I know most of the more efficient residential A/C systems (SEER 16+) have two speed compressor motors with variable speed inside fan motors.  However, a buddy of mine that works in commercial says they have variable speed compressor motors now...anyone know if/when they will make it to residential?

They have been available in mini-split systems for quite awhile.

Jon,

Thanks, I did not know that. I know in the automotive industry there have been variable displacement compressors for many years. Mostly using a control valve manipulated by refrigerant temp/pressure. However, recently they are now using PWM solenoids for the control valve.

So, when do you think, and why do you think home residential typical heat pumps (not mini-splits) are so late to the game?

Some European companies make them A/W or W/W but none sell here AFAIK.

Many of us are working on getting our VSD systems out to market but they are still rare here.

Some European companies make them A/W or W/W but none sell here AFAIK.

I have a Daikin Air to Water system for whole house heating and cooling and a Daikin minisplit, both of which utilize the inverter technology. Daikin is the second largest air conditioner maker in the world, IIRC.

Why are they late to the game? cost v benefit.
An old Army Seargeant doesn't have to tell a Chief that u gotta get bang for your buck.
I was one of the last hold-outs to 2 stage geo as the savings in my heating dominated climate was less than a hundred bucks a year while the technology often cost mch more than $1,000. Further the first generation 2 stagers had a high failure rate and some even caught fire!
Tax credits and reduced pricing due to greater volume sold, as well as working the bugs out brought me on board.
ACs and Geos will move to variable compressors very soon. In fact there are a few offerings now.
I promise my customers they won't be guinea pigs so I'm on the side lines another year or two however.

Why did mini splits get them first? They are a newer technology in general and they are trying to replace ducted systems with multiple air handlers. If you wanna have multiple airhandlers, you gotta have multiple stages, mltiple compressors (as the first mini splits) or variable capacity compressors.

Thanks for your service.

Joe
SGT MP

I have been trying to buy inverter compressors with EVI or liquid injection for some time. Copeland claims to have some but most people at Copeland don't even know of them. Danfoss has them but only in larger sizes and again, only in Europe. They are popular in Europe and it is not too hard to understand why we cannot get them here. Joe, said it correctly.......cost of the extra technology is not worth it when our cost of energy is low compared to Europe. Honestly, the difference between a single and 2 stage comp is about $20 in parts. Inverters are not that pricey now either so it could be done at a reasonable price.

Mini-splits got them because many of the houses they went in had no or inadequate heating to begin with, in Asia, and it was an easy fix, then they covered the resi cooling sector in Europe that has no ductwork. Also, (this is my own opinion) many companies won't sell into the US because we like to sue anyone for anything. This is the preception and it keeps companies from trying things until they are completely sorted out. I used to import the Schott vacuum collector into Canada and I was told by their legal dept not to sell to the US for just that reason. The Chinese don't care because they won't warrant anything anyway.

AFAIK, one can use a VFD with any 3 phase compressor to get variable speeds.

Posted By jonr on 07 Sep 2012 09:17 AM
AFAIK, one can use a VFD with any 3 phase compressor to get variable speeds.

True but have you looked at the cost of a 1ph to 3ph VFD? They are not cheap and then you need a control and you have to watch oil return to the comp. You will often need one capable of 40A@230 1ph, depending on the HP of course. It doesn't help in expanding the low end of the envelope though. For that you need to keep the comp cool and inject vapour or saturated vapour into the scroll.

Most industrial VFD's can use single phase input power and supply three phase output to the motor no problem.  Typical rule of thumb is double the power of the motor.  The reason for this is that the front end of the VFD is a rectifier that converts AC to DC then supplies DC to the inverting section which pulses transistors to create a three phase sinusoidal output to the motor at the frequency and voltage (up to line voltage) that is required.

The reasons for doubling the size are because of two reasons:

Single phase load draw higher current than three phase loads for a given power consumption, so increasing the size of the VFD gives a higher current rating on the input size.  (This usually isn't an issue).

