Energy Saving & The Government |
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CaptCosslett
Chief Pilot Joined: 20 Feb 2009 Location: Bishop Auckland Points: 1185 |
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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
Chief Pilot Joined: 05 Apr 2008 Location: NW England Points: 3731 |
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I don't know the answer, that's why I asked how Martin worked it out.... |
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ʎɐqǝ uo pɹɐoqʎǝʞ ɐ ʎnq ı ǝɯıʇ ʇsɐן ǝɥʇ sı sıɥʇ
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MartinW
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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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
Chief Pilot Joined: 20 Feb 2009 Location: Bishop Auckland Points: 1185 |
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Odai, admit it. You have more questions than answers
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Odai
Chief Pilot Joined: 05 Apr 2008 Location: NW England Points: 3731 |
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Sorry, yeah, that's what I meant.
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.
What's with you?
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. |
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ʎɐqǝ uo pɹɐoqʎǝʞ ɐ ʎnq ı ǝɯıʇ ʇsɐן ǝɥʇ sı sıɥʇ
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scampy
First Officer Joined: 22 Mar 2009 Location: russia Points: 443 |
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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
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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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
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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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...
If the above is accurate, and we consider 5 bulbs burning, as in my scenario, then a central heating thermostat is plenty sensitive enough.
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scampy
First Officer Joined: 22 Mar 2009 Location: russia Points: 443 |
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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
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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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.
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
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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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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