Conduit Transition: IMC to LFMC to IMC

[TheElectrician]

Hey guys,

I have an installation where a I transition from 4 Sets of 3" IMC with 600MCM & 3/0G to LFMC with the same conductors then again back to IMC. The first picture attached below shows the transition from LFMC to IMC and the picture 2 shows a the LFMC path to the IMC.

In order to make these transitions what are the Codes I need to abide?

The code 350.42 says "Only fittings listed for use with LFMC shall be used"

Does anyone have experience in this, can you advise how to proceed?



Thanks

 

[kwired]

I'm not seeing anything that looks like 3" IMC in your pictures. Or are you showing obstructions you will use flex to offset/saddle around?

I think wording in 350.42 was put there because there are other fittings that physically will fit this but are not listed for use with LTFMC, even though 110.3(B) kind of covers it anyway.

 

[TheElectrician]

I'm not seeing anything that looks like 3" IMC in your pictures. Or are you showing obstructions you will use flex to offset/saddle around?

I think wording in 350.42 was put there because there are other fittings that physically will fit this but are not listed for use with LFMC, even though 110.3(B) kind of covers it anyway.

It is not been installed yet, but in the picture with the red circle you can see 4 conduits which is the pre-installed IMC where the LFMC will be connected. And yes, I have shown the obstructed area where the LFMC will be used.

So, I come with the IMC to LFMC and then again connect to the IMC (Shown in the picture). Is there any codes to be followed for these transition?

Thank you

 

[kwired]

It is not been installed yet, but in the picture with the red circle you can see 4 conduits which is the pre-installed IMC where the LFMC will be connected. And yes, I have shown the obstructed area where the LFMC will be used.

So, I come with the IMC to LFMC and then again connect to the IMC (Shown in the picture). Is there any codes to be followed for these transition?

Thank you

You won't be able to use the raceway as an EGC unless you put bonding jumpers around the flex.

Flex will have different support interval requirements than the IMC run has.

Many will let you get away with threading the flex connector into an IMC coupling, technically it is not listed to do that and you would need a flex connector with female pipe thread to directly connect to the IMC.

 

[TheElectrician]

You won't be able to use the raceway as an EGC unless you put bonding jumpers around the flex.

Flex will have different support interval requirements than the IMC run has.

Many will let you get away with threading the flex connector into an IMC coupling, technically it is not listed to do that and you would need a flex connector with female pipe thread to directly connect to the IMC.

Thank you, this was really helpful, I just want to clarify that the bonding jumper around the flex is to bond IMC with the flex or both the IMCs? and for the support levels of the flex are you referring to 350.30 (B) Supports?Thank you

 

[kwired]

Thank you, this was really helpful, I just want to clarify that the bonding jumper around the flex is to bond IMC with the flex or both the IMCs? and for the support levels of the flex are you referring to 350.30 (B) Supports?Thank you

The flex in your situation can't be used as an EGC. If you pulled a wire type EGC in your raceway you are fine. If you are using the raceway as the EGC (IMC would be allowed to be used as an EGC) you need to bond around the flex to maintain continuity of the EGC. That is one situation where an external bonding jumper can be used.

 

[TheElectrician]

The flex in your situation can't be used as an EGC. If you pulled a wire type EGC in your raceway you are fine. If you are using the raceway as the EGC (IMC would be allowed to be used as an EGC) you need to bond around the flex to maintain continuity of the EGC. That is one situation where an external bonding jumper can be used.

Got it, Thank you! But I will be using a dedicated EGC inside the conduit itself in both IMC and the flex, So I think I should be good.

 

[kwired]

Got it, Thank you! But I will be using a dedicated EGC inside the conduit itself in both IMC and the flex, So I think I should be good.

If you would have a run of IMC that is isolated by having flex on each end of it, you would need a bonding jumper to that IMC, but would not need to be around both ends, just need to assure a good bond to any point along the IMC.

 

[TheElectrician]

If you would have a run of IMC that is isolated by having flex on each end of it, you would need a bonding jumper to that IMC, but would not need to be around both ends, just need to assure a good bond to any point along the IMC.

Got it! Thank you very much!