46kW PV + 144kW LFP Ground Mount Zero-Export in AZ, 100% DIY

[mikesolar]

Hey folks, wanted to share my setup and talk ground mount solar. Having done a roof setup at my last house, I am a huge proponent of ground mount if space allows. Happy to answer questions, and certainly a lot of my lessons learned are my opinions rather than hard fact.

A little bit about me...I am 100% DIY and self taught. Gained experience over the years with a lot of renos and hobby/DIY work. Work in tech and have done some embedded hardware work as well as commercial data center work that provided a bit of a foundation I guess

System components:

• 2x Sol-Ark 15K in parallel, zero-export to grid AKA sell-to-home setup.
• 12x Orient Power 48V230 LFP batteries
  • Wired in parallel in 4 groups of 3 with a class T fuse for each group
• 2x ground mount arrays, 23kW each
  • 48x Q Cells Q.PEAK DUO XL-G10.C 480W per array
  • 6 strings of 8 panels per array, strings paralleled in groups of 2 to feed 3 MPPTs per Sol-ark
  • DC disconnects with DC surge protectors at each array
• IronRidge racking. XR100 rails and associated components, no optional diagonal bracing.
• Roughly 46kW PV, 35kW AC output, and 144kWh battery storage in total.
• Maximum generation is approximately 300kWh a day +/- 15%.

Working with a pretty large property, 1 acre, a 4000sqft house and a 2400sqft guest house. 400A service coming into the property split across 2x200A panels. Guest house runs off of a 125A breaker on one of the 200A panels from the main house. 4000sqft house was pre-existing. 2400sqft guest house was new construction done at the same time as the PV.

Design considerations

• Ground mount at a shallow angle as to not exceed the fence height and be an eyesore
• Absolutely 0 power equipment / inverters mounted outside. I think people in AZ are crazy for mounting inverters and load centers outside. Service disconnects are OK but nothing else IMHO.
• All power equipment/inverters/batteries grouped together in one side of the guest house garage.
• Guest house powered 100% off of inverter load outputs. Zero-export back to the main house. Full load/backup of the main house is not practical due to split 400A service with load centers on both sides of the house and space/distance/cost constraints.
  • Having the PV/batteries act as a UPS for the networking/IT equipment co-located in the guest house is also critical, as the property has an extensive on-site video surveillance system.
• 100% off-grid / zero-export consumption offset sizing on typical full sun days
  • Property consumes roughly 275-300kWh a day with pool equipment, ACs/heat pumps, and 2 EVs.
  • Some minor grid usage (10-20kW) in April/May and October/November due to the 12kW pool heat pump running which is an absolute pig on power.
• No modification of existing service entrance or electrical at the main house for permitting complexity reasons.
• Fully permitted PV/inverters during construction time. Battery expansion at a later date.
• No flammable materials used for any battery racking and no battery wiring run inside walls. Everything in open-air or metal raceways or metal racking.

