comparing electric motors

Discussion in 'Electrical Forum discussion & Blog' started by zunden, Feb 12, 2011.

  1. zunden

    zunden New Member

    Messages:
    11
    Location:
    DC, USA
    I've been shopping cross-referenced ¾ hp blower motors and noticed that they vary in full-load current between 8.9 amps and 11.3 amps. They all are labeled for 1075 rpm and require 15/370 run capacitors. Is the difference in amps significant? Thanks.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,233
    Location:
    Cave Creek, Arizona
    The higher the amps, and the greater the service factor, the better the motor is.
  3. zunden

    zunden New Member

    Messages:
    11
    Location:
    DC, USA
    hj,
    That's good news. I stumbled onto the highest amp motor – the Toptech TT-E75-3SP1(11.3 amp) which had been advertised as “GE.” The TopTech packaging cross-referenced the following motors AO Smith DL1076(8.9 amp), Fasco D728(10.5 amp), Emerson 8904(9.1 amp), Marathon X009(10.3 amp), Mars 03589(10.3 amp). Thanks again.
  4. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Sorry, but the lower the amps and the higher the service factor makes a good motor.

    The lower amps means a higher efficiency motor; more copper and better clearances internally. better or more run caps. Does the same work for less electric draw.

    Take a 23 watt flourescent bulb VS a 100 watt resistance bulb as an example of getting more for less.

    Take a look here, some only draw 8 amps. That is what you want.

    http://www.grainger.com/Grainger/di...ors/hvac-motors/motors/ecatalog/N-9y5Z1z0o3x7

    Looks like all blower motors have a 1.0 service factor, so go for the lowest amp draw.
    Last edited: Feb 14, 2011
  5. zunden

    zunden New Member

    Messages:
    11
    Location:
    DC, USA
    ballvalve,
    Thanks for the update and link to Grainger. The 8 amp motor at Grainger is a 5-speed; my system specs a 3-speed. HVAC forums advised me that 5-speed motors will work, including more efficient and expensive ECM motors, but questioned the actual savings and the practicality of spending significant money on an 18-year old system. After some hours on the web, my gut feeling was that the risks of my screwing up the wiring or speeds and the costs of professional service and ECM motors weren't justified. I will order the lowest draw, 3-speed PSC motor as you advise. The current motor will be my emergency standby so I don't get caught again in a big snowstorm without a motor. Thanks again.
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