Interesting consumption comparison - Heating whole house, versus living room

[Harry Bloomfield]

Yesterday, the outdoor conditions were fairly temperature stable, so I thought to do a gas consumption comparison, between heating the entire house via the gas heating system and just heating the space I was actually occupying - The living room, via a gas radiant fire set to run on a continuous single burner. All I did, was move the CH thermostat, from its default position in the hall, to the living room and lit the living room fire, which fooled the stat into shutting the CH down at around 5pm. CH stat had been 'nudged up' at around 2pm.

 

[JonathanM]

Did the rest of the house get really cold?

That looks like 10p per hour for the fire. So, if you are on the capped tariff, that's 1KWh per hour. Can you show it in KWh as well?

According to my smart meter, my living flame fire uses 2KWh per hour on lowest setting. In cold weather that keeps a largeish lounge snuggly. I've no idea of the efficiency, anywhere from 40% to 60%.

 

[Harry Bloomfield]

Did the rest of the house get really cold?

It did gradually become quite cool, over several days. I was tending towards bringing the house up to temperature once per day, then back off. What I have always noticed, is that it takes me several hours after rising, before I notice the cold in the house. 11am, I am inactive, and I have yet to feel the need for any heat input. I do almost always feel the need, once it begins to go dark outside.

The graph starts, with the stat just nudged up and the CH playing temperature catchup, hence the 68p per hour.

That looks like 10p per hour for the fire. So, if you are on the capped tariff, that's 1KWh per hour. Can you show it in KWh as well?

Yes, the display can be swapped between Kwh and p per hour, but the consumption data almost always lags by 24 hours.

According to my smart meter, my living flame fire uses 2KWh per hour on lowest setting. In cold weather that keeps a largeish lounge snuggly. I've no idea of the efficiency, anywhere from 40% to 60%.

The claimed efficiency of the fire, was the first thing I checked - having raised the same discussion a few years ago, and being told using the CH was cheaper than a radiant gas fire. The manufacturer claims an efficiency of 86%, but doesn't support that with any details of the particular Kw setting.

The fire is almost continuously variable between around 700w and its maximum of 3Kw. It certainly felt cosier, in the living room, with the fire lit, and the room door shut, than with the CH running alone. There were times during the recent cold snap, when 700w was enough heat, later in the evening.

 

[robinbanks]

What's the gas fire like for moisture generation? CH should almost certainly be a drier form of heating..

 

[Harry Bloomfield]

What's the gas fire like for moisture generation? CH should almost certainly be a drier form of heating..

All the combustion gases exit via the lined chimney, so it makes no difference to the room humidity at all.

 

[robinbanks]

Ah, I thought by radiant gas fire I thought you meant a portable thing with a bottle in the back

 

[cdbe]

I recently got one of those dreadful/dreaded flueless gas fires (and accompanying big hole in lounge wall). It's 2kw and 90/100% efficient (depending on whether you consider the hole in the wall). It has just about kept our big drafty lounge warm over the cold snap @21p per hour. Rest of the house freezing as we barely had the heating on to save money - boiler is fixed 15kw and runs quite a lot when on in cold weather. I should think we've saved a few quid but at considerable discomfort - the real purpose of the fire was is to take the chill off the lounge in mild weather as my wife feels the cold, particularly in that room and constantly puts the heating on when the rest of us hardy bunch aren't that bothered.

 

[Harry Bloomfield]

I recently got one of those dreadful/dreaded flueless gas fires (and accompanying big hole in lounge wall).

How's that work, surely the hole in the wall, is the balanced flue?

 

[cdbe]

They have a clean burn and a catalyst to "remove" the combustion products - the external vent hole is to replace the air.

We don't have a chimney or suitable external wall to fit a flued fire.

 

[MNW67]

They have a clean burn and a catalyst to "remove" the combustion products - the external vent hole is to replace the air.

I thought with flueless they could be situated on an inside wall and that you don't need any sort of hole?

 

[ericmark]

I have considered heating just the rooms required, the TRV can be set to a schedule, and you can set a sequence so rooms are heated just before your going to use them.

However the main problem for me seems to be speed. Theory is sound, for £15 per room (2019 price when I bought them) you can set each room only to be heated when required.

But set wife's bedroom to 18ºC 24/7 she does not like room too hot, but allowing it to cool to 15ºC during part of the day, it was simply not re-heating on time for her to use it.

The same applies to the wall thermostat, theory great, set to 15ºC at night, and 18ºC in the morning, but in practice just takes too long to re-heat.

Last house had a Myson fan assisted radiator, I never realised how good it was, until I moved here and had not got it. It was so much faster at heating a room.

I have looked at the radiator selection charts, it says room of A x B size needs a C kW output radiator to maintain the room temperature, but that means CH running 24/7, what I want to know is no the size to maintain the room temperature but size to lift it from Eco setting at say 16ºC to comfort at say 20ºC in ½ hour.

In theory that should be easier than the size to maintain, as losses through the walls and windows will not effect it so much, but set up 4 thermometers in a room with heating on, and one can record widely different temperatures, sitting here at my PC, one shows 20.7ºC the other 18.4ºC and they are less than a meter between them.

This looks so easy showing how the heat naturally flows, but stick a fan on the radiator and it works so much better. I looked at these and thought what a good idea, so got a small fan and a thermostat which I put on radiator return pipe, so once radiator warm the fan would turn on. It turned on for about 5 minutes the radiator stone cold.

Looked at Myson, and realised the propriety type have nothing to restrict water flow, but this also means when off, hot water returned to boiler, this was OK before the condensation boiler, but with a modern boiler that return hot water will turn boiler down, OK if all rooms heating together, but selecting one room at a time, means other rooms return hot water and turn down boiler.

The fan assisted does not turn water flow on/off, but turns fan on/off or with better versions 5 speeds. This would work if radiators plumbed in series, but they are not, they are plumbed in parallel.

 

[robinbanks]

This would work if radiators plumbed in series, but they are not, they are plumbed in parallel

Note: this is may be the case for your installation but other installs may differ

 

[Harry Bloomfield]

They have a clean burn and a catalyst to "remove" the combustion products - the external vent hole is to replace the air.

A catalytic burner heater. I had one of those in a caravan I had, around 40 years ago.

 

[cdbe]

I thought with flueless they could be situated on an inside wall and that you don't need any sort of hole?

They can, the hole is a vent to refresh the air in the room, with a minimum area of 100cm. Possibly a bit OTT when the output is compared to a gas hob or cooker but those are the regs.

 

[MNW67]

They can, the hole is a vent to refresh the air in the room, with a minimum area of 100cm. Possibly a bit OTT when the output is compared to a gas hob or cooker but those are the regs.

Thanks, I didn't realise that.