MOCP for a commercial dishwasher.

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Greetings,
I'm caught between an engineer, equipment manufacturer. The existing (under-sized) ckt was contractor installed and passed by L&I. The original spec called for a 60A ckt. Apparently a field modification was requested and granted...which has resulted in significant head & rump scratching seasoned with some veiled finger pointing.
The DW nameplate lists 49A @208V-3ph. Although it's UL listed there is no published mocp value on the nameplate and the mfr would not supply a value to the engineer.
I'm thinking a 70A breaker (#4Cu) would suffice but the engineer is calling for an 80A breaker. 12Kw of the 49A is a booster heater. Thoughts?
 

Dennis Alwon

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Chapel Hill, NC
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If you take 125% of 49 amps you get 61 amps. #6 copper at 75C is rated 65 amps so that would suffice and you can use a 70 amp breaker. However if the plans call for different values then you need to do that but I am not sure why the engineer is asking for 80 amp overcurrent protective device.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Greetings,
I'm caught between an engineer, equipment manufacturer. The existing (under-sized) ckt was contractor installed and passed by L&I. The original spec called for a 60A ckt. Apparently a field modification was requested and granted...which has resulted in significant head & rump scratching seasoned with some veiled finger pointing.
The DW nameplate lists 49A @208V-3ph. Although it's UL listed there is no published mocp value on the nameplate and the mfr would not supply a value to the engineer.
I'm thinking a 70A breaker (#4Cu) would suffice but the engineer is calling for an 80A breaker. 12Kw of the 49A is a booster heater. Thoughts?

It is a combination motor load IMO. Wire size based on 430.24.

12kW @ 208V is 33A. that would leave 16A for the motor, assuming just one motor.

16*1.25 + 33 = MCA of 53 A.

I see nothing wrong with a 60A circuit.
 

GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
I see nothing wrong with a 60A circuit.
That looks adequate all right.
I guess the open question is still whether an 80A breaker as requested by the engineer (either with 60A conductors or with 80A conductors) would be Code compliant with this machine as the only connected load.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
That looks adequate all right.
I guess the open question is still whether an 80A breaker as requested by the engineer (either with 60A conductors or with 80A conductors) would be Code compliant with this machine as the only connected load.

I think you could use #6 and a 70A CB.

Unless the instructions or nameplate say otherwise you get to do whatever the code lets you do.

an 80A CB would require a #4 though.
 
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