The VFD's use capacitors between the rectifier and inverter sections to smooth the rectified voltage waveform.  A rectified three phase waveform has less "ripple" than a rectified single phase waveform.  So when you use two phase input one a three phase VFD, increasing the size of the VFD is one way to get more capacitance inside of it to smooth the greater ripple in the rectified wave form.

There are single phase VFD's, they are simply VFD's with less rectifying circuits and more capacitors.  They cost more money because fewer manufacturers make them.  Most three phase VFD's can run on single phase input power satisfactorily by doubling the size of the VFD and turning off input phase loss protection.  Input phase loss protection is triggered by detection of high DC Bus Ripple by the VFD control board.  There is usually another fault detection that is actually a DC bus ripple fault in addition to input phase loss detection, so, at least for the VFD's I have been working with, there is no risk of damage to the VFD by disabling input phase loss detection.

Many municipalities have been doing this for water pressure boosters for years in residential areas that don't have three phase available.

 

Carrier has such a unit now on the market.

Carrier model is the Infinity 20

have you looked at the cost of a 1ph to 3ph VFD?

Yes, they are inexpensive - a few hundred dollars.

Posted By tigerfan6 on 09 Sep 2012 03:40 PM
Most industrial VFD's can use single phase input power and supply three phase output to the motor no problem.  Typical rule of thumb is double the power of the motor.  The reason for this is that the front end of the VFD is a rectifier that converts AC to DC then supplies DC to the inverting section which pulses transistors to create a three phase sinusoidal output to the motor at the frequency and voltage (up to line voltage) that is required.

The reasons for doubling the size are because of two reasons:

Single phase load draw higher current than three phase loads for a given power consumption, so increasing the size of the VFD gives a higher current rating on the input size.  (This usually isn't an issue).

The VFD's use capacitors between the rectifier and inverter sections to smooth the rectified voltage waveform.  A rectified three phase waveform has less "ripple" than a rectified single phase waveform.  So when you use two phase input one a three phase VFD, increasing the size of the VFD is one way to get more capacitance inside of it to smooth the greater ripple in the rectified wave form.

There are single phase VFD's, they are simply VFD's with less rectifying circuits and more capacitors.  They cost more money because fewer manufacturers make them.  Most three phase VFD's can run on single phase input power satisfactorily by doubling the size of the VFD and turning off input phase loss protection.  Input phase loss protection is triggered by detection of high DC Bus Ripple by the VFD control board.  There is usually another fault detection that is actually a DC bus ripple fault in addition to input phase loss detection, so, at least for the VFD's I have been working with, there is no risk of damage to the VFD by disabling input phase loss detection.

Many municipalities have been doing this for water pressure boosters for years in residential areas that don't have three phase available.

 

Ya learn something new every day. Thanks.

I've installed everything around the VFD before, many times, but it has always been a 3ph VFD for a 3ph load.

Posted By jonr on 09 Sep 2012 05:06 PM

have you looked at the cost of a 1ph to 3ph VFD?

Yes, they are inexpensive - a few hundred dollars.

What does Carrier charge for the upgrade?

Posted By acwizard on 09 Sep 2012 04:23 PM
Carrier model is the Infinity 20

Its commonly called the Greenspeed since they have many products in their infinity line
Mitsubishi also makes the PUMY-PVFY variable capacity units, its a commercial line but works well for residential.
Daikin has the Sky Air system but it is not available in a downflow configuration.
Nordyne(frigidaire, maytag) have the iQ drive systems that were the "first" residential variable capacity units
WaterFurnace makes the Series 7 variable capacity geothermal heat pump with up to 41 EER and 5.3 COP ratings.

Most other manufacturers such as Trane, Rheem etc, should be coming out with inverter/variable compressors for residential shortly.
Technically Trane had the XV1500 out back in the mid 1980's but it was so expensive it didn't sell well in the market of the 80's and the technology was sold off to other countries.

IQDRIVE by Nordyne. Seer 24.5

That is what I plan to use at my new home.

"The unit can modulate from as low as 40 percent to as high as 118 percent of capacity, instantly adjusting to exactly offset the cooling demands on the house. "

http://www.iqdrive.net/