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making the best of electric heat

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Interesting.  After a little searching, I found a heated keyboard and a heated mouse:

heated keyboard




heated mouse




Since they are both USB powered, that would mean that they would use less than 2.5 watts each.



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paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Here are my quickie drawings to show what I am attempting to do. 

The first shows typical heating.  Heat the whole space. 

The second shows using personal heaters.  In my experience this cuts heating costs by 60% or more.  Note that your shins often get "too hot" while your hands remain too cold - which makes this solution unacceptable, but indicative of possible solutions.


[Thumbnail for whole-house.gif]

[Thumbnail for space-heater.gif]

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Here was my first attempt:  to direct heat to just me.   While the personal heater used 800 watts, I was able to get all of this to less than 300 watts.

And my second attempt:  to bundle up a bit and direct heat to just my face, feet and hands.  I'm currently at about 230 watts although I am working on ways to get that to under 100 watts.

I think that as I get further down the path, I might be able to eliminate the need to warm my feet and I might be able to get it all to less than 50 watts.

And some results for now:  78% reduction in heat costs


[Thumbnail for attempt-1.gif]

[Thumbnail for attempt-2.gif]

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Anybody have experience with the heated keyboards or the heated mice?

Anybody have any suggestions on fleece-wear for around the house - especially in a house that is kept pretty cold?

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Hmmmm ....  apparently, the keyboard gets its heat from an a/c adapter.  I did some research and found one claim that it uses 20 watts. 

So 20 watts for the keyboard and 2.5 watts (max) for the mouse.  That's still way better than the 120 watts for the reptile heaters.



paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
After several weeks of using the heated mattress pad and timer I have to say that this is a big win.  The bedroom is almost always exactly 50 degrees when I go to bed.  This makes getting into bed quite warm, plus I fall right to sleep.  Before, it seems like it would take an hour or more for me to fall asleep.  I think it was taking that long to get warm enough.  Maybe I just don't generate as much heat as I used to. 

I hooked up the kill-a-watt thing.  It looks like the mattress cover uses 100 to 200 watts.  A fairly hefty amount.  So that little 30 minute timer becomes a really earns its keep at ten bucks.

The mattress cover comes with a ten hour timer, but I don't want to draw that much power.  150 watts for ten hours would be 1.5kwh (about ).  But having it on for just a half hour is 0.075kwh. 

I feel plenty warm in the morning. 

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
I ordered the keyboard and mouse.  We'll see how it goes.  I would like to think that this will be, by far, the cheapest solution.  If it works. 

I further think I could rig up some clear acrylic box-ish thing to go over the keyboard and mouse to help hold in some of the heat.  The idea is that the box will be open facing me - although I think a slight improvement would be to make the box an inch taller and have an inch thick lip at the top of the box on the open side.  Complete with a two inch wide gap in the lip where my head would be - thus any excess heat that would pour out of the front would come toward my face.
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Yesterday, I redirected one of the reptile heaters to point at my face.  My face is a lot warmer and I have not noticed any eye problems.

travis laduke


Joined: Jul 20, 2010
Posts: 163
What about something like a dog heater to set on the desk and then set the keyboard and mouse on?  What if it was a slab of marble or metal or something heavy?
tel jetson
steward

Joined: May 17, 2007
Posts: 2957
Location: woodland, washington
    
  48
with all that stuff around you, you should really look into EMF.  saving a whole bunch of electricity and money will probably lose its appeal if you've got to hurt yourself to do it.  maybe you'll decide that it's nothing to worry about, but I think you should at least do some reading if you haven't already.


