Whining Pump/No downstairs Heating

[amudda]

Hi all - hoping you can provide some guidance on a rather strange problem!

I have a open vented CH system, with a feed and expansion tank in the attic, the hot water cylinder and pump in the airing cupboard on the first floor, and a boiler on the ground floor. The pump is mounted vertically, and pumps downwards. There's a vent pipe from just above the pump. We've been in the house three years, and the only real playing around I've done was to move a radiator about a year ago, and I drained and refilled the system back then, but it was fine.

The heating is set on a timer to come on between 5:30am and 8:00am, and again at 5:00pm and 10:00pm.

About two months ago, the pump started waking me up in the mornings when it came on - it's whining very loudly, as though it's straining. On top of this, the downstairs radiators don't get hot - only the upstairs ones. Hot water is absolutely fine.

Once it's woken me up, it's been on about half an hour, and I get up and switch the heating off. The pump stops, and then I hear a gurgling/bubbling sound in the airing cupboard, as though air is travelling upwards from the pump. It lasts about 4 or 5 seconds, and is quite loud and distinct. Recently, the pump has started coming back on for a couple of seconds as well, even though I've turned the heating off.

Once this gurgling has stopped, if I then turn the central heating back on again, the pump is quiet, and all the radiators get hot - and everything works fine, and I can go back to bed.

This only happens when the heating comes on in the morning - not when it comes on in the evening, which makes me think it might be temperature related, as it's currently very cold at night?

I've bled all the radiators, and there's no air in any of them. I've looked down the vent pipe when I turn the heating off, but no water comes out. The pipework in the attic is lagged, so I don't think anything is freezing. I haven't done anything to the plumping recently to cause a change.

Has anyone got any thoughts what might be causing this?

 

[croydoncorgi]

If the pump is whining that's usually the sound of a water lubricated bearing running dry. If you've allowed it to continue for any length of time (more than minutes!), chances are your pump has an appointment at the knackers.

When you say 'no air in rads', did any water come out? If not, probability is either F&E tank empty (you DID check??.....) or the cold feed pipe from the F&E to the CH system is blocked. Very common - discussed here endlessly on a daily basis.

 

[Agile]

I cannot give you any immediate quick fix.

It seems that something has changed. Perhaps there is a partial blockage in the feed pipe?

More likely perhaps is that there has been a build up of sludge and when cold the pump is sucking air down the vent pipe?

I would suggest you try buying a 1 litre bottle of Sentinel Ferroquest from a good plumbers merchant and pour it into the header tank and leave it in the system for a week or two before draining it out and refilling with the addition of Sentinel X100 IF it has stopped the problem.

Tony Glazier

 

[amudda]

Thanks for the advice! Water did come out of the rads when I bled them, and I did check the F&E tank - it's full.

The blocked feed pipe sounds like a possible cause - I've got a bottle of Calmag 3in1 cleaner, which I think is similar to the Sentinel Ferroquest? I'll drain down the system tonight and refill it including the Calmag and leave it for a week - I guess I'll also be able to see if there's a blockage in the feed pipe by how fast the wtare in the F&E tank goes down when I drain the system?

Is there any reason that this might only be a problem when the heating comes on in the morning, and not when it comes on in the evening?

One more question - could the boiler cause a problem like this? I haven't had it serviced for a while, so could it be introducing air?

 

[EliteHeat]

If you drain the system with a blocked cold feed, you will not be able to fill it up (easily).

 

[amudda]

Thanks for the advice - you were absolutely right - blocked feed pipe where it joins the main circuit, just above the pump.

I've removed the blockage and the noise stopped.

Tonight I've drained down the system and refilled with some cleaner in there - it's been on about 20 minutes and the pump has started making the same noise, and every time I turn the pump off, water comes out the vent pipe in the attic - any ideas what could cause this?

 

[Soggy_weetabix]

blockage in the neutral pressure point on the system.

David

 

[chrishutt]

amudda, you're running two threads on this problem! That it not very helpful!

 

[robcol1305]

Hi Amudda
I have these exact same symptoms. What was the final solution here?

Thanks