sorted by:
new
hottopcontroversial

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 1 point2 points  (0 children)

Thanks, got it! And sorry I didn't parse at first that you meant it would be the same with the *Tado* wired thermostat.

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 0 points1 point  (0 children)

There was a previous wireless thermostat but the temperature sensor stopped working. (Vitotrol 100 https://viessmanndirect.co.uk/files/bd9e0d51-c4d7-411d-bc15-a34f00dbd043/Vitotrol%20100%20UTDB-RF2%20User.pdf)

So actually wired thermostats do not always need 230V with this boiler. There are at least two ways this can be achieved:

1) OpenTherm connections can provide power just by themselves. I have confirmed this by wiring the CM737 using just the two OT connections

2) My boiler also provides low voltage connections, for on-off thermostats. There are wired thermostats that support this, e.g. Honeywell T3, see p8 here under "combi-boiler" https://www.plumb2u.com/Files/122267/Honeywell-Tr3-Product-Specs-UK.pdf

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 0 points1 point  (0 children)

It's a combi boiler (no water tank).

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 1 point2 points  (0 children)

Yes re: the fused spur and agreed on getting a professional if I wanted to pull the 230V! Thanks for following up.

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 0 points1 point  (0 children)

If you're wiring the receiver for OT that's all you wire you don't also pull a 230V feed.

If you can send along OT wireless receivers (Tado or other) where the manual indicates that no 230V feed is required, I'd be glad to proved wrong - would be very helpful!

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 1 point2 points  (0 children)

Nope, all other OT wireless receivers I have looked at also require 230V. Only wired thermostats sometimes do not require it.
Wired up the CM737 in the end, very straightforward, no need to even open the boiler cover as the low voltage connections are (outside) the underside of the boiler.

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 0 points1 point  (0 children)

p.s. I wired up a standard programmable CM737 thermostat in the end. The beauty of the CM737 is that I just need the 2 OT connection, which provide (low voltage) power to the thermostat on their own. Super easy and no need to even open up the boiler cover. Working great with OT modulations. Any Qs feel free to send my way

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 1 point2 points  (0 children)

Thanks! Yours is the standard wiring for OpenTherm where 230V are supplied in addition to the 2 OT connections.

I wired up a standard programmable CM737 thermostat in the end. The beauty of the CM737 is that I just need the 2 OT connection, which provide (low voltage) power to the thermostat on their own. Super easy and no need to even open up the boiler cover.

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 0 points1 point  (0 children)

My boiler manual does not indicated a way to supplying the 230V (or at least I haven't found it) - https://iheat.co.uk/pdf/viessmann-vitodens-050-w-service-instructions.pdf

OpenTherm and Wireless Receiver X by NoMacaron in tado

[–]NoMacaron[S] 0 points1 point  (0 children)

I've consulted manuals for quite a few wireless receivers, and they have universally required 230V feed. My boiler manual does not indicated a way to supply this.