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Len Ovens


Joined: Aug 26, 2010
Posts: 1237
Location: Vancouver Island
    
  13
tel jetson wrote:
with all that stuff around you, you should really look into EMF.  saving a whole bunch of electricity and money will probably lose its appeal if you've got to hurt yourself to do it.  maybe you'll decide that it's nothing to worry about, but I think you should at least do some reading if you haven't already.


would powering with DC help? A DC power supply would not be that hard to put together. Also, depending on how the heating elements are arranged, emissions could be minimized by cancellation. In other words two elements could be mounted side by side but out of phase for a net EMF of zero.... Further, the lower the power, the lower the emission... in fact, a high voltage, but very little current, should be better in this regard than low volt high current heaters of the same power.
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Temp now:  48(A)/52(B)

I bought fleece pajama pants yesterday.  I'm wearing them now with a shirt and my bathrobe.  The only thing I have turned on is the dog bed heater.  I'm curious about how comfortable I'll be after a few hours.  So far it has been nearly two hours and my nose feels a little cold.  My fingers feel fine.

EMF:  I've looked into it a little.  The mattress pad talks about it a fair deal - it says that it has been tested for it, and comes up near zero.  I saw a youtube video about EMF and lightbulbs, showing CFLs putting out hundreds of times more EMF than an incandescent.  The guy had some kind of meter.  I do think it could be worthwhile to get a meter like that at some point.

dog bed on the desk:  I thought about that - the one I have now is too big.  And a smaller one .... well, it would raise the keyboard a bit and still leave the mouse area cold.  And then I worried about how the keyboard might behave with so much heat.  I was thinking of travelling this path until I discovered the heated keyboard.

DC vs. AC re EMF:  are you thinking of making a custom heater?  I suspect that the USB heated mouse would be DC.

paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
the power bill has arrived.

The numbers are in KWH.  The first number is for the guy that was here last year and the second number is for me.

I should try to track down the guy that was here before me and ask him about his habits.  I know that he used CFLs, because I took them all out shortly after I moved in.  I'm pretty sure that he did no laundry here and that he worked away from home - so the house was empty most of the time.

jun  468/279
jul   383/308
aug 304/247
sep 352/189
oct 714/314
nov 960/695
dec 1284/460

November had some super cold weather this year.  Plus, I had company so I turned the heat up.   And I left for the last ten days of december - but I had to leave the heat on to keep pipes from freezing.   And we did have some temps below zero for december.

My november strategy about freezing pipes was to turn the heat up to 65 in areas where there are pipes that could be frozen.  My december strategy was different:  since the pipes are exposed, I set up a small fan (15 watts) to blow on the pipes and left the room temp to 50.

By looking at the numbers, I think it is fair to say that my summer power usage is about 250kwh per month.   Without any heat.  And the previous guy was about 350kwh.   So if we look at november and december, he was using about 1100kwh per month - so about 750kwh for heat.   I'm at about 600kwh, so about 350kwh for heat.  About half.   Considering how much I turned the heat all the way up in november, and all of the cooking, half is really quite good!  Maybe by the end of the winter I can get those numbers much lower.

If I look at just december, the previous guy used 934kwh for heat and I used 210.  I cut my heating bill by 78%. 
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
My face got cold.  I turned on the reptile heaters - including the one pointed at my face.
Professor Rich


Joined: Dec 15, 2010
Posts: 105
Paul,

Making some assumptions that I do not know to be true so help me out if I am off base.

Looks like electric heat.

Looks like you are choosing to operate your apartment well below average temps aka below 65 degrees.

I will also assume you have a main stream type refrigerator in your home.

Refrigerators are colder than the space so heat is absorbed into them aka heat moves from warm to cold. While it would seem lowering the temp in the space would (and does) lower the rate in which heat is absorbed into the frige, it does not equal out to less energy used.

Almost all, if not all household refrigerators use capillary tube metering devices. in order to get the proper flow rate of refrigerant the head pressure must be maintained at the right level, if it is not, you do not move enough refrigerant to cool the product and the compressor doing the work. May folks discover this with the "beer frige" in the unconditioned garage and become very confused as to why the beer is 45 and the garage is 20.

The pressure requirements for that system are actually fairly narrow. By design it can be said it will operate satisfactory with a condensing temperature of 100 to 130 degrees. The condensing temp is going to be typically 30 degrees over the ambient space temp. So when you have space temps outside of 70-100 degrees, the frige is not going to operate properly and can indeed be damaged if sustained operation continues for a long period.

