Hi, I've just swapped out a H37XL for a H3747, I have two heating zones + water. I used the existing backplate (photo enclosed) and bypassed the two Honeywell wired thermostats by joining live and switched live together (terminals 1 & 3 - photos enclosed). The problem is that the boiler does not fire up when I try to switch on either the water or heating zones.
I see in the H3747 manual that “The receiver has voltage free contacts. A link between terminals L, 2 & 4 is required for mains voltage applications.” (photos enclosed) Is this something I need to do?
As far as I can tell the old H37XL is not voltage free meaning my system must require mains voltage and hence the above connection?
Any help appreciated!
I see in the H3747 manual that “The receiver has voltage free contacts. A link between terminals L, 2 & 4 is required for mains voltage applications.” (photos enclosed) Is this something I need to do?
As far as I can tell the old H37XL is not voltage free meaning my system must require mains voltage and hence the above connection?
Any help appreciated!

