Central heating timer...

Matthew Ames · 2007-12-13T15:37:56+00:00

Help :-)I have an old Randall 3060 in my house that the timer bit has decided not work. The manufacturer tells they don't supply any parts :-( This rather a bummer as I think it is just the motor (or more likely one of the nylon cogs is worn out (it makes a rattlie noise, but when I take it apart nothing looks obviously worn). So that means I have to sell out about £80 for a new timer :-(SO I thought maybe I'll move into the modern digital age and get someone newer (house is victorian with an old floor standing gas boiler).The snag is, the house has two thermostats (one upstairs and one downstairs). So heating can be either up or down or both. It has in conjunction with this 2 valves (one for downstairs and one for upstairs heating circuits) and 2 pumps (one for heating that I replaced in feb of this year and one for the h/w cylinder)However this all means there is a total birds nest of wires everywhere :-(I would imagine, but I am not 100% there is no thermostat on the h/w tank, and that the pump is just used instead.What are my options here?!? Obviously Ill try and figure out what wires go where, but there are lot of them and many just vanish into the walls!I assume as a basic view, the timer switch comes on, and supplies power to both thermostats, if either thinks its location is cold enough to closes to complete a circuit. The returns live feed then goes to the boiler, the appropriate valve. However I have not work out "who" controls the pump yet - is that likely to be the boiler, or will that be driven from the thermostat? Given that with two thermostats it would make sense that they are independent of each other (otherwise why have the valves for up/down stairs?)Hopefully a mate is going to pop around over the weekend and we will try and figure out the wiring before doing anything, but any suggestions would be a bonus :-)Cheers,Matt

Dec 13, 2007 23 Replies

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geoff 18 years ago

In message , Matthew Ames writes

I'll look on monday

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Roger Mills 18 years ago

Except that it's a pumped HW circuit with a separate pump from that used for the CH - so there may or may not be gravity circulation when the pump's not running.

What's pretty certain is that there's no boiler interlock - so the boiler will be cycling on its own stat whenever the timer is on even if all demands are satisfied. Presumably the boiler doesn't mind not having any flow through it - which will be the case when the HW pump is off and the CH valves closed.

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Matthew Ames 18 years ago

Thanks Geoff

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Ed Sirett 18 years ago

Yes the controls could be implemented that way on an old cast iron (high water content) boiler. I'd be interested to know if such an arrangement was ever acceptable to the manufacturers.

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