New radiators not heating

[jamesythe3rd]

Having recently replaced my condensing gas boiler, i decided to upgrade two small double radiators which were located in a room which had been added to the original footprint of the house. The new radiators were tall standing double radiators approx twice size of originals. My fitter explained these risks take time to integrate into the network which could be helped by rubbing these new ones on their own then reintroducing the rest. Despite this the new rads while being bled and full of water are not getting up to same temp as all other radiators and take s long time to heat up. The inflow pipe is very hot. I was looking for any thoughts on why these new rads don't get up to full temp? I can post more specific specs if this would help.

 

[snowhead]

Has the whole system been re balanced since the new rads were added.?

 

[cjg]

if you are talking about cast tall rads then did you install the right way round, flow/return, is there a flow restrictor fitted in the rads.

 

[Ben-gee]

Most of these style of radiators have a baffle on 90% of the way along bottom rail- if the flow and return are the wrong way around - the radiator doesn’t heat up properly.
Same thing goes for if it is fitted upside down.

The other thing could be if the original extension just took a feed from one radiator rather than the ‘main spine’ of the heating circuit you could now have exceeded the limit for that loop.

 

[jamesythe3rd]

Has the whole system been re balanced since the new rads were added.?

Thanks for response. Yes, the engineer balanced the rads and i believe adjusted down the lockshield on 1st floor rads do all working perfectly but new rads still slow to heat and not as hot as the main system.