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Tecumseh's line of compressors for solar power air conditioning?

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Posted by N9WOS on June 10, 2010, 8:39 pm
 


This is something that caught my attention. For people looking for a viable
solar/dc based air conditioning system for their home. Tecumseh is making a
masterflux branded line of compressors called sierra, for 12/24/48 and
higher volt operation.

http://www.masterflux.com/products/sierra/

They also have complete condensing units built around them.

http://www.masterflux.com/products/condensingunits/

High temp is basically the same operating range as AC service. Basically an
evaporator temp above freezing.

They have a rated capacity range from 3000 to 6000BTU with a condensing temp
of 130F. In the real world, with an adequate condenser, condensing temps
will not be close to 130F. So that is the worst case scenario. Actual real
world capacities will be closer to 5000 to 10000 BTU with more normal 100F
condensing temps.

The only reason you see higher condensing temps on their complete condenser
line is because they are not really optimized for AC service. The condenser
coil isn't really large enough to support the higher evap temps and higher
capacity.

At a power draw of 374 watts for 3753BTU at 55F evap, and 130F condensing,
you still push over 10EER which pretty respectable for 130F condensing temp.

If you got a reasonable sized 1 to 1.5 ton condensing unit and put that
compressor in it, you would not see over 10F above ambient condensing temps.
That will help capacity and EER for AC service greatly. You would have to
change the condenser fan over to a 12 DC type. Inside evaporator could be
anything from a small fan coil, or a wall mount unit.

Basically the above system with two 200W panels and an AC with a couple of
golf cart batteries for a buffer and you will have climate control during
the day time. With big enough GC batts and you could carry cooling into the
night hours.

A lot more efficient than running a window shaker on your existing
inverter/solar installation.

Granted, 3 to 5kBtu isn't a lot. But in a well insulated house, or part of a
house, it will make things a lot more comfortable.

Yes, you would be talking about approximately $000 for a 5000BTU ac, but
considering How much a normal central air system cost. Even a mini split of
that size will cost over $000. And it doesn't use AC power, so no electric
bill. 4K bucks for a solar ac doesn't sound that bad.



Posted by Josepi on June 10, 2010, 9:14 pm
 


With a low humidity climate and lots of sun it may be a viable option. A few
climate zones come to mind on that account. Not here.


This is something that caught my attention. For people looking for a viable
solar/dc based air conditioning system for their home. Tecumseh is making a
masterflux branded line of compressors called sierra, for 12/24/48 and
higher volt operation.

http://www.masterflux.com/products/sierra/

They also have complete condensing units built around them.

http://www.masterflux.com/products/condensingunits/

High temp is basically the same operating range as AC service. Basically an
evaporator temp above freezing.

They have a rated capacity range from 3000 to 6000BTU with a condensing temp
of 130F. In the real world, with an adequate condenser, condensing temps
will not be close to 130F. So that is the worst case scenario. Actual real
world capacities will be closer to 5000 to 10000 BTU with more normal 100F
condensing temps.

The only reason you see higher condensing temps on their complete condenser
line is because they are not really optimized for AC service. The condenser
coil isn't really large enough to support the higher evap temps and higher
capacity.

At a power draw of 374 watts for 3753BTU at 55F evap, and 130F condensing,
you still push over 10EER which pretty respectable for 130F condensing temp.

If you got a reasonable sized 1 to 1.5 ton condensing unit and put that
compressor in it, you would not see over 10F above ambient condensing temps.
That will help capacity and EER for AC service greatly. You would have to
change the condenser fan over to a 12 DC type. Inside evaporator could be
anything from a small fan coil, or a wall mount unit.

Basically the above system with two 200W panels and an AC with a couple of
golf cart batteries for a buffer and you will have climate control during
the day time. With big enough GC batts and you could carry cooling into the
night hours.

A lot more efficient than running a window shaker on your existing
inverter/solar installation.

Granted, 3 to 5kBtu isn't a lot. But in a well insulated house, or part of a
house, it will make things a lot more comfortable.

