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  1. #14
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,923
    Well, I have seen quite a few lp systems start out on what can only be called low fire. I would imagine the idea of lp being acidic comes from the moisture content of lp which is corrosive.

    Try the low pressure switches and see if you don't stop having as many lp issues. This is the reason that equipment manufacturers require them on heat exchanger change outs.
    Government is a disease...
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  2. #15
    Join Date
    Jun 2003
    Location
    New Hampshire
    Posts
    2,666
    Originally posted by rtu
    I've been told also the LP gas is
    more acidic than Nat.gas-
    Don't know if theres any truth to that theroy.
    I've seen "some" propane boilers that have single wall smoke pipe, that get the smoke pipe eaten up from the sulfer. And heat exchangers that get a lot of sulfer in them all due to condensation. This is mostly due to improper venting issues. B vent will solve this in most cases for these 80 to 84 percent boilers. The 90 percent "furnaces" I guess I don't see too many of them yet. Although many of the new houses in my area that are being built are going with 90 percent LP warm air furnaces and AC coil. Time will tell on these. Most are Armstrong/ Concord.
    As far as overall sulfer content, I think the propane we get is probably more than some areas that have natural gas. But from what I hear the NATURAL GAS in the Michigan and upper midwest area starting in Canada is 100 times worse.

  3. #16
    Join Date
    Apr 2005
    Location
    Chicagoland
    Posts
    209
    Originally posted by RoBoTeq
    What happens on cold mornings, cloudy days or when there has been a long off time is that the LP in the line cools down, reducing its pressure.

    When the furnace calls for heat and the gas valve opens, the LP pressure may be down to 3 or 4 inchs water column of pressure rather then the 11" or so that is required. With this low burn a lot of moisture is produced in the initial section of the heat exchanger as well as on the burners. This condition can persist for several minutes each firing.

    With a low pressure cut off switch, as soon as the LP pressure drops below 6" WC, the switch cuts off power to the valve allowing the valve to close which allows the pressure in the LP line to stabilize. On the next firing, the LP has already built up the needed pressure to not underfire.
    What about 2 stage units that run on 5.5"wc in low fire?

  4. #17
    Join Date
    Jan 2001
    Posts
    7,552
    IF...you have a propane tank and piping system that is properly sized and installed...low pressure shouldnt be a problem. Proper tank sizing and pipe sizing...plus a two stage regulator system with a high pressure regulator at the tank and a low pressure regulator at the house...then you should not see pressure problems. I worked in lp for years and our biggest problems were butane in the mixture...and going behind a local lp company who seemed to only use single stage regulators at the tank..even for large appliances......not a big fan of lp...the companies around here will now give the customer the regulators and let them do start up on their own stuff....a lot of problems there...and many contractors here dont check manifold pressure and dont bother to adjust the regulator because they are supposedly adjusted at the factory.

    also..before I get flamed by someone...I am in tennessee so I dont know if the extreme cold up north has a more adverse effect on the pressures...but it shouldnt...unless the tank gets very low.

    moisture in the gas can be remedied by having the LP company come out and inject methanol into the tank...which is something they should do before the tank leaves their grounds.....the moisture will freeze in the oriface of the high pressure tank regulator...you can watch the regulator freeze over if you can be there when it happens...and this will lower the pressure...but this is a fixable problem as stated above. Its not notieable unless you can catch it...usually when it happens the equipment will shut off on a low pressure switch or the customer will shut it off or not notice it...once the load goes down...and gas flow slows...the freezing will end.. its hard to catch

  5. #18
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,142

    Smile Low pressure c/o switches

    Can anyone provide part numbers of the switches?
    TIA,

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