Square D breakers - slash vs straight rated

Status
Not open for further replies.
C

Cleveland Apprentice

Senior Member
Location
Cleveland, Oh
I am not familiar with Square D products and called a couple suppliers looking for a 3 pole, 80 amp Square D QO style breaker bolt on. The CB must be straight rated at 240 volts as this will be used on a 240 3ph Delta service. A couple suppliers I called didn't know what straight/slash rating meant so I had to explain. I told them my concern of the high leg to ground (208 volts) which was reason for straight rating. They still seemed a little confused. Anyone experienced anything like this with supply houses?

Also, I checked online for the above CB which has the identifying code as QOB380. I saw two different websites with same breaker code. They were at least $200 cost difference (both 10K aic) which adds up big if need several. Looking at the photos of both on websites, they have 240 stamped on it but not the lower 120 value. I assumed this was the straight rated and contacted the distributor online to make sure. Their response was that the QOB380 is slash rated. Now I'm confused and doubting them. I would think if it was slash rated then the lower value number of 120 would be required to be stamped on it. Thanks for replies in advance and have a Happy Easter!
 
A straight rated breaker will be far more expensive than a slash rated.
I suspect there are many slash rated in straight rated applications.
I was working on a cutler hammer panel today and there was a note on the panel trim about straight rated breakers for hi leg deltas
 
You said you asked your distributor. I would contact Square D themselves (i.e. Schneider) and ask them to confirm if that model is straight rated, and if not do they make one that is.
 
Cleveland Apprentice said:
I am not familiar with Square D products and called a couple suppliers looking for a 3 pole, 80 amp Square D QO style breaker bolt on. The CB must be straight rated at 240 volts as this will be used on a 240 3ph Delta service. A couple suppliers I called didn't know what straight/slash rating meant so I had to explain. I told them my concern of the high leg to ground (208 volts) which was reason for straight rating. They still seemed a little confused. Anyone experienced anything like this with supply houses?

Also, I checked online for the above CB which has the identifying code as QOB380. I saw two different websites with same breaker code. They were at least $200 cost difference (both 10K aic) which adds up big if need several. Looking at the photos of both on websites, they have 240 stamped on it but not the lower 120 value. I assumed this was the straight rated and contacted the distributor online to make sure. Their response was that the QOB380 is slash rated. Now I'm confused and doubting them. I would think if it was slash rated then the lower value number of 120 would be required to be stamped on it. Thanks for replies in advance and have a Happy Easter!
Click to expand...

According to this article:
http://ecmweb.com/content/understanding-circuit-breaker-markings

"​Single-pole breakers are always slash rated."
"Two-pole breakers can be either slash or straight voltage-rated, whereas 3-pole breakers are all straight voltage-rated."


In Square D's QO series of 2-pole breakers, the QO, QOB, and QOB-VH breakers are slash rated. QO-H and QOB-H breakers are straight rated.
 
Last edited:
Cleveland Apprentice said:
I didn't know 3 pole breakers are always straight rated. I appreciate that info. Thank you.
Click to expand...

Some of the justification for that is that three phase circuits, which often do not require support for line to neutral loads at a different voltage, can therefore be found as either high leg OR corner grounded OR ungrounded. Any one of these three conditions would require a straight rated breaker.
 
Last edited:
Status
Not open for further replies.
Top