Sizing a mini-split a/c


A friend is looking into putting in a mini-split air conditioner. The room does not have an outside wall. She has calculated that she needs 6000 to 7000 BTU--max. But all single zone units I find are about 9000 BTU. She very much does not want an oversized unit that leaves the room cold and clammy.
Some units I find have a dehumidifying mode. Does this mean that when it reaches the set point temperature it continues to run to remove the humidity?
Investigating the Sanyo LS093CE (115 volts, no heat mode) it appears that the unit can either be run as a/c, or run as a dehumidifier. And that there is also a condensate line that is run from the indoor unit. What would be better is a unit that above the set point it is a/c and below it is a dehumidifier. Does such exist?
Don <www.donwiss.com> (e-mail link at home page bottom).
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wrote:

    It rusn teh fan at a lower speed, to increase the humidity ratio it removes.

Don' worry about it. Get one with 'dehumidify mode' as above.

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.p.jm.@see_my_sig_for_address.com wrote:

Dammit, Paul, I told you not to buy the cheap booze.....;-p

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Yes it does exist.... and uses Variable Frequency Inverter technology. Go here;
http://www.fujitsugeneral.com/wallmountediaq9-12.htm
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says...

It does *not* mean that. Unfortunately, the mini splits do not have a very sophisticated control scheme. All the dehumidify mode means is that the unit cycles on and off on a fixed timer. It does not control temperature at all in this mode. Mine runs for something like 7 minutes on, then 3 minutes off.
We tend to have many days with high humidity but not real high outside temperatures, and the dehumidify mode works fairly well. But if it cools off in the evening, it can make the room quite cold.
--
DT



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<snipped>

thats not correct a correct statement, with the new Fujitsu mini-split heat pumps.... they use Variable frequency inverter drives and literally vary their motor and compressor speeds for demand dehumidification without turning the place into a walk in freeze box. The RLQ and RLS series literally vary their output from 40% to 115% of their rated capacity depending on demand.
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wrote:

    Dat be some nifty shit.
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I installed the 15RLQ system yesterday for a customer that is an EE... he is like a kid with a new toy :-)
Got a 9RLS that I will be installing next week for another customer. (I installed a 15RLQ in this guys shop last winter and he loves it. ) He closed in his back porch/patio and wants another one. :-)
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wrote:

That is right. I have a new Fujitsu and you can hear it ramping up and down. That is how they can advertise a 26 SEER number. (and get you the government rebate)
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says...

Nice. Sounds expensive, but nice! I have had my mini split for 4 years and when I researched them back then I was dismayed at how unsophisticated they were. One thing that might improve them is a true remote temperature sensor (not just a remote control). I added a remote sensor and controller with adjustable span to a window unit and it transformed the way it controlled the room temperature and lowered the humidity.
--
DT



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Expensive is relative..... According to ARI, $235/year to heat and cool for the 15RLQ is cheap to operate by any standard.... the ones I have put in were $2,700 plus tax installed. http://www.fujitsugeneral.com/wallmountediaq15-18_specs.htm#specs
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Hi Steve,
You've sold me. I have wanted a variable speed a/c for more than 20 years. When I put the Carrier packaged unit on the roof six years ago I wanted it. But it wasn't an option, so I settled for undersizing it a little. Then when I replaced my downstairs regular split unit two years ago it was available! This being the Carrier Infinity. It is nice to find out that this feature is finally making it to the mini-splits.
My friend (we're in Brooklyn) just now has to get a couple proposals and get the coop to approve the hole through the outside wall. There is already electricity outside on the balcony. I would think a 3/4"-1" hole would do.
Thanks, Don <www.donwiss.com> (e-mail link at home page bottom).
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wrote:

    Make sure it's the RIGHT electricity. It's likely not. It's likely 120V, you likely need 230V. However, the wire MIGHT be able to be re-purposed if needed ( if it's an independent circuit now ). Have your ( licensed insured ) contractor tell you.
The hole he's gonna have to make might be used to good avail also to bring some other 120v circuit outside, if he re-purposes the existing wire to 230 V.
And he'll need space in the breaker box to do it.
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On Sat, 19 Jun 2010, .p.jm.@see_my_sig_for_address.com wrote:

I know it is now 120 volt on the balcony.
Hmm... I was looking at the 9CQ here: http://www.fujitsugeneral.com/wallmountediaq9-12_specs.htm#specs
I see 115 volt. But that isn't the unit that gets the 30% tax credit. That is the 9RL here: http://www.fujitsugeneral.com/wallmounted9-12RL_specs.htm#specs
Which is 230 volt. And it appears that the supply voltage for the inside unit is fed from the outside unit. And not just a low voltage wire. So a bigger hole. Walls in her apartment building are poured concrete or concrete block. Running 230 out there would be a major problem.
Don <www.donwiss.com> (e-mail link at home page bottom).
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wrote:

Can you get 230 to the inside unit, maybe through the attic? When they installed mine, the raceway we took to the outside unit also brought the wires back to the inside unit. I fed it from a J box in the middle but it could have been fed from the inside unit just as easy.
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On Sat, 19 Jun 2010 22:51:01 -0400, snipped-for-privacy@aol.com wrote:

Nope. This is an apartment building. There are apartments all around her.
A little background. When the building was build in about the 1960s they put in through the wall air conditioners. They sized them generously. The apartment was originally a one bedroom. The three through the walls were in the bedroom, in the kitchen, and in the living room. Somewhere along the way the living room was chopped into a small bedroom with the windows, and a large windowless living room. That room can't now be cooled. The other rooms are cold and clammy if the a/c is used. I can't get the sizes out of her for the through the wall units. It was hard enough to get her to calculate the BTUs needed for the living room. But we are assuming that the size of those units is pretty fixed by the sleeve size.
Don <www.donwiss.com> (e-mail link at home page bottom).
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On 6/19/2010 11:44 PM, Don Wiss wrote:

Did you ever consider installing through the wall room to room ventilation fans? I've installed them in convenience stores where the clerk is inside the bullet resistant enclosure and I know the fans were designed for homes that need air moved into other rooms.
TDD
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