Radiator rattling

[dandeman]

I have a 13 year old combi system with a Worcester boiler. After all these years with no problems a radiator has started to make an annoying rattling noise from time to time. The noise only lasts for a few minutes at a time but is loud enough to be heard over the Tv.

The radiator was leaking from the inlet end last year and that joint was repaired. The rad is fitted with a Danfoss TRV which is the original valve when the heating was installed.

Any help would be greatly appreciated.

 

[JohnD]

if you turn the TRV down (or up) does the noise immediately stop?

 

[dandeman]

It stops when I turn up the rad.

 

[JohnD]

The TRV is vibrating as it closes. It might be fitted the wrong way (look for a flow arrow on the body) but, by turning down the lockshield valve on the other end of the rad, you may be able to reduce the flow enough to quieten it. Maybe the lockshield was closed to repair the leak and has been re-opened too far

I would suggest turning down the speed of the pump, but if you have a combi I hear you aren't supposed to alter them

(I don't know why)

 

[dandeman]

Thanks for the quick replies, I can't see an arrow on the body so I'll go with turning down the lockshield valve.

All my radiators have the TRV's on the same end i.e. the outlet end and have been like that for 13 years.

Cheers

 

[JohnD]

I have an idea that the older Danfoss TRVs had a rather weak spring, and the newer ones have a stronger spring. Maybe the older ones are more prone to vibrating.

 

[dandeman]

Tried reducing the flow and the noise only stopped when the lockshield was shut. Could the TRV given it's age be faulty and is it easy to replace.

 

[JohnD]

if you turn off the lockshield at the other end first, not much water will flow out when you take the valve off (no more than a bucketful), but have plenty of buckets, and a tray (such as an emulsion roller tray) to catch whatever does, and some old towels and an assistant to carry the buckets away.

The new valve will have an arrow on it, and instructions showing you how to install the valve depending which way the flow goes.

If you have not done it before, have a browse of the topics at the top of this Plumbing forum. You will need (at least) two large adjustable spanners. With luck the old and new nuts will be the same so the new valve will screw straight in. If the pipe comes out of a concrete floor and has no play on it, it is more difficult than if it comes out of a wooden floor and you can wiggle it a bit. You will have to bleed and repressurise the system after. Observe the water that comes out for colour and any sludge content. This could be a good time to top up the inhibitor even if the system is clean.