One cold radiator - what else to try?

[wilfords]

This winter, one of our downstairs radiators will not warm up. We've not made any major amends to the system since last winter, other than removing one other downstairs rad to decorate. I've read around the topic a bit and tried all of the following:

I've checked the TRV, it appears to be working fine, the pin moves up and down with relative ease

I've had the radiator off and run a hose pipe through it to clear any sludge. There was a bit of gunk in there, but nothing significant.

I've tried to balance the system, even with all other rads in the house off, the temperature appears to only be tepid.

I've had the rad off again and open each valve, inflow and return to see if there is water under pressure there, in both cases there was.

I've now replaced the valve at each end with standard (non-TRV) valves. With other rads in the house closed off, the rad has gained good heat. Other rads can be too hot to hold, but this, probably only reaches 6 or 7 out of 10. But with any flow through other rads, this drops down to no more than 1 out of 10.

I think the boiler pump is OK, other upstairs and downstairs rads gather heat within 1 to 2 mins of the combi kicking in.

What else can I try?

 

[dcawkwell]

Since the radiator works it is balancing of the system.

A normal pump can only drive about 12 or 13 radiators sometimes less
depending on the configuration of the system.

I think the pipes might do with a flushing out.

 

[martyn88]

what size piping is going to the rads ?

 

[wilfords]

It's all on 8mm microbore pipework.

We've only got 3 rads upstairs 4 rads downstairs so I guess it should be within capacity.

How do we flush the pipework?

 

[denso13]

8mm is the devils pipework. Maybe time for an upgrade?

 

[wilfords]

mmm...

Whilst I agree, an upgrade is pushing it. It worked OK last year, just trying to get it back to where we were last winter when it worked OK.

Any other thoughts?

 

[Jamesie]

Maybe the pump is on its way out, if your valves are all good etc. it must be working its nuts off to push the water through, my house had 8mm throughout with a manifold just below the combi, so some of the runs were 15m long and the house is only a 2 bed! Needless to say i didnt even test it, ripped the whole lot out!