How low can inverter go?

Jace33

11 years ago

Hi all.

So inverter technology allows the compressor to slow down according to need.

The question is: How slow can it go? What if the AC is much stronger than the room needs?

Thanks!

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Comments (6)

bus_driver
11 years ago
With single phase, induction motors that are not originally designed for use with an inverter should not be run at frequencies that differ much from the stated design frequency. Torque drops off rapidly at lower frequencies. I know little about variable speed refrigeration compressors. My guess is that they are 3-phase and the inverter supplies that power, even if the input is single phase. I would never apply an inverter for the purpose of speed change to any compressor that was not so equipped originally. If yours is variable speed originally, how would it be made to operate outside the design parameters?
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ionized_gw
11 years ago
Guess no mo in the case of Mitsubishi mini splits. The inverters and compressors are 3-ph.

The answer to the OP's question lies in publications like this for individual equipment:

http://ecomfort.com/PDF_files/Mitsubishi/multi_zone/mitsubishi_mxz2b20na_service_manual.pdf
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jackfre
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Fujitsu, whom I used to represent, posts minimum and maximum capacities. For instance my 12 RLS system will cool down to 3,600btu and up to 15 kbtu. The min/max will vary by model for each manyf. The manuf you are looking at should have that information in their brochure. Residential and light commercial equipment is 240v single phase. The big commercial equipment is 3 phase.
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brickeyee
11 years ago
"Residential and light commercial equipment is 240v single phase. The big commercial equipment is 3 phase."

The lower cost of variable frequency drives (VFDs) and 3-phase motors means even residential equipment can have 3-phase motors used.

The 240 V split-phase is turned into a decent quality 3-pase in the VFD.

This post was edited by brickeyee on Wed, Jan 2, 13 at 15:00
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roadking
11 years ago
Jace33:

The Samsung literature shows their USA 12,000 btu inverter model (19 SEER) with a cooling capacity range: 3100 - 14300 BTUs

It's lowest speed would therefore be 1/4 of a ton. Which means that even if 12,000 btus's (1 ton) is oversized for your bedroom it will reduce it's "relative size" to that of a 3100 btu unit when conditions don't call for more btus (which is smaller than any window air conditioner{{gwi:807}} I'm aware of as the smallest of those units are typically 5,000-6,000 btus).

If you can't find a 9000 btu inverter model (which in your situation with a small bedroom{{gwi:807}} being the only room your concerned with) you can get by with a 12,000 btu inverter model. As noted by another poster the information should be available (by the dealer or the manufacturers rep) for each brand and model your looking at.

This post was edited by roadking on Thu, Jan 3, 13 at 10:52
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ionized_gw
11 years ago
Don't forget the other advantages of the inverter-driven systems. Power use buy the compressor will generally be lower. Both indoor and outdoor fan/blower speeds are modulated according to need further reducing power use. The variable speed indoor blower allows settings for efficient dehumidification.

If your local sellers can't help you, maybe you can appeal to the manufacturer to give you model number for you to order.
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How low can inverter go?

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