Lessons learned

• Always run a bigger conduit than you need, makes wire pulls much easier. 20% fill on a 2" SCH40 PVC....totally fine right? Do 2.5" anyway.
• Insulated multi-tap connectors are your best friend. Polaris, Burndy, Panduit...
• A ditch witch that can go at least 24” deep is worth the rental money. Digging more than a few ft by hand for conduit in AZ clay soil is brutal work.
• Splitting AC and DC in a wire trough / raceway is a colossal PITA. I'm fortunate I was inspected under the 2013 code and didn't have to deal with it. I don't envy folks who have to deal with it.
• Always oversize conductors or run extra conductors for possible future expansion.
• If you care about the longevity of inverters and breakers and batteries, don't put them outside in dusty or hot climates despite conventional or local wisdom. Fight the inspectors and put it indoors. The NEC allows it.
• Ground screws are awesome. I did the first array with 3" mechanical pipe floated in 14 (2x7) 24" holes filled with concrete, and the second array with 2" mechanical pipe, 22 (11x2) 4ft long ground screw piers. Absolutely would use ground screws again for everything. Hiring a concrete pump and renting a skid steer to auger 2' wide holes SUCKS and adds up to more $$$ at the end of the day, not to mention the landscaping disruptions.
• U.S Wholesale pipe is the only DIY-friendly mechanical pipe supplier I've come across.
• The price premium for IronRidge racking is worth it for the design and layout tools, engineered plans, GreenLancer permit drawing services, availability of materials, etc.
• Zero-export with CTs is a necessary evil for me but adds a lot of complexity and failure points. If you are doing brand new construction...have a 3-way disconnect for service/grid/inverter switch and use the 200A passthrough of the Sol-ark.
• If you're doing Zero-Export, crank up the zero-export target from 20W to like 100W per inverter. With a very large system like this, the inverters just don't do 20W properly and inadvertently export too much, possibly getting you in trouble with the utility. You won't be truly 100% grid offset...maybe 4-5kWh of grid usage a day, but the system will operate much more smoothly.
• Nailed the panel to inverter ratio. 35kW AC capacity from the inverters at 100% load, 46kW solar....A little bit of clipping from 10AM-2PM but confident it's the right balance for long term longevity of the system and aligned very nicely with buying panels by the pallet for cost reasons. Have about 6kW of panels left over in the garage for future replacement/hail damage if it happens.
• A high quality shielded 18/4 wire from Belden is suitable for for extending CT wires by 100ft for Zero-Export. I was worried about zero-export when the inverters aren't right beside the service entrance, but it works fine.
• Did 2" mechanical pipe for one array and 3" mechanical pipe for the other. Thought minimizing holes in the ground was the priority and 3" was easier. WRONG. 2" pipe is way lighter and easier to work with and cut, by a huge margin. Make the extra holes!
• The NEC, utility regulations, inspections, permitting, etc. are one big expensive bureaucratic mess that disincentives DIY work and provides little/no safety or value, and treads on individual rights and freedoms. I "played ball" this time but haven't in the past, and gained absolutely nothing for it. I failed one inspection throughout the whole process for using a sticker instead of a riveted placard for the voltage/amps on the AC disconnect.
• I should really put some white gravel down to benefit from bifacial gain. I got a good deal on the panels but didn't strictly need bifacial ones...I just wanted the utility/XL sized panels and these were good value.
• I like the Sol-Ark hardware, but not the software. I know they're getting better, but the security aspect of their data loggers and remote firmware updates is scary. I recommend doing a 1-time update, then yanking all of that stuff and running Solar-Assistant.
• I've done the DIY battery pack from raw cells before at my last house, and I had many many regrets. The server rack batteries are a clear winner IMHO, as long as the BMS boards stand the test of time... Only other product I’d use at this scale is Tesla Powerwall because the integration and software is lightyears ahead of the DIY solar market, but they have to figure out the cost and the DIY-Installer hatred before I jump in.

Future work

• Chain-link fence/cage around the interior solar equipment and batteries for child safety.
• Test Sol-ark GEN input with the Cybertruck

 

[TK1979]

Hey folks, wanted to share my setup and talk ground mount solar. Having done a roof setup at my last house, I am a huge proponent of ground mount if space allows. Happy to answer questions, and certainly a lot of my lessons learned are my opinions rather than hard fact.

A little bit about me...I am 100% DIY and self taught. Gained experience of the years with a lot of renos and hobby/DIY work. Work in tech and have done some embedded hardware work as well as commercial data center work that provided a bit of a foundation I guess

System components:

• 2x Sol-Ark 15K in parallel, zero-export to grid AKA sell-to-home setup.
• 12x Orient Power 48V230 LFP batteries
  • Wired in parallel in 4 groups of 3 with a class T fuse for each group
• 2x ground mount arrays, 23kW each
  • 48x Q Cells Q.PEAK DUO XL-G10.C 480W per array
  • 6 strings of 8 panels per array, strings paralleled in groups of 2 to feed 3 MPPTs per Sol-ark
  • DC disconnects with DC surge protectors at each array
• IronRidge racking. XR100 rails and associated components, no optional diagonal bracing.
• Roughly 46kW PV, 36kW AC output, and 144kWh battery storage in total.
• Maximum generation is approximately 300kWh a day +/- 15%.

Working with a pretty large property, 1 acre, a 4000sqft house and a 2400sqft guest house. 400A service coming into the property split across 2x200A panels. Guest house runs off of a 125A breaker on one of the 200A panels from the main house. 4000sqft house was pre-existing. 2400sqft guest house was new construction done at the same time as the PV.

