Help calculating for two refrigeration devices on one branch circuit

[Jon456]

Actually, I want to get a better understanding of both the service load calculations and the branch circuit sizing calculations.
Service is 208Y/120V. This is what I have from the equipment specs:

Undercounter refrigerator:

115V, 1-phase, 2A, 1/6 HP, NEMA 5-15 plug​

Undercounter ice maker:

115V, 1-phase, 10A, 1/4 HP, MOCP 15A, NEMA 5-15 plug​

I'd like to place both of these on a single branch circuit (one duplex GFCI receptacle).

My question about the service loads has to do with the ice maker having a 1/4 HP rating but also 10A rating. From NEC Table 430.248, the FLC for a 1/4 HP motor is 5.8A. But I assume that since the manufacturer's specified current rating is higher, I should use the 10A value. For the refrigerator, the Table 430.248 FLC is 4.4A based on 1/6 HP (and ignoring the 2A rating by the manufactuer).

So for the refrigerator, Load = 120V x 4.4A = 528 VA
And for the ice maker, Load = 120V x 10A = 1,200 VA

Is this correct so far?

Now the branch circuit conductor and OCPD sizing is where I'm really confused. Article 440 really kicks you around all over the NEC. For example, Section 440.3(C) sends you to Article 422. Section 422.11(G) sends you back to Part VI of Article 440. Section 440.51 of Article 440 Part VI has a FPN referring you back to 240.4(G) for application of Parts III and VI of Article 440. Section 240.4(G) states that for air conditioning and refrigeration equipment conductors, to reference Article 440, Parts III, VI. (Ok, now I'm getting dizzy.)

440.22(A), it states that "A protective device having a rating or setting not exceeding 175 percent of the motor compressor rated-load current or branch-circuit selection current, whichever is greater, shall be permitted."

Is rated-load current the equipment's amperage rating from the manufacturer or the FLC from Table 430.428?

And what about the "branch-circuit selection current"? Part of the problem I have with Article 440 is that a lot of it seems to rely on the nameplate markings on the equipment itself. But how is one to design the electrical system before the equipment is acquired? As I read 440.4(C), the branch-circuit selection current appears to be based on what's printed on the nameplate (which is omitted from equipment spec sheets). Section 440.12 also requires the nameplate data.

So now I'm completely befuddled as to how to determine the branch circuit ampacity and OCPD for the refrigerator and ice maker listed above. My gut instinct tells me these these two should run just fine on a 20A/12AWG circuit (but with a 15A OCPD due to the ice maker's MOCP restriction). But I really would like to understand how to work though all the twists and turns of calculating the correct wire ampacity and OCPD values.

Could someone please help walk me through this?

 

[Jon456]

Do the lack of replies mean that most people don't bother with branch circuit calculations for situations like this and just use "rule of thumb" or gut calcs?

 

[WA_Sparky]

Actually, I want to get a better understanding of both the service load calculations and the branch circuit sizing calculations.
Service is 208Y/120V. This is what I have from the equipment specs:

Undercounter refrigerator:

115V, 1-phase, 2A, 1/6 HP, NEMA 5-15 plug​

Undercounter ice maker:

115V, 1-phase, 10A, 1/4 HP, MOCP 15A, NEMA 5-15 plug​

I'd like to place both of these on a single branch circuit (one duplex GFCI receptacle).

My question about the service loads has to do with the ice maker having a 1/4 HP rating but also 10A rating. From NEC Table 430.248, the FLC for a 1/4 HP motor is 5.8A. But I assume that since the manufacturer's specified current rating is higher, I should use the 10A value. For the refrigerator, the Table 430.248 FLC is 4.4A based on 1/6 HP (and ignoring the 2A rating by the manufactuer).

So for the refrigerator, Load = 120V x 4.4A = 528 VA
And for the ice maker, Load = 120V x 10A = 1,200 VA

Is this correct so far?

Now the branch circuit conductor and OCPD sizing is where I'm really confused. Article 440 really kicks you around all over the NEC. For example, Section 440.3(C) sends you to Article 422. Section 422.11(G) sends you back to Part VI of Article 440. Section 440.51 of Article 440 Part VI has a FPN referring you back to 240.4(G) for application of Parts III and VI of Article 440. Section 240.4(G) states that for air conditioning and refrigeration equipment conductors, to reference Article 440, Parts III, VI. (Ok, now I'm getting dizzy.)

