SER Aluminum amperage 75 amps ?

[Stevenfyeager]

I only see USE in the ampacity table. Is SER rated the same ampacity rating as USE ? Mnf says I have to install a 70 amp sub panel for 2 infratech heaters rated 25 amps each. NEC has #4 USE aluminum for 75 amps. Is SER the same rating? I realize it will not be used for service entrance, that makes it rate less? Is the NEC #4 rated for 75 amps only if used for service entrance? Thank you!

 

[Stevenfyeager]

I’m sorry USE is only 65, USE-2 is 75

 

[infinity]

Aluminum SE cable has Type XHHW-2 or Type THHN/THWN-2-insulation.

Construction​

"Southwire Type SE cable is constructed with Alumaflex® AA-8000 series aluminum alloy, compacted stranded conductors. The conductors are covered with a sunlight resistant Type XHHW-2 or Type THHN/THWN-2-insulation. A reinforcement tape is wrapped around the conductors for added strength and conformity. A gray sunlight-resistant polyvinyl chloride (PVC) outer jacket covers the entire assembly. Style SEU cable has two phase conductors surrounded by a concentric neutral while the SER style has two, three or four phase conductors and a bare neutral. Southwire Style SER Cable’s phase conductors are identified by a colored stripe on the insulation:

 

[Eddie702]

For a service entrance the cable or conductors need only be rated at 83% of the main breaker so #$ copper or #2 alum for a 100 amp service and 2/0 copper and 4/0 aluminum for a 200 amp service.

This has nothing to do with normal wiring which you use the standard ampacity tables for and derate for temperature and # of conductors if need be.

 

[infinity]

This has nothing to do with normal wiring which you use the standard ampacity tables for and derate for temperature and # of conductors if need be.

Since he's asking about wiring a feeder to a sub-panel this would fall under the normal wiring you've mentioned.

 

[curt swartz]

You are limited to the 75C column even if the wire insulation has 90C insulation due to the 75C max terminations of the equipment.

I have never seen any sizing recommendations of "sub panel" from Infratech. They will specify the feeder size when they are supplying a control panel. Their control panels have individual breakers for each heater. The size of the feeder will be the total load of the heaters * 125%.
(2) 6,000 water heaters would work out to a 62.5 amp feeder, so 70 amps is the next standard size.

 

[Stevenfyeager]

You are limited to the 75C column even if the wire insulation has 90C insulation due to the 75C max terminations of the equipment.

I have never seen any sizing recommendations of "sub panel" from Infratech. They will specify the feeder size when they are supplying a control panel. Their control panels have individual breakers for each heater. The size of the feeder will be the total load of the heaters * 125%.
(2) 6,000 water heaters would work out to a 62.5 amp feeder, so 70 amps is the next standard size.

Yes, you are correct, a control panel. But since they said it will have two 30 amp breakers, I thought I should treat it like a sub panel and use a 4 wire feeder. They actually told me to use a 3 wire.

 

[curt swartz]

Yes, you are correct, a control panel. But since they said it will have two 30 amp breakers, I thought I should treat it like a sub panel and use a 4 wire feeder. They actually told me to use a 3 wire.

Subpanel is just trade slang. It has no technical meaning.

The single phase heater control panels require 3 wires L1/L2/EGC. No neutral required.

 

[infinity]

I thought I should treat it like a sub panel and use a 4 wire feeder. They actually told me to use a 3 wire.

You can use either a 3-wire or 4-wire if there are no 120 volt loads.