Honeywell CM927C with ST9400C and Baxi Solo?...

[M2RTY]

I am going to replace our ancient Honeywell dial thermostat with a wireless Honeywell CM927C one. The old one looks naff in our redecorated house, and is located in the coldest part of the house (under the stairs!)

Details of the set up are as follows:

• Baxi Solo Boiler WM 50/4 PF
• Hot water tank/diverter valve/pump in loft
• Cylinder thermostat on side of hot water tank
• Honeywell electronic timer ST9400C located next to boiler
• Honeywell dial room thermostat located next to boiler
• Y plan configuration

I see 2 wires from the thermostat that go into the 10 way block in the loft, but I have not removed it from the wall to double-check. There are 4 terminals on it in total and I am sure 2 are empty.

Is it just a case of connecting these 2 up to the new wireless receiver, connecting it to a power supply, and then setting the ST9400C to “Constant” for the heating so that the thermostat does all the hard work (times, temp, controlling boiler etc)?

Is the power going through the wireless receiver OK or does it need some sort of relay? I cant see anything on the user manual, I might try it with a multi meter unless someone knows?

The ST9400C was put in last week to replace an old ST699 – I only need this for the hot water now I take it?

Thanks