Thread: Flexible gas pipe

Is it ever acceptable to have a flex line entering the cabinet of a gas furnace. I wrote one up the other day and the installer is saying that it is OK and will not agree to repair it. I told him since there was no permit pulled to install it that he needs to get a permit after the fact and see if it is allowed or not. I guess I could look up the manufactuers instructions, but wanted to see if someone could give me a code reference.

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Frank, you can scroll down 4 threads in this section to a thread started by Richard Stanley about Fuel Ga Codes. You can also search this site. Well discussed before. Not meaning to sound blunt but it has been addressed at length.
HTH
Bob

Frank,

I have a canned comment about this type of issue and I write it up as a repair every time I see it (whether it is a new house or one that is 30 years old). I had an inspector buddy who got chewed out by a HVAC guy for not writing it up. If the fan bearings go out or something else causes the chassis of the furnace to vibrate there is a very real chance of that thin walled pipe being cut by the sharp edge of the furnace chassis which could cause a gas leak or worse.

There may be other fuel gas codes stating this but the 2003 IRC has this to say about appliance connectors: (bold is mine)

G2422.1.2 (411.1.2) Appliance fuel connectors.
Connectors shall have an overall length not to exceed 3 feet (914 mm), except for range and domestic clothes dryer connectors, which shall not exceed 6 feet (1829 mm) in length.
Connectors shall not be concealed within, or extended through, walls, floors, partitions, ceilings or appliance housings.

I interpret that to mean no flexible connectors through the side wall of the furnace.

All (98%) of new installations I see here in central Texas have hard pipe to the exterior of the furnace and then the flex connector is connected to the hard pipe.

Eric

Someone else may have the fuel gas code reference on this.

Eric

Frank,

I forgot to list the exception:From 2003 IRC

"Exception: Fireplace inserts factory equipped with grommets, sleeves or other means of protection in accordance with the listing of the appliance."

Although your issue is with a furnace so I don't see how the exception would apply.

Many times I will see pipe insulaton (foam rubber) wrapped around the connector. I still write it up because common sense dictates that if the sheet metal can cut through the connector, there is a chance it can cut through the foam as well.

I don't know this, but some connector manufacturers may allow a grommet at furnaces.

Eric

IFGC 411.1 #2 states:

Semirigid metallic tubing shall not enter a motor-operated appliance through an unprotected knockout opening.

Dave, per the IFGC Commentary, "Item 2 refers to copper and aluminum tubing, which is rarely used today as an appliance connector. Such connectors are field fabricated. Item 3 refers to the commonly used , so called "flexible" connectors typically made of corrugated stainless steel or brass."
Item#3 under 411.1 reads- Listed and labeled appliance connectors installed in accordance with the manufacturers' installation instructions and located entirely in the same room as the appliance.

So, section 2 is for copper tubing and section 3 says read the tag on the flex connectors. However, any installation that sees a lot of vibration and movement should make provision for protecting the gas line such as with a grommet.

Bob

Here in Georgia I see many older furnaces piped this way, combustion chamber is not sealed and draft type exhaust venting not sure about codes back in the 80's when these were done I have seen. All newer efficiency models have sealed and forced exhausted venting. These all do require hard piping from the control valve to outside the cabinet. Of course most units always start the exhaust blower a little before the ignition to make sure any gas leakage at the valve has been exhausted first. I do not like the flex line going to inside on the older models but was common.

The more potential a piece of equipment has to vibrate the more I want a flexible connection to it.

Originally Posted by Rod Butler

The more potential a piece of equipment has to vibrate the more I want a flexible connection to it.

Fine. Do it outside the unit or, grommet it.

You won't find CSST prohibited in the current edition of the NFGC.

In fact, from the 2009NFGC:

9.6.1 Connecting appliances and equipment,
Appliances and equipment shall be connected to the building piping in compliance with 9.6.4 through 9.6.6 by one of the following:

(1) Rigid mettalic pipe and fittings
(2) Simirigid metallic tubing and mettalic fittings. Aluminum-alloy tubing shall not be used in exterior location

......

