the pit man said:

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You guys are so far over my head, I just a simple smoker builder

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You're doing the Lord's work though.

Looks like it's too small to upgrade the whole circuit. But you could still try some of the things mentioned earlier (upgrade just the subpanel main breaker, fan, etc).

BenTheGoodAg said:

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the pit man said:

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You guys are so far over my head, I just a simple smoker builder

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You're doing the Lord's work though.

Looks like it's too small to upgrade the whole circuit. But you could still try some of the things mentioned earlier (upgrade just the subpanel main breaker, fan, etc).

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Thanks, I'll see if I can find a 70 amp for the sub panel. I appreciate everyone's help in trying to get the problem to go away. I do have a work around, I have 2 air compressors, one in the shop (80 gal) and one outside that is 180 gal. If I fill all 3 tanks, I can turn them off and have enough air to cut a lot.

Is it wise to put a smaller rated breaker in the line feeding a larger rated breaker? I can see a 75 amp breaker feeding a 60 amp but not visa versa. Is that 6/3 wire pictured, the feeder from the house box to the shop box? If it is, isn't it rated for 55 Amps?
Do all of the other breakers for the shop feed from the 60 amp in the shop box. Lights or a fan don't pull a lot of amps but their load, if operating, are in addition to the CNC and the air compressor.

Rattler12 said:

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Is it wise to put a smaller rated breaker in the line feeding a larger rated breaker? I can see a 75 amp breaker feeding a 60 amp but not visa versa. Is that 6/3 wire pictured, the feeder from the house box to the shop box? If it is, isn't it rated for 55 Amps?
Do all of the other breakers for the shop feed from the 60 amp in the shop box. Lights or a fan don't pull a lot of amps but their load, if operating, are in addition to the CNC and the air compressor.

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Yes the 60 amp is acting like the main breaker. The rest of the breakers feed from it.

the pit man said:

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here's the photo



[img][/img]
[img][/img]

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All I can read is "essex royal 6/3 sdt with ground". Does it say anything else? Maybe at the other panel?

Dr. Venkman said:

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the pit man said:

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here's the photo



[img][/img]
[img][/img]

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All I can read is "essex royal 6/3 sdt with ground". Does it say anything else? Maybe at the other panel?

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I'll see if I find any other markings

This is all I could find....

There's a definitely a difference in "good practice" and "code".

Rattler12 said:

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Is it wise to put a smaller rated breaker in the line feeding a larger rated breaker? I can see a 75 amp breaker feeding a 60 amp but not visa versa.

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Generally, yes, it's good practice to coordinate protection where the closest device trips first. Especially in cases where you're trying to limit the number of affected adjacent systems. A lot of my early career was spent doing coordination studies for power plants - it was a fun puzzle to try to figure out in complicated systems.

But in this case, it's probably worth trying a larger device downstream. We're not trying to coordinate a complex system and the house panel breaker still provides protection. If it works, good for OP. If it doesn't, put the 60A back in the panel and it makes it easier to reset when it trips.

Technically though, the subpanel doesn't need a main breaker at all. It just needs a disconnect. A main breaker is just an easy way to accomplish this.

Rattler12 said:

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Is that 6/3 wire pictured, the feeder from the house box to the shop box? If it is, isn't it rated for 55 Amps?

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Yes, that's how I would rate it unless I knew the temp ratings were 75F (In my experience, more often ends up at 60F). I think it's good practice to bump up to the next size, and that's what I would do if I were designing it. But per code, you're allowed to round up the cable ampacity to the next standard circuit breaker rating (with caveats), which is 60A. FWIW, I think the cable is made with enough design margin that it's OK.

Just my opinion in both cases, though.

the pit man said:

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This is all I could find....

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That cable is marked THHN or THWN which is rated 65 amps.



As mentioned by someone, when a standard breaker size does not correspond to the cable ampacity, you are allowed to use the next breaker size up.



So I would replace the breaker at the house and subpanel with 70A. ASSUMING (again as mentioned earlier in this thread), that both breakers and panels are rated 75 deg C. This would be marked on both pieces of equipment. Most like it is.

Dr. Venkman said:

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the pit man said:

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This is all I could find....

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That cable is marked THHN or THWN which is rated 65 amps.



As mentioned by someone, when a standard breaker size does not correspond to the cable ampacity, you are allowed to use the next breaker size up.



So I would replace the breaker at the house and subpanel with 70A. ASSUMING (again as mentioned earlier in this thread), that both breakers and panels are rated 75 deg C. This would be marked on both pieces of equipment. Most like it is.

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Thanks