Motor terminal box KO reduction

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greeny

Member
Location
Southern NH
Hi guys,
I was wondering what method everyone uses to reduce the KO for a motor terminal box. For example, a standard 7.5 HP 3 phase motor may have a 1" KO, but is only wired with 1/2" flex. Do you use a threaded hub, hex reducing bushing or reducing tins? Or am I really supposed to order a custom peckerhead?
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I may have just been "lucky" with my motor installs but often the thickness of the metal of the peckerhead didn't allow enough exposed threads on a fitting when I used re washers alone. I often ended up having to use nipples to get enough thread so often we would use a full size nipple with a coupling and bushing on top just to get a snug fit.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
augie47 said:
I may have just been "lucky" with my motor installs but often the thickness of the metal of the peckerhead didn't allow enough exposed threads on a fitting when I used re washers alone.
Click to expand...
Have you tried flipping one of the washers over so it's the "wrong" way, or sandwiching more than one washer on each side?
 
G

greeny

Member
Location
Southern NH
I typically deal with dual voltage motors wired for 480. So I really dont want to use 1" flex for a few #14 wires, etc... I hate using reducing washers, especially when going down 2 sizes. They're just too flimsy and then the locknut loosens up eventually, not to mention it's just not a sturdy installation. And then playing that silly game Larry and Augie mentioned about flipping one over to get enough thread for the locknut. I figured there's a better method. Like using a hub to get a threaded entry.
 
W

wireguru

Senior Member
is a threaded reducer long enough to get a locknut on each side of the hole? Then flex connector could screw into that...
 
W

wireguru

Senior Member
greeny said:
Wireguru, I had thought of that. A hex-head threaded reducer would only require 1 locknnut...
Click to expand...

i had considered that, but thought vibration might cause it to loosen where the other kind of reducer (proper name escapes me at the moment) with a locknut on each side might be less prone to coming loose.
 
G

greeny

Member
Location
Southern NH
Coffeebean, I think you are correct.

Wireguru, there are not enough threads on a normal threaded reducer to work. I could barely get back-to-back locknuts on and that leaves no room for the thickness of the box.

Anyone? I need a better solution than reducing washers . . .
 
R

RETRAINDAILY

Senior Member
Location
PHX, arizona
when I worked manufacturing industrial refrigeration units
the wielders would wield plates on them and
I would punch them to the right size.:cool:

I try to hub/re-bushing..but will use washers if thats what it takes.
 
J

Joe Villani

Senior Member
Location
Westchester County NY
Motor KO reduction

Motor KO reduction

You can always install a pullbox. Close nipple it to the motor j box.

I used the following: close nipple into motor j box ,threaded coupling into close nipple, threaded reducing bushing into coupling, flex connector into threaded bushing.

Joe
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
greeny said:
Coffeebean, I think you are correct.

Wireguru, there are not enough threads on a normal threaded reducer to work. I could barely get back-to-back locknuts on and that leaves no room for the thickness of the box.

Anyone? I need a better solution than reducing washers . . .
Click to expand...
I'll try again...Place a 1" coupling on top of the peckerhead (it normally will be adequately snug but put 1x1-1/4 RE washer under it if you like, from inside the peckerhead install a 1 X Close nipple or 1x**nipple (depending on the thickness of the peckerhead) with locknut and plastic bushing then install a RE bushing in your coupling to accept your feed conduit/flex.
Can't knock it off with a hammer.
 
G

greeny

Member
Location
Southern NH
augie47 said:
I'll try again...Place a 1" coupling on top of the peckerhead (it normally will be adequately snug but put 1x1-1/4 RE washer under it if you like, from inside the peckerhead install a 1 X Close nipple or 1x**nipple (depending on the thickness of the peckerhead) with locknut and plastic bushing then install a RE bushing in your coupling to accept your feed conduit/flex.
Can't knock it off with a hammer.
Click to expand...

I just can't help myself from thinking that's cheesy. Sorry . . .

I like the welded plate. The hub with the reducing bushing seems best. Why can't the manufacturer's give us the smaller KO and let people enlarge the KO if necessary? I mean, most 20 HP motors are probably used at 460, not 230.
 
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