Pump noise and sometimes pulsing

[mattg4321]

Hi guys

Have moved into a house with a fairly old plumbing system from 70’s. However boiler has been replaced around a decade ago by a Worcester- working great. Pump is around 5 years old.

I have a bit of a strange problem (to me at least). In the morning after the boiler has been off all night everything seems to work great. All rads get hot and pump is pretty quiet and as expected. This seems to run great for at least a few hours then during the day the problems seem to begin.

The pump gets noisier and noisier with loud humming that can be heard throughout the house. Some of the downstairs rads then appear to struggle to get hot In the evening. Also in the evening the pump starts pulsing. If you turn it off it stops the pulsing and noise for a time. But usually only a few minutes before it comes back. You have to leave it off for hours (like overnight) it seems to get a good run of quiet operation with no pulsing.

Is the pump just done? Why does it run quietly and properly for hours at a time in the mornings?

Other things to note. We use hot water much more heavily later in the day, although it is on in the mornings. Also there is a short gurgling noise that happens when the pump switches off after it’s been pulsing. It doesn’t do this when switched off when it’s not been pulsing - like in the mornings.

It’s been doing this for a good week or two now since the weather turned.

Hope someone can help!

Edit. Forgot to add that it’s fed from a tank in the loft and is a y plan system.

 

[mattg4321]

I can't see where the cold feed is coming in unless its the bottom left leg of the 'H' but it looks like this may be the return from the hot water cylinder coil?

Top left of the ‘h’ is the open vent and top right is the cold feed

 

[mattg4321]

Return from the coil on cylinder is just above the stat in picture. Flow to coil is out of shot at the bottom.

 

[John.g]

The UPS2 PP settings are truly appallingly low, the reason I asked you to try it was a sort of test for the pump as its only consuming probably 12/14 watts so very little load on the electronics, if it is running for hours on end now then IMO it points more and more to a knackered pump, if it was mine I would just throw it out, install a new pump and start from there. In the mean time, to give some bit of heat, it might help to shut down say u/stairs rad until you get a new pump.

 

[Vip1969]

Agree. Points to the pump electronics. Replace the pump. Sometimes it's best to do the most obvious thing.

UPS2 had a chequered history. Grundfos withdrew it after only just over 5 years because it proved to be unreliable.

 

[mattg4321]

The UPS2 PP settings are truly appallingly low, the reason I asked you to try it was a sort of test for the pump as its only consuming probably 12/14 watts so very little load on the electronics, if it is running for hours on end now then IMO it points more and more to a knackered pump, if it was mine I would just throw it out, install a new pump and start from there. In the mean time, to give some bit of heat, it might help to shut down say u/stairs rad until you get a new pump.

I’m not sure I fully understand your logic. The pump heats up the rads fine when on fixed speed 1 (or 2 or 3), but only for a few hours as it seems to draw air into the system which causes problems until it finds a way out after the system is switched off usually.

I don’t really understand why this points to a knackered pump? Why would a new pump not just draw in the same amount of air? It seems the current pump is too powerful for the way it’s been plumbed? Or it’s plumbed in wrongly somehow?

Sorry if the above makes no sense, I just want to be able to give my plumber some good pointers come Wednesday. Thanks again

 

[ShaunCorbs]

If it draws air in your feed and vent are in the wrong position

 

[John.g]

Did you do what I suggested in post #3, if not, do so with pump as is, PP3, then repeat the test on CC2.

 

[mattg4321]

If it draws air in your feed and vent are in the wrong position

Does it look wrong in my pictures? Where should they be?

My gut feeling as a non plumber is that this is the underlying cause of my problems

 

[mattg4321]

Did you do what I suggested in post #3, if not, do so with pump as is, PP3, then repeat the test on CC2.

I’ll do this again tomorrow hopefully

 

[ShaunCorbs]

Does it look wrong in my pictures? Where should they be?

My gut feeling as a non plumber is that this is the underlying cause of my problems

The 3rd one eg right is what you want

 

[Radian]

If it draws air in your feed and vent are in the wrong position

I agree that this is the first thing to look at but there are other possibilities. I'm struggling with a similar problem and my feed and vent are in the textbook location. It's well known that restrictions in the connections can cause pressure differentials that push/pull water in the vent but in my case there's no significant displacement taking place in the vent.

What if during the overrun period boiling is taking place on heat-exchanger hot spots? I ask because I've noticed the temperature on my boiler display ramping up significantly after the burner is extinguished. I did once see a number in the 90's for a few seconds and that gave me quite a fright. This kind of event will disassociate gas within the water and make it foamy (which the pump will definitely not like). Again, it is far more likely to occur after the system has been running than from cold. I think this is the kind of reason that some systems only seem to behave at lower temperatures.

 

[mattg4321]

It looks as though my cold feed and vent pipes are exactly as they should be.

I think the last owner of this house gave up on trying to fix it and that’s why they spent good money on a nice gas fire (despite being tighter than a ducks behind by all accounts). Think I might be about to do the same

 

[ShaunCorbs]

Seal the system then you can seal it at 0.5 bar if you got any hidden pipework in concrete

 

[mattg4321]

Seal the system then you can seal it at 0.5 bar if you got any hidden pipework in concrete

That’s a good shout. Is there anything that could be a deal breaker here? Will speak to my plumber about this I think.

I think the boiler should be ok as we had the same one in our last house with a sealed system - greenstar ri.

We don’t have any pipes in the concrete/screed ground floor.

Is it a large job/cost? Not too keen on spending fortunes on a system that will quite soon be ripped out!

Most importantly will it actually work and stop air being drawn in so I can run the pump at a sensible speed!?

 

[mattg4321]

Forgot to add we have a copper cyclinder. Will the coil be able to take it?