Heating/water control unit

[Bodysnatcher]

Hi. I would like to replace our control unit that allows us to set the time for heating/water to switch on. The unit at the moment is a Honeywell. Can not find the item number or a picture etc on any web site so assuming they have discontinued it even though it's only about 12 months. Basically it allows two periods of time each day but water and heating are not independent, so when we have heating set, the water also is on. This is the reason i would like to change it for a model that has separate time settings for each, water and heating. Does anyone know if wiring would be identical, as changing the wiring is not my strong point but connecting up the wiring the same is not a problem!

[Dave Liquorice]

This maybe a limitation on the plumbing rather than the control unit. There is a recent/current thread about this ATM.

[Set Square]

I assume that your existing programmer has separate controls for HW and CH - enabling each to be switched to permanent ON, permanent OFF, or Timed - and that the limitation is simply that they use the same timer - so you can't have HW coming on at different times from CH?

Provided your plumbing setup is capable of supporting independent control of HW and CH ** the way round this is to replace your mechanical room stat with a programmable room stat - such as the Honeywell CM67. You can then leave CH turned on permanently on your existing programmer, and *actually* control the on/off times with the programmable stat. You can continue to use the existing timer for HW - which can now be turned on and off completely independently of the CH.

** If your system is fully pumped, and has zone valves (S-Plan) or a 3-port mid-position valve (Y-Plan) you can do the above. If you have a gravity hot water and pumped central heating system, it is a bit more difficult - but not impossible - and requires additional plumbing hardware.