ch expansion tank

[paddyo]

i recently fitted a wood burning stove with boiler and i notice that my radiator in a little upstairs room is not heating up. ive tried bleeding it but it doesnt work. its as if theres not enough pressure to force the air out of the radiator. Could my expansion tank in the roofspace be too small?
I have a couple of other rads downstairs that dont seem to heat properly either.

 

[WHPES]

Is the system pumped or gravity?

If pumped, is the pump functioning OK?

If gravity, I'm assuming the system was in before the boiler - is the pipework correctly designed for gravity circulation?

Is the system free from sludge (was it powerflushed before the boiler was installed?)

Has the system and pipework been altered in any way so as to adversely affect gravity circulation?

Did you remember to rebalance the radiators after the new boiler was fitted?

Could also be an airlock - if none of the above work, you could try blowing it out by connectint a mains pressure hosepipe to the drain cock but BE CAREFUL not to make a mess!

Unlikely the size of the F&E is an issue - this would only be so if you had added a LOT of extra new radiators and the F&E tank overflows when the system heats up even though the float valve is set correctly when cold.

 

[paddyo]

its a gravity system.
the upstairs rad which im referring to, if i unscrew the nut where the trv connects on, then the hot water eventually flows ok. The water in the system is fairly clean,there doesnt seem to be any sludge. Even if i turn off all other rads,the upstairs one still doesnt work.

 

[WHPES]

Theres your problem! Gravity system with TRVs!

Remove the TRV and fit an ordinary valve. Problem sorted.

 

[paddyo]

i'll try that tomorrow.
although there is one small rad upstairs with no trv but same problem.
i did notice that the water in the expansion tank is warm.
do trv's need higher pressure than ordinary valves to work properly.
i do have some downstairs rads with trvs which dont heat very well

could i disconnect the pipe which screws into the bottom of the little expansion tank,connect a piece of pipe onto it and drop it down into the bottom of the large (d.h.w.) storage tank which is positioned beside it?
this would give me the increased pressure to force the water through my rads.