How much of a problem is kettling (energysaver 60)?

iep · 21 Nov 2010

Our Glowworm Energysaver has started to kettle noticeably just before the boiler thermostat kicks in and switches it off. Turning the thermostat down does not seem to make much of difference unless it is set so low that the output temp is only 65 degrees (in which case it takes hours to heat a tank of hot water).

I guess it could be a partially blocked heat exchanger allowing some paths through the exchanger to boil before the return temperature rises high enough to trigger the thermostat?

Either way, can we continue using the boiler in this condition? Will it cause issues for the rest of the system (all new rads and pipework fitted this summer)?

I was hoping to get a few more months out of the boiler before replacing with a viessmann or WB but I am starting to suspect its days are numbered.

iep

mickyg · 21 Nov 2010

its ok to use, it will likely get worse though and may eventually get bad enough to restrict flow to your radiators. If your planning on replacing it then no point doing anything about it.

gavinda · 21 Nov 2010

the kettling itself is not a danger

however

as mickey has pointed out, there may be some serious underlying issues that may result in the blocking of your heating system. in my opinion you should get someone to deal with this even if (especially if) you are planning to get a new boiler.

iep · 21 Nov 2010

Thanks guys. I think the underlying cause is that we had a bit of a corrosion issue in the system recently. It has since been cleaned (with x400) thoroughly flushed and refilled with a double dose of x100. Despite being very clean now though, I suspect that the damage may already have been done to the HX.

I'm not sure what caused the corrosion in the first place though. The rads and pipework were all renewed in July and one bottle of x100 was added to the system. There is no sign of 'pumping over' in the f&e tank and I pressure tested the system for leaks this weekend (after capping the vent and cold feed). I'm just hoping the flush and double dose of x100 will fix it now.

I'll keep an eye on the contents of the f&e tank (for signs of corrosion) and listen out to see if the kettling gets any worse.

Meanwhile, I'll keep saving for that new boiler.

Cheers,

iep

JohnD · 21 Nov 2010

how much black sludge came out when you used the X400? how many times did you have to drain and rinse it afterwards? what colour is the water now?

do you live in a hard water area?

iep · 21 Nov 2010

There was no sludge in the system, just very discoloured water. I only used the x400 as a precaution.

I then mains flushed the system (every rad one by one) until it ran totally clean and, after refilling, the water is now totally clear.

We're in Scotland so have very soft water and no scaling issues.

Cheers,

iep

mickyg · 21 Nov 2010

these boilers get blocked quite easily even on relatively clean systems. the waters got 3 heat exchangers to contend with

gavinda · 21 Nov 2010

just curious, why replace the rads and pipes and not a boiler thats at least 10 years old

mickyg · 21 Nov 2010

gavinda said:
just curious, why replace the rads and pipes and not a boiler thats at least 10 years old

why would you replace a condensing boiler thats working ok??

gavinda · 21 Nov 2010

because they are old, the parts are starting to run out (heat exchangers) and with the expense of the rest of the work why leave an old boiler ona new system when a load more pipework MAY not be far off. Ive worked on a few of late that have had severe water leaks on the heat exchanger where condense water has rotted either the combustion chamber through or at least the heat exchanger brackets preventing a new hex going back on.

mickyg · 22 Nov 2010

gavinda said:
because they are old, the parts are starting to run out (heat exchangers) and with the expense of the rest of the work why leave an old boiler ona new system when a load more pipework MAY not be far off. Ive worked on a few of late that have had severe water leaks on the heat exchanger where condense water has rotted either the combustion chamber through or at least the heat exchanger brackets preventing a new hex going back on.

all the parts are available, and probably will be for a while. The last ones were produced in 2004 asfair. so not exactly old. The main reason these boilers suffer is lack of proper servicing. They need good servicing every year, not a poke with an fga. Else eventually the condense ways get clogged and almost impossible to clear. I look after a few and they're in perfect condition. Main problems are electrodes, and fans could be more reliable.

iep · 22 Nov 2010

We did the pipework and rads because it was an old (noisy) microbore system and the rads were all undersized for the rooms. We toyed with the idea of doing the boiler at the same time but, since it was working okay, decided to keep it for a while and see how well it performed with the new system attached.

In fairness it did used to kettle a little with the old system but seemed to be okay once the new pipework and rads were attached (increased flow I guess). I suspect that the HX has just become a little more blocked of late and so the kettling has returned.

The condense tray in our boiler is not great but does still drain so I don't think it is rotten yet.

As an update on the original corrosion problem though, I put a 'trap' in the F&E tank beneath the vent and found it full of water this moring. So, looks like we have a bit of pump over going on. That is a different topic though.

Cheers to all.

iep

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How much of a problem is kettling (energysaver 60)?

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