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Thread: New heater. System pressure is now much higher.

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    EvilTwin's Avatar
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    New heater. System pressure is now much higher.

    I had a new Pentair 300k btu propane heater installed today to replace the 20-year old oil fired unit that was here when we bought the house. I have not been able to heat the pool with it yet as I am waiting on the gas bottle hookup. But the one thing I immediately noticed was that the pressure gauge on my DE filter is now showing 20 psi whereas with the previous heater the normal pressure was around 12-14 PSI. This kinda surprised me and makes me think that the system is now more constricted than it was before, even though the plumbing has been simplified in the process. He did add a new check valve as well. Is this jump in PSI something to be expected? Is 20 PSI good/bad? I have attached before and after pics for reference.IMG_0147.jpgIMG_0246_sm.jpg
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    GreatCanadian's Avatar
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    Re: New heater. System pressure is now much higher.

    When I connected my heat pump there was a pressure increase of 4 to 5 psi. I had the same concerns as you, but the experts on this forum assured me that a 4 to 5 psi increase was perfectly normal. I don't know how similar the internals are between a pump and a gas heater, but I imagine some increase in pressure for you would be normal.
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    mas985's Avatar
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    Re: New heater. System pressure is now much higher.

    Adding a heater will usually raise PSI but replacing one should be about the same. But from the picture it looks like you had a heater bypass but no longer do so that would explain the difference.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
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    EvilTwin's Avatar
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    Re: New heater. System pressure is now much higher.

    Quote Originally Posted by mas985 View Post
    But from the picture it looks like you had a heater bypass but no longer do so that would explain the difference.
    Yes, that is true. There was a heater bypass in the plumbing but they left that out when they put in the new plumbing. The installer said it wasn't necessary. I reviewed the heater manual and it recommends a bypass if the flow rate exceeds 120GPM. I have a 1.5 HP single speed pump. Not sure if it would exceed that flow rate.
    ----------------------------------------------------
    25000 (?) gallon Plaster IG roman-end pool (18x36, give or take, 8 ft deep end), 7 ft round spa-spillover to pool
    Nautilis FNS-48 DE Filter, disconnected separation tank
    1.5HP single speed main pump. 3/4 HP pressure-side cleaner pump.

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    mas985's Avatar
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    Re: New heater. System pressure is now much higher.

    No it isn't necessary although it does lower the head loss and pressure.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
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    JasonLion's Avatar
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    Re: New heater. System pressure is now much higher.

    You are fine on flow rate, a 1.5 HP pump is never going to exceed 120 GPM.
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    Re: New heater. System pressure is now much higher.

    I've seen more of a pressure change only with certain brands of heaters. Strange. A bypass also comes into play if you should need to do a stain treatment or similar. You surely don't want that going thru the heat exchanger.
    Paul
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    mas985's Avatar
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    Re: New heater. System pressure is now much higher.

    Some heaters have a built in bypass while others don't which can make a big difference in head loss.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
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    Re: New heater. System pressure is now much higher.

    Actually they all have built in bypasses aka flow control.
    Paul
    http://www.gastekservices.com 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. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    mas985's Avatar
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    Re: New heater. System pressure is now much higher.

    Maybe now all do but I have seen some off brands and older heaters that do not have the bypass.
    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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