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Thread: Heater fires and runs...but water isn't heated!

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    Heater fires and runs...but water isn't heated!

    Everything else seems to be working fine but my heater. It fires up and is running - I can hear the gas running through the lines from in the house and the exhaust from the heater is hot - all the typical telltale signs. But the water isn't heated at all.

    There is water through the heater - there's no external bypass. The manual has troubleshooting for it won't fire - but it fires! So i'm really scratching my head.

    Anyone have any suggestions on this?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Mod Squad zea3's Avatar
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    Re: Heater fires and runs...but water isn't heated!

    You may need someone to check the gas regulator valve on the heater. There may be enough to "light the pilot" so to speak but not enough to sufficiently heat the water while it is passing through.
    TFP Moderator
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    Re: Heater fires and runs...but water isn't heated!

    Quote Originally Posted by zea3 View Post
    You may need someone to check the gas regulator valve on the heater. There may be enough to "light the pilot" so to speak but not enough to sufficiently heat the water while it is passing through.
    Not sure that sounds right if the exhaust is hot.

    How long has it been on for you to say the water isn't heating?

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    Re: Heater fires and runs...but water isn't heated!

    do you have any bypass piping in the system that might be diverting some or all of the water. I would think properly plumbed the heater would not fire with no water flow but, I have seen safeties circumvented before.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Re: Heater fires and runs...but water isn't heated!

    I'm putting my hand right next to the jet to see if warm/hot water is coming out. Admittedly the water temp is only 60 degrees to start but with a 250K BTU heater, it should do a little something.

    As far as bypass, there's an internal one but it's supposed to prevent firing up as well. Typically, if there's no water flow, I don't think the heater fires up, but couldn't swear to it.

    Then again, my PB was a collection of morons so God only knows...
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    mas985's Avatar
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    Re: Heater fires and runs...but water isn't heated!

    So is this a new pool and the first time you have tried the heater or did it work before but no longer?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Heater fires and runs...but water isn't heated!

    4th season with the pool, never had an issue with the heater. But this is the first time I've opened it myself.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Re: Heater fires and runs...but water isn't heated!

    What is the filter pressure and is it normal?

    Typically, if there's no water flow, I don't think the heater fires up, but couldn't swear to it.
    The heater doesn't detect flow but has a pressure switch so if there is water pressure, it will fire but there still may not be any flow through the heater. However, if there was no flow, the heater would soon shut down because there is a thermal limiter switch. How long did you leave the heater running?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Heater fires and runs...but water isn't heated!

    I left it running awhile. As a matter of fact, I later decided to run it for a couple of hours after the sun went down and the temp went up from 62 to 65. So I think I hit on it earlier with just the starting temp of the water itself. So I think it is actually working. However, this has led me to another thought/question....

    In reading through the manual, it mentions that if the heater is more than 5' above the pool it's more than the pressure switch can handle and a flow switch should be installed. It also says to install it externally. I have no idea what this is and I'm fairly certain that I don't have one. My equipment is about 12 feet above the pool level and about 40 feet away in a straight line horizontally.

    I've never really had an issue with the heater - what exactly does this situation do to/for me?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Re: Heater fires and runs...but water isn't heated!

    People are not so good at detecting small temperature differences around 60 degrees. The temperature increase from a single pass through the heater is usually only a couple of degrees, and difficult to notice when the water is cold.

    I suspect the pressure switch issue has already been deal with in some way. The heater probably wouldn't startup at all if this were a problem. The pressure switch is used to detect water flow. It is designed to turn the heater off if it doesn't sense water flow. It uses water pressure as a proxy for water flow. When the equipment is a long way above the pool water level there is negative pressure, all the water wants to fall into the pool, so not enough pressure to trigger the switch and the heater things there is no flow, even if there is. Something must be triggering that switch, or the heater wouldn't work. I'm not sure how, but it seems like someone must have already deal with the issue.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Heater fires and runs...but water isn't heated!

    What speed are you running at with the Intelliflo? The temperature gain of the heater will be dependent on the speed of the pump. For example:

    At 100 GPM, the temp difference of a 250k BTU heater should be about 4 degrees. At 50 GPM, the delta T is twice as much. But even at the highest speed, you should detect some temperature difference. I can usually detect my solar out of the returns which is only about 3 degree temp rise.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Heater fires and runs...but water isn't heated!

