Radiators Cold

[amj62]

Hi all

Having come from a country that doesn't have central heating as standard, I'm pretty clueless. I have however read a lot on the forum - so here goes.

System is approximately 18 years old, vented with the water being heated by a Potterton Suprima 100. Two radiators downstairs in the hall and loo never get hot and are actually cold to the touch.

Today I removed the small one in the loo and flushed it out (not very much muck in it). Then I ran the flow and returns into a bucket untill the water was relatively clear. Then I attached a clear hose (that I filled with clean water) to the return and the flow. Opened the return a little and a bit of cloudy water flowed into the tube. Opened the flow a little and the same thing. It looks like no water is is actually flowing through the pipe, i.e. there is equal pressure on both the flow and return sides.

Any insight would be appreciated.

 

[jackthom]

Do other radiators in the house get nice and hot from top to bottom?

If they are all slow to warm up and the boiler is switching itself on and off every couple of minutes during this warm up time I'd be wondering about the pump.

It could be other things and a few pictures of the system are often a help.

 

[amj62]

Yes they all get hot upstairs and down - some are hotter than others but I haven't adjusted any of them since we moved in about 3 months ago. They all warm up reasonably fast and the boiler doesnt switch on or off very frequently.

Untitled

• amj62
• 6 Nov 2013
• 1

 

[jackthom]

Try turning off all of the radiators except one of the problem ones to see if it then gets hot and then maybe add the other difficult one too to see if that also works.

It may be that the system just needs balancing, which essentially is reducing the flow through some of the other radiators so more of the circulating water is forced to take a path through these 2 radiators.

There's plenty to read about that in the FAQ sections of this forum.

 

[amj62]

Thanks, I've already done that with no joy

 

[jackthom]

When you opened the radiator flow and returns into a bucket was the water gushing out or just dribbling from either valve? It does sound like some of the pipes may be well sludged up.

 

[amj62]

No, a strong flow from both pipes and the flow side is coming out hot

 

[jackthom]

The circulating pressure exerted by the pump will be a fair bit less than the head of water from the F&E tank during the 'bucket test' but I'm still surprised you don't get at least some hot water appearing at the entrance to the radiator when all the others are off.

If possible you could try setting the pump at a higher speed to see if that forces some hot water through.

Once you get some flow through the radiator it's usually a good idea to get flushing chemicals into the system, concentrating on cleaning the paths around those 2 radiators

 

[amj62]

No, the flow side doesn't even feel remotely warm and the pump is set to max. I can't tell about the pressure without a guage, but the rate of flow from the flow and return into the bucket looks about the same.

 

[jackthom]

Is it possible that these 2 radiators are down-fed from a ceiling above where there could be an airlock?

Otherwise it's looking like some of the pipework may need a closer inspection and maybe replacing.

Is it all 15mm or has smaller microbore been used here.

 

[amj62]

If there was an airlock would water still flow from both the return and the flow? As far as I can see all the pipes come up from the floor.

All 15mm

 

[amj62]

Just an update on this: drained and flushed the hall radiator and drained about 5 litres from each of the flow and return. When I was bleeding this radiator, I could hear water running through the toilet radiator, and it got warm. Once it was bled though, I couldn't hear any water flow and both rads did not warm up. Seems like these two are connected in series?