TRV pipe cold. Return pipe hot. Rad hot at top, cool at bottom.

[rhubarbe]

Our kitchen rad is hot at the top but quite a bit cooler at the bottom. It was very cold at the bottom until the other day when e had a heating engineer to take off the rad and blast the inside with a hosepipe to clean out the built-up gunge.

Anyway, now we have the TRV valve and pipe below it which are lukewarm - no matter what setting we have dialled in on TRV, and the return pipe is red hot.

I have taken off the top of the TRV and the valve underneath moves in and out OK but doesn't make any difference if I press it in or leave it npressed, the pipe doesn't warm up.

Am I the numpty, or the man who fitted the rad?

 

[dontknowitall]

Try opening the lockshield valve more (assuming the radiator doesn't need bleeding).

 

[rhubarbe]

Lockshield valve would be the one opposite the TRV side - what I would call the valve on the return side?

 

[dontknowitall]

That's the one!

 

[rhubarbe]

Turned it three times clockwise from above. Pipe is hot, valve is hot, pipe leading from valve into rad is hot. Top of rad is hot, bottom still lukewarm. Pipe below TRV valve (the supposed flow) is on the cool side of lukewarm..

 

[rhubarbe]

Have removed TRV head, valve moves quite freely. I can't get the brass valve ferrule out because it is chamfered...

 

[dontknowitall]

Has it been working fine until recently?

It sounds as if the lockshield is on the flow and the TRV is on the return. The flow is hot and the return is the cooler water. TRVs should be fitted on the flow. Nowdays you can buy 2-way TRVs so it doesn't matter which end they go on (but best practice is to put it on the flow).

If the radiator has always been cool, then the person who came in and cleaned out the rad hasn't done anything wrong (except not checking it was working properly when he finished!)

If the TRV is at the wrong end then the valves need changing over which means draining the system. If you go down this route then it might be worth checking all the other radiators to make sure they're working properly too.

If you take the TRV to pieces you'll have a flood ...

 

[rhubarbe]

Is it possible that the TRV has been put on the return side by mistake and the rad is filling from the retrun by convection only?

This rad has never worked very well and it was a retro fit when we had a boiler fitted (we were on a back boiler before). The guy that fitted the boiler (never worked properly) and the rad (never worked properly), would have given Wyatt Earp a run for his money in the best cowboy of all time stakes.

 

[dontknowitall]

Sounds like the trv was installed at the wrong end!!

 

[rhubarbe]

We seem to be thinking along the same lines. I am reluctant to have it drained as it has a week's wages in Fernox inside the system - this is an Air Source Heat Pump system now, since we scrapped the LPG combi..

 

[PlumbingSucks]

Turn off all other rads and see if this gets the rad circulating properly. The system might just need balancing.

 

[dontknowitall]

You can always see if there's a plumber willing to do a wet change - ie without draining the system. It's risky but saves draining and I'm not sure the plumber will want to carry the can if it gets out of hand. He'll need a wet vaccuum to empty the radiator and remove it, then quick work to change the valves. Not something I'd want to do with a downstairs radiator.

Re the cost, Fernox is around £15 for 10 radiators.

 

[rhubarbe]

It's a bungalow...

 

[BLOD]

Get a plumber with an electric pipe freezer to do it - if there is enough room on the rad tails to connect it to it should be straightforward.

 

[rhubarbe]

There's about nine inches of 12mm pipe above the floor on both flow and return sides. Could be 15mm, I'm not sure.