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For fun: what's wrong with this installation....


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2 psi systems for natural gas are becoming more common by the day, so I thought this might help someone...... I inspect these systems daily, and it seems like only about half are properly plumbed. Some installations are downright dangerous.

There's 2psi inlet pressure to these Maxitrol regulators. Can you spot the defects....

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Jim,

If you're counting defects per furnace, there's quite a few more. [;)]

I'll give it a while before spilling what I see. Let's just say it wasn't safe enough to leave the gas meter turned on; the customer was far from happy with me. This 2psi system has been installed for over 20 years, and was approved by the AHJ. The defects were missed by the "home" inspector a year ago, and missed by several HVAC contractors who have had service contracts here.

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I got no idea, just guesses. Obviously, the manometer is showing pressure that's way too high, but I don't know why.

Are these sorts of defects generally acknowledged in the usual installation guidelines, or does it take a technician trained to specialize in 2 psi gas installations to find them?

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Are these sorts of defects generally acknowledged in the usual installation guidelines, or does it take a technician trained to specialize in 2 psi gas installations to find them?

The defects are covered by manufacturers installation instructions, as well as the codes.

For future reference..... would it be better not to play the "find the defects" game, and to just make a post showing the issues?

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Gas piping/ regulator issues I wrote up, that are visible in these pictures....

1) MP regulators have round bodies, while RV regulators are square. This is the easiest way to recognize that there's a problem.

MP regulators are supposed to be used to drop pressure from pounds of pressure to inches (27.67" w.c. = 1 psi) The codes require lock up type regulators for 2psi systems...RV regulators do not lock up- they slowly build. The last picture shows pressure above 14" w.c. (max. for low pressure systems) Within a few minutes, pressure on the regulators shown in the above pictures built from 8" all the way to about 46" w.c.)

Standard pressure (low pressure) systems do not require MP regulators-- regulators are typically built into equipment combination valves nowadays. If you look at these combination valves, you will see that with natural gas, they typically call for a range of inlet pressure from say 3.5" to 10" w.c. You will also see where they are listed/labeled/ tested for a max. 1/2 psi (read a combination valve on a furnace or water heater if curious).

Over pressurizing the appliance combination valves in this case most likely voids any manufacturers warranty, violates the listing, etc.

What's interesting is the combination of issues that develop. Anything from having equipment running way over or under fired, to appliance regulators locking up, to pressures pulsing (inshot burner flames pulsating) I saw all of this @ the job above-- there were 14 pieces of equipment, all of which were installed the same way.

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The improper regulators were one of the reasons I shut gas off to the equipment at this place. The other issue was that there were a bunch of gas leaks throughout the piping system.

Other minor issues:

1)These particular brass line valves are not approved for 2 psi gas systems.

2)The required sediment traps, which also function as the pressure taps are missing.

3)The required pressure taps at the downstream / low pressure side of the regulators were missing as well. This was a non- issue for the ones plumbed in with flex connectors, but was an issue with others hard piped with unions.

A properly plumbed 2 psi system should have the following, in order from 2 psi piping downstream to the equipment:

1)A line valve.

2)A sediment trap/ pressure tap.

3)The MP regulator.

4)A pressure tap.

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I thought medium pressure regulators were intended for line pressures in the 150 psi range and bring pressures down to 2-5 psi and that low pressure regulators are used with line pressures in the 2-5 psi range and reduce pressures to inches of wc.

Thanks for the note that RV regulators are always square and the correct regulators are always round. That's a really useful piece of information.

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What about the placement of the external regulators (external to the furnaces) in close proximity to ignition sources? I'm not sure how the clearance applies to regulators serving a single appliance but on main regulators such as on LP systems a clearance from ignition sources (3'?) or a vent extension is required.

I agree, I need to read up on these higher pressure systems.

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Would you be interested in presenting information on these systems at an OAHI meeting?

Unfortunately, I don't do well in front of groups, so I'll have to decline, but...

The regional Maxitrol sales rep. lives and works out of the Tualatin/ Tigard area. We recently had him come out and present at one of our commercial technician meetings. You should definitely try to get him to present at one of yours. Once he retires, you'll probably lose any future opportunity for something such as this. He's one of the last Maxitrol rep's who doesn't work out of their Michigan HQ (I think it was Michigan).

I'd assume he could cater towards home inspectors.....

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I thought medium pressure regulators were intended for line pressures in the 150 psi range and bring pressures down to 2-5 psi and that low pressure regulators are used with line pressures in the 2-5 psi range and reduce pressures to inches of wc.

Our service pressures (underground) in our class B mains (ones that feed end users) run in the 40psi range. The regulators at the meter are called service regulators. These are the ones that drop the 40 psi down to either 2 psi or inches w.c. supply pressure

Read C410.1 & 410.2 in the link below for further details regarding MP regulators...

C410.1

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What about the placement of the external regulators (external to the furnaces) in close proximity to ignition sources? I'm not sure how the clearance applies to regulators serving a single appliance but on main regulators such as on LP systems a clearance from ignition sources (3'?) or a vent extension is required.

I agree, I need to read up on these higher pressure systems.

I'm not aware of any natural gas standards requiring specific clearances between an MP regulator and ignition sources. If they exist, they would most likely be specified by the manufacturer. That, or I need to do more studying...

On MP regulators supplied with a vent limiting device, the vent limiter typically limits the release of gas to around 3 cfh (per Maxitrol), which is very little. With regulators that don't have vent limiters, they must be vented directly to the outdoors, so I don't see much of a need for any clearances to ignition sources. I haven't got a clue as to what temperatures a regulator can take-- it's never come up.

Clearances for a service regulator (at a meter) are necessary because if the internal relief mechanism opens, there can be a substantial amount of gas exiting the vent. Gas pressure blowing out could be as high as service pressures (40 psi' ish for us).

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Is this a home inspection, or an inspection by a licensed heating and air conditioning professional?

Tom,

In this particular case, this was found during a load check and subsequent odor investigation. I was supposed to have an easy job of changing out the old meter.

I haven't a clue whether any portion of what I covered would fall within the scope of a bare minimum home inspection, but most of the guys on here like to exceed said standards when possible.

I do know that the customer purchased this large commercial property around a year ago, and wasn't aware of any of these issues. They mentioned that neither their inspector, nor their mechanical contractor had said anything about this issue; they weren't happy.

There are 5 buildings @ this location, all of which are plumbed the same way. The cost for repairs to their system to make everything right was well into the 5 figures. There were other issues with their HVAC system not mentioned here.

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