Amps?

[paulmars]

Year 2002 two ton 240vac hvac compressor. Plaque says 21.4 amps. Paperwork says use 30a dbl breaker.

Is that 21.4 amps on each hot wire?

Air handler central hvac 120vac fan paperwork says 6.2 amps

2 fridges in house. Plaques say 6.5 & 4.5a. 120vac.

Both fridges on same hot. The 6.2 amp central fan is on the other hot.

Only other things running were modem\router and two phone charges. Smart tv & microwave were plugged in, but off.

Yes water heater was off and no one was washing or drying clothes.

Yes both fridges were cycled on during amp measurements.

6500 watt generator has a 27 amp breaker on each hot. My ammeter read 15 & 18 amps.

Should 21.4a 240vac compressor pull 21.4 on each hot? If not why does it need a 30a dbl breaker?

P
.

 

[u2slow]

Compressors can draw different amounts of current depending on the pressure(s) and temperature at a given time, also wether or not a defrost coil is actively powered. Power factor is also a consideration.

If your generator produces an imperfect sine wave and your meter isn't true-rms, you may be getting a false reading.

And yes, the two hot conductors on the 240V work together to deliver the full amperage. Imagine 21.4A doing the mambo 60x/sec.

 

[dcg9381]

Should 21.4a 240vac compressor pull 21.4 on each hot? If not why does it need a 30a dbl breaker?

It'll pull more than that at start up. Without a "soft start" capacitor, you're likely to be SOL with a 6500 watt generator and a 27 amp breaker.. Likely that breaker is only rated for non-continuous use.

Why does it need a 30A breaker? Because that's the standard size breaker up from 20A.

Breaker protects the wire, not necessarily the HVAC.

 

[wyliesdiesels]

Year 2002 two ton 240vac hvac compressor. Plaque says 21.4 amps. Paperwork says use 30a dbl breaker.

Is that 21.4 amps on each hot wire?

yes 21.4a on each conductor. but if your generator is rated @ 240v, the compressor would just be considered a 21a load or 5,040w....

Air handler central hvac 120vac fan paperwork says 6.2 amps

2 fridges in house. Plaques say 6.5 & 4.5a. 120vac.

Both fridges on same hot. The 6.2 amp central fan is on the other hot.

Only other things running were modem\router and two phone charges. Smart tv & microwave were plugged in, but off.

Yes water heater was off and no one was washing or drying clothes.

Yes both fridges were cycled on during amp measurements.

6500 watt generator has a 27 amp breaker on each hot. My ammeter read 15 & 18 amps.

Should 21.4a 240vac compressor pull 21.4 on each hot? If not why does it need a 30a dbl breaker?

P
.

yes you should read 21.4 on each leg for the compressor.... why is it on a 30a breaker? because of startup/in-rush current. check the nameplate on the compressor and see what the MOCP(maximum overcurrent protection) rating is.... if it says 30a breaker or fuse then you have the right size breaker

 

[paulmars]

It worked for 2 days & nights until the poco resumed. Is it safe to add another fridge & room ac if power goes out again?

 

[u2slow]

It will be safe because generators are overload protected.

Wether it will all work seamlessly or not is going to require trial and error.

 

[mm08822]

The condenser nameplate lists info for the compressor and the fan.
This information is then used to calculate the minimum circuit ampacity (MCA) and the maximum overcurrent protection (MOP).

The feeder for the motor circuit is required to be sized at 125% of the largest motor plus the fan load.
Assuming the MCA of your compressor is 21.4A:
21.4 - 2A (for the fan) =19.4A Then 19.4 / 1.25 = 15.5A

The MOP is calculated using 175% of the compressor load.
15.5A x 1.75 = 27.16A then add ~2A for the fan = 29.16A >>>30A cb = MCA.


Adding non-motor loads to a gen is pretty safe and predictable. It is the constant cycling of compressors, more specifically the in-rush start-up current that requires the extra reserve capacity. Small gens don't handle in-rush well. They can bog down creating voltage dips and change in frequency. This can reduce the life of many things.

If you manually manage your loads, you can hookup more.

 

[paulmars]

The generator operator's manual dont say much about its breakers. It does say that overloading the generator can break it.

 

[fitter30]

Any motors has lock rotor amp rating which is the amps that it take to get motor turning. Lock rotor might only last 1/2 to 30 cycle with a load of the 60 cycle power at max amps then as the motor builds speed the amps drop off. Breakers are made for different purposes. For a generator to protect the generator. Typical panel breaker for your house to protect the wire. And other breakers to protect a device (load).
6500 watts =27 amps Even it has another 1000 watts peak it will not run your ac. Maybe with a soft start. Lock rotor is at least 5 times run amps.
I use a 6500 watt generator for emergency power on lp which is less but dont know what it is because i converted it. Run some lights, wifi and tv, fridge, well pump, electric water heater and a 5k btu window unit for a bedroom NOT at the,same time. Heat lp gas fireplace. Been without power for up to two weeks.

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[paulmars]

Link says 10kw

41.7@120/240

Isnt 41.7 120 same current as 20.85 240 ?

 

[wyliesdiesels]

a generator rated 10Kw at 240v is 41.7a

If you only use 120v and have access to both ungrounded legs then you will have 41.7a available on each leg. But only if the generator is setup like that which it most likely isnt.

 

[rlitman]

Link says 10kw

41.7@120/240

Isnt 41.7 120 same current as 20.85 240 ?

No. 41.7A @ 240V = 10008VA, i.e. 10kVA. That generator should ideally be able to deliver double that to 120V loads.
Also FYI, Volt Amps (VA) are not equal to Watts (W). A 10kVA generator will likely only be 8kW rated, so if the link says 10kW, you probably need 12kVA. Pay close attention to the kVA and kW ratings, because kVA is always the bigger number, so marketers like to promote it.

 

[paulmars]

If your generator produces an imperfect sine wave and your meter isn't true-rms, you may be getting a false reading.

How much could that effect the readings?

 

[u2slow]

How much could that effect the readings?

Depends on the generator and load characteristic. A cheap inverter gen could potentially have a really 'rough' output, and a greater error.

One way to know is to use both a true-rms meter, and one that's not. Compare readings.

 

[paulmars]

Compressor LRA 82, RLA 16
Fan FLA 1.6
Maximum circuit amps 21.4
Max fuse 30

 

[paulmars]

So 18ax240v is 2320 watts

Slightly over 1\3 the 6500 watt capacity

I understand mtr start up pulls a lot more.

 

[theoldwizard1]

Any motors has lock rotor amp rating which is the amps that it take to get motor turning. Lock rotor might only last 1/2 to 30 cycle with a load of the 60 cycle power at max amps then as the motor builds speed the amps drop off.

Power electric/electronics are not my field of expertise, but locked rotor amps are NOT the same as starting amps. LRA is MUCH higher !

I use a 6500 watt generator for emergency power on lp which is less but don't know what it is because i converted it. Run some lights, wifi and tv, fridge, well pump, electric water heater and a 5k btu window unit for a bedroom NOT at the same time. Heat lp gas fireplace. Been without power for up to two weeks.

Your 6500W generator is likely 6500W peak, 5000W continuous.

Heavy loads (anything with a big AC motor, like a well pump or window A/C) already have a starting capacitor and this is part of the problem. When a capacitor is fully discharged, it "appears" to be a short circuit to the power source (i.e. it wants to be charged INSTANTANEOUSLY). Using a TRUE, "currently limiting" soft starter (not just another big capacitor) will greatly reduce that instantaneous current.

 

[paulmars]

It is not likely peak unless we state peak. My peak is 8125.