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Thread: What if heater BTU exceeds gas line capacity?

  1. #1
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    What if heater BTU exceeds gas line capacity?

    I'm replacing my heater. The current one is a 250k BTU input. Bigger is better so I want to upgrade to a 400k BTU. I've determined that the meter can handle the additional BTU requirement. However, I've received conflicting information on the gas line. It's 1" pipe about 50 feet from the meter. It seems that max BTU is about 300k. What would happen if I bought the 400k BTU heater anyhow? Would it work just fine but at a lower capacity? We're going to replace the decking and possibly add a spa within the 5-7 years, and we can upgrade the gas line at that time to optimize the BTU, so eventually the gas line will handle the 400k BTU. I'd rather get the max size on a heater now rather than having to upgrade that too when we redo the decking.

    Thoughts?

    Jill
    El Paso, Texas
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  2. #2
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    Re: What if heater BTU exceeds gas line capacity?

    If there's not enough gas, the heater wont run correctly. It wont burn hot enough (i.e. yellow flame instead of blue), or will fire up, but then quickly go out. The burner will also soot up pretty fast and can foul. You need the right size line and meter for the application.
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  3. #3
    Administrator JasonLion's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    What bk406 said. Some heaters specifically notice that they aren't getting enough gas and shut down quickly. The others will have problems, but kind of sort of work for a while, and then eventually fail.
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    Re: What if heater BTU exceeds gas line capacity?

    Check with your HVAC people. They should be able to recommend a solution. The easiest solution would be to change the pressure and add a regulator near the heater. The line capacity is determined by diameter and pressure. By increasing the pressure, you should be able to get enough flow to the heater. The regulator will convert the pressure to the right pressure for the heater.

  5. #5
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    Re: What if heater BTU exceeds gas line capacity?

    Quote Originally Posted by JamesW
    The easiest solution would be to change the pressure and add a regulator near the heater..
    That may or may not be true. What you're describing is a 2 stage system. That works if there is 2 psi service on the street. It wont work if its 0.5 psi service.
    HVAC guys wont be able to help, really. Call the gas company.
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  6. #6
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    Re: What if heater BTU exceeds gas line capacity?

    Hi I am a new pool owner and just went through this with a 400,000 btu pool heater, I already had high pressure 2psi and the meter could handle the flow with all the gas used through out the house but the line from the street to the meter couldnt, increased the diameter to 1" and replaced the meter and all is good oh and cost me 1100.00 to complete it................
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  7. #7
    Senior Member XsAllOverIt's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    I've got a 2# service now running to the house. I've got a 50' run going to my pool house with 3/4" copper gas line and I have a 400K BTU heater and all is well. I struggled with this one for quite some time when I had conflicting plumbers argue on the size. One plumber came out and told me I need 1 1/2" copper. The guy that put it in did pool heaters and said I had enough service and all I needed to do is switch out the meter which the gas company did because it had a meter with 1/2# service since all we had in the house was auxiliary heat. This plumber was very knowledgeable of the specific area since he had plumbed all the houses in the adjacent neighborhood with gas lines. I've been running my heater for over 5 months with no issues. It cost me $1800 to run the line and hook up which already exists in your circumstance. The gas company did not charge anything for the meter upgrade, but it took a little time for them to get out there and do it.
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    Re: What if heater BTU exceeds gas line capacity?

    So the gas company called. They said that our standard meter should handle the BTU capacity, but they said they'd install a larger meter at no charge, so my husband went ahead and scheduled it. Given what I've read so far it is my understanding that this still wouldn't solve the issue. I've looked up some natural gas pipe sizing charts online and they all indicate that with a 1" pipe with a length of 60 feet (I re-measured) the capacity of the pipe is approximately 260 BTU. My husband says that getting a larger meter will fix the problem. I think we still need to address the sizie of pipe. Who's right?

    Jill
    El Paso, Texas
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  9. #9
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    Re: What if heater BTU exceeds gas line capacity?

    It depends on the pressure of the gas in the pipe. A 1/2" pipe will carry more gas at 2 psi than 0.5 psi. The gas company should know what they are doing (hopefully).
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: What if heater BTU exceeds gas line capacity?

    400,000 Btu requires a minimum of 1-1/4 inch pipe for low pressure as shown in this manual. A gas supplier or installer should be able to tell you if you can use a two-stage process. If a two-stage process is available, then the installer can use the 1-inch pipe and a regulator to supply the gas.

