Radiators cold at the bottom

[minted]

Hi guys,

Wonder if you'd be able to give me some advice. I've just had two small radiators fitted in an extension. All other radiators get very hot, but these didn't warm up. I then closed a couple of the other radiators and heat transferred into the new ones. They get hot at the top but only warn at the bottom, why is this? I've bled them and the existing system is not actually that old, so I don't suspect it needs flushing.

The installer said he will come back and balance the radiators in the hope that this will rectify the problem in getting warmth to all the radiators, does this sound right?

He said he wasn't sure as to why the radiator wasn't fully heated, but that he'd investigate. Can any of you suggest what may be the problem?

Thanks in advance


Mario

 

[Bahco]

Possibly sludge in the rads but if they are new unlikely.
Have the rads been fed directly off 22mm pipes?
Could be a 15mm branch (off the main 22mm) is feeding too many radiators (usually by a lazy fitter)

 

[ChrisR]

As a rule of thumb 15mm will provide enough flow for about 4-5 kW max. add up the radiators' outputs. 1kW = 3412 BTU/hr

 

[minted]

Cheers Guys.

The original pipework was 15mm, branching from 22mm. This fed one rad upstairds and two downstairs.

The plumber teed off from the 22mm upstairs, in 22mm and brought a new feed downstairs (the old 15mm was capped off at the point it went downstairs, and now just feeds the rad upstairs).

The two radiators downstairs are now fed from 22mm. After feeding both of those it reduces to 15mm and feed the two new radiators he installed(it's about 7 metres of 15mm between where it reduces and where the last of the two new rads is fed).

I was wondering if balancing would solve this. I have read other posts where an additional pump may be required. Could this be the case and if so how would it be fitted to the set up, i.e. would it be located where the new 22mm tee'd off from the original pipework?

The current pump is a grundfos super selectric, there are now 16 radiators in the system, all single panel approx 1600mm x 600mm. Most get very very hot