Design considerations

• Ground mount at a shallow angle as to not exceed the fence height and be an eyesore
• Absolutely 0 power equipment / inverters mounted outside. I think people in AZ are crazy for mounting inverters and load centers outside. Service disconnects are OK but nothing else IMHO.
• All power equipment/inverters/batteries grouped together in one side of the guest house garage.
• Guest house powered 100% off of inverter load outputs. Zero-export back to the main house. Full load/backup of the main house is not practical due to split 400A service with load centers on both sides of the house and space/distance/cost constraints.
  • Having the PV/batteries act as a UPS for the networking/IT equipment co-located in the guest house is also critical, as the property has an extensive on-site video surveillance system.
• 100% off-grid / zero-export consumption offset sizing on typical full sun days
  • Property consumes roughly 275-300kWh a day with pool equipment, ACs/heat pumps, and 2 EVs.
  • Some minor grid usage (10-20kW) in April/May and October/November due to the 12kW pool heat pump running which is an absolute pig on power.
• No modification of existing service entrance or electrical at the main house for permitting complexity reasons.
• Fully permitted PV/inverters during construction time. Battery expansion at a later date.
• No flammable materials used for any battery racking and no battery wiring run inside walls. Everything in open-air or metal raceways or metal racking.

Lessons learned

• Always run a bigger conduit than you need, makes wire pulls much easier. 20% fill on a 2" SCH40 PVC....totally fine right? Do 2.5" anyway.
• Insulated multi-tap connectors are your best friend. Polaris, Burndy, Panduit...
• Splitting AC and DC in a wire trough / raceway is a colossal PITA. I'm fortunate I was inspected under the 2013 code and didn't have to deal with it. I don't envy folks who have to deal with it.
• Always oversize conductors or run extra conductors for possible future expansion.
• If you care about the longevity of inverters and breakers and batteries, don't put them outside in dusty or hot climates despite conventional or local wisdom. Fight the inspectors and put it indoors. The NEC allows it.
• Ground screws are awesome. I did the first array with 3" mechanical pipe floated in 14 (2x7) 24" holes filled with concrete, and the second array with 2" mechanical pipe, 22 (11x2) 4ft long ground screw piers. Absolutely would use ground screws again for everything. Hiring a concrete pump and renting a skid steer to auger 2' wide holes SUCKS and adds up to more $$$ at the end of the day, not to mention the landscaping disruptions.
• U.S Wholesale pipe is the only DIY-friendly mechanical pipe supplier I've come across.
• The price premium for IronRidge racking is worth it for the design and layout tools, engineered plans, GreenLancer permit drawing services, availability of materials, etc.
• Zero-export with CTs is a necessary evil for me but adds a lot of complexity and failure points. If you are doing brand new construction...have a 3-way disconnect for service/grid/inverter switch and use the 200A passthrough of the Sol-ark.
• If you're doing Zero-Export, crank up the zero-export target from 20W to like 100W per inverter. With a very large system like this, the inverters just don't do 20W properly and inadvertently export too much, possibly getting you in trouble with the utility. You won't be truly 100% grid offset...maybe 4-5kWh of grid usage a day, but the system will operate much more smoothly.
• Nailed the panel to inverter ratio. 36kW AC capacity from the inverters at 100% load, 46kW solar....A little bit of clipping from 10AM-2PM but confident it's the right balance for long term longevity of the system and aligned very nicely with buying panels by the pallet for cost reasons. Have about 6kW of panels left over in the garage for future replacement/hail damage if it happens.
• A high quality shielded 18/4 wire from Belden is suitable for for extending CT wires by 100ft for Zero-Export. I was worried about zero-export when the inverters aren't right beside the service entrance, but it works fine.
• Did 2" pipe for one array and 3" pipe for the other. Thought minimizing holes in the ground was the priority and 3" was easier. WRONG. 2" pipe is way lighter and easier to work with and cut, by a huge margin. Make the extra holes!
• The NEC, utility regulations, inspections, permitting, etc. are one big expensive bureaucratic mess that disincentives DIY work and provides little/no safety or value, and treads on individual rights and freedoms. I "played ball" this time but haven't in the past, and gained absolutely nothing for it. I failed one inspection throughout the whole process for using a sticker instead of a riveted placard for the voltage/amps on the AC disconnect.
• I should really put some white gravel down to benefit from bifacial gain. I got a good deal on the panels but didn't strictly need bifacial ones...I just wanted the utility/XL sized panels and these were good value.
• I like the Sol-Ark hardware, but not the software. I know they're getting better, but the security aspect of their data loggers and remote firmware updates is scary. I recommend doing a 1-time update, then yanking all of that stuff and running Solar-Assistant.
• I've done the DIY battery pack stuff before at my last house, and I had many many regrets. The server pack batteries are a clear winner IMHO, as long as the BMS boards stand the test of time... Huge fan of Tesla Powerwall too because the integration and software is lightyears ahead of the DIY solar market, but they have to figure out the cost and the DIY-Install hatred before I jump in.

