What is this device?

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jfreeman

jfreeman

Well-known member
Mar 5, 2020
62
Houston, TX
Pool Size
18000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
This is installed in the gas plumbing to my pool heater. Is it a "pressure regulator"? If yes, does the writing in the middle indicate it expects an input pressure between 6 and 15 inches of water column, or that it provides an output in that range? If the first, then what does it do if the input pressure is too low? If the latter, how does it output a minimum level of pressure?

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It is a pressure regulator. The 6" - 15" water column is "low" pressure and is the outlet side. Almost all household appliances run at these pressures (<0.5PSI). The input side could be any number of pressures, usually between 5PSI and 99PSI for distribution system pressures. You gas company's gas control department monitors system pressures at many points 24/7/365. It should never fall below a certain level, and if it does, they will shut the gas off altogether.

What's odd about this setup is that usually the regulator is at the meter. Do you have other gas appliances in your house? Where is the meter?
 
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There are two ways to run gas to a heater.

Single stage sends the gas to the heater at heater inlet pressure through a big line.

A two stage gas line uses higher pressure to near the heater (about 2 psig for natural and 10 psig for propane) and then through a regulator and into the heater.

This allows you to use a much smaller gas line from the meter to the heater.

For example, a 400,000 btu/hr natural gas heater on a single stage line 150 feet (straight pipe equivalent) would require a 1.5" pipe at 14" w.c.

Using a two stage line, you would use a 3/4" line at 2 psig to a regulator near the heater.

If the pressure going into the regulator is too low, the gas pressure going to the heater will go too low because the line won't be able to keep up with the demand.

 
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Here's the rest of my setup. I measured the outer diameters of my pipes and found 1.33 in OD = 1 in ID and 1.02 OD = 3/4 in ID. So I guess I've got 1 in pipe from the gas company through a regulator that puts out 7 IWC = 1/4 PSI, to my meter (which is marked "10 PSI MAOP"; MAOP = maximum allowable operating pressure), then splits. One side goes into the house in 1 in pipe, the other side goes into the ground in 3/4 in pipe and I assume comes out at my pool heater about 20 ft away, passes through the regulator I first posted, then into my heater in 3/4 in pipe. Does that sound and look right?

My meter is rated for 425 CFH which is supposed to be about 425k BTU, but my pool heater alone demands 400k. I've asked my gas company for a meter upgrade. They keep trying to default it to a pressure upgrade, but I've insisted on a volume upgrade. If I were to get a pressure upgrade, how would that work given the pressure regulator before my meter? Wouldn't I need to move that regulator after my meter, and out-of-line with the pool heater?


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Who installed the regulator at the heater? Gas company or plumber? The regulator at your meter should already be producing low pressure, unless you have another regulator inside the house as well?
 
MITBeta said:
Who installed the regulator at the heater? Gas company or plumber? The regulator at your meter should already be producing low pressure, unless you have another regulator inside the house as well?
Click to expand...

I wasn't here for it, but I think the plumber. I wonder if maybe in fact I do need to upgrade the meter for higher pressure and move the first regulator. Would you happen to know if the gas company would move that regulator for me when they upgrade the meter? Is that common?
 

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A low pressure single stage line from the meter to the heater would need to be at least 1.25" up to 50 feet.

At 3/4", the line from the meter to the regulator would need to be at 2 psi to supply the correct amount of gas.

A meter needs to be sized to supply the total amount of gas that can be demanded at any one time.

Besides the heater, what is the total btu/hr that can run at the same time as the heater?
 
JamesW said:
Click to expand...

How am I supposed to read the chart on the second page? I'm guessing left column is inlet pressure in PSI. Header row is what? Outlet pressure in PSI? The first three table titles are what? Inlet pipe diameter or outlet pipe diameter? I guess it doesn't matter in my case, since they're the same, but I'd still like to know. The table values are what? Flow in CFH?

My heater requires between 4 IWC = 0.14 PSI and 14 IWC = 0.51 PSI of pressure. If I've got 3/4" pipe, 2 PSI inlet pressure, and 1/4 PSI outlet pressure, the regulator will output at most 425 CFH?

This got me reading the manual for my heater. On page 15 is a chart Stage Two "Low Pressure" Gas Pipe Sizing. It seems that there is NO LENGTH of 3/4" pipe suitable for my 400k BTU heater. Am I reading this chart wrong, or does that mean I need a larger pipe installed to serve this heater?
 
Generally, the customer owns and is responsible for everything downstream of the meter. So if you increase your pressure (which I don't think is necessary here, just proper sizing downstream) a qualified gas fitter would have to install a regulator after the meter, before the house.
 
Ok, that chart is for "low pressure" only, which I guess is 1/4 PSI. If the line running through the ground is at 2 PSI, then I guess you're saying I can use the existing 3/4" pipe.
 
I think the regulator before the meter means the 3/4" pipe in the ground isn't at a high enough pressure to supply the pool heater. I'm becoming more convinced that I need a pressure upgrade for the meter, and the upstream regulator moved out-of-line with the pool heater.

I bought the house 3 months ago. The previous heater was broken and the previous owners replaced it with this heater, which I believe is much larger than the previous one, but the gas supply wasn't fixed for it. This pool heater has never run, besides when the installer tried to test it. I'm guessing the previous owner didn't pay them to fix the plumbing, just replace the heater.
 
The rest of my house has 3 furnaces, 2 water heaters, and a fireplace. With the pool heater, total demand is around 800k BTU. I'm planning to remodel the kitchen at some point and convert it to gas, and add an outdoor gas connection for a grill. That'll bring it up to about 950k. I had tried getting the pool heater installer to consult me on what I actually needed, but he's not very responsive. I'll call a gas contractor at this point. Thank you, everyone.
 
The table for the regulator has inlet pressure in column 1 and orifice size (inside the regulator) across the top. The combination of which will deliver a certain SCFH.

You're reading the heater manual correctly: 3/4" at low pressure is too small.

You don't need more pressure, you need a bigger pipe to the heater.
 
MITBeta said:
You don't need more pressure, you need a bigger pipe to the heater.
Click to expand...

That and more volume is one solution. Right now my meter can handle 425 CFH, but I need 800 for the equipment that is already installed. But I'm wondering if re-plumbing 20 ft of larger diameter pipe through the ground is cheaper than just moving the pressure regulator? I'll have to upgrade the meter regardless, and it costs the same whether I'm getting more volume or more pressure.
 
Three furnaces, two indoor water heaters, and a fireplace. They could all run at the same time if I'm in the hot tub during winter.
 

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