(5) CSST where installed in accordance with the manufacturer's installation instructions. CSST shall connect only to appliances fixed in place.

.....

(8) Materials addressed in 9.6.1 (2), 9.6.1 (3), 9.6.1 (4), 9.6.1 (5), 9.6.1 (6) shall not be installed through an opening in an appliance housing, cabinet, or casing, unless the tubing or connector is protected against damage.

Unfortunately, the definition of protection is undefined. Most could consider a grommet as adequate protection.
It is also stated that piping must be installed in accordance to the appliance manufacturers specifications, and most manufacturers require that any flexible connector be connected to hard pipe that extends outside the furnace casing.

So, what does the furnace installation instructions call out? It's hard to argue with the manufacturers specified installation instructions.

I looked in the manual of a goodman 95 high efficiency series I was looking at, the ones with force air venting and are a tight sealed combustion chamber.
Recommends running hard pipe from the gas valve through to the outside of the cabinet then connecting the flexible line to that, but outside the cabinet. That is where I had seen that before so was not sure at the time of this thread if in actual code anywhere or not but if the manufacturer recommends that specifically would that not need to be followed regardless ?

Originally Posted by Mike Clarke

I looked in the manual of a goodman 95 high efficiency series I was looking at, the ones with force air venting and are a tight sealed combustion chamber.
Recommends running hard pipe from the gas valve through to the outside of the cabinet then connecting the flexible line to that, but outside the cabinet. That is where I had seen that before so was not sure at the time of this thread if in actual code anywhere or not but if the manufacturer recommends that specifically would that not need to be followed regardless ?

A recommendation is just that,,unless they Require It, it defers to local codes

Mr. Shipman,First I disagree with your characterization.Second, there is a distinct difference between a pre-manufactured appliance connector assembly (even if made up of CSST) and the installation of CSST.Third FYI for all, the thread Mr. Harper referred to in this intially quite old and retired thread (amongst others) is this one (clickable link): http://www.inspectionnews.net/home_i...mlManufacturer instructions regarding support of, CSST, stub-outs, and securing of valves have been covered extensively on this forum in many subject category areas. (As has the distinctions between a pre-manufactured flexible gas appliance connector and site installed CSST).

HG,
You are correct. And, after re-reading my post, I can see how I've made it sound as though CSST and a pre-manufactured flexible appliance connector are one in the same.
Obviously a manufactured appliance connector could be made from CSST, but not all appliance connectors are made from CSST.

My point was to emphasize that flexible connectors are NOT prohibited from passing through a furnace casing by the NFGC, as long as they are a listed connector, and the connector manufacturer doesn't prohibit their passing through an appliance cabinet. Eric S.'s comments make it sound as though it is prohibited. The statement's he has quoted are also in the NFGC, but they apply only to portable or mobile appliances.

All appliance connectors I've seen allow for passing through a cabinet, as long as adequate protection from damage is provided. I don't agree with the idea, but again, it can be argued that a grommet at the opening will provide this adequate protection.

HG, you've been a wealth of information on this site, I would hope you do not take my response as any type of attack on your knowledge.

Mr. Shipman,

This old thread was discussing the pictured pre-manufactured 6' (six-foot length) appliance connector into furnace.

Since you're referencing NPFA's NFGC, note the length of the pictured (in original post) appliance connector would not be allowed.

Appliance connectors are manufactured/approved/listed and have usage instructions to different ANSI standards than field installed CSST and fittings. The labeled (missing tag) appliance connector's instructions and ANSI standards ALSO apply (as does the furnace mfg's instructions and the gas valve control's).

Furnace is fixed in place/installed to more than one building system, and is not a range or clothes dryer.

As Mr. Harper indicated the "issues" have been addressed elsewhere many times on this forum.