Bottom of radiator cold

[hollygolly]

Have tried a suggestion of closing off valve (opposit end of thermostatic valve) and then opening half a turn, and still have a cold section on the bottom of my rad. Had a ladrge kitchen extension a few months ago, added 3 new radiators two small ones, and one huge one 1.2m long and about 400mm high. All the radiators in the house are so hot you cannot touch them, the large one is warm on the top and luke warm on the bottom, have tried bleeding, draining, stilll the same? Any ideas what to do next? This rad is the main rad for the extension, 11,500btus

[tamborine]

Since you've added extra rads to an existing system, you might need an extra pump to increase the flow. OR, feel the inlet pipe at the bottom of the rads; if they're cold, open the inlet valve above to increase flow.

[SlackAlice]

Because you've added radiators to the system think you need to re-balance the whole system again.

http://www.diyfixit.c...ancing-radiators.html

[The Builder]

If the new rads have just been tacked onto the end of an existing pipe run, then you might have created a long, dead leg...... ie a more "remote" branch of the system that takes much longer to get its share of the hot circulating water. Insulating the run well can help keep the water hot until it gets there.
I agree with Alice, you do need to re-balance the whole system. In effect, it cuts down the supply to the "hotter" rad, and provides more for the problem ones.

[AlBags]

Re-balance.
Adding another pump is ridiculous. You only need one circulator.

[hollygolly]

Hi, thanks for the suggestions, not sure about the pump idea, the one i have is sendin plenty of hot water up the stairs! just to update, the pipes the plumbers put in were the 15mm white plastic, then going onto microbore to this specific rad, the microbore pipe into the thermostatic valve is piping hot. when the heating first kicks in it gets warm as the flow runs along the top, but it never gets anywhere near as hot as all the other rads in the house, (which are all on microbore and cover three levels) and the bottom is always lluke warm as said.If the whole system is to be balanced, do i start at the top of the house and close off each end one rad at a time then open half a turn? When that rad is hot move to the next? Will it matter that all the other rads are working perfectly well already apart from this one rad in the kitchen?
thanks

[The Builder]

Holly, easiest way is to Google "radiator balancing" ............ plenty of "how-to"s on the Net. Even on Youtube, I think.

[AlBags]

Uh Oh ...

That's a problem with micro-bore .. What is the diameter of the MB pipes connected to the radiators?

[hollygolly]

the micro bore dia is about 10mm O/D. There is another smaller rad the other side of the wall (same set up) which was an original rad on the system, but changed to a taller but smaller width during the build, and it gets red hot?
I am at my wits end with it, must get to see the correct way to balance them all?
Thanks for all the comments.
Peter

[AlBags]

Any that get red hot quickly ... turn the lockshield valve (opp end to control valve) so it's no more than 1/2 turn open. Do that with other radiators that get hot quickly.
The aim of balancing is to get a temp drop across all rads .. the same drop... and to get them all heating up at same time.
Radiators NEAR pump need only be open 1/2 turn on lockshield .. furthest away maybe 2 turns. It will help distribute flow around whole system.
Give it a try.

[hollygolly]

balanced the system, very little difference, as said before all the otehr rads were getting hot on all floors, just the one...soved it though! It turned out to be the thermostatic valve controll? i noticed when it was put on it, you had to push, thus making the valve plunger go down, so i left it off, and within 15mins the rad was piping hot?? So i can assume this controller, when on the valve must be automatically pushing the valve down and setting the rad at may be 3 or 4, so stands to reason it will never reach full temp as the valve will shut it off when it gets warm as opposed to hot? Not sure how i am going to solve the problem long tem, but as it is cold will leave it on constant, can always turn off the little one if it gets too hot!!
thanks everyone for your help.

[AlBags]

Are you sure the head was engaged correctly to the valve body? And it IS the correct head for the body, too.
The heads lock into various positions on the body moulding. If mis-aligned, it can jam the pin down and cause the lack of flow you have experienced!
Either that, or you have one with a sticky valve. They get like that when sat about with the temp turned down for long periods.
To replace valve body is a drain-down, I'm afraid.

[hollygolly]

Its a brand new rad and valve, it moves up and down with little effort when pressed down. I might change one of the thermostatic valve heads from one of the other radiators, we bought 4 at the same time, all with the same rad valve?
thanks

[Hopkirk]

Might it not just be a sludge problem?