SPA heater, what would happen?

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JamesW said:
What is the pressure in the 228 feet of 3/4 PEX pipe?

Is the 5 psi before or after the regulator?

Is the regulator near the heater rated for 400 cubic feet per hour?

Is the gas meter rated for 400 CFH or higher?
Click to expand...
  • The pressure in the 228 feet of 3/4 PEX pipe is 5 PSI.
  • Before the regulator (near the heater) for lower pressure line
  • Yes, the regulator is near (outside the service room where is located the heater)
  • The meter model is MR-8 (metric version) with a capacity of 8 m3/hr. It seems is 282.5 CFH according with an online converter :oops:
 
JamesW said:
400 cubic feet per hour (400,000 btu/hr) should result in about 0.4" w.c of pressure drop in 1" pipe.

If we use 30 feet as the Total Equivalent Length, then the expected pressure drop is about 0.6" w.c.

So, either way, the pressure drop is higher than expected.

Maybe the regulator is not rated for the capacity?
View attachment 622164
View attachment 622163
View attachment 622162
Click to expand...
I'm not sure. Below the specs of all devices:
When I was talking with the gas company, they suggest the meter and regulators according with the heater. Right now, I'm confuse if this was a good design.

Untitled1.jpg
 
For 400 CFH, you will lose 2 psi at 1,000 feet of 3/4" pipe, 0.2 psi at 100 feet or 0.456 psi (12.62" w.c ).

1735003488178.png

1735003716865.png

The loss at 1,800 feet is 3.5 psi, at 100 feet is 0.1944 psi and 0.4433 psi (12.27" w.c) at 228 feet.
 
Hulaomr said:
The pressure in the 228 feet of 3/4 PEX pipe is 5 PSI.
Click to expand...

Hulaomr said:
The meter model is MR-8 (metric version) with a capacity of 8 m3/hr. It seems is 282.5 CFH according with an online converter
Click to expand...
The meter is sized on a 0.5" w.c pressure drop.

If you allow for higher pressure drop, then you get more flow.

Pressure drop.........CFH

0.5".............................275
1"................................383
2".................................600

1735004050094.png
 
Hulaomr said:
I'm not sure. Below the specs of all devices:
Click to expand...
The 597FA is listed as a Propane regulator, so I do not think that it is suitable for natural gas.

Regulator LV4403B46 is also for propane and it seems to be undersized.

The meter can handle 400 CFH if you allow about 1.1" of w.c pressure drop.

1735004811244.png

One cubic foot of propane = 2,516 BTUs compared to one cubic foot of natural gas = 1,030 BTUs.

Propane contains more than twice the energy of natural gas.

Rego LV4403B46 Low Pressure Second Stage Regulator 1/2" x 3/4" Straight Through

Rego LV4403B46 second stage propane regulator, used on the "house". Used in conjunction with Rego LV4403TR9 First Stage Regulator.
www.propane-regulators.com www.propane-regulators.com
 
JamesW said:
The meter is sized on a 0.5" w.c pressure drop.

If you allow for higher pressure drop, then you get more flow.

Pressure drop.........CFH

0.5".............................275
1"................................383
2".................................600

View attachment 622186
Click to expand...

I cannot understand. I have a couple of questions:
  • Considering the current scenario, the pressure drop at the meter side is expected? Or there are something else (small pipe, obstruction, etc...) that I need to check to validate the pressure drop that I reported in the meter and in the heater?
    • meter has a capacity of 282.5 CFH
    • high pressure line 3/4" of 228 ft with 5psi
    • low pressure regulator
    • low pressure line 1" of 20 ft to the heater
  • If the results are as expected, I will need to change the meter or could I live like that, considering the pressure a the heater is according with the specs?
 
LV4403B46 2ND STAGE REGULATOR FOR LP GAS 935 000 BTU CAPACITY 1/2" FEMALE NPT INLET X 3/4" FEMALE NPT OUTLET.

