flushed radiator and still a problem...

[theballoonman]

Hi

I have one troublesome rad that never heats up at the bottom, unless it's on for hours then eventually it does. Anyway took it off and flushed with hosepipe, put it back on and hey presto was great, heated up straight away and thought I'd fixed the problem.

However the next day it was back to normal freezing cold at the bottom, eventually warms up a little but didn't get hot, the exit valve and pipe down to the floor were also stone cold.

It's only this radiator, there's 10 others (all upstairs inc this one) and every one works perfectly. Would normal tap pressure water have flushed out any sludge, I couldn't see what came out as the rad was stood in the snow, yes lots of black stuff but couldn't see if any lumps etc. I wonder did having the rad upside down move the sludge around, and now its settled back at the bottom? I thinking might be best just to buy a new rad but would hate it to be a problem with say the return valve on the rad...

 

[JohnD]

turn off ALL the hot radiators. Does the cold one now heat up?

 

[theballoonman]

turn off ALL the hot radiators. Does the cold one now heat up?

hi, yes I've just done that and it does heat up as I'd expect, I guess more pressure to pump the water in servicing just the one rad?

However I've just now discovered what may be the problem, or certainly may not be helping, the fancy radiator valve is on the inlet side, all my other rads its on the exit side, could this sense the hot water coming in and keep turning off, rather than sense it on the exit side like all the other rads, I assume its meant to be on the exit side?

*** Edit *** Although reading on the web it seems the inlet is the right position for the thermo valve, therefore all other 10 are incorrect...

 

[denso13]

therefore all other 10 are incorrect

No, if they are bi-directional it doesn't matter, even if not they will be ok if the valve is orientated correctly.

 

[JohnD]

hi, yes I've just done that and it does heat up as I'd expect

Your radiators need balancing.

This is done so that all the radiators heat up at about the same rate.

It is not done by opening up the valves on the cold ones, but by closing down the valves on the hot ones, to prevent the hot water circulating through the easiest route and evading the more distant radiators.

 

[JohnD]

try here

https://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

Assuming you do not have thermometers, the incoming (flow) pipe should be "too hot to hold" and the outgoing (return) pipe should be "too hot to hold for long"

Almost all the adjustment of the lockshield is in the first turn from fully closed, so to start, close them all and open by half a turn, run the heating for 15 mins and see if they want changing. Do not adjust any valve by more than a quarter turn in 15 minutes. Write down how much you altered each one, and keep the notes safe.