If you use flexible gas connectors or CSST (corrugated
stainless steel tubing) when hooking up the gas to a gas appliance, you need to
make sure and do it safely. Flexible gas connectors are made of corrugated
stainless steel and generally have no outer covering or protection. They are
often used to connect a gas appliance to a rigid iron gas line.
CSST, on the
other hand, has an outer covering over the corrugated stainless steel, comes in
large rolls, and is often used instead of black iron when piping gas lines.
There are some installation practices for each of these products that need to
be followed to avoid setting up a dangerous situation.
For flexible connectors, it is important that they not be
used to go through walls, floors, or the unit cabinet. Iron pipe should pass
through the unit cabinet to the gas valve. Contact with the metal side of the
furnace cabinet can rub a hole in a flexible connector. Another reason for
keeping flexible connectors out of the cabinet is the potential for loose
electrical wires or connections to arc against the flexible connector and blow
a hole in it. While this could also happen with black iron, there is far less likelihood
of the arc blasting a hole in the iron.
Flexible connectors can be used to make
the final connection between the black iron leaving the furnace cabinet and the
black iron piped into the furnace area. When using a flexible connector, the
flared connectors are generally considered “unions.” Don’t forget to install a
gas shutoff. Some flexible connectors are provided with a gas shutoff.
CSST is similar to flex connectors in construction with an
outer layer of protective plastic. CSST can be pulled through interior walls,
but metal nail protectors are required anywhere the CSST is inside the wall. CSST
manufacturers make striker plates for this purpose. Protection needs to be approved
by a listing agency, such as CSA or UL. Also, it is still best to use black
iron to go into the furnace cabinet. The best practice is to penetrate exterior
walls with black iron. If CSST is used to penetrate an exterior wall,
protection is required.
One of the biggest safety concerns with both flexible
connectors and CSST piping is properly grounding the gas piping system. There have
been many instances where lightning strikes near a building have blown holes in
CSST gas lines or connectors. The grounding is to avoid this. The most common
practice is to connect a bonding ground wire to the rigid black iron pipe outside
the house BEFORE the first CSST connection. This bonding ground is connected to
the ground rod or run inside to the ground bus of the electrical panel.
Here are a couple of links for more information”
Grounding: http://www.csstsafety.com/CSST-solution.html
Installation: http://www.tracpipe.com/Technical/CSST_Installation_Instructions/