Weird behaviour of my S plan system


Postby screenlux » Fri Oct 10, 2008 8:20 am

My central heating S plan system has been working fine until just recently. One morning the radiators did not get warm although everything else seemed ok. I thought it was just a sticking valve so I used the contol panel to switch off and on to see if it made a difference. This is when the weird situation occurred. When I switch the hot water off the heating comes on and vice versa but there is no way the 2 will operate together anymore. Further investigation shows that if I switch the hot water off completely, once the heating goes out of a time zone it doesn't start up again when it gets to the next time zone. However, if I switch the water back on then immediately off the heating starts up ..... anybody got any ideas :?
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Postby screech » Sat Oct 11, 2008 11:34 pm

what wiring centre have you got? if it's one with a circuit board in it could well be at fault
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Postby htg engineer » Sun Oct 12, 2008 11:43 am

It's unlikely (not impossible) that both the motorised valves will be faulty. When the heating goes off but wont come back on - have you checked the room stat isn't keeping the heating off ?

I'd be looking towards time clock / programmer.

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Postby screenlux » Mon Oct 13, 2008 9:21 pm

[quote="screech"]what wiring centre have you got? if it's one with a circuit board in it could well be at fault[/quote]

It's a Hordtmann H27 Channel Plus 7 Day programmer. It's the newest component on the system bu still 7 years old. I've a funny feeling it is the valves as the motorised valve that controls the water has now started sticking and not switching completely off - I have to manually push it over to A to get it to stop ! Thanks.
screenlux
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Postby screenlux » Mon Oct 13, 2008 9:27 pm

[quote="htg engineer"]It's unlikely (not impossible) that both the motorised valves will be faulty. When the heating goes off but wont come back on - have you checked the room stat isn't keeping the heating off ?

I'd be looking towards time clock / programmer.

htg[/quote]

The hot water valve is faulty (see my reply to screech) but the fact that the central heating only comes on when the hot water has been on then off does point to a programmer problem. When doing the checks the room stat was set to max as was the tank stat and boiler temperature as I wanted to be sure they all should be on. Thanks.

I think I will replace both the valves and the programmer just to be sure.
screenlux
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