underground imc

[difowler1]

Is it necessary to use some sort of coating on imc to install it underground?

 

[jumper]

In general, galvanized is acceptable, 342.10(B).

 

[ptonsparky]

Allowed, but I’ve done enough gas stations to see what is left of RMC after 20 years. Nothing but rust stains and colored wire in the sand. Maybe IMC is better.

 

[don_resqcapt19]

The UL Gui4de Information for both IMC and RMC says:

IMC
Galvanized intermediate steel conduit installed in concrete does not require supplementary corrosion protection.

Galvanized intermediate steel conduit installed in contact with soil does not generally require supplementary corrosion protection.
In the absence of specific local experience, soils producing severe corrosive effects are generally characterized by low resistivity less than 2000 ohm-centimeters.
Wherever ferrous metal conduit runs directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.
RMC

Galvanized rigid steel conduit installed in concrete does not require supplementary corrosion protection.
Galvanized rigid steel conduit installed in contact with soil does not generally require supplementary corrosion protection.
In the absence of specific local experience, soils producing severe corrosive effects are generally characterized by low resistivity (less than 2000 ohm-centimeters).
Wherever ferrous metal conduit runs directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.

 

[wwhitney]

The UL Guide Information for both IMC and RMC says:

. . .
Wherever ferrous metal conduit runs directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.

So what is the standard way to deal with ferrous metal conduit at the soil/concrete transition? Is it enough to use additional corrosion protection for a certain number of feet on both sides of the transition, or does that just set up a larger electrochemical cell? Use one stick of stainless steel conduit?

Cheers, Wayne

 

[don_resqcapt19]

So what is the standard way to deal with ferrous metal conduit at the soil/concrete transition? Is it enough to use additional corrosion protection for a certain number of feet on both sides of the transition, or does that just set up a larger electrochemical cell? Use one stick of stainless steel conduit?

Cheers, Wayne

We just wrap a foot of so each side of the transition point with 10 mil corrosion protection tape.

 

[Coppersmith]

Allowed, but I’ve done enough gas stations to see what is left of RMC after 20 years. Nothing but rust stains and colored wire in the sand. Maybe IMC is better.

IMC is the same material as RMC but 1/3 thinner so I doubt it would be better.

P.S. I installed a 60 foot run of IMC underground a couple of days ago. I did this to avoid trenching the 18" (plus pipe diameter) required for PVC. IMC requires only 6".

 

[Sean.Day72]

Paint it in black mastic. I believe it’s referred to as asphalt paint sometimes ? I always run PVC underground but sometimes the turn up elbows are required to be metal.


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[Coppersmith]

Paint it in black mastic. I believe it’s referred to as asphalt paint sometimes ? I always run PVC underground but sometimes the turn up elbows are required to be metal.

Read the post and this popped into my head

https://www.youtube.com/watch?v=O4irXQhgMqg

Sorry no description, would spoil the surprise

 

[don_resqcapt19]

IMC is the same material as RMC but 1/3 thinner so I doubt it would be better.

P.S. I installed a 60 foot run of IMC underground a couple of days ago. I did this to avoid trenching the 18" (plus pipe diameter) required for PVC. IMC requires only 6".

The galvanizing on the IMC does not appear to be any where near as heavy as it is on rigid (at least to me) I don't use it in underground locations.

 

[ptonsparky]

The galvanizing on the IMC does not appear to be any where near as heavy as it is on rigid (at least to me) I don't use it in underground locations.

It may be metallic and galvanized but even a first time bender if it knows RMC & IMC are not the same.

 

[kwired]

IMC is the same material as RMC but 1/3 thinner so I doubt it would be better.

P.S. I installed a 60 foot run of IMC underground a couple of days ago. I did this to avoid trenching the 18" (plus pipe diameter) required for PVC. IMC requires only 6".

Same in that both are ferrous, they are not the same alloy.