Future work

• Chain-link fence/cage around the interior solar equipment and batteries for child safety.
• Test Sol-ark GEN input with the Cybertruck

Amazing set up - and wow, that's a lot of juice used every day!

 

[summit]

so awesome!

any consideration/wiring to optimize 48v packs to keep being in balance ? the cybertruck is the other huge possible pack to tap if peak $$ shifting is wanted.

 

[Israel Keys]

Love this. It's the closest to my setup I've found on here. Would be great to rub minds and share ideas moving forwards.

 

[tmclane]

Do you think the 18/4 shielded wire could be used to go 200 feet?

 

[mikesolar]

so awesome!

any consideration/wiring to optimize 48v packs to keep being in balance ? the cybertruck is the other huge possible pack to tap if peak $$ shifting is wanted.

I measured the wires so that the lengths are all the same, that's why there's some wiring coiled up beside them. Beyond that, I have the charge voltage on the Sol-Ark set high enough that the BMS cut-off should trigger first, and effectively top-balance the packs on a daily basis...if I understand correctly

This is the biggest disincentive for using large cell packs. I suspect it's easier to keep 100Ah cells in balance vs 230Ah, but probably not worth all the extra wiring and connections at >100kWh storage. Maybe the right compromise is 5kWh batteries (100Ah cells) in one of those fancy racks with the integrated bus bars.

Love this. It's the closest to my setup I've found on here. Would be great to rub minds and share ideas moving forwards.

Always happy to chat. I'm curious to see a similar setup with different design decisions. Maybe an alternative to Sol-Ark and a more scalable battery setup with less wiring and connections? EG4 has some 400A wiring examples for their GridBoss, but I wonder if there's something even better out there?

Aside from a setup that wires up more cleanly at this scale...I think my #1 design change if I were to do it again would be to build a dedicated single purpose structure for the equipment to mitigate some of the fire/safety risk if there's a catastrophic failure. Maybe like a 10x25ft shed-like structure with a mini-split heat pump and good insulation, built entirely out of concrete.

Do you think the 18/4 shielded wire could be used to go 200 feet?

Yes, but I would pull it in it's own conduit with a little bit of separation from the service conductors if possible given the distance. I used Belden 9368. Costs a fortune and probably overkill...Sol-Ark says CAT5 cable is enough for extending the CT wires but doesn't list a maximum distance.

 

[summit]

I measured the wires so that the lengths are all the same, that's why there's some wiring coiled up beside them. Beyond that, I have the charge voltage on the Sol-Ark set high enough that the BMS cut-off should trigger first, and effectively top-balance the packs on a daily basis...if I understand correctly

I was wondering about keep the packs in balance with each other. Looking closer at the picture, each pack has just a pair of red/black; so there must be a couple of bus bars. There was a discussion somewhere here about best practice connecting parallel packs. For example, in a 3p configuration, it's best to have the final (+) from pack#1 and final (-) from pack#3.

This is the biggest disincentive for using, large cell packs. I suspect it's easier to keep 100Ah cells in balance vs 230Ah, but probably not worth all the extra wiring and connections at >100kWh storage. Maybe the right compromise is 5kWh batteries (100Ah cells) in one of those fancy racks with the integrated bus bars.

one incentive for using large cell packs is less idle consumption from the individual's pack BMS. There are 12x BMS humming there. It's a minor issue, but can become problematic in the winter with low production for some application, especially in 100% off-grid scenario.

 

[mikesolar]

Interesting point about the inefficiencies from the extra BMS units.

I am doing 12p in two steps. 4 groups of 3p with Burndy multi-tap connectors (they’re tucked on top of the batteries) and then merging those 4 groups onto a set of bus bars via 300A class T fuses with the wiring going back to the inverters. Pic attached. 2AWG from each pack to the multitaps, 4/0 from the multitap for each group of 4 to the bus bars, then 2x 4/0 from each bus bar to each Sol-ark.

