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CaptCosslett View Drop Down
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Joined: 20 Feb 2009
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Points: 1185 		Post Options Post Options   Thanks (0) Thanks(0)   Quote CaptCosslett Quote  Post ReplyReply Direct Link To This Post Posted: 07 Feb 2010 at 6:46pm
I thought you would say that. But how have you worked out the difference is actually significant enough to produce any difference in the output of the central heating (assuming it's thermostatically controlled)?
 
Come on Odai, you give us the answer.
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Odai View Drop Down
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Points: 3731 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Odai Quote  Post ReplyReply Direct Link To This Post Posted: 07 Feb 2010 at 8:18pm

I don't know the answer, that's why I asked how Martin worked it out....
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MartinW View Drop Down
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Points: 26722 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MartinW Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2010 at 9:48am
I'd have thought the amount of heat produced by an old style bulb is too small to be picked up by the CH system, creating an automatic increase in output. 
 
No, an automatic ''decrease'' in heating output.
 
I'm no expert but...
 
Central heating thermostats aren't exactly the most sensitive devices no, but they don't have to be, they respond to the ''total'' temperature within the house [or room where they are located] from all sources, the radiators, your cats flatulence, light bulbs, everything that contributes to the heat within the dwelling. They may not be sensitive enough to detect the minuscule heat from a bulb, but they can detect the sum of all sources of heat. And they do trip at fairly consistent temperatures each time, in most systems, cutting off the pump that sends water to the rads.
 
We are dealing with very small values as you say, but that doesn't bother the proponents of the energy efficient bulbs, when they tell us that air con systems don't have to work so hard in the summer, at night, when your lighting is on.
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CaptCosslett View Drop Down
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Joined: 20 Feb 2009
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Points: 1185 		Post Options Post Options   Thanks (0) Thanks(0)   Quote CaptCosslett Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2010 at 8:20pm
Originally posted by Odai Odai wrote:

I don't know the answer, that's why I asked how Martin worked it out....

 
Odai, admit it. You have more questions than answersSmile
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Odai View Drop Down
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Quote No, an automatic ''decrease'' in heating output.
 
Sorry, yeah, that's what I meant.
 
Quote
Central heating thermostats aren't exactly the most sensitive devices no, but they don't have to be, they respond to the ''total'' temperature within the house [or room where they are located] from all sources, the radiators, your cats flatulence, light bulbs, everything that contributes to the heat within the dwelling. They may not be sensitive enough to detect the minuscule heat from a bulb, but they can detect the sum of all sources of heat. And they do trip at fairly consistent temperatures each time, in most systems, cutting off the pump that sends water to the rads.
 
I know what you mean, but what I'm saying is the extra amount of heat energy the classic bulbs dump into a room is probably too insignificant to raise the temperature enough for the CH system thermostat to pick up on. That's why I asked how you worked out it is significant enough.
 
I tried doing the calculation myself last night, but there are way too many variables to take into account once you look at all the practical considerations. If you treated a room as a fixed volume, sealed, black walled box of air, it's simple. But you get all kinds of other effects happening, and I have no idea how much energy you lose as a result. It's really complicated.
 
If you were just to assume the room is as I said above, then you would get an increase in temperature of 1C every 20 min from a normal 60W bulb. But that's obviously not the case with a real room and house.
 
Quote
Odai, admit it. You have more questions than answersSmile
 
What's with you? Confused
 
Quote
We are dealing with very small values as you say, but that doesn't bother the proponents of the energy efficient bulbs, when they tell us that air con systems don't have to work so hard in the summer, at night, when your lighting is on.
 
In that case, assuming those sources are to be trusted, then the amount of energy is significant.
 
Either way though, the benefits of energy saving bulbs are definitely worth it. You'll get used to the different lighting from them eventually anyway. Big%20smile
 
 
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scampy View Drop Down
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Points: 443 		Post Options Post Options   Thanks (0) Thanks(0)   Quote scampy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Feb 2010 at 9:58am
You calculate the U value of the room first, to do that you need to know the makeup of the walls the materials and their heat conductivity. also the floor the roof, the temperature difference from each surface. Using the surface areas you arrive at a heat loss for the room. This heat loss is used to calculate the required output of the radiators and then the required output of the boiler or heating system. These calculations also must take into account the air changes per hour of the room eg air leakage.

But as far as i can remember we never take into account the emmisions from lighting in a domestic situation because the heat is radiant rather than sensible and this does not affect the required output of a domestic heating system. The heat emmisions and occupancy of a room are taken into account when calculating the power and humidity requirements of airconditioning though. Its been years since i studied this at a theoretical level but there are two types of heat, the heat energy from light bulbs is radiant.

But light is used in some cases to make people `feel` warm. If you understand what i mean.
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MartinW View Drop Down
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Points: 26722 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MartinW Quote  Post ReplyReply Direct Link To This Post Posted: 09 Feb 2010 at 10:17am
I'm not sure about that to be honest Scampy.
 
On a slightly more extreme level, I used to work in a darkroom, fairly sizable, and with low sensitivity photo-mechanical transfer paper, so there wasn't a need for a totally light tight room, plenty of drafts.
 
I operated a studio camera, with four fairly high wattage bulbs, the temperature was horrendous, necessitating the fitting of an extractor fan.
 
So yes, light bulbs can make a significant difference to the temperature of a room.
 
