I am installing an ice machine in a hospital. The minimum amp draw is 19.3, with a maximum breaker size of 25. The unit itself comes with only #14 connecting wires. Do i need to size my breaker/wires for 25 amps, and If so, why does the ice machine come with only #14 wires? Can I install #12 wire with a 20 amp breaker for this application? I don't understand how the machine can come with 14 wires, but the specs call for a minimum circuit rating of 19.3. Please help.
wire/breaker size
- Thread starter shaknbake
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: wire/breaker size
The 60?C ampacity of #14 copper is 20 amps.
The 60?C ampacity of #14 copper is 20 amps.
milwaukeesteve
Senior Member
- Location
- Milwaukee, WI
Re: wire/breaker size
Ice machines are not subject to the standards set by 240.4(d) for small conductors.
Ice machine OCP and conductor sizing is based on Article 440 for refrigerating equipment.
Your circuit wires would be based on 125% of min amp draw of 19.3. 24.125Amps is less that 25Amps. Here you could use a #14 ONLY if you could verify all points and parts of that circuit are 90C. If not, you need to use the 60C column, which means #12's.
Because that is a manufactured unit, the UL listing is based on the full ampacity level of #14 XXXX type wire (whatever XXXX is).
The OCP is based on 440 also, and is not subject to the 125% rule. This figure is based on what is needed to allow startup, yet protect on running load. The Nomenclature plate should tell you what the min and/or max breaker size is (they will have already done the calculations). If not, read through 440 and calculate breaker size.
Ice machines are not subject to the standards set by 240.4(d) for small conductors.
Ice machine OCP and conductor sizing is based on Article 440 for refrigerating equipment.
Your circuit wires would be based on 125% of min amp draw of 19.3. 24.125Amps is less that 25Amps. Here you could use a #14 ONLY if you could verify all points and parts of that circuit are 90C. If not, you need to use the 60C column, which means #12's.
Because that is a manufactured unit, the UL listing is based on the full ampacity level of #14 XXXX type wire (whatever XXXX is).
The OCP is based on 440 also, and is not subject to the 125% rule. This figure is based on what is needed to allow startup, yet protect on running load. The Nomenclature plate should tell you what the min and/or max breaker size is (they will have already done the calculations). If not, read through 440 and calculate breaker size.
abode electric
Member
- Location
- New jersey
Re: wire/breaker size
The 19.3 name plate already is a 125% of the load. The 19.3 is all you need to size the circuit for. #14 in the 60c column is good for 20 amps. Then your ocpd can be 25amps as per name plate.
The 19.3 name plate already is a 125% of the load. The 19.3 is all you need to size the circuit for. #14 in the 60c column is good for 20 amps. Then your ocpd can be 25amps as per name plate.
milwaukeesteve
Senior Member
- Location
- Milwaukee, WI
Re: wire/breaker size
Thank you Adobe Electric.
I missed that.
Since this is a refrigeration unit and is subject to article 440, the manufacturer is required to put certain information into that name plate.
That 19.3A is already calculated at 125% and is the unit running load. This would include all motors (compressor and ventalating) and any other loads (lights and/or controls).
Thank you Adobe Electric.
I missed that.
Since this is a refrigeration unit and is subject to article 440, the manufacturer is required to put certain information into that name plate.
That 19.3A is already calculated at 125% and is the unit running load. This would include all motors (compressor and ventalating) and any other loads (lights and/or controls).
milwaukeesteve
Senior Member
- Location
- Milwaukee, WI
Re: wire/breaker size
ventilating.... sorry
ventilating.... sorry
Re: wire/breaker size
Appliance wires are allowed to run hotter than building wire for several reasons:
1. Building wire can be embedded in thermal insulation willy nilly as well as soundproofing insulation. Appliances are a more engineered situation.
2. Binding screw connections have more than their fare share of connection resistance. Applicances usually use crimped connections.
3. Appliance wire for a refrigerator or washing machine is rated 105 degress Celsius. For electric ranges, stoves, or dryers higher temperature rated wire is used because of hot spot criteria.
4. The NEC people also want you to some amount of reasonable voltage drop performance. For the shorter wires that are in an appliance a smaller size is appropriate.
5. The UL tolerance for circuit breaker trip point is rather sloppy. Therefore, building wire needs a more generous safety factor. In a refrigerator, the compressor has an internal overload device that is more prescise. Door jamb heaters and defrost heaters really only have 1 catastrophic failure that can trip the circuit which is a dead short. If it fails open circuit a fire wil not occur. If a door jamb heater or defrost heater ground faults halfway down its length it usually overheats enough to go open circuit or it has a local fuse to take care of that.
Appliance wires are allowed to run hotter than building wire for several reasons:
1. Building wire can be embedded in thermal insulation willy nilly as well as soundproofing insulation. Appliances are a more engineered situation.
2. Binding screw connections have more than their fare share of connection resistance. Applicances usually use crimped connections.
3. Appliance wire for a refrigerator or washing machine is rated 105 degress Celsius. For electric ranges, stoves, or dryers higher temperature rated wire is used because of hot spot criteria.
4. The NEC people also want you to some amount of reasonable voltage drop performance. For the shorter wires that are in an appliance a smaller size is appropriate.
5. The UL tolerance for circuit breaker trip point is rather sloppy. Therefore, building wire needs a more generous safety factor. In a refrigerator, the compressor has an internal overload device that is more prescise. Door jamb heaters and defrost heaters really only have 1 catastrophic failure that can trip the circuit which is a dead short. If it fails open circuit a fire wil not occur. If a door jamb heater or defrost heater ground faults halfway down its length it usually overheats enough to go open circuit or it has a local fuse to take care of that.
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