Single Cold Downstairs Radiator

29 Feb 2024
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United Kingdom
Hi Forum People,

I have a very annoying downstairs Cold Radiator Problem :(

Our house is circa build 1999 and originally had an Ideal Classic boiler in a regular boiler conventional system. In September 2019, the boiler was replaced with an Intergas ECO RF 24 boiler configured as a conventional system and with a MagnaClean Professional 2 fitted in the upstairs airing cupboard.

There are 7 radiators upstairs ( 6 fitted with Drayton TRV4 and 1 fitted with Flomaster Manual )
There are 5 radiators downstairs ( 4 fitted with Drayton TRV4 and 1 fitted with Flomaster Manual ).
The downstairs toilet radiator fitted with the Flomaster Manual Valve is the offending one.

Recommendations carried out so far:

(1) All radiators bled.
(2) All radiators balanced with 1/4 turn and 1/2 turn lockshield process. TRV's set to 3 to 4 (6 is Max). Offending radiator is Flomaster manual so 3/4 opened until it reaches desired temperature. TRV valves tapped and none with pins stuck.
(3) When offending radiator returns to being totally cold overnight, never warms up again !
(4) Closed all other radiators and pushed hot water through offending radiator, heats up to desired temperature and is bled, little air is released. Works for a day or so then goes totally cold. Also the lockshield and TRV pipes are stone cold !
(5) Replaced radiator, but new radiator (Flomasta Type 22 600mm x 600mm 3499 BTU) still becomes cold after a day or so !
(6) MagnaClean seems to be doings it job as small amount of drained water is very clear.

Not sure what radiators are at the start and end of circuit ? Offending radiator could possibly be on the drop from upstairs ?

Intergas Boiler shows no problems, no errors and is serviced annually.

Any ideas on fix would be greatly appreciated.
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Your system sounds like mine was in a previous house (Ideal Classic boiler, hot water cylinder in upstairs cupboard, house built in year 2000). Ours also had a small water tank in the loft to supply the heating - is this what you mean by your conventional system? I had some similar sounding radiator problems every couple/few years. I learned a lot watching the Scottish Gas guy fix them. See my reply #14 on this thread, it might help. Also, my rads were piped in microbore.
Yes Alan, thanks for your reply. The tank in the loft is an expansion tank to keep the water level constant in the hot water cylinder. My pipes are also piped in microbore to increase pressure.

I do have flow from each pipe when I replaced the radiator. However the flow pressure may not be enough, so maybe the air blast concept the guy used in your thread could be the answer. I/ll check expansion tank levels too first ;)
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By checking which radiators warm up first, I was able to work out the offending radiator was not the last in the circuit but it is from the upstairs drop. The radiator it drops from upstairs is not used much so I removed TRV and fitted a maintenance cap to shut it off. The radiator omission and rebalance fixed the cold radiator immediately. Will check more thoroughly in the summer. :cool:

Thank you for peoples help.

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