I mention this because some of your savings through lowering the temp in the space are indeed lost by the refrigerators electrical system using more power than normal to keep the food cool. If your refrigerator has a fan in the back then there are easy control strategies to maintain the proper head pressure that can be adopted to minimize that loss and damage to the equipment that are cheap and easy.

Google "head pressure control" and you will likely find some good info, you would be looking for fan cycling. The key for the layman is to think a bit outside the box and not use a direct pressure control like a professional would but to achieve the same goal thermostatically. Disturbing the refrigerant system by the untrained is not recommended as it is pretty sensitive and expensive mistakes are easy to make and go un-noticed.


Professor of Thermal and Electrical Engineering, Welding/metallurgy: Licenses: PE license, Mechanical license Variety of other "certifications" from industry groups such as Refrigeration Service Engineers Society http://www.rses.org/, ASHRE http://www.ashrae.org/ Ect.
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
ned,

So your post is focused on fridge stuff?  I have to admit that nearly all of it went over my head.  Maybe it will make more sense if you tell the basics:  are you saying that when the room is 50 degrees, the fridge has to work harder?  Therefore, my attempts to save energy could be lost through the fridge, and, further, that it could lead to fridge damage?
Professor Rich


Joined: Dec 15, 2010
Posts: 105
paul wheaton wrote:
ned,

So your post is focused on fridge stuff?  I have to admit that nearly all of it went over my head.  Maybe it will make more sense if you tell the basics:  are you saying that when the room is 50 degrees, the fridge has to work harder?  Therefore, my attempts to save energy could be lost through the fridge, and, further, that it could lead to fridge damage?



Yes sir.

You posted a utility bill comparison and the utility bill encompasses the entire "building envelope" which is often what I have to consider when evaluating systems.

Please remember our differences in thought and communications, I find your question difficult to answer technically correct.

When you say "are you saying that when the room is 50 degrees, the fridge has to work harder?" the technical answer is NO, however, while it is doing "less work" it is consuming more energy to do that same amount of work.

Step back to a previous conversation where I said temp has little to do with BTU content. 10 lbs of water at 50 degrees has the same energy as 5 pounds of water at 100. So to cool it to 40 we would have to remove 100 BTU's of heat from each.

This applies to refrigerant as well.

The metering device, the cap tube is nothing but a hole and only so much of a substance will travel through a hole. So at for sake of discussion 200 psi X amount of liquid will travel through the hole. If you drop that pressure to 100 psi, less material will travel through the hole.

So if we say at 200 psi, 50 lbs of refrigerant will travel through the hole in an hour and be delivered at 50 psi, if we drop the pressure to 100 psi, we will deliver 25 pounds of refrigerant to the other side at 25 psi. Please note, numbers given for example only, fluid dynamics work to worsen the numbers but this is not a math discussion.

This is how your refrigerator "rides the load" and pushes more refrigerant when it is warm and less when it is cool. Cap tube systems are cheap, its just a hole, but operate in very narrow ranges properly.

The refrigeration system needs certain things to happen within it to operate properly. The electric motor is MUCH MUCH smaller than a normal motor like a drill or fan, it is because it can be as the refrigerant vapor coming back cools it and it does not need the same surface area an air cooled motor needs.

When the frige is operated in a cool environment, the head pressure drops which means fewer pounds of refrigerant are pushed through the hole, both in pressure and actual weight moved. While the reduction in pressure lowers the load on the motor which makes it work "less hard" the lower weight of refrigerant circulating may become so low as to not properly cool the electric motor. The refrigerant also carries the lubricating oil with it, however it depends upon the velocity of the refrigerant to suspend it and in the evaporator when you drop below a certain point the oils weight and the reduced velocity allow it to drop out of the stream of flow and it does not return to the compressor to help lubricate it as well as cool it.