Do you have a link to that thread on paralleling packs? I’d love to read more. I haven’t observed any issues with my setup at all but always eager to learn.

 

[summit]

can't immediately locate the link, a quick search resulted this thread as a starter, am sure there are others.

S

Thread 'Calculation of parallel string currents addendum'

Nov 12, 2024

First read this https://diysolarforum.com/threads/calculation-of-parallel-string-battery-currents.37937/ until at least post #61.

This post will show the theoretical calculated battery currents in parallel strings of 5, 6, 7 and 8 batteries with load currents of 100 amps times the number of batteries in the string. That is, load current of 500 amps for a string of 5 batteries, 600 amps for a string of 6, etc. For smaller load currents simply scale down the calculated battery currents in proportion.

The calculations are made assuming battery internal resistance of 1 milliohm, link...

• Solarod
• Replies: 5
• Forum: General Battery Discussion

• 

 

[mikesolar]

From Solar-Assistant. I’m using the equal length wire method. 16kW going to the batteries at the time the screenshot was taken. 54W difference between the lowest and highest pack. Seems great!

 

[Nobodybusiness]

Hey folks, wanted to share my setup and talk ground mount solar. Having done a roof setup at my last house, I am a huge proponent of ground mount if space allows. Happy to answer questions, and certainly a lot of my lessons learned are my opinions rather than hard fact.

A little bit about me...I am 100% DIY and self taught. Gained experience over the years with a lot of renos and hobby/DIY work. Work in tech and have done some embedded hardware work as well as commercial data center work that provided a bit of a foundation I guess

System components:

• 2x Sol-Ark 15K in parallel, zero-export to grid AKA sell-to-home setup.
• 12x Orient Power 48V230 LFP batteries
  • Wired in parallel in 4 groups of 3 with a class T fuse for each group
• 2x ground mount arrays, 23kW each
  • 48x Q Cells Q.PEAK DUO XL-G10.C 480W per array
  • 6 strings of 8 panels per array, strings paralleled in groups of 2 to feed 3 MPPTs per Sol-ark
  • DC disconnects with DC surge protectors at each array
• IronRidge racking. XR100 rails and associated components, no optional diagonal bracing.
• Roughly 46kW PV, 35kW AC output, and 144kWh battery storage in total.
• Maximum generation is approximately 300kWh a day +/- 15%.

Working with a pretty large property, 1 acre, a 4000sqft house and a 2400sqft guest house. 400A service coming into the property split across 2x200A panels. Guest house runs off of a 125A breaker on one of the 200A panels from the main house. 4000sqft house was pre-existing. 2400sqft guest house was new construction done at the same time as the PV.

Design considerations

• Ground mount at a shallow angle as to not exceed the fence height and be an eyesore
• Absolutely 0 power equipment / inverters mounted outside. I think people in AZ are crazy for mounting inverters and load centers outside. Service disconnects are OK but nothing else IMHO.
• All power equipment/inverters/batteries grouped together in one side of the guest house garage.
• Guest house powered 100% off of inverter load outputs. Zero-export back to the main house. Full load/backup of the main house is not practical due to split 400A service with load centers on both sides of the house and space/distance/cost constraints.
  • Having the PV/batteries act as a UPS for the networking/IT equipment co-located in the guest house is also critical, as the property has an extensive on-site video surveillance system.
• 100% off-grid / zero-export consumption offset sizing on typical full sun days
  • Property consumes roughly 275-300kWh a day with pool equipment, ACs/heat pumps, and 2 EVs.
  • Some minor grid usage (10-20kW) in April/May and October/November due to the 12kW pool heat pump running which is an absolute pig on power.
• No modification of existing service entrance or electrical at the main house for permitting complexity reasons.
• Fully permitted PV/inverters during construction time. Battery expansion at a later date.
• No flammable materials used for any battery racking and no battery wiring run inside walls. Everything in open-air or metal raceways or metal racking.

