Downstairs Radiators Not Getting Hot

[MoonPig]

Hi,

We have a Worcester Bosch 42CDi combi boiler which is just 2 years old situated in the loft. It was fitted just before we bought the house. All of the radiators were replaced at the same time.

When the central heating is on, most of the radiators get nice and hot, but there are 3 downstairs that only just get warm.

I have drained and refilled the system several times and the water is nice and clean. There is no air in the system and pressure is around 1.5 Bar.

Hot water is always OK.

All the rads have TRV's, but none seem to be sticking - I've even taken the heads off the TRV's on the problem rads, but it made no difference.

I've tried balancing the system, but if I shut down all of the rads exept for just one of the problem ones, then it will get hot, but opening a valve only slightly on one or two of the OK rads seems to stop the flow to the offending radiators.

One common factor is that all 3 offending radiators have been relocated to different parts of each room.

I can't see that there is any blockage as the system was all updated 2 years ago.

It just seems that when other rads are open, the flow is easier through them, so the water takes that pathe of least resistance.

Any suggestions? Any help appreciated!!

 

[tincup]

Hi
Sounds like a radiator balancing issue. see FAQ

HTH

 

[MoonPig]

Hi
Sounds like a radiator balancing issue. see FAQ

HTH

I've tried balancing, but no luck.

As mentioned, if I close all radiators off except for the problem ones then they will get hot.

But I only need to open any one of the other (non problem) rads by a tiny amount say 1/4 of a turn and the flow stops to the problem radiator.

Also, when I do close all other radiators except for the problem ones, although they do get hot - they take around 30 minutes to get to full temperature. The OK rads only take about 5 - 10 minutes...

 

[D_Hailsham]

The head is greater than the pump can deliver. So either the pipes may not have been properly sized for the heat flow and pressure loss; or the pump has not been correctly set.