Because these changes are proportional, you have a range of operation, when you get outside that range, damage begins to occur. Keep in mind, you are speaking about a device with a 20 year life expectancy so damage that shaves 10% off of its life will not be realized by the average person. In other words, "well it is 10 years old" might well be acceptable to a person whom just watched their frige die. The simple fact that it was indeed killed is not known to them.

During that time it is doing "less work" it is moving a lot less refrigerant but requires the same amount of energy to magnetism the stator and rotor in the motor required for it to spin. From a practical view point this means that just to turn on it will use 70% of the electrical energy so to speak. For easy math:

10 amp 100 volt compressor moves 10lbs of refrigerant. In range that does 1,000 BTU of work per hour.

So 90 inside the space, the frige has a 90/40 temp difference which would for sake of this simplified discussion has a 1,000 BTU per hour cooling load. AKA 50 td = 1000

You cut the space temp back to 60, not there is only a 20% load so to speak. aka 200 BTU.

At full load we will use 1000 watts, at the reduced load we will use 700 watts. So as you can see, we will be using 3.5 times as much electrical energy per BTU to do the work.

This does not account for the additional heat added by the compressor motor due to the lower density of the return vapor cooling it, nor increased heat because of the reduced lubrication etc.

Now as I said before, fluid dynamics cause this over simplified version to actually be much worse than these number reveal. You also have issues associated with the vapor density causing excessive compression chamber temps and since these compressors use reed valves in the thousandths of an inch thick, over temp at the valve can create warping etc.

This is much easier for me to explain on a chalk board than I can ever do in type.

The easy point, asking the fridge to operate outside its design parameters will cause it to run at a much higher watt to BTU ratio, run longer to do the same amount of work, add additional heat to the refrigeration system from the external electric, and do progressive damage to the refrigeration system that are not noticeable but are significant in the overall life of the system.

This problem is fixed by reducing the air flow on the condenser which makes it less efficient allowing additional heat to build within it raising the pressure and flow rate to the minimum levels for peak operational efficiency and cooling. It allows the system to "build enough head pressure" to flow at the proper levels.

Domestic refrigerators are not designed to operate below about 65 degrees because they are an indoor appliance and no one really allows temps to fall below that as a general rule which is why these problems only show up in the mainstream world for garage fridges.

Commercial equipment that has the refrigeration units located out doors all have this type of control built in because they will be operating in ambient temperatures outside the parameters of indoor appliance operation.

Hope this helps.
Burra Maluca
Mother Tree

Joined: Apr 03, 2010
Posts: 3932
Location: Portugal Zone 9 Mediterranean Climate
    
130
So you're saying that when it's cold, the fridge runs less efficiently.  And because it isn't having to work so hard, it's not pumping round so much refrigerant.  Which means that it's not pumping around the lubricating oil needed for a long working life. 

So keeping a fridge in a cold place reduces it's life expectancy. 

In essence.  In words a dumb-ass housewife like me could understand...   


What is a Mother Tree ?
tel jetson
steward

Joined: May 17, 2007
Posts: 2957
Location: woodland, washington
    
  48
maybe you could start a new thread about that, Ned.  I've got a freezer sitting on my porch that I'm probably dooming to an early death, since I wasn't aware of this stuff.  the instructions said cold ambient temperatures could cause problems, but I pretty much just ignored that.
Professor Rich


Joined: Dec 15, 2010
Posts: 105
Burra Maluca wrote:

So keeping a fridge in a cold place reduces it's life expectancy. 

In essence.  In words a dumb-ass housewife like me could understand...   


Yes, though it is a counter-intuitive process because within range of operation cooler is better than warmer from all points of view, what it is really saying is that either end out of range brings operational problems, too hot and too cold are both problems.

