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  1. #1
    Join Date
    Aug 2011
    Location
    Atlanta, Georgia
    Posts
    2

    Sizing Hard Start

    I am a Electrical Engineer who does primarily controls work and I know the electrical side of systems in good detail.

    I need some help with sizing a hard start for a condenser unit. The info is

    Brand. Ruud
    Model. UPFB-036JAS
    Date. 06/90
    Serial # 4890 M2390 8620
    Volts. 230
    Phase. 1
    HZ. 60
    Compressor RLA. 18.9 / 18.9
    Compressor LRA 100 / 100
    Fan FLA 1.3
    Circuit Ampacity. 25 / 25
    Design PSI High. 300 PSIG
    Design PSI Low. 150 PSIG
    Factory Charge. 94 OZ R22

    The kits at my local supply are supco eclass and i need to determine the compressor HP to get the correct kit. The above information is thats left on the unit. Can a compressor size in hp be determined from this information?

    If not what would be the next best method?

    These are the supco sizes i have access to.

    SPP4E 90V 130V 1/12 hp to 1 hp 1/8 hp to 1 hp 88 106 F
    SPP5E
    90V 277V 1/12 hp to 10 hp 1/3 hp to 2 hp 43 52 F
    SPP6E
    90V 277V 1/12 hp to 10 hp 1/2 hp to 3 hp 88 106 F
    SPP7E
    90V 277V 1/12 hp to 10 hp 1 hp to 4 hp 130 156 F
    SPP8E 90V 277V 1/12 hp to 10 hp 1 hp to 5 hp 189 227 F

    Can someone help me determine correct sizing and what the metod is if you do not have the HP stamped on the compressor anywhere?

    Thanks

  2. #2
    Join Date
    Jun 2006
    Location
    Plano,TX
    Posts
    10
    Ask for a 5-2-1 at your supply house

    http://five-two-one.com/

  3. #3
    Join Date
    Aug 2011
    Location
    Ohio
    Posts
    53
    You could use this rule of thumb in the future.

    1hp per ton for A/C

    2hp per ton for medium temp coolers

    3hp per ton for low temp freezers

    so by judging from the model number I think it is a three ton unit so possibly 3hp. Although I would verify this but I think the "36" in the model number indicates BTU output and that converted into tons is 3 tons.

  4. #4
    Join Date
    Feb 2009
    Location
    Under a bridge if things don't pick-up
    Posts
    397
    See if you can get info off of pot itself.
    Sometimes it's stamped or labeled.
    Or look in the electric cover sometimes.
    If you can't actually read it... I've snuck my cell phone to take pics in cramped places. Works well.

    When coolers are backed right up to the walls where you can't read the labels... Sneek my cell back there and take some pics.

    The HVAC Paparazzi.
    Don't go away angry... Just go away.

  5. #5
    Join Date
    Aug 2011
    Location
    maryland
    Posts
    16
    to size a custom start kit you need to measure back emf voltage. measure voltage between common and start wnen the compressor is running . mars gives you a relay guide with voltage ratings. every potential relay has different ratings so you need this chart to size the particular compessor your working on. your coil must be equal to or above to handle this voltage. then you take 80% of this voltage and it must fall between the pick up min and max of the relay. the size of the start cap is up to you. i use large if its locked , medium if its above 50% rated LRA, and small for others.

  6. #6
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
    Posts
    4,344

    Mars chart

    Thanks post time. Where did you find that chart? Can you post a link?

    I have found that it is better to properly size start components than to just drop in a ready made kit. The kits may be fine 70% of the time,
    Some Talk, Some Do
    "keeping condensing pressures low and evaporator pressures high"
    "Some customers are more interested in comfort than energy savings"
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  7. #7
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,317
    I use the 5-2-1. That's the best drop in hard start kit on the market other than sizing up the components.

  8. #8
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    what is a 5-2-1 hardstart?

  9. #9
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,317
    Quote Originally Posted by second opinion View Post
    what is a 5-2-1 hardstart?
    http://five-two-one.com/

  10. #10
    Join Date
    Aug 2011
    Location
    maryland
    Posts
    16
    acfixr , i think there is a chart provided with every mars relay.

  11. #11
    Join Date
    Sep 2008
    Location
    VA
    Posts
    1,768
    Quote Originally Posted by R123 View Post
    What is the difference in their potential relay that makes it multi-positional? Makes me wonder if it's calibration and sensitivity is as precise as say the Tyco.
    "The only true wisdom is in knowing you know nothing" Socrates

  12. #12
    Join Date
    Sep 2011
    Location
    Fort Lauderdale
    Posts
    2
    I think you can't go wrong with this: http://www.kickstartoem.com
    OEM approved
    That's all we use.

  13. #13
    Join Date
    Sep 2009
    Location
    Stumptown,USA
    Posts
    1,251
    Or you could order the factory start assist kit from Ruud and Install the kit designed just for your compressor and approved by Ruud for your unit.
    Challenge yourself, take the CM test --- Certificate Member since 2004 ---Join RSES ---the HVAC/R training authority ---www.rses.org

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