Heating but no hot water


Postby 3540MarkT » Fri Jan 04, 2008 9:29 pm

Hello all, my first post so please be gentle. My central heating system is an older gravity system (installed 1979ish) where the hot water temp is controlled by the boiler regulator. I should always have hot water but I don't have any hot water at the moment. The heating is fine. There is a one way valve coming out of the bottom connection of the immersion tank. Could this be blocked or stuck closed? It has a little plunger on the top which is free to move. I originally suspected air but this system should self bleed. (The expansion tank is full). I have spoken to a plumber acquaintance who said that there is no need for a one way valve on the immersion tank and he would remove it. Good idea or bad idea?
Thanks in advance for any help.

Mark
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Postby marrtin » Sat Jan 05, 2008 12:29 am

IT sounds like good advice about removing the valve. Maybe it has stuck.

Have you tried blowing down the expansion pipe? It could just disturb the valve enough to make it work. Another way is to remove the boiler thermostat and force the system to boil for a few seconds(be careful!).
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Postby 3540MarkT » Sat Jan 05, 2008 10:11 am

Thanks for the reply marrtin, yes I have blown down the expansion tank overflow pipe as I originally suspected air in the system but I have used this method several times now and although it has usually started the hot water, when I tried this yesterday it made no difference. Could I try a sharp tap with a hammer? before I break into the system? Also if I have to replace the valve where could I get a replacement bearing in mind the systems age. or just replace it with pipe and omit the valve.

Rgds

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Postby marrtin » Sun Jan 06, 2008 9:50 am

I always say, if in doubt hit it with a big hammer, so it's worth a try.

Theoretically, the one way valve is not required, so you could replace it with just a length of pipe. The trouble is though why did someone decide that it was required in the first place? I wonder does the system have a fundamental design flaw where the valve was installed retrospectively?

Trace the 28mm pipes from the boiler to the cylinder and try and confirm there is no shared connection with the heating circuit. Does the heating circuit have it's own dedicated connection to the boiler?

If you replaced the valve with pipe, and the system did not work properly, it would give you a better opportunity to source a replacement valve. Maybe with it removed, you may discover it can be dismantled and repaired.
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Postby 3540MarkT » Sun Jan 06, 2008 1:14 pm

Good afternoon Marrtin, I've given the valve a whack or two (more out of frustration than anything else) it made no difference.
As far as I can see the boiler (a Potterton Netaheat 10-16 MK 11 F) is connected separately to the hot water.

The fault as far as I can see is either air (have tried to bleed by blowing and sucking on the overflow pipe in the expansion tank with some success but it never lasts) a sticking / stuck one way valve (not likely but you never know) or some form of other blockage ie sludge, (this I have not tried but when I blow down the expansion tank overflow pipe little black pieces come out of the fill pipe).

So before I break into the system can I flush it effectively with a sludge / debris removal liquid?

My OH is now using the immersion tank heater to get hot water and I can see the pound coins rolling away by the dozen.

Rgds
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Postby 3540MarkT » Wed Jan 09, 2008 10:44 am

I appear to have fixed it. I'm not sure whether it was the bleeding or the flushing but it is working, although I'm not convinced yet. I'll give it a week before I celebrate but this morning I had a lovely hot shower.

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