Distance between outdoor second stage regulator relief discharge and interior appliances - code

axolLearner

This may be a silly question to experienced folk, but I want to understand this. I was reading that regulator relief discharge should be 5' away from ignition sources. Does that pertain to indoor ignition sources too? EG, with the regulator+discharge outside, what if my wall boiler was on the other side of the wall, within 5'? Or a light switch/outlet was near there?

Seems to me there wouldn't danger so long as I'm respecting the "leave 3' between openings to the building and the discharge" rule - propane shouldn't be able waft in... but what does code intend/dictate?

PS (I'm under the impression many appliances specify a minimum run of pipe regardless in order to have immediately available volume. Does that hold with experience?)

mattmia2

It only applies to things mounted on the outside with the regulator.

EBEBRATT-Ed

What @mattmia2 said.

Keep the regulator away from air intakes , flue outlets, electrical meters etc. Anything indoors is not considered.

Putting the boiler inside and the reg outside on the same wall will only be a problem if the flue and air intake are near the regulator.

hot_rod

Some gas regs have restrictor orifices to allow them to be mounted near or in the appliance. This is common with restaurant gas fired equipment. I suppose NFPA 54 code covers the requirements.

I have a 2 psi NG system in my home with the approved regs near the appliances.

https://www.maxitrol.com/2022/07/07/line-pressure-regulator-venting-vent-limiting-devices/

mattmia2

https://forum.heatinghelp.com/discussion/comment/1806109#Comment_1806109

I wanted to replace my 60 year old piping that had been in a fire with a 2 psi system but there is only 2 psi in the street.

ratio

Vent limiters are required on all indoor (unvented) regulators, and prohibited on all outdoor regulators. Outdoor regulators need to have the vent opening protected from water entry. A few street 90°s, or a plastic part made for the use, or (easiest): turn the vent down! A vent limiter doesn't count—it's prohibited to install them on a regulator installed outdoors.

You can't install a vent limiter on a regulator outdoors. You gotta keep water out of the vent on an outdoor regulator.

I have this discussion with gas pipefitters about every other install. Sometimes, I have to escalate to the GC & let them know that frozen regulators are not a warranted service call. That usually gets the issue resolved.

Bob Harper

The vent is required to equalize against the ambient atmospheric pressure. The hazard comes if the diaphragm inside blows thus spewing fugitive gas at high pressure. Therefore, when installed indoors, the vent must be limited such that in the event of a rupture, the loss is limited to 2.5 CFH NG/ 1.0 CFH LPG per ANSI. The vent must be in a ventilated space where occupants could be expected to enter and smell the odorant in the gas to detect a release. Discharging gas into a confined space turns it into a bomb. Should the space where the Medium Pressure regulator must be located is inadequately ventilated, you must extend the vent to the outdoors. You can manifold the vents of two regulators as long as the common vent is sized accordingly. Otherwise, the regs. fight each other.
All regulator vents for NG must be a minimum 3 ft. from a 'source of ignition'. LPG has two specs: 5LF for DOT cylinders and 10 LF for ASME containers. You must also observe the 4LF clearance from building openings. When using a reg., such as the Maxitrol 325 series, you must orient it and indicated when installed indoors relying on the vent limiter. It is a ball that falls by gravity against the gas pressure. If mounted in any other poise, the ball will not seal and thus will not limit. Outdoors, you can mount it however you want, as long as you protect the vent from rain/ ice. Max. makes a little blue plastic umbrella that screws right into the vent and works well.
Yes, some mfrs. especially generator mfrs. specify a minimum distance from the appliance regulator so the line downstream of the MP reg. acts as a buffer to dampen pressure waves. They also often specify a large diameter riser downstream of the reg. to act as an expansion tank rather than a vena contracta.

Note the gas code requirements for MP reg. piping: an approved shutoff within 18" upstream, union, and sediment trap. The trap not only protects the reg. but provides a convenient means of attaching a psi gauge to measure the inlet pressure. Immediately downstream of the reg. must be a means of attaching a manometer to measure the outlet pressure. The code mentions a capped or plugged tee but you can typically get Hector the Inspector to sign off on any suitable fitting with the 1/8" NPT thread for the barbed hose fitting. I've used gas cocks with drains and they work great.

A common problem is mounting a MP regulator too close to a source of ignition. Just extend the vent line the requisite distance and protect the end of the vent as above and support the vent line. I would advise on longer vents or those with ells to incorporate a union so you can remove and service the reg. without cutting the vent line. Make sure you support the reg. upstream and downstream. Most of all, ensure you have enough clear access to inspect it, turn wrenches, attach gauges or replace it.