440.22(A), it states that "A protective device having a rating or setting not exceeding 175 percent of the motor compressor rated-load current or branch-circuit selection current, whichever is greater, shall be permitted."

Is rated-load current the equipment's amperage rating from the manufacturer or the FLC from Table 430.428?

And what about the "branch-circuit selection current"? Part of the problem I have with Article 440 is that a lot of it seems to rely on the nameplate markings on the equipment itself. But how is one to design the electrical system before the equipment is acquired? As I read 440.4(C), the branch-circuit selection current appears to be based on what's printed on the nameplate (which is omitted from equipment spec sheets). Section 440.12 also requires the nameplate data.

So now I'm completely befuddled as to how to determine the branch circuit ampacity and OCPD for the refrigerator and ice maker listed above. My gut instinct tells me these these two should run just fine on a 20A/12AWG circuit (but with a 15A OCPD due to the ice maker's MOCP restriction). But I really would like to understand how to work though all the twists and turns of calculating the correct wire ampacity and OCPD values.

Could someone please help walk me through this?

Not sure how much help i can be.. Typically I will have a dedicated circuit for any large appliances like refrigerators, freezers, copiers (office).. etc.
FCL=FLA = Full load current=Full Load Amps
MCA = Minimum circuit amps
FLA*1.25 = MCA (when a motor starts it will spike higher than normal running amps)

I typically will rate my OCPD based on the manufacturers MOCP rating (max over current protection) or what ever the next breaker is above the MCA rating.
You cannot load any circuit more than 80% of its capacity. 20A*.8=16A
If your FLA for the two units is 14.4 your MCA would be 18A and doesnt work.

If you ignore the MOCP recommendation and a fault occurred, your unit could burn out or catch fire before your breaker tripped.

 

[kwired]

Not sure how much help i can be.. Typically I will have a dedicated circuit for any large appliances like refrigerators, freezers, copiers (office).. etc.
FCL=FLA = Full load current=Full Load Amps
MCA = Minimum circuit amps
FLA*1.25 = MCA (when a motor starts it will spike higher than normal running amps)

I typically will rate my OCPD based on the manufacturers MOCP rating (max over current protection) or what ever the next breaker is above the MCA rating.
You cannot load any circuit more than 80% of its capacity. 20A*.8=16A
If your FLA for the two units is 14.4 your MCA would be 18A and doesnt work.

If you ignore the MOCP recommendation and a fault occurred, your unit could burn out or catch fire before your breaker tripped.

If unit is listed and has factory installed cord with 5-15 cord cap on it - you don't need to concern yourself with branch details of 430, 440 or even 422. Just run a 15 or 20 amp circuit to a 5-15 or 5-20 receptacle, the unit already should have sufficient overload protection within.

You maybe will have some concern over how to determine the load for service/feeder calculations. I'd go with the 2 and 10 amp values on the nameplates. No idea how they came up with those vs the HP mentioned, but at same time there may be multiple loads within and the 1/6 and 1/4 HP are just the primary motor sizes but doesn't include any other loads.

Ice maker depending on design could have in addition to a compressor a circulating pump, condenser motor, evaporator motor, lighting, probably not a defrost heater, but maybe. Some of same items mentioned could be part of the under counter refrigerator.

 

[Dennis Alwon]

The problem I see is that the 1/4 hp unit calls for a 15 amp circuit. For 2 motors to be on one circuit I believe you would have to take the largest motor x 125% plus the small motor. 12.5 + 2 = 14.5 amps. I guess this is okay but not sure I would do it.

 

[kwired]

The problem I see is that the 1/4 hp unit calls for a 15 amp circuit. For 2 motors to be on one circuit I believe you would have to take the largest motor x 125% plus the small motor. 12.5 + 2 = 14.5 amps. I guess this is okay but not sure I would do it.

I think there is more to it than just a single 1/4 HP motor. If it is only one 1/4 motor and draws 10 amps, it is very inefficient.