Mysterious problem with heating

[Blitzbasic]

Hi,
I have a relatively new Worcester Bosch Combi system (3 years old). Worked perfectly until three weeks ago. But now none of the radiators get hot and some stay completely cold. I called in Worcester Bosch engineer. He says that it isnt a boiler problem. He is probably right because the outflow pipe from the boiler gets very hot but the return pipe remains cool. After a while the boiler turns itself off because the outpipe is so hot and the pump is working. The Worcester Bosch engineer diagnosed a blockage in the pipes and went away.

Since then have had two plumbers trying to sort it out. The first diagnosed sludge even though a power flush was done three years ago when the new combi system was installed. He wanted to do a new powerflush. However that was going to cost me £485 with no guarantee that it would fix the problem. I didnt go for that. May be I should have.

The second plumber has just spent a whole day failing to solve the problem. He drained the whole system and had water running through it from the filler on the boiler through the system and out of a drain fitted to the return. He claims that there is therefore no blockage. Also the water is now clear. He has also tried getting air out of the system.
I am thinking it must be air because some rad heat up a bit some of the time and others at other times. None of them get hot though.

I am running out of options and ideas

 

[wanleg]

What diameter is the pipework to the radiators....8mm, 15mm ?

 

[Blitzbasic]

I think they must be 8mm as both plumbers have commented that they are quite narrow although I did think that they had said 10mm rather than 8mm

 

[Agile]

This second plumber may have been putting water into the return in the boiler and out of the return of the pipework.

Only if he was clever enough would he have closed the flow valve on the return at the boiler.

You say the water is NOW clear! What was it like at first?

You also say it was power flushed when the boiler was fitted. How do you know that it was done? Did you see it being done yourself? Did it use a big noisy pump and take 4-5 hours? Did anyone run back and forth closing and opening rad valves?

I see so many customers who first tell me that things have been done when they haven't. The best one is how they are all so convinced their installer is CORGI registered. Quite a few are not!

Tony

 

[Blitzbasic]

The plumber put drains on two of the radiators first and flushed clean water out from them before eventually putting the drain on the return so it did seem to be travelling through at least to these two radiators.

The water was initially very black although I have been told by the original installers over the phone that this does not mean anything(I guess they would say that).

I have a vague recollection of seeing a machine about the size of a power flusher connected up during installation but could have dreamt it. You are quite right in saying that it may not have been done properly

 

[Soggy_weetabix]

I still love me DS40 as I dont own a Powerflushing machine.

Im always slated for it though.

Tough on pipes but boy does it work!

David

 

[Agile]

The water was initially very black although I have been told by the original installers over the phone that this does not mean anything(I guess they would say that).

If the water was very black and you have microbore than the first plumber was right!

There is clearly something very wrong if the water has become black! Either it was not treated ( my guess ) originally or has been leaking or something else since.

Is it a sealed system or open vented?

Tony

 

[Blitzbasic]

DS40 - is that a chemical desludger ? Do they work ?

 

[Agile]

I still love me DS40 as I dont own a Powerflushing machine.

Im always slated for it though.

Tough on pipes but boy does it work!

David

I agree but the risk is so high to the rads!

Whenever I use it I do it in small controlled doses so the concentration is always small and less risk.

I dont advise it to DIYers!

Tony

 

[Blitzbasic]

It is a sealed system if fact and has had nothing done to it since the original installation. One radiator upstairs has frequently had air in it and I wonder if it has small holes where air is getting in. With air in the system I guess corosion would occur.

 

[Agile]

If the system is pressurised as it should be on a sealed system then air cannot enter.

Gas in the system indicates corrosion and the lack of inhibitor!

Tony

 

[Blitzbasic]

Hi,
Thanks to everyone for the comment and information. It looks like the installers may or may not have done a powerflush or alternatively just didnt put any inhibitor into the system leading to corrosion and gas.

Would people recommend that I have a powerflsuh done now to solve the problem? Also is there a cheaper alternative ?

 

[ChrisR]

There's something about mains flushing in the FAQ, and you can take each rad outside and invert/flush it out with a hose.

It could also be that your pump is worn/tired. If you close all the working rads, do the others get hot? If so then they're essentially clear.
Pumps can be checked - do a search.

 

[corgigazza]

Try using this chemical works wonders

for info on it http://www.kamco.co.uk/powerflushing chemicals.htm

 

[Blitzbasic]

Hi,
Hope you dont mind me resurrecting this one:

I have tried switching off all the radiators except one or two. In each case the radiators left on started to get much hotter although not as hot as they used to get. Only one of the radiators downstairs really failed to respond - it did warm up a bit for a short while but then reverted to being completely cold. I put some sentinel sludge remover into one of the radiators one week ago. Have not seen much if any improvement though.

Is it possible that the pump is just worn (it does appear to work) or is it most likely to be sludge ?

Having spent already £300 on heating enginners and plumbers without getting any closer to a solution I am reluctant to call out anyone else - at least until I have a reasonable understanding of what is going on.