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.

 

[Deleted member 123817]

Is the pump external to the boiler, if so, what make/model and setting?

 

[John.g]

Also check for air in rads or anywhere there is a vent.

Go up to the F&E (small) tank and get somebody to switch the boiler on for a minute or so then off and watch for any pump over from the vent and feel the cold water outlet pipe (see if hot/lukewarm) watch for movement inside the tank while pump is switched on and switched off, that may help to pin down the problem.

 

[mattg4321]

Is the pump external to the boiler, if so, what make/model and setting?

External. Grundfos UPS2. Speed 2

 

[John.g]

If its 15-60 pump then would be a "5M" pump on speed 2 and probably running at around 4.2M head at normal flows so shouldn't cause a problem under any conditions.
Depending on what you find with the F&E tank above, you could try it on speed 1 which will/should still give around 85% of the flow at speed 2 and see if problem persists.
It may be just something as simple as removing the pump head and cleaning the pump ports and impeller (if a pump problem), you don't want to be throwing away a perfectly good pump if that is the problem.

 

[mattg4321]

If its 15-60 pump then would be a "5M" pump on speed 2 and probably running at around 4.2M head at normal flows so shouldn't cause a problem under any conditions.
Depending on what you find with the F&E tank above, you could try it on speed 1 which will/should still give around 85% of the flow at speed 2 and see if problem persists.
It may be just something as simple as removing the pump head and cleaning the pump ports and impeller (if a pump problem), you don't want to be throwing away a perfectly good pump if that is the problem.

Thanks John I’ll try that. It’s a 15-60.

Anyone want to hazard a guess as to why it only appears to happen later on in the day? Is it something do with heavy hot water use?

 

[John.g]

With heavy HW usage and if HW selected only then the boiler flow/return temps may be different, if the boiler has HW priority then it may increase the boiler flow temp to 80C which could have a big effect on cavitation if the pump is installed on the boiler flow and the pump impeller/ports are partially choked but this is just conjecture on my part.

 

[mattg4321]

This is happening with both hot water and heating on and calling.

When the pump starts making noise and usually a bit later on pulsing then the radiators struggle to get warm.

I’ve just got home after work and whacked the heating and hot water on. All seems fine at the moment. We’ll see a bit later on once we start using the water!

 

[mattg4321]

It’s been running fine for the last couple of hours.

Sure enough the wife has just got home and had a shower and the pump is now making noise and the radiators are struggling to heat up. The boiler keeps cycling on and off every 60-90 seconds or so and pump and pipework around it is very hot, but rads only lukewarm now.

I should add that hot water comes on in the morning too, but possibly is already fairly warm from previous evening.

I turned the pump down to lowest setting earlier and the rads were still getting hot.

Anyone?

 

[mattg4321]

Thinking aloud here. Mid position diverter valve problem?

I don’t understand why else the boiler would start cycling on and off so quickly when heating and hot water calling, when it had just been running great on heating only?

Would this also cause pump noise if the valve is slowing the flow enough?

 

[John.g]

The rads will never get hot with a cycling time of 60/90 secs.

Are you saying that the problem is more apparent when both HW and CH are calling for heat or more apparent when calling for CH only?.
Was the problem apparent during the summer when calling for HW only?.

 

[mattg4321]

The rads will never get hot with a cycling time of 60/90 secs.

Are you saying that the problem is more apparent when both HW and CH are calling for heat or more apparent when calling for CH only?.
Was the problem apparent during the summer when calling for HW only?.

Not sure why it starts cycling every 60/90 seconds at this time of day. Why does the heating work fine in the morning!!

The pump has started pulsing again now and radiators fairly cold. Even turning off the hot water makes no difference.

We didn’t notice a problem all summer to be honest. Water was hot when needed throughout the day.

I’m just wondering if the mid position valve is blocked or in poor condition. Just taken the head off and seems pretty stiff to turn…

 

[John.g]

It looks like some sort of circulation problem, whatever the reason, either the mid position valve or the pump, I would suggest switching off the boiler, shut the pump isolation valves, remove the pump head and check the impeller and ports for blockage and any other part that you see with the head removed.

