Solar and Central Air

Options
Mangas
Mangas Solar Expert Posts: 547 ✭✭✭✭
in General Solar Power Topics #1
For those interested in off grid summer applications, I thought I'd pass on my battery voltage reserve levels running two 19 SEAR (2.5 ton) Variable Speed A/C units (in winter running propane furnaces with heat pumps permanently disconnected).  Presently,  daytime outdoor temperature is running about 85 - 95 degrees and nightime 80 - 85 degrees.  Ranch house is RASTRA construction, Anderson triple pane, equipped with extensive number of appliances and 220V well pumps.  Panels are left in fixed position year round. Thermostats are set at 79 degrees.

At these parameters, we're holding voltage levels during the day between 51.5 V to 54.5 V and at sun up about 50V.  July, August, September to include the Summer rains period will assuredly use more power.  We're hoping to see above 49 V at sunup.
Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
· Share on Twitter

Comments

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #2
    Options
    Re: Solar and Central Air

    Mangas,

    Thanks for the update on your system. In order for the batteries to fully recharge, you'll need to get them up to ~59.2 V for two- to three hours several times a week. They'll also need to be equalized ever once in a while... monthly?

    HTH,
    Jim / crewzer
    · Share on Twitter
  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
    #3
    Options
    Re: Solar and Central Air

    Hi Jim,  

    Yes, the batteries do peak out a few times a week at 59 V usually around 1 PM to 4 PM then, seem to drop back to about 54 V.

    I wondered about them charging near 60 V.  What I mean is do the charge controllers cut them off at 60 V?

    Just checked, it's 4 PM full sun over the mountains and the north A/C zone battery bank voltage level is 58.8 V and south zone is 54.8V.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
    · Share on Twitter
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #4
    Options
    Re: Solar and Central Air

    Why wouldn't you use the heat pumps in fall & spring if you have the power?
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
    · Share on Twitter
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #5
    Options
    Re: Solar and Central Air
    I wondered about them charging near 60 V. What I mean is do the charge controllers cut them off at 60 V?

    Mangas,

    Yes, the chargers will limit the charge voltage to whatever the target voltages are for the various stages (absorb, float, and equalization settings in the "Charger" menu) plus an appropriate temperature compensation offset, assuming the remote BTS is used. The MX60 holds the target voltage steady in these stages by limiting current to the batteries. Assuming sufficient insolation, the charger will switch from the absorb or equalization stage to the float stage once the appropriate time or current limit parameters have been met (Advanced settings menu).

    HTH,
    Jim / crewzer
    · Share on Twitter
  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
    #6
    Options
    Re: Solar and Central Air

    Jim thanks very much for your usual clear explanation.  I'll go back and review the set up parameters.

    In answer to Brock's question, we noticed the two stage heat pumps were running quite often and, with the air handlers running too, our sun-up voltages were pretty thin.  Disconnecting the heat pumps, we monitored sun up battery voltages using only the propane furnaces and the air handlers and the overnight battery voltages came up significantly.   The propane usage was about the same. 

    But, our problems with the connected heat pumps were impeded by the fact the furnaces didn't have the motor run capacitors installed.  Without them the HVAC system was in chaos trying to continually fire the furnaces 24 hours a day when they for no reason would shut off.  We discovered later the furnace mother boards weren't firing the hot surface ignitors properly because we believe the inverters' true sine wave was confusing them.  With no help from the HVAC manufacturer engineers our semi-retired Solar Installer/Electrician and the inverter manufacturer figured this out and, after installing two $20 parts in 25 minutes, the furnaces have worked perfectly ever since. 

    You may have a point, we might reconnect the heat pumps this fall and see if they perform better now the capacitors have been installed.  I was told without the capacitors a lot of power was being used trying to run the HVAC.

    Sorry to repeat these comments but they may help someone navigate and avoid a similar problem.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
    · Share on Twitter
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #7
    Options
    Re: Solar and Central Air

    Mangas,

    Always glad to help when and where I can. Thanks for sharing your system's performance data.

    Regards,
    Jim / crewzer
    · Share on Twitter
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #8
    Options
    Re: Solar and Central Air

    Ahhh make sense. I was just thinking that in the fall and spring they are more effecient and if you had the extra energy, might as well use it?

    Sounds like a great setup!
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
    · Share on Twitter

Categories