Square d circuit breakers - Electrician Talk - Professional Electrical Contractors Forum

KEI · 07-18-2009, 11:11 PM

Does anyone know if Square D Homeline has a circuit breaker that trips at 100% of its rating?

lectro88 · 07-18-2009, 11:45 PM

what are you attempting?

480sparky · 07-18-2009, 11:59 PM

If you let a CB run at it's rated amperage long enough, it may or may not trip.

KEI · 07-19-2009, 12:18 AM

I have # 10 feeding a 27A Load. 2P 30A Breaker will trip at 80%. The wire has a 35A ampacity, but is supposed to be protected by a 30A Breaker. 80% of 30 is 24, Is it acceptable to use a 40A breaker? 80% of 40 is 32, which is within its ampacity rating. If I could find a 30A breaker that trips at 100 %, my problem is solved.

robnj772 · 07-19-2009, 12:21 AM

Quote:

Originally Posted by KEI

I have # 10 feeding a 27A Load. 2P 30A Breaker will trip at 80%. The wire has a 35A ampacity, but is supposed to be protected by a 30A Breaker. 80% of 30 is 24, Is it acceptable to use a 40A breaker? 80% of 40 is 32, which is within its ampacity rating. If I could find a 30A breaker that trips at 100 %, my problem is solved.

lectro88 · 07-19-2009, 01:53 AM

The 35a only applies to motors, welders, cranes and special applications permitted by code only. see article 240* I would NOT use a 40. try this math 35 x 80% or 35 x .8 This is Not for general purpose loads. General purpose max overcurrent for #10 is 30a. read it carefully

lectro88 · 07-19-2009, 02:08 AM

Is this for an air conditioner ? or general purpose multi outlet, or dedicated

Magnettica · 07-19-2009, 02:54 AM

Quote:

Originally Posted by KEI

I have # 10 feeding a 27A Load. 2P 30A Breaker will trip at 80%. The wire has a 35A ampacity, but is supposed to be protected by a 30A Breaker. 80% of 30 is 24, Is it acceptable to use a 40A breaker? 80% of 40 is 32, which is within its ampacity rating. If I could find a 30A breaker that trips at 100 %, my problem is solved.

27 amps protected by a 30 amp breaker will be fine until it's running at full amperage for 3 hours or more.

Quote:

Article 100 Definitions

Continuous Load. A load where the maximum current is
expected to continue for 3 hours or more.

KEI · 07-19-2009, 07:53 AM

Quote:

Originally Posted by lectro88

Is this for an air conditioner ? or general purpose multi outlet, or dedicated

This is for a dedicated lighting circuit

MDShunk · 07-19-2009, 08:32 AM

If the breaker is tripping, it might be bad or you might have a bad fixture/ballast on the circuit. Megger the circuit first. A 30 amp breaker will hold 27 amps forever. It will hold 32 amps forever, for that matter, unless the breaker itself is located in a very hot ambient.

KEI · 07-19-2009, 09:25 AM

Quote:

Originally Posted by MDShunk

If the breaker is tripping, it might be bad or you might have a bad fixture/ballast on the circuit. Megger the circuit first. A 30 amp breaker will hold 27 amps forever. It will hold 32 amps forever, for that matter, unless the breaker itself is located in a very hot ambient.

the breaker is not tripping, this is a dedicated outdoor lighting circuit the load is 27.8A. I have #10 feeding them, I am concerned if I protect the circuit with a 30A cb, it may trip. I have always been told that a circuit breaker will trip at 80 % of it rating, is that correct?

MDShunk · 07-19-2009, 09:27 AM

Quote:

Originally Posted by KEI

I have always been told that a circuit breaker will trip at 80 % of it rating, is that correct?

No, that's not true at all. Get on Square D's website and take a look at the trip curve for a 30 amp breaker.

In a non-dwelling setting, you're not allowed to load a circuit beyond 80% if the load is continuous. That has nothing to do with the breaker tripping, though.

KEI · 07-19-2009, 09:32 AM

what do you think, would you feel comfotable putting this load on a 30 A Breaker........I don't want it to trip 1/2 way through a game.

MDShunk · 07-19-2009, 09:34 AM

Quote:

Originally Posted by KEI

what do you think, would you feel comfotable putting this load on a 30 A Breaker........I don't want it to trip 1/2 way through a game.

I'm not convinced that you even have a choice at this point. Is there individual overcurrent protection in each light standard or ballast box?

You really an electrician?

KEI · 07-19-2009, 09:37 AM

There are 4 fixtures per breaker, 1500W each 240V 1PH

KEI · 07-19-2009, 09:38 AM

where is the trip curve table?

MDShunk · 07-19-2009, 09:49 AM

Quote:

Originally Posted by KEI

where is the trip curve table?

Click here.

KEI · 07-19-2009, 09:50 AM

Quote:

Originally Posted by MDShunk

I'm not convinced that you even have a choice at this point. Is there individual overcurrent protection in each light standard or ballast box?

You really an electrician?

Yeah, I'm an electrician, i am just askin some questions, to make sure all my bases are covered.

lectro88 · 07-19-2009, 09:54 AM

To be code compliant for lighting, 27 x 125% = 33.75 Needs to be #8 and 35a breaker. If I remember correctly its 1.25 for each light. (help me out guys) right ?

Speedy Petey · 07-19-2009, 09:54 AM

Quote:

Originally Posted by KEI

Yeah, I'm an electrician, i am just askin some questions, to make sure all my bases are covered.

I think Marc asked this question in part because of this statement, among others:

Quote:

2P 30A Breaker will trip at 80%

I am sure others are thinking this as well.