CH + HW - do they both have to be on?


Postby Hengist » Wed Jan 23, 2008 8:48 pm

Couple of questions for those in the know. In our rented house ...

1. We have a hot water tank separate from the central heating boiler. We've been told there isn't a thermostat in the hot water tank. Certainly, the water that comes out of the taps is often scalding hot.

We've been told that whenever the CH is on, the hot water should also be switched on for safety reasons. Is this correct?

2. We seem to have used about 800 litres of kerosene over the last month and a half and, even allowing for us using the CH more over Xmas this seems an awful lot. The system was serviced approx a year ago.

No idea how old the CH boiler is, but it's a "Riello 40", and it says "Camray Utility" on the outer casing.

Any help much appreciated!
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Postby ericmark » Fri Jan 25, 2008 12:39 am

Although my father uses gas he has same problem. It seems he can modify it to a "C" plan and add a motorised valve and tank thermostat which is wired back to programmer with 5 cores plus earth. There is also another option which also uses the motorised valve and tank thermostat but are only wired local but the latter system could cause problems with some boilers.
As it stands the central heating can't be selected without hot water and once running even if central heating thermostat has switched off it cycles the thermo siphon to check temperature every 15 minuets or so. He has today agreed that we can run cables and start on the conversion. Most fully pumped systems use "Y" or "S" system and unusual not to have tank stat and yes if you turned off the flow to tank it could on some boilers overheat. I reckoned parts will cost about £100 and I expect to complete in one day. I am an electrician and so is my son and we have problems from time to time with central heating wiring it is not really a DIY job.
ericmark

Postby Hengist » Fri Jan 25, 2008 8:32 am

Cheers for that.

I didn't make clear that we have two slider switches on our control unit ... one for CH and one for HW. We were told to keep the HW switch on "Timed", the same as the "CH" one.

If I switch the HW to off, and only put it on when needed, will this have the same effect as you mention above i.e. possible overheating of the system?

I did try it yesterday (i.e. only putting the CH on timed, and switching HW off) and nothing exploded yet ...

Angus
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Postby ericmark » Fri Jan 25, 2008 10:18 am

From memory programmers have two preset setting with turn screw and dip switches etc. These will allow 11 or 16 program settings. When 11 is selected you are unable from the front of the unit to select central heating without hot water. Often even if set to 16 unless you select hot water central heating will not work. Can't of hand see why you need to select hot water at same time as central heating if programmer will allow it except you may find central heating will not work if either wrong programmer fitted or not set to 11 program setting at the back. Remember I don't know your system I am only guessing from others I have worked on.
ericmark

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