Intermittent Boiler circulation errors

[marslandingparty]

Hi,

Looking for some opinions regarding an issue with my CH.

It's a open vented system, 5 rads and a GW HX12 which is nearly two years old and was throwing F22 & F25 errors.

I've had someone out; they've cut out the H section which was blocked, and it's been powerflushed. There was an AWFUL lot of sludge in the system. When they left, it was still throwing the above errors and next course of action was new Heat Exchanger at around £800 all in.

Since then, I have tried many combinations of on/off and have found with the hot water on, the error doesn't throw. Nor does it throw with upstairs Rads. It DOES however error when just the two downstairs ones are on and there are still large cold spots.

I'm a relatively competent DIY man so today removed one of the downstairs Rads and flushed a lot of slime out which seems to improve things. I've not done the other because it's in a carpeted room and I made quite a mess in the tiled room!

My question really is - do these symptoms point to a blocked heat exchanger or a blockage elsewhere in the system.

My simplistic mind suggests that it's downstairs and the severe sludge in the downstairs rads is what's slowing the flow.

Hope that's enough info and thank you in advance!

 

[Agile]

I would expect that you are right.

But you say its been power flushed.

In that case there should not be much dirt left in the rads!

It usually takes about 5 hours and is charged at £250 - £500 to do!

Tony

 

[marslandingparty]

Thanks for the reply.

They were here all day (9-5) and were still cleaning a lot off the magnets towards the end of the day. I'm not unhappy with what they've done so far, I'm just concerned that I may be throwing £800 away if it's not the problem. Very frustrating issue!

Should there be other steps to check before resorting to replacing the HE?

 

[simond]

I assume they were using a Magnacleanse? Did they use this with a Powerflush machine? Did they turn off all the rads bar one and then vibrate the one they were working on?

I'm not really interested how much they charged, this seems to be an obsession with Tony.....

Just asking because with a Magnacleanse you would expect to remove most of the muck - that being said we've seem some systems where 'pumping over' (typically caused by H section block) has literally rusted the system so that a 3 day powerflush might be best.....

Before you do anything else I'd clean out that dodgy radiator because it's a lot easier than doing the boiler HE. Last question, have you opened up the pump and checked the 'eye' and vanes are clear? On a heavily contaminated system they are often clogged up.

The reason the HW works better with no errors is because it's a shorter pipe run and has less resistance to flow.

 

[marslandingparty]

It was that system yes. They didn't turn off each and agitate as far as I know - they spent some time focused around the boiler as they're sure the HE is blocked.

When they were here they took apart and cleaned the pump (powerflusher was connected to pump joints). They showed me and it was FILTHY. they'd not seen one that bad in a long time. The F&E tank did quite often drip and was warm (not any more).

They're coming back tomorrow, I'll suggest they tackle the Rad, I don't fancy trashing the carpet! The good news is the rad I cleared no longer has cold spots.

 

[simond]

If they didn't isolate each rad individually, then you did not get as thorough a job. You can leave all the rads open but then it is far less effective. As you now know.

NB: If I was the technician I wouldn't be sure the HE is blocked if the HW circuit works OK. Not saying there isn't a sludge build up but signs are its in the rads.

 

[Steelmasons]

Quite simple to determine if radiator is blocked as opposed to pipework.....my guess being pipework blocked..

 

[Agile]

I have to say that I the power flushing is not done with each radiator being the only one turned on in turn then its not going to be terribly effective.

The flow through just one rad is about 5-10 times that through it when all are turned on.

Ideally each rad should be flushed first in one direction and then have the flow reversed.

I have to say that I am not that bothered by power vibrating the rads as most of the dirt is lodged at the bottom which is why the higher flow is important.

Tony