Thomas_
New Member
Hi,
I’ve been working on a grid-tie system using the great resources on this board, and I just received plan approval and now I’m second guessing myself.
This is a pergola/carport mounted system, 7.9kW DC with (20) Hyundai 395W bifacial panels using a sol-ark 15k inverter for whole-home feed through with a pytes battery backup.
https://signaturesolar.com/hyundai-...ver-up-to-470w-with-bifacial-gain-his-s395gi/
My utility still offers 1-1 net metering, so I know I will never get the battery value back, and blackouts are infrequent so that is not a great argument, but I like the peace of mind of knowing the system could function as a backup. I know financially it would make a lot of sense to get a standard (non-hybrid inverter), but even with the sol-ark my break even is only around 46 months, I would add about 9 months to that with the battery. Excess generation is paid out at ~17c/kwh, but the system is designed for 100% offset, so maybe with some future efficiency improvements I can reduce the annual consumption and shorten my payback.
The plan is for 2 parallel strings of 7 panels and 1 string of 6. Parallel using a MC4 y-connector, through a IMO DC disconnect at the pergola which is about 80 feet from the main panel/inverter location.
What I would like to get is any input/validation on my calcs. Specifically my strings, I could run (3) strings back to the inverter (8,8,4 panels) instead for example.
LOW AMBIENT TEMP VOC CALCULATION:
LOCAL LOW TEMP = -8C
690.7(A) CORRECTION FACTOR IS 1.14
PANEL VOC=48.8V
48.8*1.14 = 55.632 MAX VOLTAGE/MODULE
INVERTER MAX INPUT VOLTAGE = 500V
500/55.632 >> 8 MODULE/ STRING MAX
7 MODULES/STRING OK
HIGH AMBIENT TEMP CONDUCTOR AMPACITY CALC:
LOCAL HIGH TEMP 45C
690.31(A) DOES NOT APPLY
TEMP CORRECTION FACTOR, 90C THWN-2, 310.15(B)(1)
41-45C = .87 AMPACITY FACTOR
PANEL ISC=10.23
10.23*1.25*1.25 = 15.9588A >> 14GA WIRE OK
2 STRINGS IN PARALLEL = 2*15.9588A = 31.9176A >> 10GA WIRE OK
The plan is to use ironridge racking (I got a site specific design for the solar canopy from them). It looks like they are available locally through Greentech renewables or Wesco in the Los Angeles area, any experience with either or recommended locations to source from? I’m planning to get the Hyundai panels from SS with the free shipping, but for the other components is there a recommended or preferred supplier?
Based on some of the feedback I've seen here I'm also planning to replace the 200A disconnect with a GE 200A transfer switch to allow system bypass.
Thanks in advance for any help
I’ve been working on a grid-tie system using the great resources on this board, and I just received plan approval and now I’m second guessing myself.
This is a pergola/carport mounted system, 7.9kW DC with (20) Hyundai 395W bifacial panels using a sol-ark 15k inverter for whole-home feed through with a pytes battery backup.
https://signaturesolar.com/hyundai-...ver-up-to-470w-with-bifacial-gain-his-s395gi/
My utility still offers 1-1 net metering, so I know I will never get the battery value back, and blackouts are infrequent so that is not a great argument, but I like the peace of mind of knowing the system could function as a backup. I know financially it would make a lot of sense to get a standard (non-hybrid inverter), but even with the sol-ark my break even is only around 46 months, I would add about 9 months to that with the battery. Excess generation is paid out at ~17c/kwh, but the system is designed for 100% offset, so maybe with some future efficiency improvements I can reduce the annual consumption and shorten my payback.
The plan is for 2 parallel strings of 7 panels and 1 string of 6. Parallel using a MC4 y-connector, through a IMO DC disconnect at the pergola which is about 80 feet from the main panel/inverter location.
What I would like to get is any input/validation on my calcs. Specifically my strings, I could run (3) strings back to the inverter (8,8,4 panels) instead for example.
LOW AMBIENT TEMP VOC CALCULATION:
LOCAL LOW TEMP = -8C
690.7(A) CORRECTION FACTOR IS 1.14
PANEL VOC=48.8V
48.8*1.14 = 55.632 MAX VOLTAGE/MODULE
INVERTER MAX INPUT VOLTAGE = 500V
500/55.632 >> 8 MODULE/ STRING MAX
7 MODULES/STRING OK
HIGH AMBIENT TEMP CONDUCTOR AMPACITY CALC:
LOCAL HIGH TEMP 45C
690.31(A) DOES NOT APPLY
TEMP CORRECTION FACTOR, 90C THWN-2, 310.15(B)(1)
41-45C = .87 AMPACITY FACTOR
PANEL ISC=10.23
10.23*1.25*1.25 = 15.9588A >> 14GA WIRE OK
2 STRINGS IN PARALLEL = 2*15.9588A = 31.9176A >> 10GA WIRE OK
The plan is to use ironridge racking (I got a site specific design for the solar canopy from them). It looks like they are available locally through Greentech renewables or Wesco in the Los Angeles area, any experience with either or recommended locations to source from? I’m planning to get the Hyundai panels from SS with the free shipping, but for the other components is there a recommended or preferred supplier?
Based on some of the feedback I've seen here I'm also planning to replace the 200A disconnect with a GE 200A transfer switch to allow system bypass.
Thanks in advance for any help
