15A or 20A circuit?

[Sam Conder]

Dang Don, the hits keep on coming. Do you mind if I condense all this down into a single post and move it to the soon to be debuted Frequently Asked Questions section?

Sam Conder
http://www.bt3central.com

[don_hart]

Sure go right ahead.

[Tip]

What is a isolated nuetral and why should a sub panel have one? I looked at the boxes at Lowes but couldn't tell if the neutral was isolated.

Tip

[Thom2]

I LOVE THIS PLACE!!!!!!



Welcome Don, I hope you don't tire of being hammered with questions, I can see already that you're going to be one popular visitor!!!!

Thank You for what you've already contributed, I've learned a lot and I look forward to your posting again!

and thanks to all the other great people on this forum that allow me to learn so much <I think I'll post a 'thank you' post, you people are ALL very much appreciated>

If it ain't broke.. don't fix it!!!... but you can always 'hop it up'

[don_hart]

Isolated neutral referrs to not bonding the neutral to the ground in a subpanel. The reason you have to isolate the neutral from the ground on a subpanel is that the neutral/ground bond in the subpanel can cause neutral loads (return voltage from equipment) to be carried on the ground bus. Obvoiusly this can great a dangerous situation by comprimising you ground protection on circuits in the subpanel. This can also cause equipment damage to electronic equipment.

When you buy a panel you can buy one that specifically has an isolated neutral or you can buy a standard panel and remove the bonding jumper.

There are also isolated ground circuits. These circuits have a separate gound connection either to a metal water main or to a separate grounding rod. The reason you do this is to limit EMI/RFI (electromatic interference/radio frquency inetrference) noise on the service. They are commonly used on circuits that run sensitive electronic equipment. You can also use this idea to isolate your noise generating equipment by placing the equipment on the isolated ground circuit thus keeping the EMI/RFI off the rest of the service.

[Don Mahony]

Don,

I was always taught that you should derate a breaker rating by 20% so you should only plan on loading a 15 amp breaker to 12 amps and a 20 amp breaker to 16 amps etc. Your thoughts would be appreciated.

[don_hart]

You are right the code states that when you have a circuit connected to 2 or more recepticals or outlets you shouldn't have a cord connected load greater than 12 amps for a 15 amp circuit and 16 amps on a 20 amp circuit. Now this is for a single cord connected load. If you have a single load connected to the circuit you should not exceed the circuit rating. So I suggest that if you run the load for just the saw you use a 15 amp breaker for the reasons stated above. If you are running additional loads you should put in a 20 amp breaker.

Don Hart

You live and learn. At any rate you live.

A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.

[Tip]

Don thanks for clearing that up. The guy at Lowe's had not heard of a isolated neutral bar. Great post!

Tip

[don_hart]

No problem. I take anything an employee with lowes or BORG with a grain of salt. They used to try and hire people with some knowledge and experience in the feild but now it seems they are hiring just any joe off the street.



Don Hart

You live and learn. At any rate you live.

A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.

[Tip]

Don, thanks for that info. I think I looked at small main panels instead of sub panels. Great post.

Tip

[don_hart]

Actually a panel is a panel. All of the panels should have a bonding jumper. To use one as a subpanel you just remove the jumper.

Don Hart

You live and learn. At any rate you live.

A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.