# Slash Breakers and 120/240 Delta 3-Phase Panels



## jar546 (Sep 21, 2019)

We all know that in a typical 3 phase 4 wire grounded delta system the B phase is 208 to ground while phases A & C are 120V to ground.

Breakers with a slash rating of 120/240 are not designed for 208 to ground, therefore cannot be used for single pole circuits per 240.15(B)(3), BUT what about a double pole breaker with a slash rating being used on the AB or BC phases if it does not utilize a neutral?

After all, the only time the 208V is present is for circuits to ground, otherwise the voltages phase to phase are always 240V.

A-B= 240
A-C= 240
B-C= 240
B-N= 208


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## chris kennedy (Sep 21, 2019)

No book here but see 240.8_?


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## jar546 (Sep 21, 2019)

chris kennedy said:


> No book here but see 240.8_?


No sir, that is fuses or breakers in parallel


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## jar546 (Sep 21, 2019)

chris kennedy said:


> No book here but see 240.8_?



Ahh, I see now.  You are talking about 240.85, right?

In that case, yes.  Even though there is no neutral and the voltage of the circuit is 240V phase to phase, the fault current from the equipment grounding conductor (EGC) would be the path to ground.  Here is how it reads:


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## Norcal (Sep 25, 2019)

I wonder how many inspectors look for a 240V rating on a 2 pole breaker installed on the high leg (it's not always on the B phase as required) & another leg? It does get misused. A few years ago a friend who was doing HVAC & refrigeration (contractor) called why a Hoshizaki ice machine was displaying a high voltage trouble code, and their 208-230V 1Ø machines do require a neutral because of the pump, condenser fan motor, water valves, being 120V,  the machine was installed in a farm shop & PG&E loves 120/240V 3Ø for AG services, thought about it & after he checked the voltage, come to find out the installing electrician had used the high leg & another phase for a 120/240V circuit, and the control boards of Hoshizaki ice machines measures the L-N voltage and if it exceeds 140V, it shuts down*, after the problem was corrected all was well, but a professional should know that you cannot use the high leg with a 120/240V single phase circuit, I had nothing to do with the repair, just over the phone troubleshooting. Back to the original topic, I can understand why people do not use a 240V rated breaker when used on the high leg because they are expensive & not a normal stock item, but using a 120/240V slash rated breaker is a code violation.

*Correct the voltage issue & it automatically resets.


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