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Thread: H400FD Natural Gas Heater issue

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    Join Date
    Nov 2015

    H400FD Natural Gas Heater issue

    Hello! This is my first post, so I go easy on me. This is my first winter in TN with my new pool and spa. I have a Hayward H400 Natural gas heater, and I had a service technician come out to winter prep my pool and spa because we are not shutting it down for the winter. The freeze protect is set to come on at 34*. The heater is set on bO for remote bypass, and both pool and spa heater are set to off in the remote. Last night, the temp was in the 20's, and the freeze protect kicked in cycling between pool and spa mode to keep it from freezing.
    Here is the problem:
    This morning when I woke up, I looked outside, and my spa was down about 3 inches of water, and my heater was steaming significantly from underneath the heater. I called Hayward, and everything is set the way it is supposed to be set, and the tech said he was unsure of what happened. The service light was on for a moment, however, there were no codes lit. I turned the breaker on and off, and everything went away. I then took it out of bO mode and turned the heater on, and it worked like it is supposed to. Fired right up. I put it back in bO mode and pool and spa heater are both set to off in the remote.
    Any thoughts on what might be happening? Based on what the Hayward tech said, the heater should not be coming on unless I turn it on myself. This worries me, because if I am out of town, or not paying attention, my **** gas bill is going to be through the roof! Remember, this heater and whole system is less than 6 months old, and seems to be working properly as long as the temp is above 34*.

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    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: H400FD Natural Gas Heater issue

    Welcome to the forum!

    This is helpful for us to understand what equipment you have: Pool School - Read This BEFORE You Post

    But a few questions:

    1) Is the only evidence the heater went on is that it was steaming? That can occur when sun hits the metal housing. What about the pool water temp? Is it higher than the day before?

    2) As for the spa level. Is the spa higher than the pool? If so, the cycling between pool and spa during freeze protection can lower the spa level. Is the spa level now at pool level? Do you have check valves in the spa lines?
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
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    ps0303's Avatar
    Join Date
    Jul 2011

    Re: H400FD Natural Gas Heater issue

    So when you got up was the pump still running or had it turned off?

    A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you.

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