Thread: Propane HVAC in attic

I know that a propane fueled furnace in a confined space such as a basement requires a LP pan with a drain to the exterior for possible fuel leakage. My question is: Is the LP pan required when the confined space is in the attic? I have seen them installed with and without the LP pan when installed in the attic space.
Thanks for your reply guys.

Originally Posted by Mark Ryan

I know that a propane fueled furnace in a confined space such as a basement requires a LP pan with a drain to the exterior for possible fuel leakage. My question is: Is the LP pan required when the confined space is in the attic? I have seen them installed with and without the LP pan when installed in the attic space.
Thanks for your reply guys.

I have never heard of that requirement, and I have never seen it. How would you install a drain to the exterior from the basement. Propane is heavier than air and is a gas. How it the pan going to contain it and how is it supposed to get to the exterior?

I am in Nor Cal, not many traditional basements here, mostly the walk out type. Sorry about my wording in my post above. Any way, a metal pan with roughly 6 in walls and an aprox 4 in metal drain to the exterior is what I have seen a few times. I have also seen the floor drain set up at pictured below.
I got my info from the Code Check HVAC page 19.

Here is the illustration pic I just took

Hello Mark. I'm in northern Cal also, and have not seen many basements either. Of those that do have basements I have seen a pan type of situation like your picture, or natural gas. Even the crawlspaces are sloped with 4" drains at the side wall, if propane heaters are hung in the crawlspace.
As far as attics go, I have not seen the pan installed for an attic mounted propane furnace, except in the case where the A/C component has a pan for the evaporator coils, however, the drain line for this is insufficient to carry the gasses for propane. So....no pans in the attic, that I have seen....and some of these are relatively new installations. Question is "Why not?" Seems like a good idea to me, but expense of installing this pan with a 4" drain outlet may outweigh the requirement for such an installation. I don't know if there has been an associated problem/fire with attic mounts.

A realtor told me a friend of his died when the ski cabin he rented exploded because of the lack of a drain (or blocked drain) for the propane heater under the cabin. He told me this when I was inspecting a house for his client, and I said to him that there was a problem with this propane floor furnace installation - lack of a drain, confined area under the house. He got the picture right away.

Thanks for the reply Chris
I agree, why not if it is safer. Save a few bucks over safety.
I saw a newer install this week with the LP pan setup in an attic. Last week I had an older installed unit, maybe 12 yrs old, without the LP pan.

I agree - it would be a good idea....but so far there has been no need that I am aware of. We do not know all the reasons for attic/house fires, but has anyone heard of a fire caused by a propane gas leak in an attic? I'm not sure where to find this type of answer - fire inspectors, I guess. But it would be up the various enforcement agencies to learn of this if it is a danger, and make appropriate recommendations.

Nothing like this is required in Colorado, but I've seen installations (including mine) with a 2x4 or 2x6 caulked "pan" around the furnace and a propane leak alarm and safety shutoff. Unfortunately, whenever the electricity went off, (which in rural Colorado happens many times a year), the leak alarm would kill the propane to the furnace and resetting it was a "process". It was never as easy as simply pushing the reset button and my wife hated it. So, I removed the damn thing.

Originally Posted by Mark Ryan

Here is the illustration pic I just took

There is no FG401.2 in the IRC. There is a 401.2 in the International Fuel Gas Code (which generally does not apply to dwelling). That passage does not reference drains. In a search on the internet it seems that it is mostly a CA thing. In areas around here without natural gas propane furnaces are often used and almost always are in basements. No panes or drains. I always recommend installing a combustible gas detector near floor level, but they do not seem to be required.

Well I feel better knowing that there are gas alarms out there.
I wonder if the guy in the ski cabin heard the "Beep" before the "Kaboom"

It was in the 1991 Uniform Mechanical Code (504, f)), may have been in subsequent versions, but I don't have those. It's not in the International Codes since 2000.

I would imagine that it's not required since most attics are ventilated.

Thanks Fred W. I have the 1988 UMC - probably same verbiage. Only talks about pits and basements and underfloor. No reference to attics.
DSC08046 (Small).JPG

Jim R. Good, and valid point about the attic vents.

I have not been able to find a reference to LP gas pans in either NFPA 54 or the IFGC but I have encountered it with certain gas utilities such as Washington Gas. The theory is that should LP gas spill in an attic, a pan would catch it where it could be "drained". While LPG is heavier than air, it is not liquid. Also, a pan would only capture some gas if the leak point was directly above it. Pans don't cover the whole attic hence other joints could still cause a problem if they are not over the pan. Now, since attics are ventilated and have air movement, that air can move even LP gas. If you put LPG in a pan with a 3/4" gravity drain to a soffit vent, it will sit in the pan and slowly dissipate. It would be far better to rely on proper testing and inspection.

As for combustible gas alarms, know that most are set to alert at 20% of the LEL or Lower Explosive Limit. For a leak to hit 20% LEL means it won't take long to reach 100%. This is an immediate action alert--get out. It is not a trace. On the other hand, electronic gas sniffers can sense between 10-500ppm LPG depending upon the model. With the LEL of propane around 21,500 parts per million and most humans being able to smell the odorant added to LPG at levels of about 2-5ppm, there is a wide gap between smelling gas and going 'poof'. Only an instrument can quantify gas. However, the ones on the market are not very accurate or reliable. Still, since there is nothing else, I guess we're stuck with them. Just understand their short comings and don't tout them as being any sort of early warning device because they are not. They are an emergency warning just before you go 'poof'.

Originally Posted by Mark Reinmiller

There is no FG401.2 in the IRC. There is a 401.2 in the International Fuel Gas Code (which generally does not apply to dwelling). That passage does not reference drains. In a search on the internet it seems that it is mostly a CA thing. In areas around here without natural gas propane furnaces are often used and almost always are in basements. No panes or drains. I always recommend installing a combustible gas detector near floor level, but they do not seem to be required.

Propane not natural gas appliances located in crawl spaces require a drain to daylight outside thru the foundation with a rodent screen

Originally Posted by frazier jeffery

Propane not natural gas appliances located in crawl spaces require a drain to daylight outside thru the foundation with a rodent screen

Do you have a code reference requiring those pans and drains?

Originally Posted by Jerry Peck

Do you have a code reference requiring those pans and drains?

I think it is a CA thing.... Just like some things cause cancer in CA and not other locations!

Originally Posted by Scott Patterson

I think it is a CA thing.... Just like some things cause cancer in CA and not other locations!

That's why I asked for a code reference ... sometimes the CA causes of cancer affect the brain and things seem to exist which don't really exist ... or is that medical marijuana stuff which causes that?

Future reference for California inspectors

California Mechanical Code 303.81.. prior to this 303.71 (credit to Doug Hansen).. reference is in regards to crawlspace/basements. I know that some push had been made in areas that are a high % of propane users, having pans/duct to exterior for attic or above grade installs, where required or not for LP use.

303.8.1 Liquefied Petroleum Gas Appliances. [HCD 1 & HCD 2] Liquefied petroleum gas-burning appliances shall not be installed in a basement or similar location where heavier-than-air gas collects. Appliances so fueled shall not be installed in an above-grade underfloor space or basement unless such location is provided with an approved means for removal of unburned gas.