I am helping with the restoration of a couple of old apartments above a movie theater. The building was constructed in 1875. After that, nobody knows the history of when the apartments would have been last remodeled. They used rigid conduit for the apartments. From what I can find, this would date the earliest remodel in the '40s. What I can’t find is when EMT was first widely utilized. My logic is that nobody would use rigid if they could go with EMT.
I know that it doesn’t really matter the date of building materials. This is for my own curiosity.
Morning, Jeff. Are you referring to EMT or RMT?
I do not know if this will help but in 1899 Edwin T. Greenfield was granted the patent for Metallic Conduit for Electric Wires. U.S. Patent No. [630,501]
From EC&M The Basics of Steel Conduit.
Steel conduit has been in use as a raceway system for electrical conductors since the early 1900s. The wall thickness and strength of steel make metal conduit the wiring method recognized as providing the most mechanical protection to the enclosed conductors. An additional benefit of using steel conduit is that the NEC recognizes a properly installed metal conduit system as an equipment grounding
I inspected this very large home a couple of years ago that was built in 1908 that had the original wiring installed in rigid conduit like in the OPs pictures. At first I thought I fround plumbing supply pipes in the attic until I figured out that it was conduit for branch wires.
The original owners owned a boxing company that burnd to the ground, so when they built this house they built it with fire prevention in mind. They actually had water hook-ups in the halls to supply large quantities of water in the event of a fire.
Pretty standard for 1908. That old RMC was sometimes called black pipe because it predated the modern galvanized RMC and resembles modern gas pipe. In some really old homes it actually was gas pipe when gas lights were used for illumination.
Found this blurb in a search. The Benfield bending manual has been the bible on bending EMT.
"Jack Benfield has been identified with the electrical conduit industry since 1929. He was a pioneer in the marketing of thin wall (EMT) conduit in the U.S.A.
Republic Steel Corporation created EMT. To market this brand-new product the company selected six young salesmen to cover the U.S.A. Jack was in that original group of six. It was called the EMT flying squad.
The Great Depression of the 1930s made it no bed of roses to sell a new untried raceway. Almost every branch of the electrical industry tried to dis-courage the acceptance of thin wall conduit."
I get a lot of homes that were electrified from gas, where the old gas pipe was used as conduit (most notably for the final run to a ceiling fixture). This generally does not represent a defect.