Lessons learned

• Always run a bigger conduit than you need, makes wire pulls much easier. 20% fill on a 2" SCH40 PVC....totally fine right? Do 2.5" anyway.
• Insulated multi-tap connectors are your best friend. Polaris, Burndy, Panduit...
• A ditch witch that can go at least 24” deep is worth the rental money. Digging more than a few ft by hand for conduit in AZ clay soil is brutal work.
• Splitting AC and DC in a wire trough / raceway is a colossal PITA. I'm fortunate I was inspected under the 2013 code and didn't have to deal with it. I don't envy folks who have to deal with it.
• Always oversize conductors or run extra conductors for possible future expansion.
• If you care about the longevity of inverters and breakers and batteries, don't put them outside in dusty or hot climates despite conventional or local wisdom. Fight the inspectors and put it indoors. The NEC allows it.
• Ground screws are awesome. I did the first array with 3" mechanical pipe floated in 14 (2x7) 24" holes filled with concrete, and the second array with 2" mechanical pipe, 22 (11x2) 4ft long ground screw piers. Absolutely would use ground screws again for everything. Hiring a concrete pump and renting a skid steer to auger 2' wide holes SUCKS and adds up to more $$$ at the end of the day, not to mention the landscaping disruptions.
• U.S Wholesale pipe is the only DIY-friendly mechanical pipe supplier I've come across.
• The price premium for IronRidge racking is worth it for the design and layout tools, engineered plans, GreenLancer permit drawing services, availability of materials, etc.
• Zero-export with CTs is a necessary evil for me but adds a lot of complexity and failure points. If you are doing brand new construction...have a 3-way disconnect for service/grid/inverter switch and use the 200A passthrough of the Sol-ark.
• If you're doing Zero-Export, crank up the zero-export target from 20W to like 100W per inverter. With a very large system like this, the inverters just don't do 20W properly and inadvertently export too much, possibly getting you in trouble with the utility. You won't be truly 100% grid offset...maybe 4-5kWh of grid usage a day, but the system will operate much more smoothly.
• Nailed the panel to inverter ratio. 35kW AC capacity from the inverters at 100% load, 46kW solar....A little bit of clipping from 10AM-2PM but confident it's the right balance for long term longevity of the system and aligned very nicely with buying panels by the pallet for cost reasons. Have about 6kW of panels left over in the garage for future replacement/hail damage if it happens.
• A high quality shielded 18/4 wire from Belden is suitable for for extending CT wires by 100ft for Zero-Export. I was worried about zero-export when the inverters aren't right beside the service entrance, but it works fine.
• Did 2" mechanical pipe for one array and 3" mechanical pipe for the other. Thought minimizing holes in the ground was the priority and 3" was easier. WRONG. 2" pipe is way lighter and easier to work with and cut, by a huge margin. Make the extra holes!
• The NEC, utility regulations, inspections, permitting, etc. are one big expensive bureaucratic mess that disincentives DIY work and provides little/no safety or value, and treads on individual rights and freedoms. I "played ball" this time but haven't in the past, and gained absolutely nothing for it. I failed one inspection throughout the whole process for using a sticker instead of a riveted placard for the voltage/amps on the AC disconnect.
• I should really put some white gravel down to benefit from bifacial gain. I got a good deal on the panels but didn't strictly need bifacial ones...I just wanted the utility/XL sized panels and these were good value.
• I like the Sol-Ark hardware, but not the software. I know they're getting better, but the security aspect of their data loggers and remote firmware updates is scary. I recommend doing a 1-time update, then yanking all of that stuff and running Solar-Assistant.
• I've done the DIY battery pack from raw cells before at my last house, and I had many many regrets. The server rack batteries are a clear winner IMHO, as long as the BMS boards stand the test of time... Only other product I’d use at this scale is Tesla Powerwall because the integration and software is lightyears ahead of the DIY solar market, but they have to figure out the cost and the DIY-Installer hatred before I jump in.

Future work

• Chain-link fence/cage around the interior solar equipment and batteries for child safety.
• Test Sol-ark GEN input with the Cybertruck

Hey I’m curious.

I have the same panels and Inverters as you.

When I used the Sol-Ark panel calculator it showed 6 panels series strings paralleled. 12 panels per MPPT channel.

Of course your temperature coefficient is probably different being in AZ.

What is your voltage and amps per channel?

Mine is around 250-270vdc 18-21 amps. 5000 watts per channel.

Seems like 8 panels per string X 2 parallel would be to much per channel.

 

[mikesolar]

Hey I’m curious.

