Wiring an RF receiver to infrared heaters

[ericmark]

Nothing like a pot belly stove in corner of workshop. But for years we used bar electric fires, hard now to remember how bad they were, however this was before double glazing and K glass.

 

[mattnotfat]

taking that and multiplying by 0.33 for six hours a day gives a consumption about 1/4 Kwh compared to gas, making the cost about the same.

If, instead of adding 100kwh of heat to your house, you add only 25kWh, you are adding one quarter the amount of heat, so it will of course be colder.

To be clear about how I arrived at that "1/4 kwh compared to gas" figure.

Last year my gas consumption was 8900kwh, of which I reckon 8000kwh was CH. The total wattage of radiators in this house is about 6kwh. 6kwh x 6 hours a day for 6 months of the year x 33% of the time is 2162kwh. Close to a quarter of the consumption. 33% is probably too optimistic though, so say 50% of the time making 3000kwh. Take off the cost of an annual boiler service and standing charge for gas at £150 a year, and the fact that I'll be more inclined to switch a room thermostat to 'off' when I know I'm out of the room for the next couple of hours than ever I would be to reach down and turn off a radiator valve - and the overall cost is potentially about the same.

 

[JohnD]

the overall cost is potentially about the same.

For much less heat.

But I don't see the purchase price and write-off of the potential electric heating in your calculation.

If you think you used 8000kWh of gas energy on heating, why do you estimate heating energy demand as 2162kWh?

 

[ericmark]

I do reach down and turn radiators on, the electronic TRV head has two buttons and a dial, it has a schedule set for when I would normally used the room, and also the comfort and eco is set, so if I use a room early press one button right hand side of dial and it moves from eco to comfort, the head cost £15, try finding a programmable thermostat for that price?

The problem with any house is internal doors and walls are not well insulated, having a room with no heating does not allow it to cool that much, as it is heated from other rooms, and also you don't want cold drafts every time you leave a door open, in the main electric heating is not central heating, there is no central boiler distributing heat to different areas of the house, go into any house with storage radiators and you realise the problems with electric heating.

The total wattage of radiators in this house is about 6kwh

You seem to have power and energy mixed up, power is measured in watts or kilowatts, energy is measured in Joules, kilojoules, watt/hour or kilowatt/hour there are 360 Joules in a watt/hour. Why we use watt/hour not a clue, very confusing as there is not time involved watt is measured in energy per second and as the name implies watt/hour is using the hour which has 360 seconds in it so that is why there are 360 Joules on a watt/hour.

Most radiators are under 3 kW so do end up larger, but most gas boilers will modulate to around 10 kW so they are in a way too big to run just a couple of radiators without cycling, and every time the boiler turns off heat is lost through the flue as it cools, to reduce that loss we want the boiler to run cool, but if it runs cool then there is a problem heating the rooms, when many are turned off, so it becomes important which room is selected as the room with the wall thermostat, and it is better if that thermostat is a modulating type. So the whole control of central heating can become complex, and I will admit in most houses it is near enough rather than perfect.

To have a room with say 10 infrared heaters with a system which selects how many run to control the feel of the room so it is comfortable may I agree used less energy, however one the energy costs more, and two you need to develop a system to give that control, only way I can see to do that is rather a complex computerised system which uses outside and inside temperatures to control the amount of heaters, and I have seen the problems involved with stage heating with fan assisted radiators, if you have 5 stages of heating then you need 5 trigger temperatures and most thermostats have 5°C increments so if slowest speed is 20.5°C then fastest speed is 18°C which will work to heat the room fast, but not to maintain the room.

I am sure there is a way to use a thermostat to gradually increase or decrease the number of heaters switched on, but the cost per room will be huge compared with the simple programmable TRV head.

 

[mattnotfat]

For much less heat.

But I don't see the purchase price and write-off of the potential electric heating in your calculation.

If you think you used 8000kWh of gas energy on heating, why do you estimate heating energy demand as 2162kWh?

Right, so maybe this is where I'm calculating it wrong? This is how I've got these figures.

The radiator in the back bedroom is a one fin 1m x 0.5m. The closest I can find is this 1m x 0.6m radiator, https://www.directheatingsupplies.co.uk/stelrad-elite-radiator-p-600-x-1000 rated at 1400w on the specification tab, so about 1100-1200w for my radiator. With that switched off I've got 1000w of IR heating, which I think is slightly under what's needed and it's drawing power about half of the time it's on. So I'm calculating the IR heaters required for the whole house on a like for like swap of wattage, about 6000w.

I had read if IR heaters are properly spec'd expect them to be 'on' 1/3 of the time, so 6000w x 6 hours a day x 182 days x 0.33 = 2162kwh. But 1/3 is probably optimistic, so x 0.5 to get 3276kwh. Even so it's not 8000kwh.

What's 'write-off'? I've not included purchase price because I'm working out what to do when my 25 year old Worcester boiler finally dies. The cost of installing a replacement boiler or a house full of panels is about the same. The last time I had the boiler serviced the bloke said it's almost running like new, the problem will be getting the parts, and a modern condensing boiler would only be 10-15% more efficient. So I suppose I could take 10-15% off that 8000kwh.

 

[mattnotfat]

I do reach down and turn radiators on, the electronic TRV head View attachment 182953 has two buttons and a dial, it has a schedule set for when I would normally used the room, and also the comfort and eco is set, so if I use a room early press one button right hand side of dial and it moves from eco to comfort, the head cost £15, try finding a programmable thermostat for that price?

Ok, thanks. I didn't know about TRV heads. Generally I've not considered programming heating, I only switch my CH on and off manually. When I had it on the timer one winter my bills went up by about a third. For a Victorian 3 bed terrace my total gas consumption was about 9000kwh last year, which is considered on the low side.

 

[ericmark]

You can split programmable TRV heads into three groups, very cheap start around £10 like the eQ-3 and terrier i30, next wifi enabled allowing geofencing, and finally linked to wall thermostat.

Geofencing and occupancy detection I have not found that good, for a TRV to adjust a room temperature takes around 2 hours, any faster and likely they will over shoot, and I do not live 2 hours from work, I am not impressed with the Energenie TRV heads at around £45 each because you can't adjust manually, I don't walk around the house with a phone in my pocket, I want the option to manually set temperature up/down as well as with phone, the bluetooth on the eQ-3 is only used to make it easier to set up, only reason you NEED bluetooth is if two radiators in one room and you want to pair them so both work together, but I only paid £15 for bluetooth version.

So setting slots

I can ensure at those times the TRV returns to a low setting after I would normally use the room, also it has open window detection, so if I come home and leave the back door open while unloading the car, the TRV closes down for time set, in my case ½ hour, in many ways the cheap eQ-3 actually work better than the expensive Energenie, so I have 4 Energenie and five eQ-3 if a room is not used, it's not heated.

Clearly with the cheap versions they will not fire up the boiler, if the boiler is not running the room will not heat. The Hive TRV will tell the Hive wall thermostat to fire up the boiler, so in theory far better, as to if actually better depends on design of house, I am using Nest Gen 3, but since not used Hive, EvoHome or Tado can't say how it compares, but reading averts I like Hive as it allows you to slowly add to the system, you don't need a huge lay out to start with.