EvoHome with Underfloor Electric Heating

[sergeantash]

I'm getting a small utility room fitted with underfloor heating and have chosen the following set to install:

http://www.theunderfloorheatingstor...warm-electric-underfloor-heating-150w-mat-kit

I've got the HoneyWell EvoHome system and want the underfloor heating to be controlled and monitored using that system, here's the applicable relay and thermostat:

https://theevohomeshop.co.uk/honeyw...tat-y87rf2024.html?search_query=y87&results=4

However, the electric flooring provider have stated that this relay isn't sufficient for this kind of flooring due to the ampage?

Is this right, and would I need an additional box between the two?

 

[JohnW2]

I'm getting a small utility room fitted with underfloor heating and have chosen the following set to install: ....

Are you thinking of installing jsut one of those 150W mat kits?

I've got the HoneyWell EvoHome system and want the underfloor heating to be controlled and monitored using that system, here's the applicable relay and thermostat: .... However, the electric flooring provider have stated that this relay isn't sufficient for this kind of flooring due to the ampage? Is this right, and would I need an additional box between the two?

Unless I'm missing it, the page you've linked to does not seem to give any indication of the current switching capabilities of the EvoHOme relay, so we can't really answer that question - although I'd be surprised if it were not capable of switching 150W (if that's all you plan to install).

However, do you realise that a 150W underfloor mat will have very little effect on the temperature of (the air in) the room, such that the thermostat/relay you are thinking of using would probably not achieve anything particularly useful?

Kind Regards, John

 

[big-all]

i am assuming its 150 per square metre

 

[JohnW2]

i am assuming its 150 per square metre

Indeed, that's what it is, and available from 1m² to 24m² kits. We therefore need to know exactly how what the OP is thinking of installing.

Mind you, whilst that might have a bearing on the suitability of the relay for switching it, I still rather doubt that such a mat in a 'small utility room' would have enough impact on the room temperature for a room stat controlling it to be relevant or needed!

Kind Regards, John

 

[big-all]

i fully agree underfloor heating is a very inefficient way to heat a house if you have gas central heating and rely on perhaps running it say twice a day

 

[JohnW2]

i fully agree underfloor heating is a very inefficient way to heat a house if you have gas central heating and rely on perhaps running it say twice a day

Indeed. Apart from the issue of running cost, I think a major problem is that it will usually take hours (if not 'for ever') to have any appreciable impact on room temperature, since the floor has to remain cool enough to stand on (with bare feet, in the case of a bathroom). Imagine how long it would take for wet central heating to heat a room if one reduced the radiator temperature to a temp that one could stand on with bare feet!

Kind Regards, John

 

[big-all]

yes people read the blurb with words like "100% efficient" or "clean and safe"
or other positive spins that fully ignore the downside off around 3 times the price to heat the same area as compared to gas

 

[JohnW2]

yes people read the blurb with words like "100% efficient" or "clean and safe" or other positive spins that fully ignore the downside off around 3 times the price to heat the same area as compared to gas

Indeed - but, as I said, quite apart from issues of running costs there are plenty of other downsides.

The electricity/(natural) gas running cost comparison does not, of course, apply equally to everyone. For me, the comparison is electricity vs. LPG (the latter currently around 9p per kWh at standard rates) and, although electricity is still cheaper more expensive, the difference is much smaller than for those who have natural gas.

Kind Regards, John
Edit: Freudian slip of typing fingers corrected!

 

[ban-all-sheds]

The basic question to be asked of the OP:

sergeantash - what are you hoping to achieve with the heating?

If it is to warm the room, you could well be disappointed, and if it's to take the chill off a tiled floor then quite honestly wearing shoes is a better solution....

 

[winston1]

Indeed - but, as I said, quite apart from issues of running costs there are plenty of other downsides.

The electricity/(natural) gas running cost comparison does not, of course, apply equally to everyone. For me, the comparison is electricity vs. LPG (the latter currently around 9p per kWh at standard rates) and, although electricity is still cheaper, the difference is much smaller than for those who have natural gas.

Kind Regards, John

Read that again. "although electricity is still cheaper"

 

[JohnW2]

Read that again. "although electricity is still cheaper"

Whoops - corrected!

In fact, with my E7 and LPG, gas is cheaper than electricity only during the daytime; during the 7 cheap-rate E7 hours, my electricity is appreciably cheaper than gas. That's why I do all my water heating with E7 electricity, and why I tend to turn off the gas CH and use fan heaters if I'm up and around during cheap-rate hours.

Kind Regards, John

 

[ericmark]

I have fitted electric underfloor heating, main job is to dry the wet room floor so mother would not slip on the wet floor. As already stated it has very little effect on room temperature. At a maximum temperature of 29°C for a solid floor it is never going to heat a room, unless the temperature is never altered, and heat recovery units plus very good insulation is used.

Also because there is a limit of 29°C the temperature control has two sensors, one for room, and one for the floor temperature. The link shows a relay box with a 5 amp resistive and 3 amp inductive load, so should work with up to 1000 watt however the T87RF2033 Wireless Thermostat only measures air temperature so is unsuitable for the application.

I use a cheap manual thermostat for my late mothers wet room, it is there to ensure I can walk on the floor with bare feet, the room is heated by a towel rail which has no independent thermostat, i.e. no TRV. This is not ideal but door is normally left open so one can see if vacant or not so temperature is controlled by the hall TRV and wall thermostat, the under floor thermostat is set high, and the heating is only used after a shower to dry floor.

Since it is unlikely you can heat the room with just under floor heating, I would not even attempt to connect it to EvoHome, just have the primary radiator connected to EvoHome and have the secondary under floor heating on an independent under floor thermostat mainly to stop it getting too hot i.e. less than 29°C if a solid floor, other floors are less than that.

You can use EvoHome with under floor heating, when using water the water temperature is controlled to the 29°C so there is no need for a sensor in the floor, also I think reychem do an electric version where the resistance of the chemical alters with temperature so the mat is self regulating, I have used raychem as frost protection but not for under floor heating. It needed special termination tools, so suspect not a DIY job. The kit you link to has a thermostat with it able to switch 16A and it states "Can be either an air only / floor only / Air & Floor 7 day programmable (each day can be set different)" you could set this to floor only mode and use EvoHome as well, there are IFTTT relays able to switch 3 kW and I think EvoHome does support IFTTT however not having to use it, I have not looked into what will work with EvoHome.

 

[ericmark]

Found RayChem as said similar to stuff used to stop pipes freezing, the cable has two wires with a chemical compound between them which increases in resistance as it heats up. It has a maximum of 45°C which is over the 29°C permitted so still the "The GREENLEAF thermostat is an “in wall” mounted programmable thermostat for electrical floor heating. The thermostat can work in floor sensing mode, room sensing mode and room sensing mode with floor temperature limiter." so it still monitors floor as well as air temperature, however unlike the cheaper versions, if furniture is put on the mat it will not cause damage as limited to 45°C. I know with my late mothers wet room it never gets that warm, so even without the sensor in the floor it would not over heat, but once laid it is hard to fit a pocket after to take the sensor, called a pocket it is a tube which the sensor is threaded down so if it fails it can be renewed without lifting floor, do insure no sharp corners on the pocket, rather an expensive thing if it fails and jams in the pocket.