Natural gas pressure drop, pipe sizing and pressure

I bought a 200,000 BTU pool heater, to be installed outdoors.
The model is Hayward H200FDN.
The size of the piping that leads to it is somewhat iffy and appears just a bit undersized according to various tables. Depending on the actual pressure in the system, may be inadequate and not able to supply enough gas.
The manual says:
``Based upon an inlet gas pressure of 0.5 psig or less at a pressure drop of 0.5 in-wc''
Later it says:
``Hayward will not be responsible for heaters that soot up due to improper .. natural gas line sizing''.
If I cannot provide this heater with adequate gas flow, I can upgrade most of the piping from 3/4" NPT to 1" NPT, it is roughly a day or work and some money.
To question is, do I need to do it?
So, I thought, I could turn to measurement of the gas pressure right at the inlet of the pool heater. If the gas pressure at the inlet, when the heater is running, is above the recommended value, then I am fine.
I do have a pressure gauge that I could use.
My question is, and here's where I am not sure, what is that "recommended inlet pressure". Is that 0.5 PSIG when the heater is running? Am I reading that right?
thanks
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On 5/16/2015 10:29 AM, Ignoramus6769 wrote:

I think you are interpreting it correctly. But, 0.5 psig seems high for regular natural gas. Or, is it propane? Either way, 1 psi is 27.7 in-wc. So that would make the inlet pressure almost 14 in-wc. But as most gas appliances have regulators, I guess that might be ok.
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On Sat, 16 May 2015 09:29:54 -0500, Ignoramus6769

You are correct. You need the pressure at the appliance when it is running. With the appliance NOT running you would have the correct pressure on even a 1/4" line.
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I agree. It makes sense based on simple physics.
The question is, what exactly pressure should I see on the onlet when the heater is running.
i
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On 05/16/2015 10:49 AM, Ignoramus6769 wrote:

...

"...an inlet gas pressure of 0.5 psig or less ..."
It's not any _specific_ pressure; it's that it's not too high and that whatever it is can be maintained under flow conditions.
--


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OK, an update: I have decided that
1) This is a very good heater because it can heat the pool quickly before use, and thus I do not need to waste energy "maintaining" temperature when the pool is not in use.
2) I need to hook it up correctly and will install proper gas piping comprised of about 40' of 1" pipe.
i
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On Sunday, May 17, 2015 at 4:37:03 PM UTC-4, Ignoramus4261 wrote:

Before you plumb it all in, have you figured out how much it's going to cost to heat the pool? Around here, NJ, almost no one uses them because of the huge operating cost. They have them sitting there, because they were installed with the pool, but they rarely if ever use them. I guess if it's small, it might not be too bad. But for an inground one that's 30 or 40K gallons, which isn't unusual, it costs a lot of money. The fact that it's 200K BTUs tells you something. The largest home gas furnace is 120K btus.
If you have some room for a solar array, you can operate it for close to free. But they have drawbacks too, the large size needed being one. Whether you want one on the roof or have a space out of sight in the yard is another.
You can use a pool cover with either, which helps a lot. But that's a pain and some folks won't put up with it, don't like the look, etc.
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Ignoramus6769 wrote:

Isn't there a pressure regulator near the meter at entry point.
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On Sat, 16 May 2015 11:40:50 -0400, snipped-for-privacy@snyder.on.ca wrote in

+1
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