2 radiators revert back to a barely warm state

[derbybloke]

OK guys. Had some TRVs fitted all around the house about 4 years ago. Since then, had a problem or two with 2 of the radiators in particular.

I have looked up balancing techniques on this forum and applied them and is a whole lot better. Problem is, just when I think everything is OK, I check the 2 suspect radiators and they are not hot whereas earlier they were well hot!!. All TRVs are on 'full' by the way. There doesn't appear to be any blockages in the 2 rads as when the system comes on from cold, they get hot in the same way as the rest of them. This appears intermittently and driving me nuts. When these rads are cool, the inlet pipes are very hot, outlets are cool. No amount of adjustment to the LSVs makes the slight bit of difference to the flow.

Then, if I let the system cool down, turn off all the rads except the problem 2, and then fire up the heating, the LSVs have a noticeable effect

I've just done a final tweek and all are hot at the time of typing this up but there's a litle voice inside my head saying "it's gonna happen again".

Pump is on setting 1 of 3, boiler in good condition, and both are serviced yearly by Gritish Bass No air in rads.

Just in case this problem does occur again, is there any advice to give?

 

[John506]

What was your final tweak? Closing other lockshields?

 

[derbybloke]

It was to have the system on (after being cooled down) and only having 1 of the 2 problem rads TRV turned on. All other TRVs set to off. When this rad was hot, I adjusted the LSV so that the outlet pipe temp was a bit coller than the inlet. Once set, I let it run on its own for a bit and then repeated procedure with the other problem rad. When satisfied, turned on all TRVs to full.

Before posting this reply, I've just been around the house to have a feel. All are piping hot except 1 of the 2 problem rads which has coled considerably. The inlet pipe however is still very hot. The other problem rad is hot although when I felt the otlet pipe on that one I must say that it is not as hot as I would expect.

 

[mogget]

Pump is on setting 1 of 3, boiler in good condition, and both are serviced yearly by Gritish Bass No air in rads.

I'd try turning the pump to speed 2 if it happens again.

 

[numpty1]

maybe the trv is working and turning off the rad when the room has reached temp?
what boiler and how many rads ?what controls?

i would also suggest turning the pump up to no2 for a while to see if that helps with circulation.

 

[derbybloke]

I don't think (though I ain't no expert obviously) that the room has reached desired temp. Opposite prob-rad1 (this is downstairs in open plan diner/living room) there is a master thermostat about 3 paces away. Walk to the other end into the living room area and a radiator there never goes cool unless the master thermostat 'clicks' off. Regardless of what temp I set the master thermostat to (21 degress to 24) the same thing happens. Must be said that when I have the master tehmostat set to a higher temp for this time of year, prob-rad1 can go cool and heating continues to be on so thermostat never gets to click off.

Prob-rad2 is upstairs in the master bedroom.

The boiler is a Glow Worm Space Saver MkII. It serves 10 rads in total, all with Optima TRVs on them.

If I ever set the pump to speed setting 2, it makes a bit more noise and when the heating goes off I can then hear what I can only describe as gulps of water/air movement in the pipes. There are also air valves above the pumps, one associated to the hot water and the other to the heating. More often then not, when heating switches off and I am upstairs, I hear it dispell some air.

I'm turning to pump speed 2 now though just to see what happens. Is this enough info for you?

 

[D_Hailsham]

10 rads in total, all with Optima TRVs on them.

What, even the two rads in the living room where the wall thermostat is?
You should not have TRV on a radiator controlled by the wall stat, as this can cause problems.

If the TRV is set lower than the wall stat, the wall stat will never reach temperature, so the boiler will run continuously. If the TRV is set higher than the wall stat, the TRV never works as the wall stat has control.

A TRV set to max is effectively the same as having a fully open wheel valve - it's doing nothing.

Did you balance the rads with the TRV head on? Wrong! You must take the heads off to balance properly. Read Balancing Procedure

 

[bengasman]

clean system
set pump on 2 or 3
balance system properly for which you need thermometers

 

[derbybloke]

Ok peeps. Sounds like the first thing to do is get the TRVs taken off the downstairs radiators, would you agree? Even though they are always on 'max'?

And if this doesn't have a positive effect, get the system cleaned?

 

[derbybloke]

By the way.....when I had the TRVs fitted, the guy came back and also fitted 2 x Bottle Air Vents in the airing cupboard above the pump. The system never had these before and wonder if they are necessary?

Should I lock them off, or leave them open for air to escape?