It's also true that in a domestic environment, we aren't dealing with a single bulb. In the evenings, in my home there will be many 60 watt bulbs burning in synchrony. Probably 5, so 300 watts.
 
Wouldn't the heat from your central heating radiators, be radiant as well?
 
 
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MartinW View Drop Down
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Points: 26722 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MartinW Quote  Post ReplyReply Direct Link To This Post Posted: 09 Feb 2010 at 10:23am
When we consider that incandescent bulbs are actually used for heating in incubation chambers, brooding boxes for poultry, heat lights for reptile tanks etc, we can assume it's a significant effect.
 
Did find this...
 
Quote About all I can find on this kind of question is based on using the size of 12x12x8 foot room a 60w filament bulb will raise the temperature of the room approximately 5 degees Farenheit an hour
 
 
Quote An incandescant (GLS)lamp / light bulb generate light by running current through a "metal wire" so it glows to emit light. This is a very costly way of generate light, since only 5% of Wattage is generating light, the rest (95%) is emitting heat. If you use a 100W lamp, 5W is light and close to 95W heat is emitted (there are some losses in base, material (absorbed) etc. A CFL - Compact Fluorescent Lamp - generate light by running current through a gas mixture which contains mercury or a mercury substitute. This effects an ultraviolet radiation that is converted into visual light by a powder on tube walls in the lamp. The effect is that whenever a mercury atom is hit by "current" it emits an energyburst - a quantum - that is like a snowball effect. This way of making visual light is much more efficient (around 80% better), in terms that you only need 20W CFL to generate simular outbut as the before mentioned 100W GLS. The heat emitted from a GLS is generated both from the tubewalls - but also from the Gear in base of CFL lamp. Some 28% of Wattage of CFL is light and some 72% is heat. Since the CFL is 20W, the heat emitted is appr. 14W (compared to the 95W of GLS).
 
If the above is accurate, and we consider 5 bulbs burning, as in my scenario, then a central heating thermostat is plenty sensitive enough.
 
Quote In cold weather the heat shed by incandescent lamps contributes to building heating, but in hot climates lamp losses increase the energy used by air conditioning systems.
 
For a given quantity of light, an incandescent light bulb produces more heat (and consumes more power) than a fluorescent lamp. Incandescent lamps' heat output increases load on air conditioning in the summer, but the heat from lighting can contribute to building heating in cold weather.[34]
 
 
For commercial and industrial lighting systems the comparison must also include the required illumination level, the capital cost of the lamp, the labor cost to replace lamps, the various depreciation factors for light output as the lamp ages, effect of lamp operation on heating and air conditioning systems, as well as the energy consumption. The initial cost of an incandescent bulb is small compared to the cost of the energy it will use.
 
 
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scampy View Drop Down
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Points: 443 		Post Options Post Options   Thanks (0) Thanks(0)   Quote scampy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Feb 2010 at 11:48am
Originally posted by MartinW MartinW wrote:

I'm not sure about that to be honest Scampy.
 
On a slightly more extreme level, I used to work in a darkroom, fairly sizable, and with low sensitivity photo-mechanical transfer paper, so there wasn't a need for a totally light tight room, plenty of drafts.
 
I operated a studio camera, with four fairly high wattage bulbs, the temperature was horrendous, necessitating the fitting of an extractor fan.
 
So yes, light bulbs can make a significant difference to the temperature of a room.
 
It's also true that in a domestic environment, we aren't dealing with a single bulb. In the evenings, in my home there will be many 60 watt bulbs burning in synchrony. Probably 5, so 300 watts.
 
Wouldn't the heat from your central heating radiators, be radiant as well?
 
 


The situation with a dark room is correct you would assume a high heat output in that area, the same with a room full of computers but was the dark room internal? because if there are exterior walls thats were the greatest heat loss is. If you have an exterior wall the heat loss in the room is huge compared to an internal room.

If you imagine a room has a heat loss of 2000w a 60w bulb is like a mouse raping an elephant. It doeant matter how many bulbs you have in the whole house each single room is different.

If honestly i have to go to work but ill be back to finissh later, id got myself confused before. A light bulb provides latent heat.

Radiators are a misnomer, a radiator is actually a convector.
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MartinW View Drop Down
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Points: 26722 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MartinW Quote  Post ReplyReply Direct Link To This Post Posted: 09 Feb 2010 at 12:22pm
There were two outside walls Slopey, regarding the darkroom.
The other two were partition walls.
 
At any rate, as you can see form the quotes above, all sources I've checked, regard incandescent bulbs as contributing to building heating. 
 
Quote Incandescent lamps' heat output increases load on air conditioning in the summer, but the heat from lighting can contribute to building heating in cold weather.[34]
 
It doeant matter how many bulbs you have in the whole house each single room is different.
 
People usually leave interior doors open though, so one larger space with many bulbs.
 
 
 
 
 

 
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MartinW View Drop Down
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Points: 26722 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MartinW Quote  Post ReplyReply Direct Link To This Post Posted: 09 Feb 2010 at 12:51pm
Originally posted by CaptCosslett CaptCosslett wrote:

We have to also take in to account the energy involved in the the production and disposal of ES bulbs. As for providing heat, yes of coarse a light bulb is not as efficient as CH, but it does also produce light and heat at same time. I think LED lighting is the way forward.
 
The thing is though... energy efficient bulbs have a far longer lifespan, so the energy cost and CO2 production is lower than incandescent bulbs.
 
As I said, they are more efficent, but it's not as clear cut as many think.
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