I have the same panels and Inverters as you.

When I used the Sol-Ark panel calculator it showed 6 panels series strings paralleled. 12 panels per MPPT channel.

Of course your temperature coefficient is probably different being in AZ.

What is your voltage and amps per channel?

Mine is around 250-270vdc 18-21 amps. 5000 watts per channel.

Seems like 8 panels per string X 2 parallel would be to much per channel.

At peak sun I’m at approximately 338V and 16.7A or 5600W per channel. My understanding is that the MPPTs max out at 26A on the 15K. Worth noting I am exceeding the capacity of the inverters by ~20% so I'd expect that current to be closer to 20A if I wasn't limited by overall output.

My goal was to keep my voltage as high as possible to keep resistance losses on the wiring down. I’m actually pretty close to maxing out the voltage limit on the inverters with the max Voc voltage on the panels! Voc=53.6V doesn’t leave a lot of wiggle room for me!

 

[Nobodybusiness]

At peak sun I’m at approximately 338V and 16.7A or 5600W per channel. My understanding is that the MPPTs max out at 26A on the 15K.

My goal was to keep my voltage as high as possible to keep resistance losses on the wiring down. I’m actually pretty close to maxing out the voltage limit on the inverters with the max Voc voltage on the panels! Voc=53.6V doesn’t leave a lot of wiggle room for me!

definitely higher than mine but I guess you don’t really have to worry about cold sunny days out there.

I’ll have to look at my voltages in winter to see how high they get.

 

[Coloskibum]

Amazing set up - and wow, that's a lot of juice used every day!

Yeah I was like "holy cow I use that much in most MONTHS even when charging my car". While not having freezing winters is appealing, I'd bail as soon as I had to deal with that kind of A/C load.

 

[mikesolar]

Yeah I was like "holy cow I use that much in most MONTHS even when charging my car". While not having freezing winters is appealing, I'd bail as soon as I had to deal with that kind of A/C load.

Surprisingly, the AC load isn't the worst offender. The pool heat pump and filter pumps are the biggest constant load, especially during the Spring/Fall. Our usage is actually a little lower in the peak of the summer vs. the spring/fall because the heat pump doesn't run much. It's a quality-of-life thing for sure, but the heat pump really helps even out the pool temperature and extend the swimming season from 4 months to 8 months.

The pool equipment adds up to approximately 100kWh a day, and the two EVs total up to about 40kWh a day for the average charge. The other 50% gets chewed up by the AC loads (6 exterior units total), two heat pump water heaters, 3 fridges, a freezer, computer networking equipment, etc.

My biggest lesson learned in terms of power consumption is that good insulation and properly zoned AC like the Mitsubishi Multi-splits can radically reduce the cost of heating and cooling. Our 2400sqft casita has 7 interior zones across 3 exterior units (20K, 36K, and 36K BTU) and the peak usage on a 110F day across that entire setup is 5.75kW, with the interior temp set to 72F! In practice I'd estimate it's about half the operating cost per sqft as the traditional ducted air handler setup in our main house, though certainly more complicated and expensive to set up. And that's just power consumption...if you factor in noise and comfort it's not even a contest.

 

[summit]

what your winter production/consumption looks like ? is the pool's 100kwh/day mainly for heating or cooling ? our grid-tie 20-yrs contract is scheduled to expire in 2027, at which time the "grid-battery" becomes null.

 

[mikesolar]

what your winter production/consumption looks like ? is the pool's 100kwh/day mainly for heating or cooling ? our grid-tie 20-yrs contract is scheduled to expire in 2027, at which time the "grid-battery" becomes null.

The pool consumption of 100kWh/day is 75% heating and 25% the filter pumps. In the very rare event we need to cool the pool (like maybe 3-4 days in the whole year) we have a rain curtain/waterfall thing with it's own pump that has a cooling effect. Our Raypak heat pump isn't the one with the cooling function. We only run the heat pump in October and April/May/early June, and generally don't heat the pool between November and April. For the rare special occasion in the winter we use the propane heater because the heat pump can't keep up when the nights get super chilly. And unfortunately we don't have natural gas to the property and propane is expensive AF so year-round heating is a non-starter. We do run the filter pumps all year round though, and have a separate standalone hot tub we use during the winter.

