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#37053 04/21/04 12:51 AM
Joined: Dec 2003
Posts: 524
Member
... Hi gang, I have a prospective customer who needs 3 phase in a single phase restaurant...Why you may ask ?? ... His central A/C system that is slated to be installed needs 3 phases.. as it will be alot cheaper for him to run... So he's been asking me..everyday now, what can I do...I told him I "think" that a converter can be used... Am I correct ?? Can it run a compressor and the air handler, or are they used only for motor loads...
... He suggested a buck/boost xfrmer,..but I don't think that'd work...Help me PLEEEZE and tell me something I can tell this pest...(he's actually an old friend o' mine)
Russ


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#37054 04/21/04 12:56 AM
Joined: Feb 2004
Posts: 1,437
Member
Russ...
http://www.phase-a-matic.com/

Tell me if this helps [Linked Image]

-Randy

PS... They state Air Conditioning equiptment as an application [Linked Image]

[This message has been edited by Lostazhell (edited 04-21-2004).]

#37055 04/21/04 12:59 AM
Joined: Jan 2004
Posts: 105
C
Member
Howdy Attic Rat- this place is pretty good at applications and there's some good info on their website: http://www.kayind.com/index.htm

Be sure to mention that you will be powering a compressor and the converter is sized for starting that. Your customer may reconsider when he gets the price. Good luck

#37056 04/21/04 01:04 AM
Joined: Dec 2003
Posts: 524
Member
...Thanx sooo much guys!! [Linked Image] [Linked Image] [Linked Image] [Linked Image]


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#37057 04/21/04 01:43 AM
Joined: Apr 2002
Posts: 558
C
Member
I would like to see the numbers on this. How can it be cheaper to run 3-phase HVAC equipment off single phase using a phase converter instead of using 1-phase equipment? Phase converters are not 100% efficient.

I think your customer/friend saw the circuit sizes for 3-phase and single phase equipment and figured the 3-phase equipment must be cheaper to run since the circuit size is smaller.

Curt

[This message has been edited by caselec (edited 04-21-2004).]


Curt Swartz
#37058 04/21/04 01:53 AM
Joined: Jun 2001
Posts: 642
N
Member
It's not cheaper to run the phase converter.
It is usually 3 phase power is not availble from the POCO. The installed cost of the phase converter is usually less expensive than a new 3 phase service and the POCO charges. Sometimes 3 phase equipment is all that is availble for the size of load the equipment serves.


ed
#37059 04/21/04 01:59 AM
Joined: Apr 2002
Posts: 558
C
Member
Nesparky,

I agree with you. It was the comment as it will be alot cheaper for him to run that I’m questioning.

Curt


[This message has been edited by caselec (edited 04-21-2004).]


Curt Swartz
#37060 04/21/04 07:35 AM
Joined: Sep 2003
Posts: 650
W
Member
Three phase motors are generally regarded as more efficient than single phase motors, but you have the inefficiency of the phase converter to consider, which depending upon type is either a mess of power electronics (static phase converter) or essentially a single phase motor/three phase generator rolled into a single rotating machine (rotary phase converter). You can even use a plain ordinary three phase induction motor as a rotary phase converter; you power it from your single phase supply through two of the leads, do something mechanical to start it spinning (since a single phased 3 phase motor won't _start_), and once it is spinning you can draw the third leg from the motor terminal.

For air handling equipment, rather than using a phase converter, it is worth while considering using a variable speed drives. Air handling is the classic case where variable speed can save energy. For a given duct system, the power required to move air scales roughly as the cube of air speed, but the volume of air moved scales linearly with the air speed. Rather then running your motors at full speed, and then throttling the airflow or turning the system on and off, operating at low speed continuously with minimum resistance to air flow can save lots of energy.

-Jon

#37061 04/21/04 07:37 AM
Joined: Dec 2003
Posts: 524
Member
...Caselec,thats what he thinks,someone must of told him that it'd be cheaper for him in kilowatt/hours to run the A/C at 3 phase rather than at single... Down the line,wouldn't the usage come out the same?? I mean a 60,000 btu unit is gonna consume the same amount of power,whether it's 3 phase or not, it's just divided by 3...or something like that...no..??
Russ


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#37062 04/21/04 08:52 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Russ by using a phase converter down the line it will just cost more money in electricity.

Even the highest quality (expensive) phase converter will not be 100% efficient.

Any heat coming off the phase converter is wasted energy.

The best option from a energy consumption standpoint is a true 3 phase service if available.

The next would be having single phase HVAC equipment if it is available in the BTUs needed.

The least electrically efficient method is the phase converter.

In the end watts are watts no mater how many phases or what voltage, it will take a certain amount of watts to remove a given amount of heat.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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