Disconnect size for Heater

[jap]

Heater nameplate indicates 12kw 240v 1ph, 52FLA, suggested wire size #6, Max Circuit Breaker 70 amp (which I plans on using)

In that case, shouldn't the wire size be #4, and, should the disconnect size for this be 60 amp? or 100 amp rated?

Planning on installing the disconnect within sight. Pipe and wire.

Thank You,


JAP>

 

[don_resqcapt19]

The conductor must have a rating equal to or greater than that of the OCPD, so yes, you need 4 AWG copper.

 

[jap]

Thank You it was throwing me off.

JAP>

 

[wwhitney]

The conductor must have a rating equal to or greater than that of the OCPD, so yes, you need 4 AWG copper.

What rule would prohibit the use of 240.4(B) here?

125% (assuming that factor is required here) of 52A is 65A, and the 75C ampacity of #4 Cu is 65A, so it appears a 75C wiring method with #6 Cu and a 70A breaker per 240.4(B) would be fine.

Cheers, Wayne

 

[jap]

What rule would prohibit the use of 240.4(B) here?

125% (assuming that factor is required here) of 52A is 65A, and the 75C ampacity of #4 Cu is 65A, so it appears a 75C wiring method with #6 Cu and a 70A breaker per 240.4(B) would be fine.

Cheers, Wayne

I think you're meaning the ampacity of #6 is 65 amps in the 75d C column.

JAP>

 

[wwhitney]

I think you're meaning the ampacity of #6 is 65 amps in the 75d C column.

JAP>

Yes, a particularly poor typo! I meant #6 Cu has a 75C ampacity of 65A. So the #6 Cu stated in the manual is correct, unless you are using NM cable, or LFNC/LFMC in a wet location, or a handful of other options that are limited to 60C. In which case you'd need #4 Cu.

Cheers, Wayne

 

[jap]

Yes, a particularly poor typo! I meant #6 Cu has a 75C ampacity of 65A. So the #6 Cu stated in the manual is correct, unless you are using NM cable, or LFNC/LFMC in a wet location, or a handful of other options that are limited to 60C. In which case you'd need #4 Cu.

Cheers, Wayne

I am using Pipe and wire.

I'm still no sure whether to size the disconnect on the 52 FLA and use a 60a rated disconnect, or, base it on the 70 amp breaker and bump it to a 100 amp.

My gut's telling me the latter of the two.

JAP>

 

[letgomywago]

I am using Pipe and wire.

I'm still no sure whether to size the disconnect on the 52 FLA and use a 60a rated disconnect, or, base it on the 70 amp breaker and bump it to a 100 amp.

My gut's telling me the latter of the two.

JAP>

I'd say do a permanent breaker lock but if you do a 100 amp disconnect they make the breaker type usually cheaper than the non fused type.

 

[Sberry]

If there is room a 6 space is about cheaper than the 70 2 space that is just. The make a 2 space 60, Challenger or GE about 15$ back in the day and over a decade must have replaced about half a dozen cheap suckers all they did was provide a place to cut a perfectly good wire in half.

 

[letgomywago]

If there is room a 6 space is about cheaper than the 70 2 space that is just. The make a 2 space 60, Challenger or GE about 15$ back in the day and over a decade must have replaced about half a dozen cheap suckers all they did was provide a place to cut a perfectly good wire in half.

QO has a locking cover type 3r for like 35 to 50 bucks I think it's a 100 amp buss is the only down side

 

[Sberry]

Ok, in the same vein is a 14 cable good to a 3.6 K I believe wall oven? Crap, maybe it was 3.4?

 

[letgomywago]

Ok, in the same vein is a 14 cable good to a 3.6 K I believe wall oven? Crap, maybe it was 3.4?

Depends on nameplate and instructions for the oven. I think that situation will need a smaller breaker.

 

[Sberry]

I was backtracking this train of thought. I ran across an old install I did/modified quite some time ago. The oven croaked and got a hard to fit replkacement but it came 4 wire. The old was whip connected and married to a 3 wire cable on a 30 with the stove top. It was a 240 unit. As I recall we simply removed the oven from that circuit and ran a 3 wg and put it on its own breaker, prolly a 14 on a 15.

 

[Sberry]

As best I recall that was the nameplate, was a long time ago and remember,,, cant you simply size the wire and the circuit and was later kind of figured out it was basically because its not the same as the max allowable circuit with the min wire if whip and single wires were used,,, something of that nature. I am waiting (I am not patient, I want instant gratification) for a couple comments and see if I get the same answer from the same guys from 25 years ago,,,, hahaha

 

[Sberry]

We might do it different than someone else, in my own case its likely I might use same panel for additional equipment, 2 air comps a service light and a recept. I can see making it simple also. 2 ungrounded conductors and a 2 pole switch.

 

[electrofelon]

I am using Pipe and wire.

I'm still no sure whether to size the disconnect on the 52 FLA and use a 60a rated disconnect, or, base it on the 70 amp breaker and bump it to a 100 amp.

My gut's telling me the latter of the two.

JAP>

We had a recent thread on this where it appears at least some manufacturers are requiring a NF disco be protected at not above it's rating. My reading of this for Siemens is it may only apply when utilizing series ratings to obtain above a 10k SCCR, but it's not entirely clear.

 

[jap]

We had a recent thread on this where it appears at least some manufacturers are requiring a NF disco be protected at not above it's rating. My reading of this for Siemens is it may only apply when utilizing series ratings to obtain above a 10k SCCR, but it's not entirely clear.

Thank You,

JAP>

 

[jap]

I'd say do a permanent breaker lock but if you do a 100 amp disconnect they make the breaker type usually cheaper than the non fused type.

Yea, a CHPL would suffice I just wish they were a little more robust.

JAP>