Thread: Regulator question for Bob Harper

Bob,

I have a question (have not gotten a response back from Maxitrol and it's been almost a week):

Gas regulator in a non-ventilated space, fire resistance rated floor/ceiling system. These have vent limiters in them, but don't these need to have the vents vented to the outdoors - this is not like a vented attic, it is actually the fire separation system between units, and it is (of course) not ventilated.

I can see a regulator leaking gas, however slowly through the vent limiter, into this non-vented space, until one day, maybe when there is a fire, maybe not, and something causes that gas to go Boom!, then there a fire - inside the ceiling/floor system which is supposed to protect the units from each others fire.

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see these docs from Maxitrol:

Venting Code - Maxitrol Company
www.maxitrol.com/pdfs/mp2037.pdf

I guess it really comes down to the AHJs opinion if gas leaking into this space at 2.5cc/hr represents a hazard or not. If there is a possible source of ignition in a non-ventilated space, it definitly should be vented to the outside. I would argue putting the possibility of a gas explosion into a fire rated assembly seems counter-intuitive.

Keep in mind, the concept of a vent limiter is twofold-
limit escaping gas in the event of diaphragm rupture to a low enough level that:
a) in a ventilated space, it dilutes out quickly so it cannot reach 20% of the LEL and
b) hopefully, someone will smelll the leak and take action

If the leak is undiscoverable without fire trucks dousing the flames, what good is it?


Side note; ANSI Z21.80 for MP regulators now requires an overpressure device for inlet pressures over 2 psi. Don't hold your breath for everyone to spend the extra money on these....They are usually non-stock items that must be ordered and of the few plumbers who are even aware of this std. would wait for an OPD reg. to come in.

Jerry, HTH,
Bob

Originally Posted by Bob Harper

I guess it really comes down to the AHJs opinion if gas leaking into this space at 2.5cc/hr represents a hazard or not.

In this case, that's basically me, but I wanted backup for my knowledge before I wrote it up, which is why I contacted Maxitrol by e-mail and by phone last week, with no response from either - I figured you would know. Thank you.

If there is a possible source of ignition in a non-ventilated space, it definitly should be vented to the outside. I would argue putting the possibility of a gas explosion into a fire rated assembly seems counter-intuitive.

My position exactly.

Keep in mind, the concept of a vent limiter is twofold-
limit escaping gas in the event of diaphragm rupture to a low enough level that:
a) in a ventilated space, it dilutes out quickly so it cannot reach 20% of the LEL and
b) hopefully, someone will smelll the leak and take action

Yep. The key being "in a ventilated space", and this is not, for obvious reasons (because you cannot ventilate a fire rated space, in fact that space must be sealed (smoke and draft).

If the leak is undiscoverable without fire trucks dousing the flames, what good is it?

Good way to put it.

Side note; ANSI Z21.80 for MP regulators now requires an overpressure device for inlet pressures over 2 psi. Don't hold your breath for everyone to spend the extra money on these....They are usually non-stock items that must be ordered and of the few plumbers who are even aware of this std. would wait for an OPD reg. to come in.

I've read a few things indicating something to that effect, I'll have to see what standard the code references.

My intuition said that ain't gonna produce good results if there is a diaphragm rupture - having the charred remains of parts of a 4 story frame structure picked up out of the street is not the kind of news item you write home bragging about.

Certainly did help, thanks.