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Restrictions on Flex Connectors


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I was always under the impression that flexible connectors had to be protected by a bushing if they passed through a cabinet wall. The directions for the last boiler I installed provided a part number for the bushing.

I have always had the same impression, it's mentioned in chapter 24 of the IRC as well. However, the printed instruction seems fairly clear that the connector shouldn't be used inside the cabinet at all - at least not in Lennox and Ducane furnaces.

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As noted by Katen, IRC Chapter 24, G2422.1.2.3 Prohibited locations and penetrations. Connectors shall not be concealed within, or extended through, walls, floors, partitions, ceilings, or appliance housings. (exceptions follow)

I have seen bunches of the flex connectors that have leaks from vibration on the wall of the furnace. That knock out has sharp edges that will slice through appliance connectors after years of vibration.

I suppose the code writers wanted to err on the side of caution in prohibiting them within the cabinet due to the numerous components and potential sharp edges if a connector is wound around inside a furnace cabinet.

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As noted by Katen, IRC Chapter 24, G2422.1.2.3 Prohibited locations and penetrations. Connectors shall not be concealed within, or extended through, walls, floors, partitions, ceilings, or appliance housings. (exceptions follow)

I have seen bunches of the flex connectors that have leaks from vibration on the wall of the furnace. That knock out has sharp edges that will slice through appliance connectors after years of vibration.

I suppose the code writers wanted to err on the side of caution in prohibiting them within the cabinet due to the numerous components and potential sharp edges if a connector is wound around inside a furnace cabinet.

So it's your interpretation that a flex connector inside the cabinet of a furnace is "concealed" within the appliance housing?

If so, I disagree. It seems to me that this section is talking about areas that are not readily accessible, like the space behind a pre-fab fireplace.

If they're prohibited from being in a furnace cabinet, why have the exception that allows them to pass through the cabinet when protected?

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So it's your interpretation that a flex connector inside the cabinet of a furnace is "concealed" within the appliance housing?

If so, I disagree. It seems to me that this section is talking about areas that are not readily accessible, like the space behind a pre-fab fireplace.

If they're prohibited from being in a furnace cabinet, why have the exception that allows them to pass through the cabinet when protected?

The exception that I see pertains to semi-rigid tubing, not connectors. I see this as CSST, copper pipe, etc. not flexible connectors.

"Connectors shall not be concealed within, or extended through, walls, floors, partitions, ceilings, or appliance housings."

When they say connectors shall not be concealed within appliance housings, it seems pretty clear the flexible connectors should not be within or pass thru the furnace cabinet. Obviously the label posted takes this view.

In any case, the furnaces I see don't have room to conceal the connector totally within the cabinet and it obviously is prohibited from passing through the cabinet wall, the only feasible option left is to use iron pipe to go through the cabinet wall.

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Good question James.

Some time ago, I asked this question of a State code official and the reply was:

"Flexible connectors are permitted to extend through an appliance housing where the connector is protected by means of a factory equipped grommet".

A local gas company official responded with the same.

So I assumed it was allowed, but then:

I have found a few furnace installation instructions that state what you found.

The installation instructions of one popular brand of connector states: "DO NOT conceal connector or run connector through enclosed outdoor BBQ pits, walls, partitions, floors or appliance panels.

So the answer to the question of connectors passing through a furnace or boiler cabinet is yes and no.

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The IRC/ OR's ORSC leaves this up for interpretation in my opinion; I could argue this one either way.

Some equipment and flex connector manufacturers don't leave this up for interpretation, and indicate the connectors must be installed outside of the equipment.

Jim,

I'm not aware of any of our service technician's writing this issue up on any of their inspections.

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I like black iron pipe coming through the furnace sidewall.

Flex pipe coming through the side wall of a furnace that is "hanging" in an attic and "moving" can quite easily cut through the flex and end up with a gas leak.

I am not fond of the grommets and actually have seen very few and the ones I have seen are dry rotted and worthless.

So ... for 13+ years down here in TX when I see flex going through the sidewall I write it up. Pretty much the same as Jim L.

Keep in mind that a rather large percentage of furnace units are in the attics in Texas and are strapped and hanging and thus 'swinging' when in operation.

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. . . When they say connectors shall not be concealed within appliance housings, it seems pretty clear the flexible connectors should not be within or pass thru the furnace cabinet. Obviously the label posted takes this view.

In any case, the furnaces I see don't have room to conceal the connector totally within the cabinet and it obviously is prohibited from passing through the cabinet wall, the only feasible option left is to use iron pipe to go through the cabinet wall.

Chapter 24 includes a very clear definition of "concealed location" and it specifically excludes the inside of furnace cabinets.

CONCEALED LOCATION. A location that cannot be

accessed without damaging permanent parts of the building structure

or finish surface. Spaces above, below or behind readily

removable panels or doors shall not be considered as concealed.

It also says:

Semirigid tubing and listed connectors shall be

permitted to extend through an opening in an

appliance housing, cabinet or casing where the

tubing or connector is protected against damage.

Why have this provision if the connectors aren't allowed inside the cabinet?

I see gas connectors passing through furnace cabinets about once a year - it's very rare. The installers around here seem to understand that this is a no-no. I see flexible gas connectors installed inside furnace cabinets on roughly 99% of gas furnaces in my area. They fit in there just fine, with room to spare. The iron pipe comes through from the outside and transitions to a short connector inside the cabinet. Never seen or heard of a problem associated with this practice.

I don't see much here in the way of a requirement from the IRC. It's clearly not prohibiting the practice.

The manufacturer's instruction however, is very clear. I'm just wondering if this instruction extends beyond Lennox/Ducane. Is it a widespread requirement? A recent requirement?

I only ask because I've seen many thousands of installations done this way and, before I begin citing it in my reports I'd like to have some notion of how defensible it's going to be.

If, per Brandon, my local gas company isn't citing this, I'm probably not going to start unless there's a really good reason to.

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There is no good reason for it. It's probably corporate legal telling engineering to spec it for some obscure or imagined reason. I think they're trying to limit the hambone installation practices made possible with flex in the hands of morons ending up inside their enclosures.

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"Connectors shall not be concealed within, or extended through, walls, floors, partitions, ceilings, or appliance housings."

Seems to prohibit the practice for flexible connectors.

While I have not taken the time to re-read the entire chapter, this one passage taken at face value seems plain enough for me to call it out. I could let it slide if I found the connector totally contained within a furnace and it fit with no abrasion or interference but again this is a situation I rarely if ever see. I can see the confusion written into the code enough to see your take though.

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I saw this just 2 days ago and was very worried. It was an outdoor boiler. The flame was just behind the metal in the photo and the flex was attached on the right side right behind the conduit strap shown.

I was extremely worried that the connection could deform as easily as the sheet metal - or that the flex sidewall would not have the strength of the surrounding area.

It is just by chance that I am reading this a few days later.

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"Connectors shall not be concealed within, or extended through, walls, floors, partitions, ceilings, or appliance housings."

Seems to prohibit the practice for flexible connectors.

While I have not taken the time to re-read the entire chapter, this one passage taken at face value seems plain enough for me to call it out. I could let it slide if I found the connector totally contained within a furnace and it fit with no abrasion or interference but again this is a situation I rarely if ever see. I can see the confusion written into the code enough to see your take though.

I just think that the word "concealed" doesn't apply here.

Here's what I see on almost every gas furnace here.

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