I would skip the "dumb-ass" part myself though, the refrigeration process is a very complex application of many facets of science and common sense while almost always correct is at times incorrect. A good dose of common sense I can assure you will result in far fewer failures within life than a deep understanding of physics and engineering.
Professor Rich


Joined: Dec 15, 2010
Posts: 105
tel jetson wrote:
maybe you could start a new thread about that, Ned.  I've got a freezer sitting on my porch that I'm probably dooming to an early death, since I wasn't aware of this stuff.  the instructions said cold ambient temperatures could cause problems, but I pretty much just ignored that.


It is often a slightly lesser problem in freezers because a lot of them do not have the fan cooled condenser, it is instead built into the outer walls and around the door frame to help with condensation prevention.

If it is indeed a fan cooled unit (most often in upright freezers) it would be a very similar problem, the others would find ambient of perhaps as low as 50 still within range of operation without too much life cycle taken from it, once below perhaps 20 it would be tough on it however it would also tend to lose the heat at such a slow rate the unit would not run nearly as much, particularly on a chest type.

The reason it impacts a refrigerator more, you open the door and let the cold air fall out a lot more. The unit will indeed run more simply due to usage, if you did the same with the freezer the results would likely be very similar.
Muzhik McCoy


Joined: May 26, 2010
Posts: 278
Location: Iowa, border of regions 5 and 6
NedReck, based on the above discussion, would I be correct in saying that designing a heat pump for use in your standard household refrigerator would be a non-trivial task? 
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Here is what I think I understand so far:

96) at 50 degrees, the fridge will use less power overall, but more more power per shifted BTU.

97)  since the lube isn't getting moved around as much, the fridge life expectancy can be cut from 10% to 50%.

9  it is possible to design fridges to work well in an area that can be 40 degrees to 90 degrees (or even greater extremes) but it is cheaper to be able to optimize for 65 degrees to 85 degrees.

I think that I am trying to achieve several things here:

E)  things that people can do to save money in the short run.

F)  come up with a way to save energy that is three times more efficient than the whole "CFL" scheme.  Long term solutions to save on pollution, building new power plants and reduction of energy based wars.  This might include coming up with contraptions that don't currently exist - like refrigerators that can function more efficiently over over broader temperature ranges.



paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
After turning the reptile heaters on again, I feel warm as toast.  So the room is now 52 (thermometer A).  It was probably warmed slightly by having my laptop (40 watts) monitor (90 watts) and the two reptile heaters (120 watts) running in the room.  Oh, and my understanding is that people produce heat similar to a 75 watt light bulb.

I should mention that it is now the warmest part of the day (2 in the afternoon) and 26 degrees outside.  There is a bit of a wind.

Professor Rich


Joined: Dec 15, 2010
Posts: 105
Muzhik wrote:
NedReck, based on the above discussion, would I be correct in saying that designing a heat pump for use in your standard household refrigerator would be a non-trivial task?   


It already is a heat pump, it pumps the heat from inside your refrigerator to the space the refrigerator is stored in and if that is a conditioned space, the "air conditioner" pumps that heat out of the space to the outdoors.

In the sense that the term "heat pump" is broadly used, it is no different from an air conditioner in that it pumps the heat from the outside into the space in winter and the opposite in the summer. Because the conditions of operation are more variable, the "heat pump" as it is known has more controls built into it to keep it operating within its parameters, but the task it performs is identical.

Common misunderstandings around heat pumps exist that lead folks to dramatic misunderstanding of fairly simple stuff. For instance it is often said that a heat pump is "only good to about 20 degrees outside" which is false. A standard residential heat pump lacks the controls and design parameters to make it economically viable beyond that point, however I have indeed worked with systems that are efficient to -10F with controls built into the system to prevent any damage.

I suppose a good way to simply what I was saying about Pauls situation, think of the water hose with a handle sprayer. If you barely crack the valve, the hose will indeed fill up and build to whatever pressure is available but when you pull the trigger, that pressure will rapidly drop and you will have very little water come out the nozzle. If you were trying to cool something with it, you might not have enough water to get the job done.

