Ask the Question

Rob · Joined: 11 Dec 2003 Posts: 2 Location: Leics

As part of a house extension, my heating system was also modified, incorporating a new Jaguar/Glow worm 100,000 btu combi boiler and increasing from 7 radiators to 12.

The boiler works fine but three of the original downstairs rads are not working, although if the heating has been on long enough, the inlet and return pipes below the radiators can warm a little bit.

The plumber said that we have a blockage in the pipework. This has now been flushed and has made no difference.

Radiators have been bled.

If we close off all other radiators, they do heat up and slowly cool as we open up the others.

The next suggestion appears to be trapped air in the pipework. How do we shift this?

AlanE · Posted: Fri Dec 12, 2003 1:29 pm Post subject:

Have you tried balancing the system since the new radiators were put in? This really should have been done when the installation was changed.

Basically you need to close down the radiators nearest the pump using not the normal valve but the lockshield one the other end. To adjust this you need to remove the plastic cap.

Then close down each of the hottest radiators and open about two turns. This will give you a starting position. You then need to check all the radiators to see if they are all getting hot or not. These valves need to be adjusted either open slightly or close slightly then leave a while then again check them all. This process is repeated until they all get equally hot. Any thermostatic valves should be fully opened.

The reason for all this is simply water is a lazy medium and takes the shortest and easiest path ie the rads closest to the pump.

Alan

Rob · Joined: 11 Dec 2003 Posts: 2 Location: Leics

The system has been balanced and this has no affect at all.

I should say that 2 or the 3 rads not working are on microbore with the main rad not working on 15mm.

Other plumbers have now been out, saying it is likely that these rads are being starved by the system but depends on where the manifold is?

If we close off 2 of the 3 rads, the last one (and smallest on microbore) which is nearest the boiler does give out a small amount of heat. This has again been bled and there appears to be no air in the rad.

Plumbers are also saying that because the ground floor of the house had some mircrobore, they should have left the system alone and installed a 2nd boiler for the extension!!

Seems to be very complicated now. The last resort is going to be removing the rads in these rooms, capping them off and fitted underfloor heating downstairs.

Any suggestions?

thescruff · Moderator Joined: 03 May 2003 Posts: 4680 Location: Bath

Mind boogling stuff this plumbing lark.

I would suggest you get a plumber that knows what he's doing, but I alway's get told off for saving such things.

Whats the size of the main heating pipes from its origin and the size of each split.

Whats the model-make and head of the pump, and what speed is it set on.

scruff