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Pool heater will not fire up.

kcopp Member Posts: 4,396
New install. LP gas.
2# system.
3/4" underground gas line in Constab PE. 30'
Runs to a maxitrol 325-5L.
About 20-24" of run from the maxitrol to the Pool heater.
Pool heater is just under 400k btu.
Pressure set at 14"wc static @ maxitrol
When the unit goes to fire up the pressure plummets to just under 6" w/c...
Anyt thougts?
Bad regulator?
Piping between the Maxitol and the Pool heater too short?



    JUGHNE Member Posts: 11,021
    How well does the 2 PSI supply hold up on the inlet side of the Maxitrol regulator when firing?
    rick in Alaska
  • kcopp
    kcopp Member Posts: 4,396
    edited May 2020
    I did not check that . There is an existing boiler and gas range on the other side that has been running fine for 6 months. That is inside on another 325 regulator.
    I will check that tomorrow. Thanks.
  • unclejohn
    unclejohn Member Posts: 1,833
    Does it stay low or just a blip?
  • ratio
    ratio Member Posts: 3,605
    Vent limiter installed? I hate 'em. Pull it off & see what happens. The vent limiter restricts the ability of the regulator to respond quickly to pressure (flow) changes, which it must do due to the limited volume of the short nipple between the regulator & the heater. Could also be something in the pipe, even a short run like that.

    & of course it could be the 2# line, as well. If that were restricted, you'd see similar issues.

    EBEBRATT-Ed Member Posts: 15,346
    What size pipe between the Maxitrol and the pool heater? I would check the Maxitrol vent connection and the inlet pressure as mentioned above. Possibly a bad regulator.
    EBEBRATT-Ed Member Posts: 15,346
    Checked the Maxitrol chart. They only talk about 0.64 specific gravity gas which is natural but reg is approved for LP as well. Don't know it this changes capacity but 325-5l there are a couple of different models-48 may be undersized-600 would do it.

    Like I said couldn't find a specfic chart for LP so I could be all wrong
  • kcopp
    kcopp Member Posts: 4,396
    There is a vent limiter on there. I was going to pull it off and stick in the standard cap.
    This 325-5L is specifically for LP.
    Everything is piped in 3/4"
    Ideally I wanted to put the Maxitrol at the other end of the underground pipe. However @30' the 3/4" would have been undersized by 25k.
  • lchmb
    lchmb Member Posts: 2,997
    I prefer a minimum of 5' and generally try for 10' from the unit. The vent limiter should not be installed outside anyway and when venting away I always upsize my line one size.
  • kcopp
    kcopp Member Posts: 4,396
    Turns out to be a couple things... The 325 was not working properly and the igniter right out of the box was bad. Go figure.
  • Jamie Hall
    Jamie Hall Member Posts: 22,952
    Don't you love it when you have multiple failures? Makes trouble shooting so simple...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ratiokcoppAlan (California Radiant) Forbes
  • rick in Alaska
    rick in Alaska Member Posts: 1,457

    Don't you love it when you have multiple failures? Makes trouble shooting so simple...

    I have got to the point in my career that I think all jobs have more than one problem. It just never fails :)
    JUGHNE Member Posts: 11,021
    And there is probably a tag/sticker indicating "This unit was test fired at the factory". ;)
  • kcopp
    kcopp Member Posts: 4,396
    I am thinking that the igniter issue was an install issue from the pool company.
    I don't think they were exactly gentle w/ the heater...
    EBEBRATT-Ed Member Posts: 15,346
    I don't know how many times I have gone down that rabbit hole thinking , well it's new equipment thinking there is one problem and it turns out to be 2 or more.

    I am better at it now in my old age, more cynical I guess I go in now and troubleshoot better instead of looking for a problem rule this out rule that out sooner or later the problem child shows it's ugly face!
    Alan (California Radiant) Forbes