Flexible gas appliance connector thru furnace cabinet

Can a flexible gas appliance connector pass thru a furnace cabinet wall if it is protected by a rubber bushing?

The way I understand it, first if the manufacture’s installation requirements allow it, and if so, does the line meet the requirements for that use. Most installation manuals will state how and what can be used.

I have seen it done in proper installations, and recommend the rubber bushing when one is missing.

Around my area, if the gas company see’s that they will turn off the gas and padlock the meter.

Ah yes, I forgot to mention what the local or state jurisdiction dictates. Not a problem in my neck of the woods. :wink:

You will need to follow the manufactures installation instructions on the appliance connector. Every new appliance connector has a clear set of instructions printed on the label. And than there’s this:


Thanks for your comments!

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Thanks for your comment. Trying to track down my local what is acceptable in Nevada.

Thanks! Yes I have seen this. Now trying to figure out what qualifies as “protected”.

Although it may be “allowed”, it’s a poor practice. Neither unions nor a flexible connector should be inside a cabinet. This is often done by a rookie plumber/HVAC or a homeowner.

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Don’t overthink this. An opening in a cabinet large enough to facilitate the entry of a appliance connector is considered protected. A rubber grommet around said opening is also considered protected.

Steel piping is becoming a thing of the past. New gas piping systems are constructed at CSST tubing and appliance connectors that is all. The only steel piping I see on new homes is the sediment trap and connection to the gas meter. This is how the professionals are installing fuel distribution systems.

CSST tubing is to steel pipe as PVC drains are to cast iron pipe. There will always be somebody in the camp of one material or the other.


I thought there are some approved grommets, but I am having trouble finding any info.

If required the grommets normally do come with the unit. Same with air handler line set grommets.

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How about this fuel oil line entering the cabinet of a Thermopride oil furnace? Protected or not?

Right. Seller agreed to make all repairs using licensed contractors.

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Right. Unfortunately I don’t have access to those docs. But you gave me my answer. They must check the manufacturers installation instructions and a licensed HVAC contractor. Not my call.

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Thank you all very much!

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Change of heart, Mr Martin? PEX, SharkBites, ProPress, Snappy Traps, and now flexible connectors inside furnaces and boilers :smiley: Well, let’s see some of these new wonder homes and their cute CSST+flexible connector installs. BTW, we still like our black pipe here in any house that’s not a hack executed by licensed “professionals”.

I see black pipe here as well. CSST with manifolds was popular years back but black pipe has returned. In most cases, the only time I see new CSST is after some modification such as an added fire place, stove etc. and some commercial.

I just inspected a manufactured home today with steel pipe under the home. It was heavily corroded. This wouldn’t happen with CSST. Lack of maintenance was the problem.

Both materials have their advantages. If you thread steel pipe you must have a degree of skill such as:

  1. Thread depth is everything. Can the installer set the dies?

  2. Thread length. How much is too much and too little?

  3. What is too tight and not tight enough? Fittings can crack if the craft uses the threading machine to tighten the fittings on the machine.

If installed correctly and maintained steel pipe is my choice. It’s not very common here.

Outside, here, we use galv steel, not black pipe. When galv steel starts to rust (20+years), it needs to be painted. Good paint will last another 20 years. So you paint it 3 times in 60 years, not bad. Still better protected than flimsy CSST noodle.

Come on Martin! these are licensed “professionals”!!! You said it LOL not me. PEX and propress, same thing, a lot less skill required, but I’m not the one calling them “professionals”. I just refer to them as Joe plumbers :slight_smile: