Central heating power flush, boiler now cutting out

falconers · 11 Jan 2009

We have a potterton profile 80 boiler, I just power flushed it the other day and the central heating isn’t working, it fires up then shuts off, the hot water works fine, I have checked for air in all rads and bled the nipple below the tank in the loft where the flow and return are located and there appears to be no air left in the system.

I power flushed from a radiator if that makes any difference, when I tried it the other day on radiator started to get warn then the boiler shut off.

i also left the pump in place and bled that after also via the centre screw

Any idea what i ahve done wrong

Softus · 12 Jan 2009

falconers said:
We have a potterton profile 80 boiler, I just power flushed it the other day

Why?

the central heating isn’t working, it fires up then shuts off, the hot water works fine

Where did all the sludge go that you flushed out?

gavinda · 12 Jan 2009

falconers said:
Any idea what i ahve done wrong

tried to save money without understanding the principlies of the job

.

wish i could do any old job without traing.

falconers · 12 Jan 2009

Hi,

i flushed it as some of the rads were not getting hot and they had been bled and all air removed.

The sludge hopefully went back into the machine and then out the dump valve at the end, but i have no way of knowing for sure other than what i saw going doing the sink which looks like charcoal and then rust.

And yes i tried to save money as i could not afford £400 to get someone to do it and having read about it it sounded straight forward, obviously not as i have found, but we live and learn.

Softus · 12 Jan 2009

gavinda said:
tried to save money without understanding the principlies of the job .

wish i could do any old job without traing. roll:

Why are you posting here if you don't want novices to attempt work on their heating systems? In case you hadn't noticed, the purpose of the site is to assist people doing DIY work.
___________________________

falconers said:
i flushed it as some of the rads were not getting hot and they had been bled and all air removed.

The sludge hopefully went back into the machine and then out the dump valve at the end, but i have no way of knowing for sure other than what i saw going doing the sink which looks like charcoal and then rust.

OK. Given that you removed sludge and rust from the system, it appears to have needed flushing.

And yes i tried to save money as i could not afford £400 to get someone to do it and having read about it it sounded straight forward, obviously not as i have found, but we live and learn.

Nothing wrong with that - that's what this site is for.

However, flushing is never a guaranteed way of removing everything, and can loosen deposits that then remain in the system causing problems.

For example, a more common way of flushing is to remove the pump, so it's possible that there is some muck partially blocking one of the pump ports. There might be enough flow for heating the cylinder, but not enough to reach distant radiators.

If it were mine I'd drain again (carefully watching the quality of what comes out), then remove the pump and pump valves and check that all is clear.

If you have TRVs then you also face the risk of small fragments of rust blocking the TRV inlet port (i.e. port on the pipework side), as these get very small as the TRV is closing. Then you can get a dam of material built up that stops the flow to the radiator even when the valve is open.

A few drain downs, rinses and refills won't do any harm. Another very good thing to do in your circumstances is to fit a Magnaclean. Preferably a TwinTech. This is the best way of addressing the long-term need to catch things that are still circulating around your system.

falconers · 12 Jan 2009

Thank you foir the constructive advice i will drain the system down a few times and have a look at the pump also.

The magnaclean is a good suggestion also and i will look into that.

Agile · 12 Jan 2009

If it works OK on hot water nut not on heating then it would be the first thing to do to check the motorised valve.

One might wonder what you did with that when you were power flushing the system!

Tony

falconers · 12 Jan 2009

Hi Tony,

How can i check the motorised Valve ?

Softus · 12 Jan 2009

Agile's extremely valid point is that you couldn't have flushed in both directions without manually opening the MZV.

What was the flushing procedure that you did use?

falconers · 12 Jan 2009

The flushing procedure i used was as follows, we have 11 radiators, some had practically no heat coming out at all, so i took them off the wall and used the power flush machine hired from HSS, i did about 5 like this, i connected them to the flusher and started the process and changed the flow every few minutes and banged the rads with a rubber hammer.

then i connected both flow pipes to a radiator one on each tail and started the flush process again, i added the flush solution also during the processes.

I had to cap off both the flow and return pipes in the loft and shut off the water feed also, the water was then topped up via the tap directly into the machine.

When i did the full stem flush i turned all the rads off, and then opened one rad at a time to be flushed.

Agile · 12 Jan 2009

When power flushing the system from radiator tails you should have been taking the setting the motor valve into account!

Perhaps you were only power flushing the hot water cylinder heating coil?

Tony

falconers · 12 Jan 2009

just had a plumber round to give me his opinion , i described what i had done as in this post.

He concluded that the whole system needs flushing again, he never checked the pump or anything else, he looked at the boiler and witnessed it switch off after a few minutes and noted the slight heat from 2 of the radiators and wrote me a quote for £350.

Does this sound normal practice or would some plumbers have delved a little deeper.

falconers · 12 Jan 2009

Tony,

When i flushed the system, i could definitely hear water flowing on each rad as i did them in turn ?.

Agile · 13 Jan 2009

falconers said:
Does this sound normal practice or would some plumbers have delved a little deeper.

Well I would have diagnosed the fault ! But then I would have charged you £84 if you were in our local area!

If you call someone round "to give an opinion" then they are not going to spend much time diagnosing the problem and so they just quote a lot of money knowing that they can solve the problem within that price.

Its all too common!

But if you call people round expecting to have diagnostic work done for nothing then I would say that you have got what you paid for!

Tony

EliteHeat · 13 Jan 2009

falconers said:
Does this sound normal practice or would some plumbers have delved a little deeper.

That's what is called 'work' which you have to pay for.

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Central heating power flush, boiler now cutting out

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