Nameplate interpretation

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karn

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Electrician
I have 2 units,

Unit 1; MOP 40A, MCA 24A, RLA 17A, LRA 123A

Unit 2; MOP 40A, MCA 24A, RLA 16.5A, LRA 102A

From what I understand I can have a 40a Breaker with #8 wire and a 30amp receptacle for unit one, or I could also choose to have a 30a breaker and #10 wire with a 30amp receptacle

And for unit 2 I can have a 40amp breaker and number 8 wire on a 20amp receptacle or I can choose to have a 20amp breaker with #12 wire on a 20amp receptacle
IMG_20170608_134839.jpg
 
You cannot install a single 30A or 20A receptacle on a 40A circuit. 210.21(B)(1)

Can these units be hardwired?

If so and using conduit, a 40A breaker and #12 THHN/THWN wire would work for both units.
 
jumper said:
You cannot install a single 30A or 20A receptacle on a 40A circuit. 210.21(B)(1)

Can these units be hardwired?

If so and using conduit, a 40A breaker and #12 THHN/THWN wire would work for both units.
Click to expand...

I agree, conduit or #12 AWG MC cable.
 
infinity said:
I agree, conduit or #12 AWG MC cable.
Click to expand...

The print says to install 50a 3phase receptacles for these units, and shows them on 40a breakers,

But the units came from the manufacturer with L14-30 and L14-20 plug ends, yes, L14, not L15, and they are 3 phase units, the print did not specify a wire size
 
These units are manufacturer to be cord and plug connected or someone installed a cord and plug on them? Also the nameplate says "Branch Circuit Selection Current A: 18" whatever that means.
 
The refrigeration contractor installed the units, when I asked, they told me they came from the factory with the plug ends, I don't know if their electrician put them on or not, I was going to call the manufacturer but they have an overseas number, the whole thing seemed weird to me as they were L14s on a 3phase unit,
 
infinity said:
These units are manufacturer to be cord and plug connected or someone installed a cord and plug on them? Also the nameplate says "Branch Circuit Selection Current A: 18" whatever that means.
Click to expand...
In Europe, they can use adjustable circuit breakers. We can't (unless it is a single motor protection device) so that statement is superfluous for us.

I'd say it's a good bet that they were made (and UL listed) for hard wiring and some distributor here in the US added the plugs.
 
So, I can use #12 wire, or #10, with a 40 or 30amp breaker,- and possibly a 20 amp breaker on the smaller unit? But they have to be hardwired?, And I should discard the plug ends?
 
petersonra said:
I thought MCA was minimum conductor ampacity. That would suggest a #10 is required.
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12 is good for 25 amps if you have 75C terminals and at least 75C conductors.

MCA already has 125% for continuous load of the largest motor factored into it.
 
karn said:
So, I can use #12 wire, or #10, with a 40 or 30amp breaker,- and possibly a 20 amp breaker on the smaller unit? But they have to be hardwired?, And I should discard the plug ends?
Click to expand...
MCA = Minimum Circuit Ampacity is a calculated value for all components in the unit, not just the motor but, yes, takes the 125% of the motor FLA into account. It's the highest current that the circuit will see when operating correctly and what the conductors must be sized for (so yes, Bob, you were essentially correct).

So you can use #12 wire under the conditions that kwired just said, but you can't run 24A through a 20A circuit breaker continuously, you can only run 20A. Same with the plugs (and the receptacles with the same ratings), and in fact assuming they used #12 SO cord for those plugs (since they used 20A devices), that's no good either (20A max). So yes, no matter what you would need to remove those plugs and then either replace them with #10 SO and 30A fittings, or hard wire them, in which case you could use #12, but a 25A circuit breaker.
 
I will ensure the sizing of the so cord and either hardwire or most likely replace plug ends with L15-30's, should I also swap out the 40 amp breakers or are 25, 30 and 40 all acceptable for these units?, also I may need #10 as the furthest unit from the panel is around 200', and the closest one is probably about 100'
 
Any of those breaker sizes would be acceptable, but the 40 would be least likely to cause a nuisance trip. If you already have 40s in the panel, I would keep them.
 
I am still uneasy sizing the Conductors to the MCA and the breaker to the MOP. 12GA on a 40A breaker makes me scared. I guess they are assuming that the motor overloading is already taken into account with the 125% addition to the overall FLA, and that any of the other loads will not overload they will short circuit..
 
karn said:
I will ensure the sizing of the so cord and either hardwire or most likely replace plug ends with L15-30's, should I also swap out the 40 amp breakers or are 25, 30 and 40 all acceptable for these units?, also I may need #10 as the furthest unit from the panel is around 200', and the closest one is probably about 100'
Click to expand...

sounds like a voltage drop calculation needs to be part of the solution.
 
fifty60 said:
I am still uneasy sizing the Conductors to the MCA and the breaker to the MOP. 12GA on a 40A breaker makes me scared. I guess they are assuming that the motor overloading is already taken into account with the 125% addition to the overall FLA, and that any of the other loads will not overload they will short circuit..
Click to expand...


It really shouldn't. This has been a safe and reliable method for decades.
 
fifty60 said:
I am still uneasy sizing the Conductors to the MCA and the breaker to the MOP. 12GA on a 40A breaker makes me scared. I guess they are assuming that the motor overloading is already taken into account with the 125% addition to the overall FLA, and that any of the other loads will not overload they will short circuit..
Click to expand...
Typical condensing unit is a compressor and a blower motor. Both will have motor overload protection.

Should you have resistance heat elements involved - they don't change resistance they can not overload, they can develop faults though, but unless you fault to ground or line to line very near an end of the element, you still won't have overload level (in relation to supply conductor ampacity) of current.
 
infinity said:
These units are manufacturer to be cord and plug connected or someone installed a cord and plug on them? Also the nameplate says "Branch Circuit Selection Current A: 18" whatever that means.
Click to expand...

440.2 Definitions.
Branch-Circuit Selection Current. The value in amperes
to be used instead of the rated-load current in determining
the ratings of motor branch-circuit conductors, disconnecting
means, controllers, and branch-circuit short-circuit and
ground-fault protective devices wherever the running overload
protective device permits a sustained current greater
than the specified percentage of the rated-load current. The
value of branch-circuit selection current will always be
equal to or greater than the marked rated-load current.
 
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