Question on gas regulator vents Bob Morrison

Bob Morrison_2

In a commercial rooftop unit application line regulators are being installed at each appliance. The distribution system is 2 psig; the regulators drop to low pressure at the appliance. This building is in Massachusetts.

How high above the roof should the regulators be? Also, how high above the regulators should their vent terminations be?

Thanks for all responses.

Bob Morrison

Jacob Myron

Gas Regulators & Vents

The question you asked can be answered in 200 different ways.

Heights of gas vents, and placement of gas regulators is a code question.

The answer starts in the AGA handbook.
Each State, City, Township, County or gas Utility may have jurisdiction over the gas piping.

Your 2 PSIG gas inlet pressure clearly makes this a high pressure gas installation, up to the gas regulator.

After the gas regulator, you have a low pressure gas installation.

Since you are talking about roof top units I can offer you this peice of advise, Call the gas company and get the approved utility gas installation drawings for the type of units you will install.

Remember this also....

Do not put the vent pipe in any location that will permit vented gas from going into the units combustion chamber.


Jake

Dale

Regulator Vents

Since this is a rooftop installation the regulators that cut the pressure from 2 # to inches should not need any tubing attached to the vents unless as the other post suggested the vent is under an air intake. If you're using the typical Maxitrol regulators they often come with a vent limiter that you don't want to use outdoors as they ice up. We have had problems with vent limiters outdoors. Most people here just use the bug screen version of the vent fitting and turn the regulator upside down. A u bent tube facing down works too. Maxitrol is very helpful and the local rep can put you in touch with them. We have found that a larger pipe size from the maxitrol to the appliance helps alot with lightoff pressure problems, kind of like a gas shock absorber.

j_4

Gas Regulators & Vents

Do not put the vent pipe in any location that will permit vented gas from going into the units OUTSIDE AIR INTAKE

Bob Morrison_2

job already installed

Jake,

The project has been through all approvals and is installed. However, the plumber located the regulators (Maxitrol) at the same elevation as the distribution piping, which sits on 4"x4" wooden sleepers lying on the roof. I'm concerned about the regulator vents being blocked by snow. There's a less likely possibility of the regulator becoming partially submerged if the roof drains block.

I was surprised that the plumber didn't raise the regulators to at least a couple feet above the roof.

What's your opinion on the current location?

Bob

Dale

Now I see the issue

Sure, absolutely nothing wrong with putting little vent stacks on the regulators to keep them above any snow or water. Just U them down at the top and put on some sort of bug screen, Maxitrols are an amazingly good product, they make other stuff too like ddc controls for giant make up air heaters.