CSST though knock out

[Frank Bombardiere]

Is it OK to run CSST through a knock out under a fire box as shown in my pic?

[Nick Ostrowski]

Wow! The installer actually installed some foam around the line to act as a buffer......but not on the other one. As long as there is protection installed around the CSST similar to what you have in your pic Frank, I'm OK with it.

Whenever available, I read the fireplace manufacturer's installation guide and see what it says about the installation of the gas line. Some manufacturers will spell out the exact type of piping that needs to be used. I've read some manuals that specifically called for the use of solid iron pipe at the penetration through the knockout. Other manuals are a little vague and state "refer to local code requirements".

[Gunnar Alquist]

Is it OK to run CSST through a knock out under a fire box as shown in my pic?

Frank,

I have not read the installation instructions in a while, but I would guess that would not be a good idea for the same reasons that it cannot be done with a flex connector.

[Stephen Tilleux]

In my area the CCST would need to be in a sleeve, for example a chunk of flexible metal Condit or other metal debured tubing at the penetration (this is also described in at least 2 CCST manuals) without it's plastic sleeve.

That foam is a combustible and not rated for the temps that can happen in that compartment, also not very good protection after it melts.

Appliance connectors are a whole other story.

My 2c

[Bob Elliott]

The Csst jacket itself is combustible and not allowed inside the casing.
I would suggest you recommend black pipe be run to the outside of the appliance casing where the Csst can be hooked up safely.

[Bob Harper]

That upper tubing appears to be a "flexible appliance connector" passing through the floor of the firebox to some sort of appliance, such as gas logs above. Once again, we are presented with insufficient information to make a determination of fact. Info. lacking includes:
make and model fireplace
make and model if separate gas logset
make and model CSST
Make and model flex connector

Armed with this information, you can look up each mfr.s requirements. The code itself is very vague on this issue and basically puts it back on the mfrs..

Now, as to the heat issue: we have two claims there is too much heat in this area for these materials and therefore the plastic must be stripped away. No one provided their source for this information. It certainly is not in the listing of a gas direct vent fireplace or for ventfree enclosures. Those listings only test temperatures external to the appliance such as walls, floors, and ceilings.

Let's assume this was a gas direct vent for a moment, (which btw it appears not to be). The gas combination control valve is rated for 175F. There are combustible paper tags usually found on the floor of this compartment and sometimes information sheets such as pilot lighting instructions attached down there. So, what is the maximum acceptable temperature for all gas fireplaces? The answer is, there is no single fixed number. It all falls back on the appliance mfr.. Some of their models have ventilated valve compartments that run rather cool while some run very hot. Still others with a 'clean face' look are not ventilated and may or may not run hotter. I will tell you that the hotter the box the longer the mounting brackets that suspend the valve under the firebox so it doesn't overheat.

If you read the various CSST mfrs., you should see where they do not prohibit penetrating an appliance cabinet per se. However, all I'm aware of do require protection such as the aforementioned flexible conduit or other approved means. They are looking to protect the flex tubing from physical damage.

Now, some mfrs. require their CSST be electrically isolated/ insulated from the chassis of the fireplace but do not prescribe how or with what materials. This is often met with a wad of insulation.

Some mfrs. will also recommend a plug of insulation to minimize air infiltration. You cannot however use combustible foams as a general practice but again, I know of no actual written prohibition of foams. I can tell you foam is a bad practice because of odors offgassing.

You can rule steel pipe out the side and connect in the wall cavity to CSST since it is listed and approved for concealed connections unlike soft copper flares and many black iron fittings.

Now, that flex connector should not be penetrating the floor of the fireplace. Again, refer to the mfr. but in general, you should not penetrate cabinets with these connectors. However, some mfrs. do tell you if you must then at least protect them. Therefore, it may be a bad practice but not illegal per se.

I'd like to see some other pics of that lower compartment and what that upper flex is connected to.

[Tim Fuller]

This is an interesting photo. What is all the gray stuff on one of the CSST lines but not on the other? I was also curious about what appears to be an electrical outlet there also.