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IMC vs RMC #53384
06/22/05 09:19 PM
06/22/05 09:19 PM
V
VOLTS  Offline OP
Member
Joined: Jun 2001
Posts: 21
What are the difference between IMC & RMC. I have an electrical contractor telling me there is no difference. I have always spec'd RMC in an explosion proof area. I know the Code states IMC is legal, But I was always taught RMC was stronger and had better grounding of interferance for control circuits using 4-20ma. I would like to stay with RMC what would be a good argument not to use IMC?

Work Gear for Electricians and the Trades
Re: IMC vs RMC #53385
06/22/05 09:30 PM
06/22/05 09:30 PM
R
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
IMC is less expensive and can be used in all areas that RMC can be used. I am also told that it is stronger, but I have never read anything on that. IMC also has a bigger cross sectional area and is easier to bend.

I would not install RMC unless I was forced to.


Ryan Jackson,
Salt Lake City
Re: IMC vs RMC #53386
06/22/05 10:01 PM
06/22/05 10:01 PM
J
Jps1006  Offline
Member
Joined: Jan 2004
Posts: 615
Northern IL
I have always found IMC much stiffer and more difficult to bend. I always opt for RMC because it is easier to bend.

Re: IMC vs RMC #53387
06/22/05 10:33 PM
06/22/05 10:33 PM
R
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
Really? I haven't bent either of them in about 6 years or so, so I might not be remembering properly. [Linked Image]


Ryan Jackson,
Salt Lake City
Re: IMC vs RMC #53388
06/22/05 10:43 PM
06/22/05 10:43 PM
E
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
IMC has a thinner wall, and more tempered/stiffer, not sure why.

RMC is slightly thicker, weighs more, less tempered, but seemingly about the same to bend. Costs a penny more.


Mark Heller
"Well - I oughta....." -Jackie Gleason
Re: IMC vs RMC #53389
06/23/05 12:44 PM
06/23/05 12:44 PM
R
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
I agree that IMC is much stiffer and harder to bend and thead than RMC. I have also seen problems with the IMC breaking at the threads on the 1/2 and 3/4" size. This is caused by the reduced wall thickness of this conduit. There is very little strength left after you cut the threads.
Don


Don(resqcapt19)
Re: IMC vs RMC #53390
06/23/05 09:19 PM
06/23/05 09:19 PM
R
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
I used a fair amount of IMC and GRC in hazardous locations including 4-20 mA control circuits and VFDs. Never noticed a diffrence in EMI or RFI problems in one over the other.
Although lighter in weight the IMC was indeed harder to bend, and keeping the shoe tight against the pipe for an accurate radius was difficult even at the 3/4" size. I would avoid using it for hand bending.

Re: IMC vs RMC #53391
06/24/05 10:39 AM
06/24/05 10:39 AM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,166
Estero,Fl,usa
From an RF standpoint a wrap of properly grounded metal window screen is as effective as RMC. The difference is physical protection.


Greg Fretwell
Re: IMC vs RMC #53392
06/24/05 01:53 PM
06/24/05 01:53 PM
V
VOLTS  Offline OP
Member
Joined: Jun 2001
Posts: 21
Thanks for the feed back.

Re: IMC vs RMC #53393
06/24/05 07:29 PM
06/24/05 07:29 PM
W
walrus  Offline
Member
Joined: Jul 2002
Posts: 680
Bangor Me. USA
I prefer working with IMC, lighter and easier to bend IMHO. Never had a problem with it breaking underground and Maine frost can break anything. My suppliers don't stock it anymore though so I use RMC all the time now anyway. What are people paying for 3/4 rigid, last time I checked it was 17 bucks a stick up here??

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