View Full Version : anti-short bushing sizing

Mr T
April 14th, 2005, 10:44 PM
I am preparing to run some 1/2" flexible metal conduit. Will be running 12ga x 2 + insulated ground (all THHN). I know you need a anti-short bushing on each end to keep the metal from digging into the wire.

I picked up some red #1 bushings. (says for 12-3, ect). The bushing looks like it will fall into the conduit. (too small) Is this normal? How do you install these?

April 14th, 2005, 11:00 PM
If it says it's for 12-3, then the bushing you got is most likely for MC cable--which would mean it's too small. FMC runs bigger!

April 14th, 2005, 11:00 PM
The #0 and #1 bushings are for the smaller sizes. I think it's the #2 bushing for 1/2" greenfield. I'm not really up on the sizes. I just go by eye. If it falls into the conduit, it's too small. You can often use 1 size too big if need be, since the split down the side allows it to overlap a little.

April 14th, 2005, 11:06 PM
If it says it's for 12-3, then the bushing you got is most likely for MC
Most of these anti-short bushing packages nowadays list the AC or MC sizes on the package. No longer do I notice any of them listing the equivalent greenfield trade sizes on the package. I dug up an old book, and found the equivalent Greenfield (pipe) trade sizes to translate the anti-short bushing numbers. Here it is:

#0 - 5/16" trade size
#1 - 3/8" trade size
#2 - 7/16" trade size
#3 - 1/2" trade size
#4 - 3/4" trade size
#5 - 1" trade size
#6 - 1-1/4" trade size
#7 - 1-1/2" trade size
#8 - 2" or 2-1/2" trade size

By this chart, a #3 anti-short bushing would be the absolute smallest size permitted to be used with Greenfield, since 1/2" is the smallest Greenfield size that the code permits to be used. The #0, #1, and #2 bushings can only be used with cable assemblies like AC and MC.

Mr T
April 14th, 2005, 11:24 PM
Wow.. quite a few sizes.. Good ol Home depot sells the conduit, but not the bushings to go along.. i'll take em back.... and head down to the supplier in town since they will be open when im around tomorrow.... Where are the 24/7 supply houses!?!?!?!? Not everybody works on stuff during the day...

SPeaking of home depot.. THey just put in those self-scan checkouts here. I'm gonna have to take a few 4x8 sheets of 3/4" MDF through them sometime for the fun of it. "Please place the item you just scanned in the bag"...."You have not placed your item in the bag.. Please place the item you just scanned in the...." *thud*

April 14th, 2005, 11:39 PM
I HATE those self scanners. One of the 24 hour grocery stores near my house goes to self scan only after 10pm. I make the person who oversees the self scans ring them up for me because I hate them so much.

My next all time biggest pet peeve in the stores (especially Wal Mart), is the RFID scanners on the exit doors. Is it my fult that something did't get deactivated at the checkout? Heck NO! It's frustrating paying for something, walking 30 feet, and have that thing go off and then you have to prove you just paid for the stuff 30 seconds ago. I got so mad recently when at that thing when it went off on me that I shoved my whole cart load of stuff out the doors and into the parking lot and told the "gaurd" at the RFID scanner to run after it if he wanted to check out my stuff. Made me feel redeemed.

April 14th, 2005, 11:41 PM
I still have this nagging feeling in the back of my head that #2 red heads work just fine in 1/2" greenfield. You might want to try the #2 and #3 to see which one works out better. That's the way I do it anyhow... by eye.

Mr T
April 14th, 2005, 11:57 PM
I was in a store with the security tags. I bought something, and the tag was messed up and they couldnt deactivate it (set the alarm off 3 times). so they let me go with it. I kept the tag. I am a field service tech of office equipment (printers, copiers, ect). We are all in the office on fridays for meetings/parts/ect. I put that tag in another tech's tool kit. (Stuck it on the inside of a screwdriver pocket for a tool he rarely uses (a screwdriver :D ). This tech works on the machines in the grocery stores. (that have the alarms). I never asked what happened (paybacks are a biiiiiiitch), but i looked in his kit a few weeks later and it was gone.

If you something that has one of these tags (pre packeaged in the item) but no scanners at that store... please send them to me.. as they are still active!!! :D :p :eek:

April 15th, 2005, 03:19 AM
when were anti shorts required on greenfield?
Also noticed these self checkers as a matter of fact today, sure seems impersonal.(home depot)

April 15th, 2005, 03:17 PM
I'm with wannabee on this one. I don't believe you have to use anti-shorts on MC cable or on any raceway. Only AC cables. You do need a bushing of some type where the FMC connector comes into the box, and one of those threaded grey bushings is what most people would use.

There are two styles of connectors for FMC -- one that goes around the conduit and squeezes it, and another that threads into the conduit. The second type doesn't require that you smooth/deburr the cut conduit and provides more protection to the wires. But it also reduces the diameter of the conduit and you may have difficulty if you're pushing the conduit fill.

This being said, I think you can use anti-shorts if you want to and can find them in the appropriate size.

Mr T
April 15th, 2005, 04:12 PM
I have the outside clamp style connectors. (didnt have access to the internal screw in type.. wish i did though) Found my bushings though.. Amazing how a small piece of plastic can generate so many posts....


April 15th, 2005, 05:13 PM
Wanna questioned using anti-shorts on Greenfield (type FMC). You do not have to use anti-shorts on type MC, but you do have to use them on type AC (BX) and FMC (Greenfield).

Mr. T, what size did you end up using with the 1/2"? #2's or #3's?

Mr T
April 15th, 2005, 06:02 PM
I grabbed #3's, but could have gotten away with #2's. I got the flexible conduit installed from the well pressure switch down to the well conduit (so now I can do #1 and #2). No more yellow and black wires hangin around (brag board pics)

April 15th, 2005, 07:02 PM
Wanna questioned using anti-shorts on Greenfield (type FMC). You do not have to use anti-shorts on type MC, but you do have to use them on type AC (BX) and FMC (Greenfield).

Where is this (anti-shorts on FMC) in the code, as I looked and saw no mention of it?

Any raceway should be at a much reduced risk from chafing/cutting conductors, as it is larger and there is a bushed connector on the end. A cable, like AC, can have the conductors right next to the sharp metal edge with just a simple hold down keeping the cable in a box. Pulling hard on the wires could easily cut them without an anti-short.

April 15th, 2005, 09:14 PM
Where is this (anti-shorts on FMC) in the code, as I looked and saw no mention of it?

True, it's not in the code. This thread is in the code forum area, and I may have caused some trouble with my statement. It is part of many manufacturer's instructions for the connector and is often specified by the engineer. Many FMC connectors can be used without the redhead, but many cannot. Keep in mind that many styles of type AC connectors are dual rated for use with FMC and would still need the red head. Reference (for instance) the T&B 3110 and 3130 series of connectors, which require the red head when they are used on type FMC. Most catalog pages for red heads will list the use of the red head for AC and FMC. Reference this Crouse Hinds catalog page. (http://www.crouse-hinds.com/CrouseHinds/newproducts/relatedinfo/Anti%20Short%20Bushings%20Sell%20Sheet.pdf). Here's the scanned in FMC section of the specifications for some prints I've been looking over for a few weeks. Note that the use of red heads is called for when using FMC.

Mr T
April 15th, 2005, 09:32 PM
Here is the connector I used. (and yes I installed a bushing)

April 15th, 2005, 10:12 PM
This connector you used is a NEER FC-5501 connector, for use with type AC cable and FMC raceway. In accordance with NEMA FB-1,3.2.2 (the listing under which this particular connector is governed), you do need to use the redhead with this particular connector.