Did you have a look in the attic to see what's happening, if anything?. Is the tank clean internally?.

 

[mattg4321]

It looks like some sort of circulation problem, whatever the reason, either the mid position valve or the pump, I would suggest switching off the boiler, shut the pump isolation valves, remove the pump head and check the impeller and ports for blockage and any other part that you see with the head removed.

Did you have a look in the attic to see what's happening, if anything?. Is the tank clean internally?.

Nothing much doing in the attic. Although I haven’t had a chance to look when the pump is pulsing yet. Tank is pretty clean.

I’ve just found a hand written receipt from a plumber to replace the pump a few months before we moved in. Looks like mates rates and second hand pump was fitted. £90 all in. Date stamp on pump is 2015!

Seems this problem has been going on a while…

 

[John.g]

Only other reason apart from pump problem or diverter valve I can think of is that there is a blockage/partial blockage where the cold feed tees into the system, can you see where this is done, if the circ pump is on the flow then you will have the vent, cold feed and then the pump (suction) all very close together. Sometimes the vent and cold feed are tied into a dirt/air separator (can't think of its name) and this can get blocked up.

Also check that the arrow on the pump body is pointing towards the mid position valve.

 

[Vip1969]

You say that you have a Grundfos UPS2; is it set to Constant speed II or Proportional speed II? Some forums have reported issues with electronics in this pump. I would set t to Constant speed II if on Proportional speed II.

 

[John.g]

Constant speed(s) are a solid green LED, if on PP control the LED is flashing, the setting button must be pressed for 5sec to change from CC to PP mode or vica versa, OP has tried CC2 and CC1 (fixed speeds).

 

[mattg4321]

The led is on constant speed 1. I had no idea there was another setting!

After problems all evening I’ve just tried cutting power to the boiler and all controls then turning back on.

Rads then started getting hot and pump quieter immediately. Thinking there’s something going on with the valve for certain now.

 

[John.g]

The next time it happens in CH mode, do not switch off the power etc, just remove the actuator, then switch the power etc off and on and see if problem persists, if so, turn the valve spindle manually to HW only (which is the default position with all power off) if problem still persisting in this position then switch the power off and on and if problem still there then probably not a valve problem and maybe a pump cavitation problem which the stop/starting clears for awhile.

Just to add that if/when you may decide to change the pump I would suggest a DAB Evostsa 3 which has better settings than a UPS 3 and also displays the flow and head (and power) which can be very useful in trouble shooting like above.

 

[mattg4321]

The next time it happens in CH mode, do not switch off the power etc, just remove the actuator, then switch the power etc off and on and see if problem persists, if so, turn the valve spindle manually to HW only (which is the default position with all power off) if problem still persisting in this position then switch the power off and on and if problem still there then probably not a valve problem and maybe a pump cavitation problem which the stop/starting clears for awhile.

Just to add that if/when you may decide to change the pump I would suggest a DAB Evostsa 3 which has better settings than a UPS 3 and also displays the flow and head (and power) which can be very useful in trouble shooting like above.

Just as an update to this.

We've noticed that the heating/hot water works to a just about satisfactory level for a couple of hours after being switched on (as long as it;s been off a while). After a couple of hours or so it just doesn't really work that well and the pump starts getting noisy and sometimes pulsing etc. At this point the downstairs rads go cold and stay that way.

This happens on both hot water and heating. I strongly suspect this issue has been a problem for quite a long time prior to us buying the property a few months back. Pipes have been cut in places that don't really make sense unless you are looking for a blockage. I've had them all apart again over the past few days and even run my nylon draw tape down the primary flow/returns and they all seem completely clear. I'd be very surprised if it's a pipe blockage.

Given the pump has already been changed a while back and when first turned on it runs smoothly and quietly I'm going to discount that too.

I've also taken apart the mid position valve and that is working fine. Had it completely off the pipework and all clear inside and moving smoothly.

I also cut out the Myson airjec and connected back up in an 'H' arrangement instead. The airjec was fairly gunked up but not even close to being blocked.

I've also tried running the pump on the lowest speed with no real improvement.

