Central heating Stopped Working - Brrrr Urgent Please!

[GB]

We just noticed that the house is getting really chilly.

The boiler seems to be working.

Hot water is still hot.

The circulation pump is making noises.

The flow and return pipes are really hot. We have two circuits, upstairs and downstairs, with one pump. The downstairs flow and return are both really hot but the radiators are stone cold. The flow and return to upstairs are a bit less hot, and the return is a bit cooler than the flow. The upstairs radiators are slightly warm at the top of the radiators, cold at the bottom.

My thought is that we need a new pump, and the upstairs radiators are just warmish because the hot water is rising. But I don't see why the pump is making working noises and vibrating?

Any alternative explanations, please or tests I should carry out?

Thanks in advance.

[Wesley]

Are these normal or abnormal noises??

[GB]

Normal sort of whirry noises as far as I can tell.

[geoff]

In message , GB writes

Impeller come off the pump shaft ?

when you put your hand on a pipe can you feel any evidence of flow?

[Tim Streater]

Has anybody been fiddling with the system since whenever it was working fine? No one opening up the lockshield valves? Is water running into the header tank (i.e., is there a running water noise)?

[GB]

Not AFAIK.

Pressurised system. I did top it up from 1 bar to 2 bar, after it stopped wor5king, but it's made no difference.

[GB]

That was my thought. Is that at all common? The pump is 12 years old btw.

No, but I'm not sure what to expect?

[Another John]

I'm no expert (they will be along shortly), but this sounds like the problem that I had last October, and which I fixed because the boys here helped me do so: my Honeywell motorised valve had packed in. It was [relatively easily fixed, once UK.D-I-Y had told e what I needed to do.

You can read all about it in the thread at Google Groups:

some reason which I can't fix, that URL dumps you in the middle of the thread -- you need to scroll right to the top of the page for the saga.)

John

[geoff]

Yes, the shaft is usually ceramic and if some crud gets caught behind the impeller when its turning the impeller can shear off

You should be able to feel the "rush" of the water against the pipe as it circulates

[GB]

I took the large screw off the front of the pump, and the shaft is definitely turning.

Can say that I do feel any rush of water.

Another John mentioned that it might be the motorised valve. There is one - a Honeywell VC4013-02. There is a little lever on the side that is fully down but can be lifted up. It goes down again immediately I let go.I've held it up with a bit of string for 5 mins to see if that makes any difference. Better let it go now!

[SS]

To hear noises place a screwdriver on the bit you want to hear and the handle part on your ear. If pumping I suspect you should hear it (a swooshing of water) If nothing else try it anyway the sounds are interesting.

[geoff]

And the impeller?

Read what I said

Was that can or can't ?

[GB]

Spot on, John. Thanks very much.

[GB]

Ah, I assumed that what I could see was the shaft. Is that the impeller, then? The water is very hot (72C) so it's difficult to say exactly what's going on in there, as some of it's spurting out all the time.

It must be turning actually, as now I've sorted out the problem with the three-way valve it's all working for now. ;)

Can't. There are lots of vibrations from the pump but no swishing noises.

[The Natural Philosopher]

Motorised valve stuck: water is not being pumped to rads if return hot.

[Adrian Simpson]

The impeller is a something that fits over the shaft that will move the water, designs vary.

shaft may be going around, but the impeller needs to grip the shaft in some way, otherwise the shaft could just turn inside the impeller (I've seen that happen).

Adrian