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  1. #1
    Join Date
    Nov 2011
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    St.Louis
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    Gas pressure issue

    Installed new Lennox 110btu. Old unit had crack in heat exchanger. Unit came with the spring to change out which did. Tech at house before I got there called Lennox tech support and said he needed to get different gas vavle with conversion kit. So he did and returned to house. I got there few mins after he had new vavle on. Also had propane company on site.
    Tech support said should be 11-13 in and 10 out at gas vavle. Gas guy put 2 new regulators on trying to correct problem. At end of day he said something is in gas pipe.

    Regular pressure was set to 11.5 while system was running and when it wasn't. Gas vavle input was 8-9 and output highest we could get was 8.1. Also checked at shutoff by furnace and was getting same as input to vavle.
    Gas guy there whole time while we did this. After he left we pulled apart lines to see if something was in there. Nothing inside at all. Black pipe just past shut off then 18in flex and short piece of black pipe coming out of furnace. 1 inch pipe 5 90 on 1in side. 1/2 line came off T and was 6ft long. Nothing else was on while we were doing this. Put everything back together same issue.
    Any ideas?

  2. #2
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    Did you change the burner orifices?

  3. #3
    Join Date
    Nov 2011
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    St.Louis
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    Thread Starter
    When installed no. Just changed spring that came with unit for propane. After new vavle yes it was part of the kit

  4. #4
    Join Date
    Sep 2007
    Location
    edmonds wa
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    Sounds like his regulator on the side of the house. Did the propane guy verify the pressure at that reg while you were running the furnace? Whats the max input pressure for propane in the conversion instructions. Thats what needs to be at the furnace valve .the lock up pressure may be higher. when the furnace stops.

  5. #5
    Join Date
    Nov 2011
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    St.Louis
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    Thread Starter
    He put 2 new regulators on thinking he may have had bad one. Gas guy had it at 11.5 while system running when it shut off jumped to 15. He also had it at 11.5 with system off.
    With system off reg and input was same. Soon as it fired up was losing 1 5-2 from reg to input.
    Not sure what was on the kit. Other tech got whatever Lennox tech support told him to get and we tried to get pressure to what he said also. I will have to get ahold of him to see if he hasn't or if he left it with homeowner.

  6. #6
    Join Date
    Sep 2007
    Location
    edmonds wa
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    I would try 13 while its running the lock up should be the same. The piping was always sized and used for propane right. any other appliances see this drop off in pressure. And i take that the propane reg on the side of the house is sized for all the combined load. His reading on his reg, i would think would stay the same ,if there was a blockage in the pipe downstream while the furnace is on. If it drops more than 1 inch at his reg when the furnace, and or all the combined load is on, it,s his reg. If his outlet stays within that 1 inch drop and then you see a lot more drop at the appliances inlet then it could be blockage or a pipe sizing problem.

  7. #7
    Join Date
    Nov 2011
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    St.Louis
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    Thread Starter
    Sounds like it's on his side then from that. All other things in home were capped off but water heater after furnace. Wasn't able to check pressure there. He said there was no way there was blockage on his side. I always thought you lose pressure after block. He said he didn't lose pressure at reg but then said few mins later how he had 11.5 while furnace was on then 15 after it shut off.
    Forgot too homeowners had tank filled up few days after furnace was installed.

  8. #8
    Join Date
    Jul 2009
    Location
    Columbia, MD
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    He might have wrong style regulator. If all else fails, you may have to put the regulator at the furnace.

    Is there a regulator at the tank and another one in the house?


    Sent from my iPhone using Tapatalk

  9. #9
    Join Date
    Apr 2014
    Location
    West Haven, CT
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    106
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    Did you check the inlet pressure as it tried to fire? Last week I had 2 calls where I had 13" WC before the gas valve and when the unit fired the pressure would drop to 0"wc. Both tanks were 70% full but the regulators were frosted over. So the propane line would build up pressure but couldn't keep up to stay lit. In those cases they just changed the regulator but maybe in your case there is ice in the line past the regulator.

  10. #10
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    Quote Originally Posted by gravity View Post
    He might have wrong style regulator. If all else fails, you may have to put the regulator at the furnace.

    Is there a regulator at the tank and another one in the house?


    Sent from my iPhone using Tapatalk
    I think your thinking the same thing I am. If this was originally set up as LBs {red regulator} off the tank and " from a regulator {gray} at the house and someone put the gray regulator at the tank the line from the tank to the house is your restriction as it would be to small. If your trying to run a 100k furnace plus other appliances without a two stage regulator set up you need some really big line from the tank.

  11. #11
    Join Date
    Feb 2008
    Location
    Altmar, New York, United States
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    was this a brand new lp tank?

  12. #12
    Join Date
    Nov 2011
    Location
    St.Louis
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    Thread Starter
    I will have to check when I go back out. Want to say red was at tank then had black at house.
    There was half inch soft copper tube from ground fitting to reg on their side. Home is 17 years old and gas was put in then. That's all history I have on home. The new family has only been there few months.

  13. #13
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
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    1" line of that length on LP should not show much of any pressure drop @ 110k btu's, 1/2" maybe.

    I'd start back at the beginning and take my own measurements, not trusting what the LP gas guy was telling you. Not that I don't trust what he says, it's I don't trust anyone when it comes to trying to resolve an issue that gets to the point of not making sense.
    Last edited by firecontrol; 02-07-2015 at 02:05 PM. Reason: Put too much info and then realized what forum I was in.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

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