Now if you had an automatic valve on the house that was monitoring what you were trying to cool and it could open and close to allow as much water as needed based on the cooling need, you could get the right amount of water all the time so to speak unless you did not have enough pressure feeding the valve, so now if you put a pump in front of the valve, you could supply it varied water based upon need as long as you had enough water to supply the pump, valve it based on need and very well match exactly how much water you needed across a lot more conditions than you could with the valve just "barely cracked open".

So such a heat pump would have just such controls, a variable valve and a way to assure the proper pressures to meet the needs over a large set of operating conditions and a way to store the excess refrigerant while operating in conditions when it is not needed.

I am not opposed to another thread since this is getting way off Paul's original intent, I only brought it to light because he indicated temps in his space below the design of the fridge and his bill to bill comparison will not reflect accurate numbers as to his efforts, by cutting his energy usage in the furnace, lighting etc, he has inadvertently caused his refrigerator to consume more and if he adopts some simple controls on it as well, he will indeed see those savings are even more than he thinks at this time. If his fridge has a condenser fan, simply putting a fan cycling control on it would indeed bring it back into its operational parameters for peak efficiency and running shorter cycle times that would save him a bit more. Without doing the math I can not say for certain, but I would venture that it would be very significant, perhaps 60% or better increase in efficiency compared to operating the fridge in the colder environment without the controls.

I will however be very sporadic in such a thread the rest of the weekend and next week as I am preparing for a totally different subject matter for court next week and this is serving only as break time escape as I clarify my thoughts on that case.
Professor Rich


Joined: Dec 15, 2010
Posts: 105
...inserted responses for clarity

paul wheaton wrote:
Here is what I think I understand so far:

96) at 50 degrees, the fridge will use less power overall, but more more power per shifted BTU.
...more power per BTU AND longer run times resulting in MORE power consumption

97)  since the lube isn't getting moved around as much, the fridge life expectancy can be cut from 10% to 50%.
...Lube and excessive cylinder temps internally, rate of wear hard to predict, 50% used as an example to show where one would not "blame more than age" for the failure when indeed the device was killed prematurely, depending on conditions it could be 80 to 90% life reduction of the device. In your posted temp ranges I would estimate the math would indicate a 20-50% reduction in life expectancy but I have done none of the supporting math to confirm.

9  it is possible to design fridges to work well in an area that can be 40 degrees to 90 degrees (or even greater extremes) but it is cheaper to be able to optimize for 65 degrees to 85 degrees.
...A domestic refrigerator is designed as an indoor appliance and those are expected indoor temps, commercial refrigerators, walk-in coolers etc have broader ranges required, the controls are included in them. They build them as cheap as possible, adding to controls serves no purpose for 99% of them so the expense of even a few dollars is of no value. The cost to adapt is not much, but since it is uncommon there are not really any over the counter type add ons. The key is to keep the condensing temp high enough thereby proving enough flow exist. A switch on the liquid line assuring it is 80 or it cuts the fan off would really broaden the range, a bulb type thermostat with the bulb tied to the line and insulated would achieve the goal and cost less than 30 bucks. Might even be a version for 10 or under, would have to look, it is kind of an unusual request most folks would freak if it was 40 inside their home.

I think that I am trying to achieve several things here:

E)  things that people can do to save money in the short run.

F)  come up with a way to save energy that is three times more efficient than the whole "CFL" scheme.  Long term solutions to save on pollution, building new power plants and reduction of energy based wars.  This might include coming up with contraptions that don't currently exist - like refrigerators that can function more efficiently over over broader temperature ranges.



The fridges exist, but only on the commercial level, the same inexpensive control schemes are easy for a domestic refrigerator, there is just not enough call for it for anyone to bother with mass production.

I will take a look about next week for what you would need in order to so this safely without disturbing the internal refrigeration system. I am fairly sure I can talk you through the installation of the devices and find what you can use effectively.

Ned
Professor Rich


Joined: Dec 15, 2010
Posts: 105
paul wheaton wrote:
  Oh, and my understanding is that people produce heat similar to a 75 watt light bulb.