    When measuring the length of pipe, you have to include extra length for the fittings. For example, every 90-degree fitting has to be counted as about 5 feet of pipe.

  11. #11
    Senior Member Davegvg's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    I had to do a meter relocate & replace and a larger pipe run to handle my 400K unit -I went from a #1 mounted in the sidewalk to a #4 meter mounted to the house - It cost me 5K by the time I was done.

    Sounds like you are getting a deal.


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    Re: What if heater BTU exceeds gas line capacity?

    I feed after the meter with a 3/4 line just under 1 million BTU's, but I also have an whole house generator and a on demand water heater and everything works fine. BGE subcontracted the engineering and they came to the house and figured out the "full on demand" of everything in the house using gas and came up with the requirements......
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  13. #13
    Senior Member XsAllOverIt's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    If you're getting the meter and you have a 3/4 inch line right now, why not try it. I believe you will be fine. If not, you haven't lost anything but time and by the time you have it in, you won't need heat until the fall..
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  14. #14
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    Re: What if heater BTU exceeds gas line capacity?

    Quote Originally Posted by XsAllOverIt
    If you're getting the meter and you have a 3/4 inch line right now, why not try it. I believe you will be fine. If not, you haven't lost anything but time and by the time you have it in, you won't need heat until the fall..
    You can't just try it. First of all, it has to be done according to the building code. It would be illegal to deliberately do it in violation of the code. Second, it could damage or destroy the heater, and the damage would not be covered under warranty. Third, it is not safe. It could potentially start a fire.

  15. #15
    Senior Member XsAllOverIt's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    After reading the manual and from my own configuration, a 2# meter, a 3/4" line run at 60' is sufficient for the heater indicated. I too have a 400K BTU heater with a 2# meter and a 50' run and I'm getting plenty of gas at my heater. I only have one other appliance (auxiliary heat) in my house, so they aren't very often conflicting, but that heater is a 60K BTU heater and I haven't had any problem running my hot tub throughout the winter.

    Bottom LINE: Get a plumber that is familiar with pool heaters to come in to insure that you have a sufficient line. I had two plumbers come in and the ones that weren't familiar with pools indicated I needed a 1 1/2" line run from the house which was resultantly wrong and VERY costly. I'm getting the proper pressure at my heater with the 3/4" line and the plumber that installed tested that prior to operating the heater.

    I am not one to deliberately do it in violation of any code ESPECIALLY with gas. I believe the configuration you have with a 3/4" line and a 2# meter is sufficient to run a 400K BTU heater. I readily admit I'm not an expert and that's why I had a certified plumber with permits and inspections to get it done properly (mine was a new install). Mine had a 3/4" pipe and the inspector was there 3 times during the installation. I would think they wouldn't have allowed it if it weren't according to building code. You should do the same, but what I was trying to say is that I belive you have the proper configuration. Spend a couple hundred dollars to get a plumber to insure it's correct. That's what I intended to mean when I said try it. I wouldn't do it myself. Gas is the only thing I won't work on myself.
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  16. #16
    Senior Member XsAllOverIt's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    Actually reading the Natural Gas charts in the manual that JamesW referred to, if you have a 5# meter installed, all you need is a 1/2" line running to the heater and staging it down to 3/4". For a 2# meter, it indicates you can go 150' with a 3/4" pipe.
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  17. #17
    Administrator JasonLion's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    XsAllOverIt, all true, but nearly everyone has 1/4# service, and various things rjmac said strongly support the theory that she has 1/4# service.

    The pipe size required depends on the pressure. Assuming standard pressure then the existing pipe will never work. At that point there are two choices, either upgrade the service to higher pressure, or upgrade the pipe to larger pipe. Upgrading to higher pressure is not allowed in all areas. In any case, both options require getting a licensed plumber in, and possibly the gas company as well, and they will be able to say exactly what is going on and exactly what the option are in that area.
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  18. #18
    Senior Member XsAllOverIt's Avatar
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    Re: What if heater BTU exceeds gas line capacity?

    Plumbing gas is an art. She also said that the gas company would be bringing in a bigger meter just like they did for me. Bottom line, if you can get a 2# service coming to your house (and if they don't have 2# service running to your house, they charge you to upgrade the line), then you will be set. As Jason said, you need both the gas company and a plumber. I worked with both of them...
    18 x 36 Inground Gunnite, White Plaster 21K gallon
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    Lamotte ColorQ PRO 7-Plus test kit
    TFT-100 test kit

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