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Thread: New Motor, Lower Pressure

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    New Motor, Lower Pressure

    I just replaced my motor Century Centurion B2854. When we bought the house I never knew that pool motors were not supposed to be so loud so we went with it until it died last week. I ordered the motor and replaced the shaft seal, put everything together and turned on the pump and was amazed at how much quieter it was. Looking at the pressure gauge though I noticed the pressure is now at a 7-8 instead of a 12-14, which is where the old motor was. Is this drop in pressure normal or should I start investigating for clogs? I have a sand filter as the medium if that makes any difference. Thank you for any advice you can give.

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    Re: New Motor, Lower Pressure

    I didn't get the go kit for all the other seals, I didn't really see it as nessessary since all the other seals were working fine for everything else. . .

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    Re: New Motor, Lower Pressure

    Welcome to the forum.

    Identical motor? Same Service Factor?
    Dave S.
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    Re: New Motor, Lower Pressure

    yep. it was a motor for motor swap. Also when I checked the pump this morning it was still holding prime which tells me the seals should be working properly.

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    Re: New Motor, Lower Pressure

    Kind of curious. Lower pressure would lead me to think impeller. Even if you had changed motor sizes you shouldn't have seen a pressure change unless you changed the impeller too or went to a variable or two-speed motor.

    How is flow from the returns?
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    Re: New Motor, Lower Pressure

    Just thinking out load here but could the new motor be working more efficiently than the old motor.
    8500 gallon IG Pebble Sheen with Spa. 3hp Pentair VS Intelliflo ( pool ), 3/4 hp WhisperFlo ( water feature ),Pentair Racer, 400K Pentair heater, Pentair 500sqft Cartridge filter, EasyTouch 8, Stenner 45mp2 15gallon wired to ET8

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    Re: New Motor, Lower Pressure

    Quote Originally Posted by JohnT View Post
    Kind of curious. Lower pressure would lead me to think impeller. Even if you had changed motor sizes you shouldn't have seen a pressure change unless you changed the impeller too or went to a variable or two-speed motor.

    How is flow from the returns?
    I see the point about the impeller but what confuses me is that the Impeller was working right before the pump went out.

    - - - Updated - - -

    That's what I was thinking too about the efficiency. But why would that be the case. As for the outgoing pressure it too is not as strong. It still moves the water relatively well but you can tell there are no more ripples in the water like there were before

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    Re: New Motor, Lower Pressure

    Quote Originally Posted by scarecrow55 View Post
    I see the point about the impeller but what confuses me is that the Impeller was working right before the pump went out.

    - - - Updated - - -

    That's what I was thinking too about the efficiency. But why would that be the case. As for the outgoing pressure it too is not as strong. It still moves the water relatively well but you can tell there are no more ripples in the water like there were before
    Though it's easy to think something is different about the motor, it really can't be the motor unless it is a differentRPM than the original. The amount of water being moved has virtually nothing to do with the motor. The impeller alone determines the flow rate of the pump. You could hook a half horse motor or a 4HP motor to your impeller and nothing would change. The smaller motor would overheat, but before it did it would move just as much water as your original motor. Same RPM, same impeller, same flow.

    So you are left with the impeller or flow restriction before the impeller. I guess a pressure gauge failure coincidental with the motor change, but that's pretty long odds. I'd power the pump down and take a look through the strainer basket at the impeller for debris or some other problem.
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    Re: New Motor, Lower Pressure

    What voltage is the supply and what is the pump wired for?

    Does the rpm of the motor sound different?

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    Re: New Motor, Lower Pressure

    The stock pressure gauges we get with our filters are not top of line gauges. I would suspect the gauge right along with other possible culprits. Flick it with your finger a couple times. Also, it may have something clogging it.
    ----Chris----
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    Re: New Motor, Lower Pressure

    Okay so I looked at it The daylight and the output pressure seems the same. When talking to the local "Pool Guy" who I get my chemicals from and has no interest in selling me anything because I don't use him to clean my pool said its normal for the pressure to be lower since the pump works more efficiently. after vacuuming the pool this afternoon everything seems normal I suspect it's either the gauge or it truly is normal. the noise difference between the old pump and the new pump is very and I emphasize very significant I think the old pump was dying long before I knew it was dying. but I'm still open to investigating things if you guys have any other suggestions, the reason I don't suspect debris in the impeller is because I just replace the motor and everything was cleared and cleaned. now the impeller itself has no cracks and does not look or appear to be broken but then again I'm new to this Pool stuff, would it be expensive to replace the impeller?

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    Re: New Motor, Lower Pressure

    Efficiency should not have anything to do with it. If it's running at the same rpm and it's the same impeller, it should be moving the same amount of water.

    Possibly a restriction on the suction side?

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    Re: New Motor, Lower Pressure

    That could be, we had a huge storm come through three weeks ago and blew several branches and leaves into the pool, consequently it turned green, I remember clearing out a leaf clog from the skimmer. How would I go about clearing a clog internally in the piping if that is the case? with a plumbing bladder?

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    Re: New Motor, Lower Pressure

    Jam a garden hose turned on into the pipes an see if you can flush anything out. Go with the easy access points first like your skimmer and then work towards disconnecting things like your pump and/or filter to gain access to those pipes. You could also try a plumber's snake or electrician's tape.
    ----Chris----
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    Liquidator, Fafco Solar Heat, Polaris PB460 Booster Pump w/280 cleaner, Katchaleaf Cover, TF100 Test Kit, FAKE MAIN DRAIN

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    Re: New Motor, Lower Pressure

    Quote Originally Posted by Agent99 View Post
    Jam a garden hose turned on into the pipes an see if you can flush anything out. Go with the easy access points first like your skimmer and then work towards disconnecting things like your pump and/or filter to gain access to those pipes. You could also try a plumber's snake or electrician's tape.
    ok its worth a try I'll let you know what happens

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    Re: New Motor, Lower Pressure

    so I tried putting the hose in the pipes and even the plumbing bladder and not difference, I suspect maybe the seals might be the issue after-all I'll report back after I get a "go kit" if anyone has any other suggestions I'm open to them.

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    Re: New Motor, Lower Pressure

    Quote Originally Posted by scarecrow55 View Post
    so I tried putting the hose in the pipes and even the plumbing bladder and not difference, I suspect maybe the seals might be the issue after-all I'll report back after I get a "go kit" if anyone has any other suggestions I'm open to them.
    It's not the seals and not the motor unless it is running different RPM from your original. For a seal problem to change the pressure that much you'd be leaking many gallons per minute. If you have a problem, it is at the impeller or the suction side plumbing.
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    Re: New Motor, Lower Pressure

    Same thing happened to my new pump motor....turned out to be the wiring was wrong for the voltage. Rewired the motor and problem went away.

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