    I was checking at my lower speed (normal running mode for me) and not full bore. Based on calculations done here about 3 years ago it should be about 35 GPM at that speed. That would rate out at about 12 degree difference which I'm not sure how easy that is to tell going from 60 to 72 with your hand immersed in water. Most times, the heater will raise the pool temp about 1-1.5 degrees per hour (that's theoretical and observed, IIRC) and the two hour run last night it raised up about 3 degrees. The sun was down so the only thing that could have done that would be ambient air (which was just under 80), but I don't think that would've raised the pool temp that fast would it?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Re: Heater fires and runs...but water isn't heated!

    Definitely at 35 GPM, you should feel the temp difference. Put one hand in front of the return and the other off to the side. You should be able to feel the difference.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Heater fires and runs...but water isn't heated!

    I just had a brand new 255btu heater installed, and when they fired it up for me, the water temp was sixty. The guy put his hand by the jet and declared that the water coming in was warmer. I put my hand by the jet and declared that it wasn't warmer at all. 22 hours later, the pool was 84. I guess I imagined the water returning to the pool with a greater temp differential.
    17.5 K gallons (16x32) vinyl inground pool with 1 hp pump and an old Triton sand filter. >20 years old. New 2015 Rheem gas heater. TF-100 Test kit. Little red robot and a Pool Blaster Max.

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    Re: Heater fires and runs...but water isn't heated!

    It's definitely warm water coming out. Like daleyfolk said, it's just really hard to tell when the water is that cold.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Re: Heater fires and runs...but water isn't heated!

    If you have had this heater for a few years and it's worked all this time then you don't need any flow switch. Also, 60 degrees is pretty cold water and it would be hard to sense warm water coming out of the inlet in the pool. It just simply to hard to tell.

    If the heater is firing and running, then you also have enough flow going thru it. 1-1.5 degree an hour for a 250K heater is more than I've ever seen n real life. Those numbers are more like for a 400K heater.
    Paul
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    Re: Heater fires and runs...but water isn't heated!

    Quote Originally Posted by ps0303 View Post
    If the heater is firing and running, then you also have enough flow going thru it. 1-1.5 degree an hour for a 250K heater is more than I've ever seen n real life. Those numbers are more like for a 400K heater.
    It depends on the size of the pool, actually. So let's do a little rough math...

    My pool is actually 15,400 gallons. Since a gallon of water weighs about 8.33 pounds, that means my water weighs 15,400*8.33 = 128,282 pounds of water.

    My heater is rated at 250,000 BTU which is in actuality, 250,000 BTU per Hour. And, more importantly, the mastertemp runs at 84% efficiency, so that means that it really provides about 210,000 BTU in that hour.

    Now, since a BTU is actually the amount of energy it takes to raise the temperature of one pound of water by one degree, that means that if I divide my 210,000 BTU by my 128,282 pounds of water, I should be able to tell how much the heater can do in an hour. That works out to about 1.6 degrees.

    Of course this is all theoretical and doesn't take into account things like air temp and numerous other little things but the cool part is that it pretty closely matches what I see in my real world.

    Or is there some glaring hole in my math above?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Re: Heater fires and runs...but water isn't heated!

    I think you are spot on. There is heat loss to be taken into account but that should not be more that 10%. Also, I still maintain you should be able to easily detect a 12 deg difference between the return water and the pool water.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Heater fires and runs...but water isn't heated!

    Quote Originally Posted by mas985 View Post
    Also, I still maintain you should be able to easily detect a 12 deg difference between the return water and the pool water.
    I could tonight a little better. The water was already a little warmer from a day of sun, but I'm tellin' ya - if I don't put my hand right next to the jet, it's really hard for me! The strange thing now for me is that the deck jets never seem to get warm where it used to be after running a little while they would. I was counting on them to really be able to tell the difference, but they didn't feel as warm as sticking my hand in the pool.

    I do think there are some wonky things here and there and this heater thing definitely will be watched. But I *think* it's okay.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    Re: Heater fires and runs...but water isn't heated!

    Watch all your burners and make sure have blue flames on them like it should.

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