excessive air in the central heating system. In this case, you may want to vent/bleed the radiators in your home also. If noise still persists, further investigation is necessary.

Have you tried bleeding from the AAV to check its working and not blocked with gunge.
 
Rtplumb said:
The Grundfos UPS3 does not have a bleed screw as the pump is self venting. You can aid in the ventilation process by following the steps below:

• Step One: Set the Pump to Speed III: Find the button on the pump’s operating panel and set it to Speed III, which is the highest setting.
• Step Two: Run the Pump for at Least 30 Minutes: This helps the pump push any trapped air out of the system. How fast the pump vents depends on the size and design of your system, but 30 minutes is a minimum.
• Step Three: Listen: The system should now be running quietly. A low hum is normal but loud banging, whirring or clanking could mean air is still trapped or another issue is at play.

When venting is complete, adjust the pump back to the recommended speed setting for regular operation.

After venting, let the pump run for a few minutes to ensure it’s operating quietly and smoothly. Regular venting isn’t usually needed, as the UPS3 self-vents over time. However, if you hear unusual noises, repeating this process should help. Noise on starting is normal and will cease as the pump clears.

If you are still experiencing noise every time your system runs, it could be a sign of excessive air in the central heating system. In this case, you may want to vent/bleed the radiators in your home also. If noise still persists, further investigation is necessary.

Have you tried bleeding from the AAV to check its working and not blocked with gunge.
Click to expand...
Thanks for that. I have managed to get everything working on CC2 so fingers crossed. I bleed the AAV quite often and all rads are bled. Will definitely follow the instructions above if (when!) it happens again. Cheers.
 
garyevans said:
Hi Shaun. This worked perfectly. Until last night. Every day we had a quiet pump and hot water and central heating worked great. Last night, I was upstairs when I heard the heating come back on and the pump was making that noise again. I turned the heating off, put it back on and tried CC3 to vent the system but nothing would make that noise disappear. Decided to turn heating off and wait til this morning. Same issue. What I can't work out is why it would be great for a full week and then just stop. You mentioned cavitation. What causes this and how do I avoid it? I am not a plumber by the way. Thanks.
Click to expand...

This is very strange

Cavitation means no flow, can be caused by no flow / shut valves etc or dirt in the impella

My recommendation would be to split the pump and see if there’s dirt in the impella
 

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