Have spent all day balancing the system and still no heat!!

Separate, brand new pump-Grundfos, Alpha 2L.

And extra rad as a vent? surely a automatic air vent (or manual even) would have made more sense rather than more load on the system? (unless you needed the extra rad?)

You say they heat up ok when the other rads are closed down ? Have you tried cranking down the lock shields on the existing rads more - you don't necessarily need them open very much.

I should shut down the lockshields on the existing rads entirely. (note the number of turns if you want to be able to return to the existing state). Then just open them a little bit (say half a turn to start with), see how hot the different rads are getting and then work from there.

It shouldn't need to be said that if this is an open vent system, the feed and expansion tank MUST be higher up than the highest rad. But I'll say it anyway.

You could try turning the boiler stat to a medium level and put the pump on maximum fixed speed.

Then open all the lockshield valve several turns on all rads. Using the TRV's / wheelhead valves to shut down every rad bar one, turn on the system. Then go round the system opening the next rad before closing the other one. Make sure at least one rad is open at all times.

If there is air in the system, and this doesn't shift it, you'll be looking at larger problems ranging from installing air bleeds, to redesign of the pipework.

If it is a sealed system set the pressure to 1 - 1.5 bar cold and keep it topped up as you bleed the rads.

I have noticed that Galoka posted as I was writing this so some info may be duplicated.

We live in a bungalow and used to have to do the process of turning off all but one radiator to force out an air lock a few times a year. Since I have fitted a Spirovent on the feed pipe from the boiler we have had no problems (apart from refilling after doing the work).

(We have long runs of horizontal pipes in the loft that drop down to the radiators, so there must be lots of “local high points” on the pipe runs that air used to build up in.)

It's a sealed system and we've bled all radiators and doesn't appear to be air. Plumber has suggested that next steps might be to cut pipe work where it goes into extension & attach hose pipe to push water through rads and out of other pipe to see if it flows ok and take it for there.
It's got us all completely stumped.
(I've just turned off all the rest of the radiators in the house and now they're not getting warm at all!?!) It's not that complicated a loop of pipe work it's only over two floors with a slight step up into extension upstairs!
Thanks for your suggestions.

Coolhurst said:

Thank you for all these questions and for taking an interest! Yes that's why he put in the extra radiator upstairs to act as a vent. Do you think there could be a restriction somewhere and how can I track it down?

Click to expand...

That is a sensible way of dealing with a high point on the system. I really don't think adding another pump into the system is the answer. If the pipes are sized correctly and the main pump is good enough to move the volume I would look elsewhere for the problem especially as it is only the new circuit that is affected.

As for the restriction, I think that is your best bet at the moment. Assuming just flow or return is partially blocked the blockage would be immediately between the last good radiator and the first cool one on either of those pipes. I am also assuming it is a two pipe system fitted in a conventional way. So I would look for ways to test the flow of water in between those two radiators.

Edit: Oops missed reading page two!