Should I replace electric heater with a/c unit in bedroom?

[JohnW2]

Those are the ratings from the installation manual. I haven't measured the efficiency - to do that I'd need an accurate value for the rate of heat loss from the room per degree temp difference inside to out, which I don't have. However, even if I only want to heat that one room (which at this time of year is the case), if I use the central heating I have heat loss from all the piping in the house even if all the rads except those in the living room are turned off. The pipes in the first floor are not insulated, so I am heating the floorspace and thus, to some extent, the other rooms too.

I wouldn't expect you to experience much heat loss from the pipes through which there was no flow. In my house, most of that issue would not arise, since zone valves close to the boiler isolate pipes in parts of the house not being heated. Like you, I have been heating just my living room in some recent evenings, and that has not involved hardly any pipework other than that from boiler to living room getting hot. How efficient a boiler is when only heating one room, I'm not so sure.

I guess one way I could do a comparison is to measure the gas usage for one evening, and then compare it to the electricity usage (I have plug-in meter and the aircon runs on a 13A socket) on another evening with similar outside temperature and wind conditions.

That would be interesting. If you ever do it, do tell us the answer!

Kind Regards, John

 

[davelx]

I wouldn't expect you to experience much heat loss from the pipes through which there was no flow.

I think there is a bypass valve at the far end of the upstairs pipe run under the floor, so there is always some flow, though I don't know how far open it is.

That would be interesting. If you ever do it, do tell us the answer!

Kind Regards, John

If I do, I will!

 

[JohnW2]

I wouldn't expect you to experience much heat loss from the pipes through which there was no flow.

I think there is a bypass valve at the far end of the upstairs pipe run under the floor, so there is always some flow, though I don't know how far open it is.

Fair enough but, even in the presence of such a bypass valve, there wouldn't be any flow if, like my arrangement, the flow pipes to upper floors were isolated (by zone valves) when heating up there was not needed

Kind Regards, John

 

[davelx]

I wouldn't expect you to experience much heat loss from the pipes through which there was no flow.

I think there is a bypass valve at the far end of the upstairs pipe run under the floor, so there is always some flow, though I don't know how far open it is.

Fair enough but, even in the presence of such a bypass valve, there wouldn't be any flow if, like my arrangement, the flow pipes to upper floors were isolated (by zone valves) when heating up there was not needed

Kind Regards, John

Of course - but I don't have any zones in my system (it's not a large property)

 

[JohnW2]

Of course - but I don't have any zones in my system (it's not a large property)

Fair enough, but it doesn't necessarily have to be a large property to justify investment in a motorised valve (and switch) or two - we are, after all, talking of a situation in which the ability to isolate the upstairs circuits could (per your suggestion) be of benefit, even in your 'not large' property....

....I frankly doubt that the flow through the upstairs circuit via the bypass valve (when all upstairs rads were turned off) would result in any appreciable heat loss - but it was you who suggested that as a possible issue, so I merely pointed out that it could be eliminated by a 'zone valve'

Kind Regards, John

 

[MoonMan2]

Hi guys, I really didn't expect a massive response to my original posting, but hey thanks.

I have just had an a/c inverter installed in my living room, I bought it primarily for cooling but when I realised it could heat as well, I thought I would try.

I originally used 2 x 2400W heaters to heat my living room. In one hour it would increase the temperature of the room by 10 degrees.

With the air con unit, which is around 993W, it heated the room by 10 degrees in one hour as well. This is with the outside temperature being 9 degrees. So by my calculation that means it can heat the room by the same amount for less than a quarter of the price. It wasn't cheap to install, but with savings like this, I expect it to pay itself back in approximately 5 years. The units last for around 12-15 years.

The reason why I was asking about my bedroom is I don't like to sleep in a warm room so the heating would not be on as much (or as high) as it would be in the living room, so clearly an expensive inverter a/c unit would not pay itself back in the same time frame or at all??

Yes the a/c inverter unit I am considering for bedroom is 800W'ish, which is clearly less than 1000W that the electrical heater is.

The big question is; for maintaining a temperature of just 17 degrees during the winter nights and the a/c inverter unit likely not operating on full power, am I going to get my money back soon enough to make it a worthwhile investment?

Oh and by the way just to be clear, a/c units operating in heating mode do not absorb water from the air, the air is blown over HOT pipes. Dehumidifying occurs when air is blown over COLD pipes.

 

[slup]

I've got three of the cheapest possible split air conditioning units in the world. They are 'Airforce' ones sold by B&Q and I bought them for £99 each when R22 got banned a while ago.

When run in 'heating' mode, they warm a room up in just minutes, and work well as long as the outside temperature is above about +5. Below that, they are useless.

I reckon the heat output from them is at least double the energy consumption.

I never use the bedroom one for heating though - I like my bedroom icy cold!