Hi all, first post on here but have had some good tips from this forum so I thought I'd pass along my experience in fettling. I've got the Evohome Wi-Fi multi-zone controller and have a 3 bedroom detached house. We only moved in back in November and it needed a new central heating system so we got a Weismann combi-boiler to feed 7 radiators and fitted HR92s to 6 of them leaving the bathroom towel radiator as the bypass.
However, I wanted underfloor electric heating and wanted the Evohome to control it but everyone I spoke to said, "no mate, can't be done" so being an obtuse kind of bloke, I found a way of doing it.
I purchased a BDR91 & Y87RF single zone kit and an underfloor heating kit and wired it thusly:
So what you have in effect is two relays in series, both with permanent live feeds. In operation it's quite simple to set up.
Bathroom gets too hot (controller gone mental or faulty DBR91) then the heating kit thermostat cuts out. Other than that, it's pretty much on all the time and it is the BDR91 that controls the power to the heat mat and that is triggered on/off by the Y87RF installed in the bathroom.
Now I can do this despite the bathroom radiator being the by-pass one because it is in the same room so effectively it works in tandem with the heat mat and both come on if the bathroom zone calls for heat. Only the radiator comes on if the zone is set for off but another zone call for heat - this is because the bathroom is the bypass radiator. Annoying but almost everyone says you have to have one, I'm still 50/50 as to whether that is strictly speaking an actual fact.
If you don't have a radiator in the bathroom then it won't work like mine does and there may be some quirks such as the boiler firing when the heat is called for and heating whatever room you have the bypass radiator in - you can figure out if that will be an issue on your own system.
Comments? Questions?
Happy to help.
However, I wanted underfloor electric heating and wanted the Evohome to control it but everyone I spoke to said, "no mate, can't be done" so being an obtuse kind of bloke, I found a way of doing it.
I purchased a BDR91 & Y87RF single zone kit and an underfloor heating kit and wired it thusly:
- Mains feed from consumer unit to a switched fused spur.
- Separate L&N feeds from the spur to both the BDR91 mains feed in and the Thermostat mains feed in. Terminated at both location - no onward feed.
- Heat Load (power to the heat mat) neutral from the thermostat to the heat mat, live to port A of the BDR91
- Live from port B on the BDR91 to the heat mat
- Heat mat kit thermostat sensor to the thermostat sensor connections - this is your overheat protection cut out and first line of defence
So what you have in effect is two relays in series, both with permanent live feeds. In operation it's quite simple to set up.
- Heat mat kit thermostat set for 80-90% of max (or as hot as you'll ever have it)
- Heat mat kit thermostat controls the power going through the BDR91 relay as on/off
- Y87RF bound to the BDR91 controls the on/off of the actual mat power based on the local temperature of the Y87RF
- Bind the Y87RF to the Wi-Fi controller and create a zone called Bathroom
Bathroom gets too hot (controller gone mental or faulty DBR91) then the heating kit thermostat cuts out. Other than that, it's pretty much on all the time and it is the BDR91 that controls the power to the heat mat and that is triggered on/off by the Y87RF installed in the bathroom.
Now I can do this despite the bathroom radiator being the by-pass one because it is in the same room so effectively it works in tandem with the heat mat and both come on if the bathroom zone calls for heat. Only the radiator comes on if the zone is set for off but another zone call for heat - this is because the bathroom is the bypass radiator. Annoying but almost everyone says you have to have one, I'm still 50/50 as to whether that is strictly speaking an actual fact.
If you don't have a radiator in the bathroom then it won't work like mine does and there may be some quirks such as the boiler firing when the heat is called for and heating whatever room you have the bypass radiator in - you can figure out if that will be an issue on your own system.
Comments? Questions?
Happy to help.
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