An insulated pool cover would make the pool costs significantly lower but we find them expensive, ugly, and cumbersome especially with the size of our pool.

Winter consumption is very low...about 50% of summer. Ballpark 130-160kWh for the whole property per day, and this also includes increased usage of both EVs since we tend to do a lot more outdoors activity in the AZ winter.

What state are you in with expiring grid-tie contracts? Do you have to move to a zero-export system once the contract expires?

 

[summit]

The pool consumption of 100kWh/day is 75% heating and 25% the filter pumps. In the very rare event we need ...

Winter consumption is very low...about 50% of summer. Ballpark 130-160kWh for the whole property per day, and this also includes increased usage of both EVs since we tend to do a lot more outdoors activity in the AZ winter.

What state are you in with expiring grid-tie contracts? Do you have to move to a zero-export system once the contract expires?

your pool must be on the larger size. We're in CA in PGE territory. There will be still a grid-tie contract, but the grid feed will no longer be at retail price. We have been banking higher $/kwh during summer over production and drawing lower $/kwh for winter heat along with less production. The utility bank will effectively become one-way flow. Zero-import would be the ideal but can't be achieve over multi cloudy winter days.

Is propane also your heat source ? propane is indeed expensive. We've gone all electric with whole house heat-pump, mini-splits, heat-pump water heater. Propane is now only for the stove, wife likes the flame. I cook with induction stove. Our propane tank was last filled in 2013.

 

[mikesolar]

your pool must be on the larger size. We're in CA in PGE territory. There will be still a grid-tie contract, but the grid feed will no longer be at retail price. We have been banking higher $/kwh during summer over production and drawing lower $/kwh for winter heat along with less production. The utility bank will effectively become one-way flow. Zero-import would be the ideal but can't be achieve over multi cloudy winter days.

Is propane also your heat source ? propane is indeed expensive. We've gone all electric with whole house heat-pump, mini-splits, heat-pump water heater. Propane is now only for the stove, wife likes the flame. I cook with induction stove. Our propane tank was last filled in 2013.

CA electricity prices are mindblowing. I have nothing to complain about in AZ. I'm looking at 8-9 years to break even on my system. I imagine your ROI must be much quicker than that?

Our pool is about 30K gallons. We have a 500 gal propane tank exclusively for the pool heater and the outdoor BBQ. The house is entirely electric (cooktops, heat pump water heater tanks, heat pump HVAC, electric dryer). We fill the tank once a year just heating the pool with propane for 6-7 days during the year for special events. The 400K BTU heater is an absolute pig. It'll run through the whole tank in a week.

Our heat pump water heaters are new additions. We have a 80 gal and 58 gal unit from Stiebel Eltron. Couldn't be happier with them, and they cool the garages indirectly too! Longevity concerns went away when I added whole-home water filtration and water softening at the same time we upgraded the water heaters.

 

[Nobodybusiness]

The 400K BTU heater is an absolute pig. It'll run through the whole tank in a week.

My old next door neighbor had NG pool heater that big.
When he ran the heater he would pantomime digging a hole and jumping in.

I think he said it cost him $50 a day to run it and that was 25 years ago.

 

[zanydroid]

All power equipment/inverters/batteries grouped together in one side of the guest house garage.

Isn’t 144kWh of batteries in one place way over residential code limit?

 

[summit]

Our pool is about 30K gallons. We have a 500 gal propane tank exclusively for the pool heater and the outdoor BBQ. The house is entirely electric (cooktops, heat pump water heater tanks, heat pump HVAC, electric dryer).

how much is the annual fill up ? propane is quite high here. Kinda wish there's a pool here, can serve as a decent solar battery for winter heat

Our heat pump water heaters are new additions. We have a 80 gal and 58 gal unit from Stiebel Eltron. Couldn't be happier with them, and they cool the garages indirectly too! Longevity concerns went away when I added whole-home water filtration and water softening at the same time we upgraded the water heaters.

our 2013 Geo-Spring has been quite reliable, fingers crossed. It's set to run in heat-pump mode day one. In fact, both upper/lower heat rods are disconnected in order to operate from battery back up. Newer models now have built-in timer for time-of-use, but our temperature sensor is hacked with a simple xmas light timer to think it's warm during peak cost hours.

Besides cooling the basement, it also dries it out. Collected condensate, which is practically distilled pure water, is great for cleaning stuff and house plants.