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?
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 06/22/0510:01 PM06/22/0510:01 PM
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
Re: IMC vs RMC#53390 06/23/0509:19 PM06/23/0509:19 PM
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 06/24/0510:39 AM06/24/0510:39 AM
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??