pump noise

[billybear]

My pump, a Grundfos UPS 25-80 130, started making a dreadful noise Sunday. At first I thought it had seized, but now begin to suspect that it's full of air. It seems to be turning but whirrs and gurgles very loudly, sometimes racing and sometimes just making bubbling noises. The needle of the pressure meter vibrates unhappily while all this is going on.

There is what looks to my hopelessly ignorant eye an automatic bleed above the boiler - it's the highest point in the plumbing cupboard - and I assume this should clear out any air in the system?

Any advice? How can I bleed the pump? I've had the big metal screw off (without the pump running) and it just dribbles water. Anything else to look for?

All help appreciated.

Billybear

 

[oilman]

You need to check the expansion vessel is ok. What is the pressure on the gauge when water is cold. Then comes a problem, if the pump has air stuck in it you can't heat up the system to see what the pressure is when hot. You will have to go to basics. Reduce the pressure to zero and check the air pressure in the expansion vessel (search the forum for more info) set to 0.5 bar then set system pressure to 0.7 bar (cold) this might allow auto air valve to bleed. It 's possible it's jammed and wont bleed.

 

[oilman]

 

[ChrisR]

make sure that any cap on the auto air vent is loose!

 

[billybear]

Oilman: the pressure now, very cold is 0.6 bar. The red line is set around 1.25, but it has been losing pressure very slowly. I've sorted odd small leaks around the manifolds (it's an underfloor system) and the two towel rails over the 18 months since it was installed. They were part of the reason, also various odd dribbles in the plumbing cupboard which tend to go away as they get gunged up with corrosion (I hate those little screwdriver shutoff things - how do you stop these random leaks?). There may be something else I don't know about, but no sign of anything major. (Which said, since it stopped I now have two small but steady leaks, one on each side of the mixer under the secondary pump - one got better on tightening, the other got worse. Tighten more and risk disaster? leave it as it is and hope operating temperature will close it? Pretend I'm a determined professional and take it all apart to do it again? Sigh.)

Chris: Yes it's loose. After the last time I tried to restart the system it had a drop of water on it, but nothing more, and nothing since. It is higher than the expansion tank, although the pipe to it does rise an inch or so higher but I can't see that that's of any significance.

Thanks Billybear

 

[billybear]

Edited away to stop site stutter...

 

[oilman]

Seems like we're all suffering the double postings today.

So you hate the things with the screwdriver slots, do you? Welcome to the club, theyre rubbish in a lot of installations, because they were cheap. If you need a service valve, when you've got some enthusiasm, replace them with lever types. This would cure the leaks as well. The leaking joints, replace the bad ones, and use some jointing compound in the not so bad ones.

If it's only been in 18 months, did you put it in? If not where's the guy who did it?

 

[billybear]

Yes - it's just slow - shows the virtue of patience.

As for the plumber, well he works for the builder. And the builder and I don't talk anymore for all the usual reasons associated with big building jobs, like taking 20 months for a job that was contracted at 8 months.

I've done various odd plumbing jobs in the past - just fixing bursts and the like - and I understand vaguely how these things work in theory, but it's a big step from that to taking apart a rather complicated central heating system. But as it seems to be impossible to get a professional on less than two weeks notice, I'm trying to help myself by finding and sorting any obvious and easy problems.

Billybear

 

[oilman]

Don't worry about it being a complicated system, the bits you need to fix are just simple bits, and if you can deal with bursts, what else is there?

 

[billybear]

Thanks oilman - flattery will get you anywhere! Keeping warm running up and down stairs between PC and boiler...

Expansion vessel releases air, not water. Factory precharged to 1.5bar. Seems like a decent pressure as far as I can tell just by pushing the valve although of course there's still water pressure. Given the youth of the system I'd have thought a diaphragm problem was unlikely.

Next? 1) Where is the PRV? What's it look like? 2) what's the best way of lowering the water pressure so I can check uncharged pressure - do I need to drain the system?

Thanks, as ever. Billybear

 

[billybear]

I continue to fret at the problem. I'm trying to get as much straight in my mind as I possibly can before doing anything drastic. I have checked other topics but not found precise answers to my questions – please bear with me.

I've brought the system up to full working pressure. Bled a little air out of the top floor towel rail. There are three underfloor manifolds. Each inlet and outlet has a little pot with small threaded hole covered by green plastic screw-on cap, which looks to me like an air vent. Is this correct? Do they vent automatically or do I have to do it manually, and if so, how? System is Thermoboard.

If I drain the system, do I have to open the top floor towel rail bleed valve to let air in? If not, where does air normally enter? Presumably ditto for refilling? Which is done from the re-pressuring tap?

The pump now seems a bit quieter but still sounds exactly as though it's entraining air. I've tried bleeding it, but it doesn't seem to be having any effect – either stationary or running I just get a small flow of water. How long should I do this for? Running? At fast or slow speed?

Of course it pumps downwards, so air might not be making it to the bleed valve. However in a straight line 1m above it is what I take to be an air vent – a little brass pot with a small screw cap on the side. This, if opened one turn, does nothing. If opened more, it releases the occasional drop of water, but no sign of air. It could be faulty, but if it's releasing water, it can't logically have air in it.

So I'm really at a loss – if I take the pump off, and the problem is air in it, I'm only going to make it worse. If it isn't, what could it be – pump bearings? What would that sound like?

signed Desperate of London

 

[oilman]

Don't do any bleeding running. Will suck air in. Are your electric valves working?
You don't have to let air in, an automatic vent will do this for you.

 

[billybear]

Too late re the bleeding - tried both - forum instructions tend not to cover the 'obvious'. Will redo in off state, but didn't seem to make any difference either way.

Letting air in for draining - makes sense, should have thought of that.

'Electric valves'? Have two motorised valves - one to hot water cylinder, and one to basement radiators. Haven't checked the HWC valve, the one to radiators stayed closed, but don't know why it's there (basement only used for storage, radiators all have own temperature control, in practice always set off), hence don't know why/how it's switched anyway.

Thanks
Billybear