Central heating - noisy pipes

[jamieboy]

Our hot water / central heating is about eight years old now (new build house) and used to be more or less silent.

A couple of months ago the pump started making a noise, so we got a plumber in who diagnosed it was dead and replaced it about ten days ago. The old pump was a WILO Gold 50, new one is a Grundfos - I think the model is UPS 15-60 130.

The morning after the pump was replaced, all the pipework/radiators are noisy while the pump was running - an entirely different noise than before.

Stretching my plumbing skills to the maximum, I bled the radiators - only got air out of two of them, and kept bleeding them over a couple of days until no more air came back. Still getting the same noise, though.

Plumber is coming back today or tomorrow, but I just wondered if there was anything obvious that I / he should look at first?

[touching cloth]

Pump speed, it may well be set too high - slowest is very often quite enough.

[Wings]

touching cloth said:

Pump speed, it may well be set too high - slowest is very often quite enough.

Agree, had the same with a recently replaced pump, set to the lowest, then check the radiator farthest away from boiler/pump for heat.

[Ricky_M]

How big is the house? A 15-60 pump is quite a powerful pump if its a small heating system.

Has the pump been bled? There should be a silver coloured cap with a slot on the face of the pump. Slacken it slightly to release any air.

[jamieboy]

Thanks for the replies.

Plumber came out yesterday - there's a motorised valve about six inches along the pipe from the pump, and it apparently had air trapped in it which meant it couldn't open or close properly, and the noise I was hearing was a result of the pump forcing water through the partially opened valve. Apparently.

Fixed now, anyway.

[Ferg]

jamieboy said:

Thanks for the replies.

Plumber came out yesterday - there's a motorised valve about six inches along the pipe from the pump, and it apparently had air trapped in it which meant it couldn't open or close properly, and the noise I was hearing was a result of the pump forcing water through the partially opened valve. Apparently.

Fixed now, anyway.

I'd almost put money on it that he forgot to fully open one of the pump valves. Air trapped in a motorised valve? That'd be a first for me in nearly 30 years.....

[jamieboy]

Doesn't really surprise me to read that...

No real complaints, it's all working now. He's a nice enough guy, and I think he's relatively new to his trade (two or three years) so if he's learned something from doing it then fair enough.

[spikeyhead]

Ferg said:

jamieboy said:

Thanks for the replies.

Plumber came out yesterday - there's a motorised valve about six inches along the pipe from the pump, and it apparently had air trapped in it which meant it couldn't open or close properly, and the noise I was hearing was a result of the pump forcing water through the partially opened valve. Apparently.

Fixed now, anyway.

I'd almost put money on it that he forgot to fully open one of the pump valves. Air trapped in a motorised valve? That'd be a first for me in nearly 30 years.....

given how hard air is compared with water, it's easy to see how it could hold a valve open...

I've heard some crap excuses in my time but that takes the biscuit.