Gas tight going straight to appliance there is black iron coming out of furnace but no union. Is one needed??
It depends if the furnace manual says you need to install a union. Some do, some don't.
You can't run CSST or a gas connector through the furnace casing.
https://www.hvactechgroup.com/hvacforum/index.php?topic=1463.msg8763#msg8763
QuoteClause 6.2.21 - Corrugated stainless steel tubing (CSST) shall not be used as a gas connector.
Ok ..... but by that code , u need a union .....
Quote from: NoDIY on November 24, 2017, 10:55:31 PM
most appliance installation manuals ask for a ground joint union. So that pretty much makes you go black into the cabinet of most furnaces and water heaters
4.1.3 would be the warning tag pointing to the installation manuals requirement for a ground joint union.
Use of union is not in the B149.
The reason they say you need a union on gas copper and csst is because the fitting are not suppose to be taken apart. It can be done but it's not supposed to be. When I was in gas school many years ago, we had a tssa inspector as our teacher and he specifically brought this topic up.
Quote from: Hvacpimp on March 27, 2019, 09:31:00 PM
The reason they say you need a union on gas copper and csst is because the fitting are not suppose to be taken apart. It can be done but it's not supposed to be. When I was in gas school many years ago, we had a tssa inspector as our teacher and he specifically brought this topic up.
It is also because if you dont possess the certificate to each every brand of CSST you cannot handle it. Basically if you don't hold the certificate for the brand that is on site and there is no union you wouldn't be able to touch the CSST if you had to change the gas valve or something similar.