Generator Sizing

[Kevin Holland]

What are the risks/ramifications of starting/attempting to start an HVAC system condensing unit pump with an LRA of 109 Amps with a portable genset with a "surge" amps rating of 15KW (6.5A @ 240V)? Instant windings damage? 50 Amp circuit breaker trip? And can "hard start kits" reduce LRA by 50%?

 

[Ethnan]

Hello Kevin,

I assume your HVAC runs also at 240V and the motor starts on DOL, in which case your stating current will be almost same as your LRA of 109Amps. If your genset(6.5A @ 240V) surge rating is 15KW, the 50Amp circuit breaker will trip. Yes I have seen some hard start kits that can be used to start compressors/motors of high LRA. In doing this, you have not necessarily reduced the LRA, you only have effectively provided an equal but opposite reactive power that results in reducing the overall current drawn at start up. Its similar to what folks do by connecting capacitors to their inductive loads to reduce their utility bills.

 

[waross]

First, sort out your numbers,
What is the rated Full Load current of the HVAC?
6.5 Amps at 240 Volts is about 1500 Watts.
15,000 surge kW is unreasonable.
I have started a lot of HVAC units on small standby generators.
Any answer that I give you based on some of your numbers will be wrong based on other numbers.

[link ]Bill[/url]
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"Why not the best?"
Jimmy Carter

 

[Ethnan]

@waros

He mentioned 15KW surge power, that's 62.5 surge Amps at 240V. I am sure you are mistaking the 15KW for 15,000 Amps.

 

[waross]

Rated Amps = 6.5, surge Amps 62.5?
I stand corrected, 10/1 should have been 9.6/1
6.5 Amps x 240 Volts = 1.56 kW generally rounded to 1.5 kW or 1500 Watts.
I would consider 15,000 Amps to be unreasonable by a factor of about 1000/1.

[link ]Bill[/url]
--------------------
"Why not the best?"
Jimmy Carter

 

[Ethnan]

I am still wondering where you got 15,000Amps from? Can you explain?

 

[waross]

Sorry. Correction made.

[link ]Bill[/url]
--------------------
"Why not the best?"
Jimmy Carter