Maximum current


Old 06-13-01, 06:55 PM
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I installed 150ft of #6 THHN wire (black, red, and white) in an underground conduit from my main panel to supply a panel at a detached structure for a hot tub and a few outlets and lights. The spa calls for a 50a 220v circuit, but I don't know its actual load.

My question is, how much current can this wire handle (what size breaker should I put in my main panel?)?

I relied on advice from a guy at Home Depot and I hope this wire will work, because I'm not sure I can pull this wire out much less put anything bigger in my conduit!

I appreciate the help, I have no training but I'm trying to learn. Thanks!

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Old 06-13-01, 07:48 PM
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Part D of Article 680 says that Parts A and B apply to hot tubs. 680-25(d) in Part B requires the use of a green #10 to provide an equipment grounding conductor. If the unit calls for a 50 amp cicruit that is what you should use. A 40 amp load on 150' of #6 will result in a 2.4% voltage drop. Most breakers are only to be loaded to 80% of rating so that is why I used 40 amps. 2.4% is an acceptable voltage drop. There are serious safety issues with the electrcial installation for a hot tub so I urge you to contact a qualified electrical contractor if you are not 100% sure of how to make the required connections.
Old 06-13-01, 07:52 PM
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The distance shouldn't hurt you. The 6 Ga. you speak of has an ampacity of 55 amp. If this wire's ampacity lands between 2 breaker sizes as per Article 240-6. Therefore you may increase to the next larger size breaker which would be a 60 amp breaker. You should have just enough power out there to provide for convenience lighting and for receptacles.

Be aware that you must not install any receptacles within 5' of that hot tub. Also remember those receptacles within 10' of that hot tub must be GFI protected.

Also there are several wiring design requirements concerning hot tubs including 240 volt GFI protected feeder, bonding grid and equipment grounding requirements, and clearance minimums concerning light fixtures or paddle fans.

Ask if you don't know these requirements concerning your hot tub.

Old 06-13-01, 08:46 PM
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I'll use a 60 amp breaker to the panel, then a 50 amp breaker from the panel to the tub. In hindsight, I should have installed larger conduit and wire...but it's 2 feet under my lawn now!

I will have the city inspector out, and I'll be sure he takes the time to check all the safety issues with the spa and outdoor receptacles.

I appreciate the help!


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