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Thread: How hot should a pool motor get?

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    How hot should a pool motor get?

    I'm sure this has been asked many times but I'm new to the forum and haven't yet mastered the search function. I have a new 1-1/2 Marathon 1246 driving an older Sta-Rite system (new seal, impeller and diffuser). The motor is thermally protected and hasn't cut off during operation yet but it runs so hot I can't keep my hand on the back portion of it for more than a second. Up closer to the the impeller housing it is not as hot. I just need to know if this is more or less normal. I jury rigged a backflush of the skimmer line and got a good flow of water with no significant debris. I'm waiting for a Drain King to arrive so I can blow out the drain line. Right now I'm running it with both lines open and have a good strong flow into the pool. The heat thing just troubles me.

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    bobodaclown's Avatar
    Join Date
    Apr 2011
    Lakeland, FL

    Re: How hot should a pool motor get?

    I just read some place that pump motors run about 140F.

    Here's a cut and paste:
    Motor Cycling

    If the motor runs for a short while, shuts itself off, and turns itself back on later, it may be overheating. Normal motor temperature is over 140 degrees, so all motors run hot. But a cycling motor may indicate that the thermal overload is kicking it off. If this motor was just replaced, make sure that the electrical supply connections are correct and the wire size is correct for the voltage it is carrying. Low voltage can cause overheating. Inadequate ventilation can cause overheating, so make sure that the air vents are unobstructed. Usually, old motors that suddenly begin to overheat will need to be replaced.

    Here's the link:http://<br /> <a href="http://www.po...pumps1.htm</a>
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    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: How hot should a pool motor get?

    One other thing to keep in mind is that a standard efficiency 1.5 HP full rated motor will have an efficiency of around 77%. The motor will draw over 2200 watts near full load which means that 500 Watts of energy is being dissipated in the motor and if the motor doesn't have a fan, that dissipation occurs mainly in the motor housing. 500 watts is a lot of wasted energy so the housing is likely to get very hot.

    Unless the thermal limiter is shuting it off, it is probably normal.
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    Re: How hot should a pool motor get?

    Quote Originally Posted by A.O Smith
    TIP: A running motor that is too hot to touch is not necessarily overloaded. Class B insulated motors have a maximum operating temperature of 130 degrees Centigrade (266 degrees Fahrenheit). If the automatic protector is not tripping and the actual running amps do not exceed the maximum amps on the nameplate, the motor is not overheating. ... &libID=609
    You could measure the voltage and current to make sure that they are within specifications. Voltage at motor terminals should be + or – 10% of the voltage on the nameplate.

    You could get an infrared thermometer to check the temperature. It will measure the outside temperature, which will be lower than the internal temperature, but it should give you an idea of how hot the motor is getting. What does the motor label say for Insulation Class? (Probably abbreviated "Insul Class"). Most pool and spa motors use class “B” or class “F” insulation.

    Non-Contact Infrared Thermometer with Laser Targeting ... spx?id=841

    Some other things to consider are ambient temperature, wind speed, altitude and solar loading (from sitting in the hot sun). Surface temperature can be over 160 degrees Fahrenheit in a properly functioning motor (Insulation class = B). I think that a surface temperature over 230 degrees Fahrenheit could indicate an overheating condition, but surface temperatures are not necessarily a good way to diagnose proper motor operation. Internal temperatures can be about 15 to 30 degrees Celsius higher than surface temperatures.

    Typically, when a motor does begin to overheat, the paint and label will begin to discolor and bubble.

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