Blocked central heating.....not one rad working

[Juddy16]

Hi All,

I wonder if you can give me some advice please.

I've just moved into a house 2 weeks ago, the house is 7 years old and the previous occupier turned the boiler off 6 weeks prior to me moving in. The property is a 3 storey town house.

Problem....on moving in day the heating didn't work!

The central heating system is a vented s plan with micro bore pipes. The boiler works fine as it produces hot water, it also produces hot water for the central heating but this all goes down the auto bypass pipe as there appears to be a blockage somewhere in the c/h system.

I've had the system powerflushed but this hasn't helped. The diverter to the c/h works as British Gas came out and tested it but suggested that there is a blockage or a valve somewhere in the system that has been turned off.....why someone would turn off a seemingly hidden valve I do not know! The pump is fine also.

As no single radiator receives heat , I'm inclined to think that the blockage is between the diverter and where it splits to the various legs of the heating system. Do you think this assumption is correct? And if so should drain the system, remove the diverter and pour some cleaning chemicals down in an effort to loosen up expected blockage?

Also so you think that there might be a hidden valve somewhere as the British Gas guy suggests, I cant see any.

Thanks for reading....any advice greatly appreciated!

 

[Agile]

This seems odd.

You call someone to power flush and he does that and then gets paid whilst leaving the system not working.

Then British Gas magically appear, supposedly check a motor valve and then leave.

If you had called BG to repair the system then that is what they should have done or if they could not then should not have charged.

I don't know what is in your house as I have never been there. In fact I don't even know what part of the country you are in.

It would be very unusual for valves to be in the heating system but there could be. Have you asked the seller?

I always advise anyone buying a house to get the heating system professionally checked to ensure it is safe and to explain how to use the controls.

Tony

 

[Tay7]

Is there any water in the radiators?

 

[Juddy16]

Yes, there's water in the radiators.

 

[fezster]

How could they have done a power flush if the pipes to the radiators were blocked?

Have you tried draining the system down and refilling? If it fills, then at least some water is managing to get through to all of the rads. There could still be some obstruction causing increased resistance to the radiator circuit, but I would expect at least some hot water to go to the rad circuit. If you put your hands onto the pipes going to the radiators, do they get warm at all?

I had a faulty ABV once which was passing far too much water, regardless of the setting. However, some water was still flowing around the rad circuit.

 

[Agile]

Typically an ABV should be set at about 0.3 bar.

At that setting it would leave that pressure to create circulation through the rads.

But with a microbore system the flow resistance can be very high so a much higher setting is better. Depending on the pump head perhaps 0.4 bar for a 15-50 pump and 0.5 bar for a 15-60 pump.

But has the ABV setting been changed recently?

Silly me is wondering if just the ABV was power flushed!

Tony

 

[gas112]

is any heat getting to the pipes by the rads ?

 

[Juddy16]

No the pipes by the rads are not warm.

When it was powerflushed the guy took off the rad nearest the garden only, he said that he was going to turn off all the rads and only have one on at a time the flush that one then turn all rads off to flush pipes.

I haven't drained the system and refilled yet....guess that's the job for the weekend!

Is there any mileage in putting cleanser down if I take the diverter off also do you think? Is there any way of checking if the ABV is faulty?

 

[fezster]

Post a pic of the ABV. How much access to the radiator flow pipe do you have? Just check it (starting at the ABV) all the way along to as far as it's visible, and see at what point it stops getting hot. If it's not hot at all more than a metre or so after the ABV, then the ABV may be faulty, or there may be a blockage near the ABV. The hot water has to go somewhere - it's either all going through the ABV, or some of it is flowing through the radiator flow pipe - you just need to know how far it's getting.

 

[Agile]

Seems posts above are invisible.

How could the powerflushing person do that work and leave when the system was not working?

All that draining the system will do is to get rid of the inhibitor that the power flusher is meant to have put in.

Tony

 

[Juddy16]

Hi Tony

The powerflush guy suggested that the diverter was faulty as there was not hot water going through it, not knowing as much as I do now I had to take his word.

 

[Agile]

Why did power flusher not investigate the boiler then?

Can you comment on the ABV setting?

It would be normal for a power flusher to turn that to maximum when flushing. But I have serious doubts about any of the people you have had there.

Tony

 

[mazperks]

A friend of mine called out BG service for a similar fault. Diagnosed blockage in pipework somewhere, recommended powerflush, but not confident. Said better to repipe whole system, plus new boiler - why not!
I had a look and there was flow at the rads on doing a bucket test, so checked pump, the problem was blocked pump valve.

 

[Juddy16]

Thanks, I will take a picture of the system and look at the ABV setting tonight and post a picture on here when I get home from work.

 

[Agile]

A friend of mine called out BG service for a similar fault. Diagnosed blockage in pipework somewhere, recommended powerflush, but not confident. Said better to repipe whole system, plus new boiler - why not!
I had a look and there was flow at the rads on doing a bucket test, so checked pump, the problem was blocked pump valve.

Sounds pretty typical of BG.

They also get a small commission of they can arrange a free quotation for a replacement boiler.

Not sure about just for a power flush though.