Central heating Flow and Returns seem to be mixed up

[Philpee]

Hi guys,

I am having an extension added to my 1930's house. The builder has installed pipework for radiators and towel rails, upstairs and downstairs. Yesterday a heating engineer Gas Safe), came to move my boiler. I don't have any concerns about his work. However, I can get heating upstairs, but nothing downstairs. I left the heating on overnight, and everything upstairs works, but downstairs there is nothing. The internal temperature is 10.5C.

As the floorboards are still loose, I have checked upstairs and downstairs, and where the builder has put an F and an R, the R is definitely hotter then the pipe marked F.

The pipes under the floor downstairs are both very hot (R hotter than F), but the heat isn't making it to any of the radiators. The radiators downstairs are all brand new this year, as are the TRV's.

The system I have is an open vented (F&E) system, with a WB 24RI condensing boiler

Any ideas what needs to be done, please?

Thanks very much

 

[Swwils]

Call the engineer!

 

[Philpee]

Fair enough. I have phoned, but no reply, so I have sent him a message.

I just wondered if there was anything I can try in the meantime.

 

[oldbutnotdead]

Did the downstairs rads work before the boiler was moved? Did the engineer recommission the whole system or just the boiler? Does the f & e tank have any water in it? Any closed valves up there? Was the whole system drained before the boiler was moved? Have you tried bleeding the downstairs rads? Are they even on (both ends)? Any zone valves on the system? Pump working?

 

[Philpee]

Hi,
The rads did work before, but never seemed to get as hot as upstairs. He only recommissioned the boiler ( I think that was all the builder paid him to do, and it was getting late when he finished 18:30).
The F&E tank has water, and there are no other valves up there. He didn't go anywhere near the airing cupboard, which has the motorised valves and pump, etc. The whole system was drained, and there is no air in the downstairs rads. The pump is working, but I can hear air in the system, although none in any radiator. The radiators are on at both ends (he didn't touch them at all). Two zone valves, one for heating and one for hot water. Grundfoss Alpha2 pump is circulating on maximum (45w).

 

[oldbutnotdead]

Does sound like trapped air somewhere. You could try;
Switch off a downstairs rad, both ends.
Remove valve from one end of the rad (yes you'll get water out of the radiator, bowl and cloths required)
Turn the disconnected valve on, let it run til you get hot water and lots of it. (A spare bit of pipe in the open valve end to direct water into the bucket would be wise)
Repeat with the other valve.
Reconnect valves to radiator, turn them on, bleed radiator, see what happens.

 

[Philpee]

Thanks.
I’ll give that a go

 

[Philpee]

Tried that ,but no change. Hopefully the Heating Engineer will answer me soon. It's a bit chilly tonight

 

[oldbutnotdead]

Tried that ,but no change. Hopefully the Heating Engineer will answer me soon. It's a bit chilly tonight

Odd. You got hot water out of both valves yes? And the main (22mm) runs under the ground floor are hot?

 

[Philpee]

Correct on both counts. One of the radiators is starting to heat up, but not very quickly. The other is stone cold.

While the system was drained down yesterday, the builder came in and blanked off a pipe that was looped together. That was for a radiator that has been removed and not to be replaced.

 

[Philpee]

BTW
I know that there is a lot of air in the system, I can hear it at the pump, but none of the radiators have air in them.

 

[oldbutnotdead]

Interesting. Especially the mysterious loop pipe- you don't happen to have a pic of it (either in place or where it was).
Is the rad you pulled the valves off the one that's warming up?
Re the stone-cold radiator. If you want to, you can try the valve removal trick AND see if pump running/not running affects the flow rate/pressure on both valves (with pump running, the flow/pressure at the flow valve should increase and at the return valve should decrease. Won't decrease to zero cos open vent but should reduce significantly.
Or if boards are still loose just have a look, make sure rad pipes are from different main runs, make sure there isn't a link pipe between the main runs.

 

[gas112]

put just the heating on and turn off all the rads except one down stairs this will force the air out once that rad is hot turn another one on downstairs and turn first one off keep repeating this till they have all got hot then have all the downstairs rads on for about half hour before turning upstairs on . This will get rid off airlocks in the pipework once all hot bleed the rads

 

[Philpee]

Sounds like a good idea. I’ll give that a go, thank you

 

[ericmark]

I would guess air lock, and radiators need bleeding, this is done twice, once with only feed open, and once with only return open, this one proves both feed and return free, and also ensures any air locks removed in both feed and return.

It is also likely the system needs re-balancing, the lock shield valves are throttled back so there is some pressure on all radiators, and also there is slow enough flow for the TRV to have time to respond.

With central heating left running one would expect each TRV to close as that room heats up, and so force water through the radiators in rooms not already warm, but if hot water returns to boiler, then the boiler will likely modulate, (turn down output) so the water is cooler. And a wall thermostat can if not set higher than the TRV's turn off the boiler before all radiators are warm.