Designed to reduce first stage pressure of 5 to 20 PSIG down to burner pressure, normally 11" w.c.

935,000 btu is about 371 cubic feet of propane.

935,000 BTU/hr converts to about 382 btu/hr or 382,000 btu/hr for natural gas.

You really do not want to use propane regulators on a natural gas installation.
 
JamesW said:
The 597FA is listed as a Propane regulator, so I do not think that it is suitable for natural gas.

Regulator LV4403B46 is also for propane and it seems to be undersized.

The meter can handle 400 CFH if you allow about 1.1" of w.c pressure drop.

View attachment 622189

One cubic foot of propane = 2,516 BTUs compared to one cubic foot of natural gas = 1,030 BTUs.

Propane contains more than twice the energy of natural gas.

Rego LV4403B46 Low Pressure Second Stage Regulator 1/2" x 3/4" Straight Through

Rego LV4403B46 second stage propane regulator, used on the "house". Used in conjunction with Rego LV4403TR9 First Stage Regulator.
www.propane-regulators.com www.propane-regulators.com
Click to expand...

The heater is propane according with the label inside.

The residential gas is defined as a mixture of propane and butane. The terms they used locally is Liquefied Petroleum Gas (LPG).
 

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JamesW said:
LV4403B46 2ND STAGE REGULATOR FOR LP GAS 935 000 BTU CAPACITY 1/2" FEMALE NPT INLET X 3/4" FEMALE NPT OUTLET.

Designed to reduce first stage pressure of 5 to 20 PSIG down to burner pressure, normally 11" w.c.

935,000 btu is about 371 cubic feet of propane.

935,000 BTU/hr converts to about 382 btu/hr or 382,000 btu/hr for natural gas.

You really do not want to use propane regulators on a natural gas installation.
Click to expand...
I think there is a misunderstanding, the local gas company use Liquefied Petroleum Gas (LPG), which according with my research is more about propane.
 
For the final leg, the pressure drop is about 0.5" w.c for 80 feet, or 0.625" w.c per 100 feet or 0.1875" w.c for 30 feet.

For the 228 feet at 5 psi, the pressure drop should be about 3.24" w.c.

So the pressure at the final regulator should be ok.

The final regulator seems like it is sufficient.

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In Panama, residential energy delivery primarily relies on natural gas rather than propane, as Panama does not produce its own natural gas but imports it and uses it extensively for heating, cooking, and power generation in homes and industries;.
Key points about Panama's energy usage:
No domestic gas production:
Panama does not produce its own natural gas or oil, making it reliant on imports.
Pipeline usage:
Natural gas is delivered to Panama through pipelines, allowing for widespread residential usage.
Propane usage:
While propane might be used in some isolated areas where natural gas infrastructure is not available, the primary residential fuel in Panama is natural gas.
 
JamesW said:
That is not a hard limit.

The capacity is for a design pressure drop of 0.5" w.c.

The meter will pas more gas through but at a higher pressure drop.

It will pass 400 CFH, but the pressure drop will be about 1.1" w.c, which can be acceptable.
Click to expand...
A drop of 1.1” wc in the meter is a fraction of the drop at the high pressure regulator of 1 psi.
I don’t understand where the rest of the pressure drop comes from.
Considering we are talking about propane, please, may you let me know what are the expected drop in the 228ft 3/4” line plus the 20ft 1” line?
The goal is to understand if the pressure drop is something expected or there is something else to look (for example, obstruction, etc…).
 
Your low stack flue temperature shows that the combustion is running lean from low gas volume. You are not getting the rated 400K BTU heat from the heater.
 
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JamesW said:
Are you sure that it is propane and not natural gas?

Do you have a tank or a connection to a utility?
Click to expand...

The residential area where I live has a big tank of gas (for around 100 houses). This is distributed to each house meter.
Periodically, a big gas tank truck come and recharge the tank.

Below some similar / real tank and truck

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1735007187710.jpeg
 

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