Can anyone help/advise me please!

[boxermike7]

Hello!

I have moved into this house of mine only 3 months ago to find the central heating / hot water controller is not very flexible.
I can run the hot water, or the hot water plus c/heating, but I am unable to run the heating on its own.

I have a brand new controller by Sanvic which gives me these options, and I had this controller on my previous sytem in the other house, it was brilliant.
Can I just take off the old controller and wire up the Sunvic? (is it easy?are there many wires?)

I do have a Sundial Y plan diverter valve on the system.
The old controller is a Switchmaster 400

UPDATE! I am advised that the diverter valve has no midway position, and so will not give me just central heating, so I have to get a three way valve. Thought the diverter was one, as the Gas Board engineer told me it was ok for what I wanted to do.

Many thanks

 

[stem]

Any restriction on the lone central heating function is dependant on the design of the plumbing.

As you have a 'Y' motorised valve, if this is installed correctly this allows separate control of the hot water and heating, so on face value, the answer will be yes.

Unfortunately the wiring issue is not so cut and dried. Although the basic design of the wiring is standard, where connections are made, the colours of the wires used, and the runs the cables take, are down to the preference of the person wiring it up. (For example I have seen earth wires used as a live conductor )

For a definitive answer, you would need to give details of the wires connected to the existing Switchmaster 400 terminals (A photo of the connections would be good). Even after that more clarification maybe needed. You may also need to install an additional wire between the programmer and motorised valve / cylinder thermostat to give a "hot water not required" signal.

I'm not sure what you think you will achieve by making this change, if your 'Y' motorised valve is connected to a cylinder thermostat as it should be, then when your hot water cylinder is heated up (& this only takes minutes) then the hot water heating facility is shut down by the cylinder thermostat anyway, and assuming your cylinder is well insulated, it will sit like that for hours, possibly all day. Unless you use up the hot water, then it will heat it up again. But don't you want to do that anyway?

Don't be looking for energy savings, any savings made will be so small you won't even notice them, unless you intend never to heat any hot water at all of course.

If you don't have a cylinder thermostat, then you will make some savings, but if that was the case you wouldn't have a 'Y' diverter.

 

[stem]

I do have a Sundial Y plan diverter......

UPDATE! I am advised that the diverter valve has no midway position, and so will not give me just central heating.

No...Midway position of three port (Y diverter) valve gives hot water and central heating. The three positions are explained below.

1) When the valve is at rest, a spring pulls the valve across to one side, blocking off the central heating port and giving hot water only.

2) When the valve is in the central position it blocks neither of the outlets and both the heating and hot water are on.

3) When the valve winds fully across to the end furthest from where it started, then the hot water port is blocked off and only the central heating is on.

It's possible you may have some sort of alternative diverter that is an integral part of the boiler, that doesn't have a central position. In that case you would have either hot water only in one position and central heating only in the other position. It's not correct to call it a "Sundial Y Plan" though.