Any comments about DC inverter technology?

Posted by Jean on February 28, 2009, 11:00 am

wrote:

>> Inverter technology has been around for years.

>Zero torque at low Hz input and how are you going to maintain windings temps
>?

The motors are DC so torque can be controlled at all speeds. Here's
the best URL I've found so far:

http://www.toshiba-aircon.com.au/web/toshibaweb.nsf/668d4ee488131f104a2564d5002c772f/6f5f04cfc75d1186ca25691d001dec97?OpenDocument

With PWM, the power to motor is continuously varied according to load
therefore winding temps are directly controlled by the amount of
coolant passing through the unit.

Posted by Steve on February 28, 2009, 8:59 am

> Inverter technology has been around for years.
> Quiet enough to set the unit outside grandmas bedroom window.
> (you know, the grandma that can still hear you coast up the driveway with
> the lights & the engine off at 2:30am)
> Trane built some of the first & gave up on it "mis-forecasting" the
> future...
> The Nips took it on like a storm.
> Today variable speed & inverter drives are no longer cutting edge,
> products not offering them are falling off the pace.
> Even Trane has got to be looking a VFRZ... They've started relabling
> everything else...
> Though your question wasn't about EER's & SEER's, here's my $.02:
> Where I come from EER & SEER be damned... typical residential cooling
> hours run between 5-650 per year.
> Heating Degree Days, on the other hand, are anywhere from 8500-10,000.
> When I look for a HP I'm looking for HSPF. Anything under 7 is out of the
> running, 8-9 looks good...
> A 2 stage unit, oversized on the cooling side has some great benefits.
> As always, duct size & airflow will be one of the biggest deciding factor.

In my neck of the woods, the heating and cooling hours are reversed. We have
4 seasons in south Mississippi.... December, January, February, and summer.
I only posted those links and explained the difference between SEER and EER
because the SEER numbers are so misleading. Yes I have sold and installed
mini-splits, and the Mitsu brand costs the customer more than a conventional
split system(including ductwork).

The only way anybody can figure out what they *NEED* is to do the math for
correct sizing, and how many heating and cooling degree days in their
particular location. Then and only then should they be concerned about the
actual quality, efficiency, warranties, etc. of the equipment they want
installed.

Posted by Noon-Air on February 28, 2009, 3:02 pm

> That didn't come from the nose end of the bipolar bear...

How could you tell the difference??

Posted by The King on March 1, 2009, 1:48 am

snip

So far your question has produced 14 replies including mine. What is
the ratio of useful and useless.

Posted by Jean on March 1, 2009, 12:13 pm

On Sun, 01 Mar 2009 01:48:40 -0500, The King

>snip
>So far your question has produced 14 replies including mine. What is
>the ratio of useful and useless.

Looks like I'm batting zero......

In any event, it looks like this new technology is going to shake up
the HVAC tech's life. He'll have to become more of an electronic
instrumentation tech.

Have a look at this service manual. I'm impressed with the self
diagnostics. EVERYTHING is monitored.

http://www.mrslim.com/UploadedFiles/Resource/PUY-PUZ-A12~42%20Service%20Manual%20OC367C%206-27-07.pdf

Another interesting feature is the linear expansion valve controlled
by a stepper motor.

I've never seen such a complete technical manual and I think it is
worth a perusal by you HVAC guys. It's the way of the future. The old
heat pumps are going to go the way of tube TV's.

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Any comments about DC inverter technology? - Page 2