gas fire, how much gas?

qwertyjjj

Any ideas how much a small gas fire in a living room uses?

penrhyn

Typical figures for an open type gas fire:

• Energy input (kW) = 6.2
• Max heat output (kW) = 3.1
• Min heat output (kW) = 1.75
• Efficiency (net) = 50%

If you know the make and model then you could Google it.

qwertyjjj

penrhyn wrote: »

Typical figures for an open type gas fire:

• Energy input (kW) = 6.2
• Max heat output (kW) = 3.1
• Min heat output (kW) = 1.75
• Efficiency (net) = 50%

If you know the make and model then you could Google it.

So approximating, that's 6.2 Kw per hour?
4p per kwH
So, about 25p an hour?

How does that compare to central heating or running the boiler?
And lastly ( ), if you turn off say 5 radiators in the house during the day, but leave 5 on, does that reduce the gas consumption from the boiler by 50% or does the boiler use the same amount of gas regardless as it's just heating water in the pipes (no thermostat).

dave_ave

Yes, 6.2kW used for an hour would be 6.2kWh, and yes around 25p an hour would be correct.

If you shut off 50% of the radiators, the hot water returning to the boiler should be hotter than if all were on and so the boiler is not having to reheat the recirculated water so much, but I wouldn't have thought you'd get a 50% reduction, perhaps 15-25%?

Combi boilers are around the 28kW mark I think, so cost around £1 an hour if run continuously, but they don't as the boiler cuts in and out to reheat the recirculated water.

qwertyjjj

dave_ave wrote: »

Yes, 6.2kW used for an hour would be 6.2kWh, and yes around 25p an hour would be correct.

If you shut off 50% of the radiators, the hot water returning to the boiler should be hotter than if all were on and so the boiler is not having to reheat the recirculated water so much, but I wouldn't have thought you'd get a 50% reduction, perhaps 15-25%?

Combi boilers are around the 28kW mark I think, so cost around £1 an hour if run continuously, but they don't as the boiler cuts in and out to reheat the recirculated water.

According to the manual, a BAXI 100 HE uses about
9kW and 30kW variable.
So, during the daytime if someone is in the lounge, then it would make sense just to use the fireplace and leave the boiler off?

HappyMJ

qwertyjjj wrote: »

According to the manual, a BAXI 100 HE uses about
9kW and 30kW variable.
So, during the daytime if someone is in the lounge, then it would make sense just to use the fireplace and leave the boiler off?

A Baxi is 90% efficient so you would get about 8kw of heat on tht minimum setting. That's enough for your lounge, kitchen, hallway and a little for the bathroom and bedrooms. So for an extra 9p an hour you are getting an extra 5kw of heat output. You might not need it on as long as the gas fire would be on so you would save more even though it appears to cost more.

qwertyjjj

HappyMJ wrote: »

A Baxi is 90% efficient so you would get about 8kw of heat on tht minimum setting. That's enough for your lounge, kitchen, hallway and a little for the bathroom and bedrooms. So for an extra 9p an hour you are getting an extra 5kw of heat output. You might not need it on as long as the gas fire would be on so you would save more even though it appears to cost more.

That was my point though...during the daytime (in winter of course ), if you are mainly downstairs in the lounge, is there really any need to have the boiler on when the gas fire could do the same heat for less...or have I got my calcs wrong somewhere?

Lgas

Don't forget that fires are inefficient; most of the heat goes up the chimney, and radiators retain heat for a while so you still get latent heat after turning the boiler off.

HappyMJ

qwertyjjj wrote: »

That was my point though...during the daytime (in winter of course ), if you are mainly downstairs in the lounge, is there really any need to have the boiler on when the gas fire could do the same heat for less...or have I got my calcs wrong somewhere?

Yes calcs are wrong. Gas fire 3kw of heat output for 24p. (6kw*4p)....The gas boiler 8kw of heat output on minimum setting for 36p (9kw*4p). You could if you turned radiators down in unused rooms only require the gas boiler to be on half the time instead of all the time costing you only 18p per hour.

In the middle of winter on a freezing cold day the gas fire won't be able to put out enough heat to keep your downstairs warm enough. Apart from 50% of the heat just going up the chimney a lot of heat will leak into the kitchen and hallway and any other adjoining room including a bit leaking into the bedrooms through the ceiling. Assuming you don't have a bungalow.

qwertyjjj

HappyMJ wrote: »

Yes calcs are wrong. Gas fire 3kw of heat output for 24p. (6kw*4p)....The gas boiler 8kw of heat output on minimum setting for 36p (9kw*4p). You could if you turned radiators down in unused rooms only require the gas boiler to be on half the time instead of all the time costing you only 18p per hour.

In the middle of winter on a freezing cold day the gas fire won't be able to put out enough heat to keep your downstairs warm enough. Apart from 50% of the heat just going up the chimney a lot of heat will leak into the kitchen and hallway and any other adjoining room including a bit leaking into the bedrooms through the ceiling. Assuming you don't have a bungalow.

But the boiler won;t be 50% improved if I turn half the radiators off, so that 18p is more like 24p anyway. Also, it won;t be on minimum setting as it regulates itself so won;t it be more like 15kW+?

HappyMJ

qwertyjjj wrote: »

But the boiler won;t be 50% improved if I turn half the radiators off, so that 18p is more like 24p anyway. Also, it won;t be on minimum setting as it regulates itself so won;t it be more like 15kW+?

The 15kw or even the maximum setting of 30kw is only consumed whilst the boiler is running. If you listen to the boiler it shuts off till the water cycling around the system cools down enough then it starts up again. I'd say the 30kw is only used for about 30 minutes whilst the house comes up to temperature from cold then it regulates itself down to a fair and reasonable usage till you turn it off.