Honeywell T45 to Drayton wiser 2 channel

[MrBishop]

Hello,

My Honeywell T45 has stopped working and so I thought I'd replace it with a smart device. I have bought a Drayton Wiser unit and need to wire it in. Can anyone advise on how the wiring should go please?!
Additional info: I have a conventional Baxi boiler with a pressurised water tank. 2 valve (HW and CH) and there is a pump (which i replaced recently when the previous one died)
The house doesn't have a thermostat and I won't want to add one other than the TRV units.

I am happy to rewire the unit and install the new one, but just can't make head nor tail of the diagrams I have seen.

20210915_164910

• MrBishop
• 15 Sep 2021

Honeywell T45

 

[oldbutnotdead]

Which Wiser did you buy- the WT724R?
One irritant with the Wiser is that the common contact on both HW and CH is tied to 240v rather than being volt free. Do you have a multimeter- if so, check on your existing backplate that there is 240v between pin 8 and N and also between pin 5 and N.
Provided there is, it's a simple swap.
L goes to L on the Wiser.
N goes to N.
8 and 5 are redundant. Mark and make safe (terminal block) or remove if they're links to L.
6 (Honeywell) goes to 3 (wiser)
3 (Honeywell) goes to 4 (wiser)
You'll need to bridge out and remove any existing room thermostat (presumably you're using the room stat that comes with the hub) or just set the old one to 30 degrees.
Cylinder stat will still function.
Done.

 

[CBW]

Which Wiser did you buy- the WT724R?
One irritant with the Wiser is that the common contact on both HW and CH is tied to 240v rather than being volt free. Do you have a multimeter- if so, check on your existing backplate that there is 240v between pin 8 and N and also between pin 5 and N.
Provided there is, it's a simple swap.
L goes to L on the Wiser.
N goes to N.
8 and 5 are redundant. Mark and make safe (terminal block) or remove if they're links to L.
6 (Honeywell) goes to 3 (wiser)
3 (Honeywell) goes to 4 (wiser)
You'll need to bridge out and remove any existing room thermostat (presumably you're using the room stat that comes with the hub) or just set the old one to 30 degrees.
Cylinder stat will still function.
Done.

The Honeywell states on the white sticker, that a supply of 220-240ac is required, I’m guessing it won’t work without. Also OP states no existing thermostat? Although, I think the Wiser will have one built in.

 

[oldbutnotdead]

The Honeywell states on the white sticker, that a supply of 220-240ac is required, I’m guessing it won’t work without. Also OP states no existing thermostat? Although, I think the Wiser will have one built in.

Yes the controller runs on 240v but the control relays are volt free....much more flexible but a potential beartrap when swapping out for the Wiser

 

[MrBishop]

Which Wiser did you buy- the WT724R?
One irritant with the Wiser is that the common contact on both HW and CH is tied to 240v rather than being volt free. Do you have a multimeter- if so, check on your existing backplate that there is 240v between pin 8 and N and also between pin 5 and N.
Provided there is, it's a simple swap.
L goes to L on the Wiser.
N goes to N.
8 and 5 are redundant. Mark and make safe (terminal block) or remove if they're links to L.
6 (Honeywell) goes to 3 (wiser)
3 (Honeywell) goes to 4 (wiser)
You'll need to bridge out and remove any existing room thermostat (presumably you're using the room stat that comes with the hub) or just set the old one to 30 degrees.
Cylinder stat will still function.
Done.

So I've finally built up courage to have a go at this after much procrastination...

My multi meter shows 8 and N as being 240v but 5 and N being zero.

I knew it wouldn't be straightforward!

 

[CBW]

Did the heating work? If so, then could just be wired differently?

 

[MrBishop]

Yes. To clarify I've only checked the volts as suggested - on the basis if that info was correct for mine then I'd have a go. It wasn't so the old unit is still in place and I'm back to pondering...

 

[CBW]

You won’t know unless you swap it though

 

[MrBishop]

So I've installed it and thermostat etc.

Now.... when I tell it to turn on heating you can hear it click etc and it's as if boiler wants to fire up but then the pump etc don't kick in.

Any ideas?

The Old honeywell has a link wire from live to heating com and hot water com.

I followed the instructions above and all seemed perfect. Just not getting the pump etc firing

 

[CBW]

Does the hot water work?

 

[MrBishop]

It works!!! Oh wow. I've done a thing!!

Thank you @oldbutnotdead for the initial instructions and also to you @CBW for your continued support today. Greatly appreciated

Thank you!

(Now I just need to remortgage to buy all the extra trv thermostats to save a fortune on my energy )

 

[oldbutnotdead]

Excellent. Yeah the TRV heads aren't cheap, I've been buying them when I see offers on (Amazon had a good one over Easter, saved about £15/head)
Things to watch- does your boiler have an Opentherm control input- if yes then the Wiser you have can control the boiler more subtely than turning it on and off. If your boiler doesn't modulate you may find it cycling on and off it only 1 or 2 rads are calling for heat.
The WiFi TRVs are a bit of an all or nothing- once you start scheduling individual rads to call for heat on their own timetable, any non-WiFi rad will also get heat (until their manual TRV reaches setpoint).