Your thermal value is 85 BTU per hour per person Equates to more like 25 watts FYI
Muzhik McCoy


Joined: May 26, 2010
Posts: 278
Location: Iowa, border of regions 5 and 6
NedReck wrote:
Your thermal value is 85 BTU per hour per person Equates to more like 25 watts FYI


That may be, but some of us have more thermal mass than others.
Professor Rich


Joined: Dec 15, 2010
Posts: 105
Muzhik wrote:
That may be, but some of us have more thermal mass than others.



You would find me in agreement with that, and at the risk of violating a rule on politics, I would offer that Washing DC has little need for heating in even the coldest of seasons due to the excessive hot air expelled by pretty much everyone there no matter their affiliation.

SadlY, THE IRONY: That is really not funny because it tends to be far too true!

Ned
Professor Rich


Joined: Dec 15, 2010
Posts: 105
Something just occurred to me, some folks may not understand a big difference in these discussions.

Wood burning, electrical lighting are both "energy conversions" where they literally convert one form of energy to another.

Vapor compression refrigeration is NOT an energy conversion, it is an energy transportation system that uses electrical energy for the drive for the most part.

To explain it best, electrical watts can be converted to heat energy, the rate is 3.413 BTU's per watt. When electrical energies are converted to mechanical, they can transport many more BTU's than they can convert, about 10 times as many in practical terms now days.

In other words 1 watt has enough energy to carry enough refrigerant that has 30 BTU's of heat energy capacity.

Like a gas truck, it carries a lot more energy in the fuel on board than it uses to deliver it.
Len Ovens


Joined: Aug 26, 2010
Posts: 1237
Location: Vancouver Island
    
  13
paul wheaton wrote:

DC vs. AC re EMF:  are you thinking of making a custom heater?  I suspect that the USB heated mouse would be DC.



No, an "AC" heater would work just fine with DC of the proper voltage... Run 120AC through a bridge rectifier and stick a big cap across it to smooth things out. This would probably give a too high voltage (about 170VDC) because the grid has a really low resistance... an auto transformer may be needed to bring the input voltage down to 80VAC or so.
Past Tense


Joined: Nov 28, 2010
Posts: 4
If Ned is right about the refrigerator, can't you measure it by putting a Kill-a-Watt meter on it?
Professor Rich


Joined: Dec 15, 2010
Posts: 105
PastTense wrote:
If Ned is right about the refrigerator, can't you measure it by putting a Kill-a-Watt meter on it?


No ifs o tat one sir, tis long established facts before you.

Google:

Head pressure control strategies
Headmaster control
Fan cycling control

If you want to learn more.

A watt meter if it has logging capabilities to log the run time would indeed show it to you in a graphic form if you felt the need.
Burra Maluca
Mother Tree

Joined: Apr 03, 2010
Posts: 3932
Location: Portugal Zone 9 Mediterranean Climate
    
130
I've been thinking about why it is that I seem to be worrying about things like damp and keeping the old man comfortable, while everyone else is focusing on the need to heat people, not houses.   Then it dawned on me that I have absolutely no idea what temperature my house actually *is*, and in any case, I work in C, not F, so the figures everyone was using were going right over my head.

I dug out a thermometer that had F and C on it, and discovered that my kitchen is 50F and my living room 52F.  I haven't dared take a thermometer into the old man's room else he'll be convinced I'm up to no good, but I'm guessing his room is about 60F as he does have  little heater in there but it doesn't feel exceptionally warm to me when I go in so it's not a huge amount different. 

Do people *really* keep their houses at 'average room temperature' of 65F  Seems excessive to me.  Though I guess I am sitting here wearing a woolly hat..
paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
The norm in the states is 72F.  People that are eco will often go as low as 68F.  A house at 65F is pretty rare, although people will turn their thermostat down to 60F at night or while they are at work (although I think the savings with that practice is pretty small). 