Yes, you would be talking about approximately $000 for a 5000BTU ac, but
considering How much a normal central air system cost. Even a mini split of
that size will cost over $000. And it doesn't use AC power, so no electric
bill. 4K bucks for a solar ac doesn't sound that bad.




Posted by vaughn on June 10, 2010, 10:09 pm
 




But our high-efficiency window shaker claims 6000 BTU for only 500 watts.  I
could run it from a modest PV system and still afford the inverter loss.


Perhaps not always.  Some inverter mini-splits in that size range do far better
than our humble 12 EER window shaker.


Our bedroom mini-split already has a DC fan on the inside unit.  They did that
so it could operate from low voltage wiring.  Is that common these days?.


Even here in hot-humid south Florida, it might cool one room very well.


Since the wife and I are empty-nesters, we save on our power bill by using a
"cool room" concept most of the day.  The central unit stays off until just
before supper while we cool the study with a 12 EER 6000 BTU window shaker.  At
night, the central unit goes off again while we cool our bedroom with a little
mini-split.  That solar AC would sure be nice in our study to replace that loud
window shaker, and our need for cooling would exactly track the period when the
panels were producing full capacity.  But not for $,000!  At that price, no
unit would  last long enough to pay for itself.

Anyhow, thanks for the links.  Now I can dream!

Vaughn



Posted by N9WOS on June 11, 2010, 1:11 am
 


The system I am referring to is not for people on the grid. It is for off
grid houses. Most of the 4K price tag I listed was solar related stuff to
power it. In an off grid situation, the price of the panels and equipment to
power it always comes into the price factor. The total actual cost for just
the DC powered air conditioner components is only about $200. The solar
equipment related stuff is about $800. And throw in about $000 for labor.

I would say that if you compare that $K price to the rest of the system
needed to power a window shaker from solar power, in an off grid situation,
it wouldn't be so clean cut.

500W + inverter losses.
Assuming 90% inverter.
That makes it 550W
Plus other losses.

So, 600W of PV for continuous run during the day time. (Same as the layout
for the other system.)

That is $800 in panels.
$00 to $00 for the charge controller.
$00 for batteries.
$00 to $00 for pure sine wave inverter.
Paragon Eco Air Conditioner $60

Total real world price. $260 to $750
And that is not including labor.

And just so you know.

That 12 EER rating for the window ac you referenced is based on relatively
mild conditions, with a warm house. 95F outside condenser intake air, and
80F inside air. A 15F split. EER varies depending on the temperature split
you are moving the heat across. When outside temp goes up, and the inside
goes down, then the energy required for moving heat goes up, and EER goes
way down. When it gets over a 15 degree split , then 12 EER is out the
window. If you want the inside set to a more reasonable 75F and the AC is on
the sunny side of the house with 100+ ambient intake air. Your 6000 BTU unit
will be pulling more like 600W to 700W. With a real EER of around 9 or less.

The one compressor I listed was rated at 130F condensing which is around
110F to 120F ambient. Or around 15F to 25F higher outside ambient than your
12 EER unit was rated at.

So, to match the specs of the one I listed, you will probably need 800 watts
worth of panels. That will push the total price of over 4K before labor.

Yes, you may already have the inverter and batteries. But the additional
panels, charge controllers, will still have to be dedicated to supplying it's
consumption. So, you are still talking about $k+ for the equipment
dedicated for the AC.



Posted by vaughn on June 11, 2010, 1:27 am
 



Oh yes, I realize that EER ratings are rarely achieved in the real world, much
like auto MPG ratings.  Still, they are somewhat useful for comparing one
product to another.  In my case, I have verified the power draw of that window
shaker, but that really means nothing because I have no way of measuring how
many BTUs it is actually moving.


Yep, you just can't win.  Someday I do hope to splurge and replace that window
unit with a little mini-split unit.  The one I have in my bedroom makes every
window unit I have ever qwned seem crude.  It is so quiet you have to look at
the display to see if it is running.

Vaughn  WB4UHB



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