I now strongly suspect it is air causing the problems, but not sure why/how. Pump castellation? I don't fully understand this to be honest. Often when the pump switches off after being on for a while and getting noisy/pulsing we get a load of gurgling/air noises immediately after it's switched off.

I have a trusted plumber coming, but he can't make it to me until Wednesday. Anything else I can try before then?

Help! It's cold!

 

[John.g]

You seem quite handy yourself so I would suggest, shut down the boiler, shut the pump isolating valves, remove the 4 securing bolts, lift out the the pump head and inspect the pump impeller vanes for deposits/sludge, check/clean pump ports, re assemble. It will only take 1/2 a hour or so and maybe rule the pump out of the picture.

 

[mattg4321]

You seem quite handy yourself so I would suggest, shut down the boiler, shut the pump isolating valves, remove the 4 securing bolts, lift out the the pump head and inspect the pump impeller vanes for deposits/sludge, check/clean pump ports, re assemble. It will only take 1/2 a hour or so and maybe rule the pump out of the picture.

Thanks John, I have actually already done that and it all looked great in there. I must've had the system apart in more than 5 different places in the last couple of weeks and never really seen any sludge, just dirty water in places, which is probably to be expected of a 50 year old installation!

I'm fairly convinced it's not a blocked pipe, although I suppose I could be wrong.

What would cause a system to run ok for 2-4 hours, then suddenly start misbehaving? It happens like clockwork. Downstairs rads go cold/pump gets a bit noisier and eventually pump starts pulsing.

 

[Deleted member 123817]

Mysterious alright, what is the boiler flow & return temp when this happens ?.
What you might just try is press the pump settin button for 5 secs until the LEDs start flashing then just press the setting button until setting 3 which is PP3 and see what happens.
I would ask your plumber also to bring any pump he may have and install it temporarily, you may finally have to consider a sealed or semi sealed system even though no guarantee of a solution with that either. Someone on here could only get his system to operate at 60C at - 65C the system gave similar symptoms to yours.

 

[Radian]

Thanks John, I have actually already done that and it all looked great in there. I must've had the system apart in more than 5 different places in the last couple of weeks and never really seen any sludge, just dirty water in places, which is probably to be expected of a 50 year old installation!

I'm fairly convinced it's not a blocked pipe, although I suppose I could be wrong.

What would cause a system to run ok for 2-4 hours, then suddenly start misbehaving? It happens like clockwork. Downstairs rads go cold/pump gets a bit noisier and eventually pump starts pulsing.

Just a thought - maybe the pump itself is overheating (perhaps the control electronics)? I wonder what would happen if you dialled down the boiler temperature to the lowest value that still keeps the pump running and left it all running to see if it still goes bad?

It sounds to me as though the pump might be self-heating which could either be due to mechanical reasons such as cavitation or contamination or electronic issues that would be much more a function of operating time.

I get that you think you've eliminated the pump because it seems to have been replaced as part of a prior fault finding mission - and that it also seems fine from a cold start but, just maybe, some other issue was fixed (blockage or valve?) after the second hand (possibly dodgy) pump had already been swapped in.

 

[Deleted member 123817]

Would certainly substitute the pp if only to rule it out

 

[ShaunCorbs]

Sounds like pump is knackered

 

[mattg4321]

I’ve Been trying the pump on the variable setting (flashing light). It seems to be running a lot slower than even speed 1 fixed setting.

Boiler has now stopped cycling so much and the pump is quiet and everything runs nicely for as long as I want.

However none of the rads really get more than lukewarm and the boiler never really fires up ‘properly’. Green light is on but it’s in a sort of ‘tick over’ state.

Seems like a catch 22? Slow the pump down and rads don’t get hot. Speed it up and it draws air in.

What are my options!

Cheers for all help so far

 

[Radian]

Can you put up some photos of the pipework around the pump?

 

[mattg4321]

Can you put up some photos of the pipework around the pump?

A complete mess I’m sure you’ll agree. I know it need’s ripping out and starting again ideally but this airing cupboard won’t even be there in a couple of years! We’re planning quite a bit of work and will be entirely re plumbing the house.

Edit. Just out of shot at the bottom is the mid position valve

 

[Radian]

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?

 

[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