Noisy central heating pump - Sometimes !!

Hi there just after some thoughts on a heating / hot water problem we have.

Install is a conventional boiler with vented cylinder. Boiler is only 4 yrs old and seemes to be functioning correctly and is fittted with a magnetic filter. Central heating and hot water both appear to work OK however.............

When just the CH comes on, pump and associated pipework is fine with no undue noises just the usual pump running noise. When the HW is operating on it's own it is a completely different matter. Pump and pipework very, very noisy (sounds like cavitation or similar). It is so bad it wakes you in a morning as the HW comes on at 06:30, before the central heating.

If I operate the thermostat on the cylinder so the 3 way valve closes off the HW circuit, the noise subsides and then starts again when you turn the stat up to re-open the valve. It is definitely only linked to the HW side of things. Again if just the HW is heating up and the CH is turned off, all you can hear is the noise from the airing cupboard (which is situated right next to the master bedroom :mad:).

Many thanks in advance.

Sounds like a restriction in the hot water circuit. Maybe the grading valve on hot water return is closed down too much ( gate valve on bottom pipe out of cylinder), could also be the 3 port valve is blocked up with sludge or return from boiler is partially blocked.

What speed setting is the pump set on? If 3 try setting it to 2.

---------- Post added 07-01-2018 at 21:33 ----------

That's return from cylinder is partially blocked.

That situation sounds familiar. We have a magna clean micro filter, supporting a baxi boiler. 9x out of ten the heating side is ok but as soon as we switch on the hot water side we get a noise like a small aeroplane taxiing on a runway which lasts 5-10 minutes.

we had baxi out... and even though they fitted the filter and the boiler they said the filter didnt come under the warranty??? The remedy was to remove the filter and rinse out all the magnetic gunge that came from the old rads apparently.

the silence lasted maybe three weeks.

Why not operate the heating and the hot water at the same time then?

You said there is no noise when they are on together?

Why not operate the heating and the hot water at the same time then?

 

You said there is no noise when they are on together?

That's certainly a temporary solution but having your central heating on every time you needed hot water would hike up the fuel bill.

it's a definite blockage and probably sorted by flushing out the whole system top to bottom.

Why not operate the heating and the hot water at the same time then?

 

You said there is no noise when they are on together?

Sorry for misunderstanding my own post but where did I say that ? I wrote....

If I operate the thermostat on the cylinder so the 3 way valve closes off the HW circuit, the noise subsides and then starts again when you turn the stat up to re-open the valve.

So when using the HW side of things whether it is with or without CH it makes the pump noisier.

Apologies if my original description was unclear.

Powerflushing can only remove so much. If it's a really clogged piece of pipe then it would require replacing. I'd say grading valve will be shut down too much. Causing it to whistle.

---------- Post added 08-01-2018 at 21:22 ----------

That situation sounds familiar. We have a magna clean micro filter, supporting a baxi boiler. 9x out of ten the heating side is ok but as soon as we switch on the hot water side we get a noise like a small aeroplane taxiing on a runway which lasts 5-10 minutes.

 

we had baxi out... and even though they fitted the filter and the boiler they said the filter didnt come under the warranty??? The remedy was to remove the filter and rinse out all the magnetic gunge that came from the old rads apparently.

 

the silence lasted maybe three weeks.

Have you tried cleaning out the filter since? I've never seen a manga clean totally blocked. but if the system was really bad I could see how if clogged up it would cause quite a bit of restriction. But you would think if installed correctly it would case the noise alll the time as it should be fitted on return to boiler or between the pump and valve.