Central Heating / Radiators Help

[Andyb350z]

Hi All

I have recently had an extension built and have had x2 new radiators added to my existing central heating system, it taps into both the flow / return. However, where as the rest of the house radiators are working just fine, the new radiators are only get slightly warm, far from hot. I have bled the system twice, and turned of all the valves both TRV and lockshield to off on all the radiators exepct the new ones so all pressure could be directed to them. After about 10 mins they instantly got hot, but as i put the rest back on, the went back warm.

Any idea whats going wrong ?

I thought maybe the following...

The Boiler is under too much demand ? But does not make sense to me why these rads (3rd closest to the boiler) wouldnt get hot.
The Flow / Return are maybe the wrong way round when they were connected underfloor ?

im a bit stumped and was wondering if anyone could offer me some futher advice ?

 

[porker]

Was the system balanced beforehand? Excuse me if you already know this. The lock shields should not be wide open on all radiators but just enough to let flow to warm them up sufficiently. if not balanced then the flow takes the easiest path back to the boiler and the ones on the far end of the circuit don't get any flow. Just open quarter of a turn at a time. You can usually tell which is the flow and the return by feeling the pipe (flow being hotter). Can you up the pump speed a bit? - often they have settings on them. Doubt the boiler is the issue unless it is fired all the time. Interesting that the ones that are cold are near the boiler but depends on the piping and airlocks can sometimes be hard to shift. Try the above and see if you are any the wiser.

 

[Andyb350z]

Thanks Porker for the info, i balanced the system yesterday, well, i turned the lockshields approx 50%. I may shut them off completley updtairs and see if that helps, then open 0.5 turns at a time, (takes about 10 half turns to fully open).

The pump speed is not something i have looked into, but i will now ! Thanks again

 

[RobinBHM]

I recently had a new ch pump fitted as the old one was stsrting to get noisy bearings. The new pump has more speed settings and on maximum 2 rads which never used to get fully hot, now get piping hot. Pump speed was not something I had considered as a possible improvement, but it certainly has made a difference in my case.

 

[Hemsby]

Sounds like a Rad balancing issue. This may help

http://www.muswell-hill.com/foxandco/pa ... ancing.htm

Regards

Keith

 

[Water-Mark]

It's not microbore pipework is it?

 

[Silas Gull]

Was the system drained right down prior to the installation? Air locks can occur in the flow and return, and play all sorts of tricks. Bleeding the rad in the conventional manner won't shift it. The technique employed in this video has worked for me many times:
https://m.youtube.com/?#/watch?v=bAeRurEExBs

As pointed out before in the thread, a rebalance may be necessary, if things are really out of whack.
Good luck.

 

[Robbo3]

Was the system drained right down prior to the installation? Air locks can occur in the flow and return, and play all sorts of tricks. Bleeding the rad in the conventional manner won't shift it. The technique employed in this video has worked for me many times:
https://m.youtube.com/?#/watch?v=bAeRurEExBs

As pointed out before in the thread, a rebalance may be necessary, if things are really out of whack.
Good luck.

I think your link is wrong. Takes me to a page of 'What to watch'.

 

[Doug B]

Won't be air if the new rads got hot when the others were turned off, balancing might help but if it's as poor as it sounds then probably the new rads have been connect in a poor place which is giving insufficient flow, is the rad pipe work they come off one of the longer runs on the circuit?

If it's been taped off micro bore pipe 10 or 8 mm then you've no hope & need to get them connected to the manifold or at least to the main heating circs

 

[Silas Gull]

This is the vid for airlock.
https://m.youtube.com/?#/watch?v=Ru-nNFqBzqk
Worth giving it a go, see if it shunts the mother.