Electric Radiator

[Scointer]

Sorry to ask a dumb question but this forum has been so helpful in the past.
I have had an Evohome s-plan system up and running for a few years now, over time I added zones using HR92's and recently upgraded to the wi-fi controller which now has the most recent update. One of the reasons I did this was because it mentioned control of an electric zone.
My house runs fine with just 10 rads but I have a garage converted into a office. It is separate from the house (only by a couple of feet and quite close to where the evohome controller is mounted in the house) but their is no heating in it. I was hoping to be able to fit electric radiator/s and control them from the evohome panel. Unfortunately this recent post seems to suggest that isn't really supported.

https://ensupport.getconnected.honey...trical-heating

Can any one advise if it can be done reasonably simply and what would be needed to do this. Many thanks for anyone that can help

[DBMandrake]

That information on the website is out of date, and doesn't reflect the new "electric heating zone" that was added in a recent firmware update.

So yes you can control an electric radiator from Evohome now. However two things need to be kept in mind:

1) You'll need a wall thermostat such as a DTS92 or YT87RF as the sensor for the garage zone.
2) The BDR91 is limited to at most 5 amps, which is not enough to drive anything other than a very small electric load. So if the heater is more than about 1000 watts you'd need to get another relay box to do the heavy lifting of switching the radiator (keeping in mind it will cycle on and off every 10 minutes on a TPI cycle when the room is near the set point) and then use the BDR91 to control the additional relay box at a much lower power level.

A BDR91 has isolated relay contacts (volt free) so the control input of the larger relay box doesn't necessarily have to be mains voltage controlled.

[paulockenden]

You can use an HC60NG instead of a BDR91 - that gives you 10A resistive load rather than 5A. But I guess that still might not be enough.

Most underfloor heating suppliers will sell you a relay box for around £50 (although you could easily make one for less than a tenner). Or you could be fancy and use a Solid State Relay - no clicks on nearby radios then every time the contacts spark! Just don’t buy a cheap SSR on eBay - I’ve had two of those fail.

[G4RHL]

I had thought of doing this in my conservatory. It currently has an HR92 and water filled radiator connected to the central heating. It is sort of at the end of the line and struggles to generate enough heat. Thus my thinking of replacing this with an electric radiator. I considered an Evohome connection but then realised the easiest and cheapest solution is just a normal radiator designed for a conservatory with a thermostat and time switch. A lot come with them built in. I have not done it yet but at some time need to. Strikes me as cheaper and simpler than going the Evohome route for a small scale task.

[DBMandrake]

Keep in mind that the temperature regulation of those wall mounted electric radiators with built in thermostat is pretty darn awful due to the proximity of the sensor to the very hot element.

Far worse than a locally sensing HR92 let alone a remote wall mounted sensor. The poor temperature accuracy of that kind of radiator would annoy me, as would the constant manual adjustments required to keep the room temperature comfortable in changing conditions. I should know - we have one in our office at work!

[G4RHL]

Keep in mind that the temperature regulation of those wall mounted electric radiators with built in thermostat is pretty darn awful due to the proximity of the sensor to the very hot element.

Far worse than a locally sensing HR92 let alone a remote wall mounted sensor. The poor temperature accuracy of that kind of radiator would annoy me, as would the constant manual adjustments required to keep the room temperature comfortable in changing conditions. I should know - we have one in our office at work!

Yes, but the ones I looked at have remote sensors. Far more accurate.

[mylesm]

You can use an HC60NG instead of a BDR91 - that gives you 10A resistive load rather than 5A. But I guess that still might not be enough.

Most underfloor heating suppliers will sell you a relay box for around £50 (although you could easily make one for less than a tenner). Or you could be fancy and use a Solid State Relay - no clicks on nearby radios then every time the contacts spark! Just don’t buy a cheap SSR on eBay - I’ve had two of those fail.

I have done this With an Electric Heater in A Bedroom HC60NG and a Round Stat as Temp Sensor all Done through Evohome Electric Zone, Works Perfect Using Evo means I can schedule Zone or Switch it on From Phone on way home etc

[bruce_miranda]

I would be careful driving any load directly on the relay boxes, even the 10A ones. Much better to use them to drive a contactor which then handles the load.
Also if you are making a contactor using a SSR buy a decent one and mount it on a heatsink. I use a SSR to drive my cylinder immersion as part of a self built solar diversion set up. I bought the SSR from RS, comes with a LED and a current limiting resistor inside the SSR itself.