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  1. #1
    Join Date
    Jun 2008
    Posts
    45

    System Performance

    Hi group,

    I am looking for opinions on the performance of my Heat pump. It is a 3 ton 13 SEER Goodman cplt 42 heat pump with matching indoor coil with two Thermostatic expansion Valves (tx5n2 factory adjusted) and a GMV950905DXA 95% efficient 92,000 btu gas furnace with a variable speed blower running at 1400 cfm

    The system has been charged to the Manufactures specification of 106 oz of R22. A sight glass (Sporlan SA13S) is installed at the condenser and indicates a full liquid (clear no bubbles) line and the moisture indicator shows no moisture present.

    This is installed on a two story home with a below grade finished basement for a total living space of 3,750sq ft.

    I realize that the system is undersized for the application but I wanted it that way to get somewhat longer cycle times and better dehumidification. The basement being below grade and insulated does not put much of a load on the system. The rest of the house is well insulated and is only 2500 sq ft.


    Readings were taken with an outside air temp at 94.7 Degrees F, the relative humidity was 67%

    Liquid side pressure 210psi
    Suction side pressure 80psi @ the evaporator
    Suction side temp @ evaporator 58.7 Degrees F
    Amp Draw 13.12
    Return air Temp 75 Degrees F Relative humidity 48%
    Plenum air Temp 51.5 Degrees F
    Cycle time 18 minutes on 22 minutes off

    Thanks

    Carl

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,104
    What is the ramp profile set for.
    If its set for a slow ramp up, did you take those readings before it reached full speed.
    Don't see a liquid line temp. Can't tell SC with out it.

    Accually, it sounds over sized.
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  3. #3
    Join Date
    Jun 2008
    Posts
    45
    Sorry I forgot to add the liquid line temp. It was 95.6 Degrees F.

    system had been running for 15 minutes when reading were taken Blower was at rated speed 1400 cfm confirmed by led.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,104
    You got a problem somewhere then.
    Liquid line temp to close to ambient temp.

    Sensible comes close to what it should be. But something is not right.
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  5. #5
    Join Date
    Jun 2008
    Posts
    45
    current readings at service port are liquid side temp 97F Suction side temp 63.5 ambient temp 89.3.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,104
    Partial readings mean nothing.
    System performance can only be checked by taking all teh readings.
    With out know teh sat temps, those temps tell me nothing.
    Plus indoor conditions need to be known, along with coil delta.
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  7. #7
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,989
    Carl,
    I input the saturation temps to get the SH & SC, we don't have the Supply Air (SA) wet bulb or Relative Humidity to run a psychrometric. Guess we could figure close to what it would be, lazy today, could use someone's brain help on that.

    AC TROUBLE SHOOTING DATA:
    Tonnage & SEER Rating _3.5-Ton_TXV_Heat Pump, 13seer

    Square Footage of home & major city near you _2500sf w/o basement

    Indoor Total-ESP _?_
    Airflow in CFM: _1400-cfm (?)_
    Is it actually delivering 1400-cfm?
    Target delta-T | @400-cfm per/ton or1400-cfm| is too high 23.5* & Target Split says @75-db & 62-wb entering air, airflow is lower than 1400.


    Suction line pres. _80-psig_
    Suction-Vapor line temperature: _58.7*_
    SST - Gage - Suction Saturated Temperature. _48*
    Superheat _10.7*_TXV metering device Okay

    Indoor RA 75-db 48%RH or 62-wb = target delta T of 19.3* to 19.8* NOT 23.5*
    Airflow could be considerably lower than 1400-cfm.


    Head pres. _210-psig_
    SCT - Gage - Saturated Condensing Temp _105*_
    LLT - Liquid line temperature: _95.6*_
    Subcooling: _9.4*_sounds close - what does Goodman say?

    Return Air temp DB &, WB or %RH: _75*_48%RH__62*-wb
    Supply Air temp DB &, WB or %RH: _51.5*_?_
    RA/SA delta T _23.5*_
    Indoor RA 75-db 62-wb = target delta T of 19.3* to 19.8* NOT 23.5*

    My advice to everyone with an A/C: get a low cost humidity gage at a local hardware store & see what the percentage-RH is in your home or RA/SA %RH, I can cross-reference that to the wet bulb depression.
    Last edited by udarrell; 06-29-2008 at 04:07 PM. Reason: 62*-wb - was in wrong place

  8. #8
    Join Date
    Jun 2008
    Posts
    45
    First let me say Thank you to Beenthere and Udarrell for responding to my post and giving me valuable information.

    Beenthere, I now understand that all of the data must be collected at the same time in order to make a accurate assessment. I will get that data and post it ASAP. Again thanks for the reply.

    Udarrell,

    I think i will have to read your post a few times in order to understand it all. Since I am a homeowner and not an HVAC tech (can't you tell). I know i could have provided more information I just didn't know exactly what information was necessary. As far as the Air flow is concerned I can only say that the dip switches are set for a blower speed of 1400 cfm and the LED is blinking 14 times for what it is worth. I don't know if the led just blinks according the the dip switch setting or if it really has a mass air flow sensor the know how air is actually passing.

    Thanks again for all you input.

    Carl

  9. #9
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    Until you know the true CFM through the evaporator coil the other readings mean nothing. Air flow must be set first.

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