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diy solar

question about wiring panels in series

Thank you!!
One of my thoughts, and unfortunately there are many, was to have 2 solar panels and all the equipment needed per circuit, so each circuit would be a "unit" as you described. Then I would have 10 separate mini power systems for the building. Bad idea? One of the reasons is I could put the panels on the roof, and I have a place well ventilated above the second floor to put my batteries and equipment. This would keep everything away from vandals.
 
Next question...concerns voltage drop on my DC circuits. If I run a 24 volt system, and had 400 watts per circuit, how long can the run of the circuit be if I use 12 awg?
 
If I run a 24 volt system, and had 400 watts per circuit, how long can the run of the circuit be if I use 12 awg?
A "24V system"? Are you talking about from solar panels to the SCC or from battery to loads? Your array will have a much higher voltage than 24V.

400W / 24V = 17A

Based on voltage drop (staying below 3%), 40'.

Screen Shot 2022-11-14 at 8.46.46 AM.png
 
A "24V system"? Are you talking about from solar panels to the SCC or from battery to loads? Your array will have a much higher voltage than 24V.

400W / 24V = 17A

Based on voltage drop (staying below 3%), 40'.

View attachment 120203
Thank you MisterSandals...I am talking about battery to loads. I guess to be sure, I need to get some wire, run it out 100' or so, hook up a 24 V light at the end, and put 400 watt load right after the battery connection, and see what I get. Then test it again as I shorten the run. I know I will lose some volts for the EMT, taps, etc. Thank you for sending that calculator...I'll hunt it down on the internet...I am going to run into problems with the 2 hallways that run the length of the building--100'--I was going to wire them all together, but I guess maybe switch them in middle of hall....I hope a 10 awg will be enough for that...The plan is to put panels on roof, put equipment in an area above second floor I have that runs whole length of the building-well ventilated- and then drop straight down with my circuits into the rooms so I can limit length of run. Then have multiple power "units" (Distribution points) instead of one big distribution panel. Thank you, again. Luckily, the school buildings to be wired after this are all smaller...this building 10,000 sq ft, the others are all 1500 or less.
 
If I were shopping for charge controllers over 100 amps I would get an all in one 48V inverter instead, like a EG4 with 120 amp charging ($1200) and just a couple of EG4 5kW batteries ($1400 each).
You could turn the inverter off when not in use for AC power but you will want AC power sometimes for power tools or something.
A simple system with 10kWh of batteries and a 6.5kW charger/inverter could be purchased for well under $5k and it would provide emergency power at night as well. If you want to run DC lighting put lights two in series to make it 48V and use voltage converters for 12V power near the loads to keep the wire cost down.
I think they may be small enough to bring on a plane.
 
Thank you, Pete. I think I decided upon multiple 24 volt all DC "units/circuits". I am only putting a 320 max watt load on each unit/circuit...13.33 a= 320w/24v...2 -230 watt solar panels wired in series and 2 250 Ah batteries in series per "unit/circuit". I need to keep it simple because unskilled Haitians will have to service it until I can get back to Haiti. I do value your opinion on the following...I was going to pipe the whole building in 3/4" and 1/2" EMT, but since it's 24 volts, what is your opinion of just wiring it ( 24 volts) in just split loom plastic wire cover? no more than 4 wires in any piece of the split loom. (trying to save money) It is just lighting and fans...the only piece accessible to the public would be the switch leg. I agree with you I do need a couple of 120 volt inverter circuits to run AC tools and appliances should the need arise. The school will use laptop computers as money become available to purchase...I am building a lockable case for the computers where i will put in a 24 volt charging station for them, and step the voltage down to 19.5 to charge the computers inside the cabinet, but in my testing I find that DELL puts a chip in their computer so you have to use their charger. Right now the school has some Lenovo laptops, which allow me to charge using a stepdown transformer. But who knows about the future, so I should allow for future inverter use for the computers. Thank you for taking the time to answer.
 
Thank you, Pete. I think I decided upon multiple 24 volt all DC "units/circuits". I am only putting a 320 max watt load on each unit/circuit...13.33 a= 320w/24v...2 -230 watt solar panels wired in series and 2 250 Ah batteries in series per "unit/circuit". I need to keep it simple because unskilled Haitians will have to service it until I can get back to Haiti. I do value your opinion on the following...I was going to pipe the whole building in 3/4" and 1/2" EMT, but since it's 24 volts, what is your opinion of just wiring it ( 24 volts) in just split loom plastic wire cover? no more than 4 wires in any piece of the split loom. (trying to save money) It is just lighting and fans...the only piece accessible to the public would be the switch leg. I agree with you I do need a couple of 120 volt inverter circuits to run AC tools and appliances should the need arise. The school will use laptop computers as money become available to purchase...I am building a lockable case for the computers where i will put in a 24 volt charging station for them, and step the voltage down to 19.5 to charge the computers inside the cabinet, but in my testing I find that DELL puts a chip in their computer so you have to use their charger. Right now the school has some Lenovo laptops, which allow me to charge using a stepdown transformer. But who knows about the future, so I should allow for future inverter use for the computers. Thank you for taking the time to answer.
I would not use conduit for 24V unless rodents are present.
Maybe considder using armored wire if necessary because the price of EMT has gone up so much (more than $1/ft.)
 

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