[Greenbuilding] [BULK] Re: Propane in Attic

Fri Nov 2 13:16:25 EDT 2007

The catch pan is for condensation from an air conditioning coil. It has little to do with draining propane leaks. There is no reason Propane furnaces can't be installed inside.  If the pipeline is properly pressure tested, it should remain leak free unless it is disturbed.  The flue, of course, needs to be properly vented.  Sealed combustion furnaces, with a blower that can draw in outside air for combustion, are a good idea but this isn't to keep propane out of the house - it is to prevent the furnace from wasting previously heated air, for efficiency.  There really isn't any big safety problem with leaking propane, any more than any other fuel.  The odorant in propane is an extra safety measure, if there is a leak you'll know about it way before it is dangerous.  

Lawrence Lile, PE, LEED AP
Project Solutions Engineering

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org [mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Steve Houlihan
Sent: Wednesday, October 31, 2007 7:08 PM
To: GREENBUILDING at listserv.repp.org
Subject: [BULK] Re: [Greenbuilding] Propane in Attic
Importance: Low

OK, let me try this again.  I often see advice on this list to move your 
ducts and (I assume) your FAU into the heated space.  Use a condensing 
furnace and draw all your combustion air directly in from outside.  This is 
great, because all the heat losses are inside the heated envelope and that 
ups the efficiency.  But this creates a problem, especially with propane 
which is heavier than air.  If any leaks occur then they will collect under 
the furnace and could cause an explosion.  How is this handled?  Or do I 
have this wrong!  Should the furnace stay out of the envelope and just the 
ductwork inside?  I've seen the diagram many times about moving the 
insulation from the ceiling up to the roof and it always shows a furnace and 
ducts in the  (now heated) attic.

I have seen propane furnaces in unconditioned attics with large catch pans 
under them and a drain in the pan to take any propane outside by gravity. 
Natural gas doesn't need such a drain system.

Natural gas furnaces in attics have become the standard here in Northern 
California now for new construction.  I don't want my furnace in the attic, 
especially crammed between a spiderweb of trusses like so many I see, but 
was wondering about how to deal with the propane if I brought the furnace 
inside the envelope.

Thanx
Steve
----- Original Message ----- 
From: "Bruno M." <brunoM1 at telenet.be>
To: <GREENBUILDING at listserv.repp.org>
Sent: Wednesday, October 31, 2007 3:41 PM
Subject: Re: [Greenbuilding] Propane in Attic

Steve,

You didn't give all the specifics of your setup,
is it a water heather or a central heating system, or combo,
is this appliance a modern closed unit ( forced air in and out)?
Were you thinking of setting a bottle of liquid
propane besides this appliance, in the house?

Anyway, if you look into the MSDS of Propane, e.g.:
www.amerigas.com/commercial_msds.html
you'll notice that propane has the next properties:

         BOILING POINT: @ 14.7 psia = -44° F (@1.00 atm.pressure = -42°C)
         SPECIFIC GRAVITY OF VAPOR (Air = 1) at 60° F (15.56°C): 1.50

Meaning that the vapors are heavier than air; and
may collect at low levels.

         VAPOR PRESSURE: @ 70° F (20°C) = 127
psig; @ 105° F (45°C ) = 210 psig; @ 130°F (55°C) = 287 psig
         EXPANSION RATIO (From liquid to gas @ 14.7 psia): 1 to 270
         APPEARANCE AND ODOR: A colorless and
tasteless gas at normal temperature and pressure.
         An odorant (ethyl mercaptan) is added to
provide a strong unpleasant odor.
         Should a propane-air mixture reach the lower limits of 
flammability,
         the ethyl mercaptan concentration will
be approximately 0.5 ppm in air.

         SPECIAL PRECAUTIONS: Use piping and
equipment adequately designed to withstand pressure to be encountered.
         NFPA 58, LP-GAS CODE and OSHA 29 CFR
1910.10 require that all persons employed in handling
         LP-gases be trained in proper handling
and operating procedures, which the employer shall document.
         Contact your propane supplier or
AmeriGas to arrange for the required training.
         Allow only trained and qualified persons
to install and service propane

You can learn from this that if you have a gas
leak, the gas will not rise to the ceiling,
but rater gather at the floor or a lower levels in the house.
So a gas detector should be placed near the
floor, if that attic is closed-off from the lower levels.

Also, if you like to do everything yourself with
the installation, check your (fire-)insurance papers,
they can require that al gas equipment is
installed by certified technicians otherwise in case of an
incident the insurance is void.

Grts
Bruno M.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 21:45 31/10/2007, Steve wrote:

>How do I handle the problem of collecting
>leaking propane if I move my furnace into the
>conditioned space?  I don't want a bomb in my attic.
>
>Steve
>_______________________________________________
>Greenbuilding email list

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