Propane tank ventilation..

[Iver]

I think I have it written down somewhere but could someone refresh my memory as to the number of square inches required to ventilate an enclosed propane compartment.
For example with 2 thirty pound tanks.
    Thanks, Iver.

[Sean]

I strongly recommend you purchase a copy of the publication ANSI/NFPA 1192.  This document details everything you need to know about LP systems as well as many other RV systems.  The publication can be downloaded for $38 from NFPA.

My own copy is from 2002 (when I started my conversion).  The latest revision is 2008, which may differ.  My copy says:

5.2.6.1 Ventilation of Compartments Containing LP-Gas
Containers. Compartments shall be ventilated at or near the
top and at the extreme bottom to facilitate diffusion of vapors.
The compartment shall be ventilated with at least two vents
having an aggregate free area equal to at least 1 in.² for each 7 lb
(1 cm² per 500 grams) of the total LP-Gas fuel capacity of the
maximum number of largest cylinder(s) the compartment can
hold. The vents shall be equally distributed between the floor
and ceiling of the compartment. If the lower vent is located in the
access door or wall, the bottom edge of the vent shall be flush
with the floor level of the compartment. The top vent shall be
located in the access door or wall with the bottom of the vent
within 12 in. (305 mm) of the ceiling of the compartment. Vents
shall have an unrestricted discharge to the outside atmosphere.
Doors or panels providing access to valves shall not be equipped
with locks or require special tools to open.


So for your two 30lb cylinders, you will need a minimum of 8.6 square inches, evenly divided between the top and bottom of the compartments.

Note that you need to make the vents large enough to support the largest cylinders that can ever be put in the compartment.  So if you can fit, say, three 30# tanks, you'll need 12.9 square inches, or if you can fit two 40# tanks, 11.4 square inches, etc.  -- you can't just ventilate for the cylinders you plan to use today.

-Sean
http://ourodyssey.blogspot.com

[TomC]

I mounted my Manchester tank (100lb) under the bus with no floor to it-so there is complete opening to the ground.  It is a chassis mount tank and designed to be mounted as such.  My outside door has no lock on it.  Good Luck, TomC

[JohnEd]

Went through this a long while back and it was verified to me by the BB.  The reg that I inquired about was for the "overflow vent on permanent tanks bigger than 50 gal(?) to be plumbed to the extreme rear of the bus and exhausted at a height of 6 feet or more".  The rational was that it would better diffuse the gas on the drop from the 6 foot height and be less volatile.  The little tanks that vent at the bottom of the bus could conceivably bleed of gas and leave a trail back to the bus that could burn you down.   100 gal tanks can apparently vent large amts of gas if filled in the hot summer.  That had nothing to do with relieving the requirement for vents in the tank locker space.

I thought it was interesting.   Especially as i plan to install a 100 gal propane tank,

John 

[Sean]

...  The reg that I inquired about was for the "overflow vent on permanent tanks bigger than 50 gal(?) to be plumbed to the extreme rear of the bus and exhausted at a height of 6 feet or more".

Can you cite a section/paragraph number?  I've read all the way through the LP section of my code, and I don't see this requirement anywhere.  Of course, the RV code deals (and permits) only "vapor-withdrawal" systems.  LP withdrawn as a liquid for engine fuel is covered in a completely different code, NFPA 58.

-Sean
http://ourodyssey.blogspot.com

[TomC]

I think he's confusing the LP regulation with natural gas.  You'll notice on all natural gas buses a small "exhaust pipe" at the rear top of the bus.  Good Luck, TomC

[Sean]

I think he's confusing the LP regulation with natural gas.  You'll notice on all natural gas buses a small "exhaust pipe" at the rear top of the bus.  Good Luck, TomC

That makes sense, Tom.  I do know about the NG venting requirement.  NG, of course, is lighter than air, whereas LPG is heavier than air.  Big difference.

-Sean
http://ourodyssey.blogspot.com

[skipn]

One little item I might add.......

    If you look at the different committees and their specific area

  1192   RV
   58      LP
   59A   LNG PNG

    Each one has a scope on what is covered.
   If your particular design is outside that scope then one needs to be very careful. (insurance voided etc)

    IE.   IF and a big If   the RV lp tank scope is for tanks under 200 gals. and you wish
    to put a 400 gal tank..........You would be outside compliance.

     Just a thought


      For fun and see what our(USA) committees do follow the link for last years proposed changes and votes.

    http://www.nfpa.org/assets/files/PDF/ROP/1194-F2007-ROP.pdf
     Skip