Electrical calculation question

[RingSteel]

Does anyone know the formula for converting the required starting wattage for a 240v A/C?
The A/C is rated 21.2 RLA (rated load amps) and 104.0 LRA (locked rotor amps).

Just trying to figure out the correct sized generator watts to operate the A/C.

[Brazos Hunter]

Amps times Voltage gives you watts




Michael

[Bill]

W=V x A but with the initial current draw, it's a bit more complicated.

I'd call the manufacturer of the AC and ask.

[alien_scones]

Too bad we banned that AI earlier

[Texas Made]

240V x the LRA would give you a good starting place for the generator KVA. It gets a little more complicated with power factor, and the NEMA starting codes for the motor. Should be able to have the manufacturer run a sizing report with their software and all the loads you want to run on the generator to verify the calculated size and ensure the generator will start the AC unit and other loads.

[Txhunter3000]

Add a soft start kit to your ac so that it ramps up slower. That way you can get by with a smaller genset. Micro air is a brand name you can look up.

[Greenheadless]

Nec430

LRA is inrush.

[db@100]

240V x the LRA would give you a good starting place for the generator KVA. It gets a little more complicated with power factor, and the NEMA starting codes for the motor. Should be able to have the manufacturer run a sizing report with their software and all the loads you want to run on the generator to verify the calculated size and ensure the generator will start the AC unit and other loads.

By this, he will need a 25 KVA generator just for the a/c unit? 104 x 240 = 24960.

[Stolle]

I'm running mostly everything off a 13000 Duramax on NG. I have the Micro Air Soft start on my AC 5 ton Lennox unit. Tons of people in the Houston area are using this type of set up over stand by generators.

[RonRon]

The RLA is the amperage that the unit pulls while it is running. The LRA is the amperage that the unit pulls when it starts up [lasting around a second or 2] These amperage ratings are a result of the efficiency of the unit. Your unit will use 5088 watts [21.2a x 240v ] Size the generator accordingly. The generator should be able to handle the start up. You can put a start kit on the unit to allow it to start up quicker,........they cost less than $75.00

[RingSteel]

Thanks for the help.
After watching my neighbor power his whole house (similar 4 ton a/c as mine) with a portable 13k generator, it's confusing when the installers are telling me that I need a 24k backup generator.
Both houses are all NG appliances and water heaters, so just the 4 ton a/c is the largest electrical load.

I'm starting to think of backup generator installers as used car salesmen, ha ha.

[denimdeerslayer]

Thanks for the help.
After watching my neighbor power his whole house (similar 4 ton a/c as mine) with a portable 13k generator, it's confusing when the installers are telling me that I need a 24k backup generator.
Both houses are all NG appliances and water heaters, so just the 4 ton a/c is the largest electrical load.

I'm starting to think of backup generator installers as used car salesmen, ha ha.

I ran mine with a 9k last week a few days. I did make sure ac was off on fire up as the well and water heater would both be drawing then. Give well a few min and turn ac back on. Only real issue was when cousions kid used blow dryer.

[Stolle]

Thanks for the help.
After watching my neighbor power his whole house (similar 4 ton a/c as mine) with a portable 13k generator, it's confusing when the installers are telling me that I need a 24k backup generator.
Both houses are all NG appliances and water heaters, so just the 4 ton a/c is the largest electrical load.

I'm starting to think of backup generator installers as used car salesmen, ha ha.

Main reason I went the portable route. During testing I’ve ran the entire house including 3 freezers, a wine cooler and 2 refrigerators in the house while running the AC. I haven’t attempted the pool. I would probably have to load shed the freezers or AC.

If you have Facebook look up the group portable generators - portable generators to power entire house. Tons of great information and testimonials.

[RingSteel]

Main reason I went the portable route. During testing I’ve ran the entire house including 3 freezers, a wine cooler and 2 refrigerators in the house while running the AC. I haven’t attempted the pool. I would probably have to load shed the freezers or AC.

If you have Facebook look up the group portable generators - portable generators to power entire house. Tons of great information and testimonials.

Thank you.

[Bill]

Good information