BTW, I am right now at 41F(A)/46F(B).  Outside temp is 13F (well below freezing).  I am plenty comfortable with the reptile heaters, dog bed heater and my 100 watt light bulb.  I am not yet dressed - just wearing a bathrobe and pajama bottoms.

I once visited a cousin in san francisco in january.  It doesn't get too cold there, although it might drop to freezing once in a while.  While I was there it was probably getting close to freezing at night and getting into the 50's during the day.  I was miserable.  It seems like I just couldn't get warm.  I remember we once turned on the heat and gathered around this heating grate.  For ten minutes we felt the wonderful warmth.  And then we turned it off.  It was a treat.  I thought my cousin was pretty awesome living like that.  There were three people living in a small space - all adults.  And they were all just bundled up all the time while in the house.  They are more awesome than me.  I cannot bear to be that uncomfortable.  But now, my house is probably that cold and I am comfortable.  I think I make a great guage for those people that would be uncomfortable at such low temps.


paul wheaton
steward

Joined: Apr 01, 2005
Posts: 14156
Location: missoula, montana (zone 4)
    ∞
Ned,

Supposing that some US Department of large-and-in-charge were to come here and read this stuff and think "we need to require that fridge manufacturers meet a minimum criteria of __________ so that people can save energy by turning their heat way down."  What would be the requirement? 


Jordan Lowery
volunteer

Joined: Sep 26, 2009
Posts: 1526
Location: zone 7
    
  11
its a nice balmy 39 in here where im at right now, 34 outside. no heat.


The ultimate goal of farming is not the growing of crops, but the cultivation and perfection of human beings. - Masanobu Fukuoka
travis laduke


Joined: Jul 20, 2010
Posts: 163
This chest freezer + temp controller might be of interest

http://screwdecaf.cx/yatc.html
Professor Rich


Joined: Dec 15, 2010
Posts: 105
paul wheaton wrote:
Ned,

Supposing that some US Department of large-and-in-charge were to come here and read this stuff and think "we need to require that fridge manufacturers meet a minimum criteria of __________ so that people can save energy by turning their heat way down."  What would be the requirement? 





A little larger condenser for storage of refrigerant not needed, a head pressure control of some sort, most would choose fan cycling because it is cheap, and it would depend upon the range, if it was fairly broad a Thermostatic Expansion Valve (TEV or TXV same thing) would be a practical device that they could maintain the EER rating.

If they added a liquid receiver instead of the larger condenser (has limits in size for other reasons) they could operate it over whatever range you want, just like a walk in cooler, here in St Louis they run from -15 through about 115 with normal ranges of perhaps 0 to 100 expected.

50 to 100 bucks in parts, 20 hours or less engineering and perhaps 1/2 to 1 full hour additional manufacturing time to hit that goal.

As long as you do not seek to run it below 40 (at which point it will not run a lot anyway) you could get away with the fan switch alone, it will not be at peak operation but it will not be killing itself in the process.
Professor Rich


Joined: Dec 15, 2010
Posts: 105
travis laduke wrote:
This chest freezer + temp controller might be of interest

http://screwdecaf.cx/yatc.html


Actually that is not a good idea either. The controller may be fin and dandy, swap out a fridge thermostat with the freezer stat and you have the same temp control.

The problem is, that is going to be a low temp refrigeration system with a 0 to -10 expected set point. You are going to be running about -20 degree refrigerant through it and expect that refrigerant to be about 0 to 5 above returning to the compressor. instead it is going to be about 30-35 which is going to result in not enough cooling on the compressor, over expansion of the refrigerant due to excessive superheat, overheating at the valves at temps likely well over the oxidation point of the oil resulting in acids being produced etc etc etc.

A freezer needs controls for a "hot pull down" and intentionally running a freezer in a constant hot pull down will result in huge energy usage, very fast destruction of the internal refrigeration system, and pin hole leaks due to the hydrochloric and hydrofluoric acids that are formed as the refrigerant and oil break down.

I would not expect a freezer operating in that configuration to last beyond 5 years.
 
 
subject: making the best of electric heat
 
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