Metal back boxs and r2 reading

[Tetris1985]

Might be a dumb question, but do metal back boxs have an effect on the R2 reading

I feel like they dont as when you times r1 or rn by 1.67 you get the expected r2 of the cable

 

[James]

They can have an effect.
For instance, consider parallel paths when they are bolted to steel building parts or if fed with metal conduit.

 

[sinewove]

Might be a dumb question, but do metal back boxs have an effect on the R2 reading

I feel like they dont as when you times r1 or rn by 1.67 you get the expected r2 of the cable

Also,if you had a duel box with a lighting cct on one side you would get a false reading.