DIY boiler repair safe?

ed1178 · 31 Mar 2018

So, as is usually the way, my boiler chose the most inconvenient time to break down- Easter weekend when expecting a houseful of guests! I have bodged a repair but just wondering if it is safe...

The problem is the diverted valve (glowworm betacom 24c) which appears to have been leaking into the valve motor causing it to fail in the CH position.

I cannot obtain a valve repair kit and replacement motor until after the weekend, so instead removed the motor, opened it up and manually rotated the internal wheel to the DHW position (centre stem fully extended to fully depress diverted valve)

I then clipped the motor back onto the diverter valve, which depressed the valve to DHW. I did not reattach the wires to the motor as I don't want it to switch, just stay on DHW. I suspect it is knackered anyway, I could hear water sloshing inside it...

So now I have hot water at least, but am slightly concerned that by essentially forcing the valve to remain permanently directing water to the DHW side I have overridden some kind of safety feature? Is there supposed to be any diverter valve bypass to CH under certain conditions (overheat perhaps) that is now no longer possible with the valve disconnected from the power? All seems to be operating perfectly, I just don't want to risk it if remotely dangerous!

Obviously the motor will be replaced asap and the leaking valve repaired but I really want to avoid huge call out fees if not strictly necessary. Any advice incredibly welcome!

muggles · 1 Apr 2018

Should be fine, the boiler has an internal bypass to allow the pump to circulate water once the hot water demand is finished

ed1178 · 2 Apr 2018

Great, many thanks! We seem to have survived Easter without blowing the house up so looks like it worked ok. Can't wait to rip out the combi and replace with a nice old fashioned heat only boiler, stored hot water, separate pump and expansion vessel when the house is renovated! I know the arguments for combis, but they are a pain when they fail which they seem to with monotonous regularity. With our hard water I have skinned my knuckles so many times trying to access and descale or replace the heat exchanger, I curse the designer who decided the best place for this was right at the back behind everything else. Presumably the same guy who decided the pressure vessel valve should face the wall at the back so it can't be checked or topped up without the skills of a contortionist.

Pharcycle · 2 Apr 2018

I did almost exactly the same with mine (ended up being the PCB at fault... well one of many faults) but I left the motor housing off so I could open the front of the boiler and then just wind the nut of the lead screw to switch between hot water and heating... this was just before the last 'beast from the east' though so probably a bit unnecessary for you now it's spring.

ed1178 · 4 Apr 2018

Some further advice needed please!

Just fitted the new diverter valve stem, plungers and washers etc which has resolved the leak. However the kit included a very small washer which was not present on the one removed. I fitted it around the valve stem between the spring and the black valve cap through which the stem protrudes- is this correct? I assume that the spring pressure compresses it against the stem and cap to reduce the chance of water seeping up the valve stem and out of the cap. Just a bit concerned that there doesn't appear to have been a washer initially?

Also fitted the new motor.

All seems to be working BUT the water at the hot taps is only lukewarm. I have run the taps for ages and it never gets hot. Thermostatic shower set to 40 degrees also very cool. The boiler is firing continuously as the taps run, but the CH flow remains cold- where is 24kw of heat going?! I suspect the heat exchanger is scaled up to a certain extent, but why isn't the boiler cutting in and out? Have I overlooked something stupid? Would removing and descaling the secondary heat exchanger help? It's a pig of a job I would rather avoid...

Thanks in advance for any useful advice!

anotherfinemess · 4 Apr 2018

Do you have a pressure equalising valve before the shower? The diaphragm went in mine, giving the same issue. If you isolate the boiler dhw flow and turn on a hot tap, you can soon check.

ed1178 · 4 Apr 2018

Sorry I'm not sure I fully understand. At the moment it doesn't matter if im running the bath tap, the kitchen tap or shower the boiler is only supplying luke warm water. I realise the shower valve could somehow have become unbalanced (I hope not, it's tiled in and inaccessible!) but my other taps should be capable of supplying hot water even if the shower has developed a fault surely? I'm convinced the fault lies with the boiler rather than the plumbing, as all was fine until the diverter valve leak and consequent motor failure. I hoped repairing the diverter valve and putting a new motor on would resolve it. I can get my radiators piping hot but DHW only warm... that's why I'm thinking scaled or sludged Secondary heat exchanger but clearly I'm no thanks expert and appreciate any other pointers!

anotherfinemess · 4 Apr 2018

If the cold side we’re getting through to the hot on your pressure equalising valve, it would flow and make its way to any hot tap/outlet in the system. It’s easy to check though. Just isolate the domestic hot water from the boiler and try any hot tap. If water flows, you know it’s the diaphragm. This is only if you have one of these valves fitted of course. Ignore me if not. Just a suggestion from my experience. Hope that makes sense.

AlanE · 4 Apr 2018

Let the system go compleatly cold. Now run only the hot water.

Does the pipe from the boiler supplying hot water get hot or just luke warm? Do either of the heating pipes also now also get hot?

Did it work ok previously?

ed1178 · 4 Apr 2018

No heat is escaping to the central heating circuit, the flow and return pipes are both stone cold. The DHW flow from the boiler is only lukewarm. The boiler was firing continuously which is why I was concerned- the heat doesn't seem to be going anywhere! Now the boiler is cutting in and out so I'm getting alternating cold and lukewarm water from the taps. I haven't had piping hot water for a while, but it's not been this bad. I put I think down to the failed diverter valve motor and hoped replacing it would help, but it hasn't, just stopped the small leak. I'm thinking it's either bypassing the secondary heat exchanger, or the secodary is scaled / sludged up. Would you agree this is most likely?

ed1178 · 4 Apr 2018

Sorry just saw the first part of your reply. So you are suggesting cold water from the shower valve could be flowing back along the hot water pipes to other outlets? I guess it could, I have no idea what type of shower valve I have but it seems odd that this would fail just when my boiler was also dodgy... from what you're saying, if I isolate the cold feed to the boiler, and open a hot tap, if I get anything like an ordinary flow I'm getting some back flow through the shower valve?

anotherfinemess · 4 Apr 2018

Not the actual shower valve, but maybe the pressure equalising valve normally fitted just before the shower valve. If there is one? But yes that’s how you would check it. Any sort of flow would potentially reduce dhw temp. Just something that’s easily ruled out.

ed1178 · 4 Apr 2018

Ah ok- didn't know these were a thing! Pretty sure I don't have one, the house is ex rental, no money been spent in about 30 years so very basic- combi sited where old cylinder once was, a maze of plumbing, capped off pipes etc.

Still worth checking as you suggest. Have just done so- zero flow from any outlet when cold feed to boiler isolated. Think I'll have a go at the secondary heat exchanger tomorrow and if that doesn't work accept my limitations and call a pro!

anotherfinemess · 4 Apr 2018

Best of luck!

ed1178 · 4 Apr 2018

Thanks! Stocked up on Elastoplast for the skinned knuckles and deep heat for the pulled back trying to get at the bloody thing!

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