DISCONNECT USE: FUSED VS. NON-FUSED

1PUMPGUY

New member
Location
WV, USA
FOR YEARS, I'VE WORKED WITH PEOPLE FOLLOWING A "36" RULE FOR MOUNTING A NON-FUSED DISCONNECT IN LINE BETWEEN THE WEATHER HEAD AND A PUMP CONTROL. IN OTHER WORDS, IF YOU USE A NON-FUSED DISCONNECT, IT CAN BE NO FURTHER THAN 36" FROM THE CONTROL (WHICH CONTAINS AN MCP). I'VE BEEN DIRECTED (VERBALLY) THAT ANY DISCONNECT THAT EXCEEDS 36" MUST BE FUSED. WHAT SECTION OF THE CODE CAN I LOCATE THIS INFORMATION? I'M STRUGGLING TO FIND THIS. IN MY MIND, THIS WOULD BE CONSIDERED A BRANCH CIRCUIT...CORRECT? THANKS MUCH!
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
I don't have my code book handy, but I don't believe there is any such rule.

Let me ask what your role is. When you claim to be a "pump man" and a journeyman, are you a plumber or an electrician?

Also, please turn off the ALL CAPS feature. It makes your post difficult to read, and is considered by some to be impolite (as though you were SHOUTING at us).
 
Perhaps you could expand on the setup a little. Is this a service? If so, the use of a non fused disconnect can be problematic for several reasons. A service disconnect is required to be "immediately adjacent to" the OCPD so perhaps that is where this 36" is coming from.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Engineering
You mention weather head.
Is this set-up a service (POCO) or a feeder from a service?
If it is a service a non fused service disconnect is allowed "immediately adjacent thereto" or right next to the overcurrent/short circuit protection.
I know of no distance limitations just needs to be beside it.
OOPS! Electrofelon beat me to it!

Look at 230-91 2014 NEC
 
Last edited:

ron

Senior Member
THE CONTROL (WHICH CONTAINS AN MCP).
Is the control a starter with overloads (heaters). Your reference to an MCP indicates a motor circuit protector which is instantaneous protection only.

Between the overloads and MCP, you effectively have similar protection as a regular circuit breaker, so the downstream disconnect wouldn't require fuses for conductor protection.

I generally put fuses in the motor disconnect if the available short circuit current is higher than 5kA, or the pump assembly specifically says maximum fuse size, as opposed to maximum overcurrent protection, which them allows other protection types instead of just fuses, like a breaker.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
...MOUNTING A NON-FUSED DISCONNECT IN LINE BETWEEN THE WEATHER HEAD AND A PUMP CONTROL...
This implies what has been said, that as a SERVICE disconnect, it must be immediately adjacent. I'll copy and paste something I posted a while ago in here because it actually addresses this specifically, but I've removed a couple of statements that were relating to that previous thread..
UL98, which is what covers disconnect switches, only allows a maximum SCCR of 10kA for an unfused switch. But... many manufacturers have submitted them for series ratings with either their own specific breakers or with fuses, and that fuse or breaker can be down stream. ... So bottom line you must chose a supplier that has a series rating, then follow their instructions exactly.

If your meter feeds a service panel with a main breaker, the NF switch would have to be the same mfr. to have a chance at all of having a series rating...
So bottom line, you have two issues going on here:

First is the issue of whether or not you CAN EVEN USE a non-fused disconnect switch as a Service Switch if the service has more than 10kA available fault current. You didn't actually ask that question, but it's probably more important than you realized. In that older thread, the subject was a NF disconnect ahead of the meter, it seems you are talking about it being behind the meter. So although sometimes the AHJs consider anything ahead of the meter to be the utility's issue, in your case that would not apply. That mike make everything else a moot point. One way around that of course is to just used a Fused Disconnect, even though it's redundant to the main breaker. If you size the conductors correctly, you could fuse it slightly higher than the rating of the main so the breaker would (presumably) trip before the fuses clear.

The question you did ask, as to the separation distance, is not actually addressed as a number of inches in the NEC, they use the term "immediately adjacent to" (230.91). What you have likely experienced is an AHJ's local interpretation of what "immediately adjacent" means. I've had it interpreted as a close nipple adjacent, i.e. the boxes are almost touching. Obviously YMMV because you indicated that you have done this before and used 36" as a maximum. Most likely that came from some specific AHJ, but I don't think you can count on everyone being that generous.
 
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