Wiring House For DC

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mbrooke

mbrooke

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I need a few pointers. Solar panels + storage batteries. 12/24 volt DC to lights and outlets.

What does code require in summary? Anything special? How do I ground the system? Do I need an EGC? OCPDs? Charge regulator?
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
mbrooke said:
I need a few pointers. Solar panels + storage batteries. 12/24 volt DC to lights and outlets.

What does code require in summary? Anything special? How do I ground the system? Do I need an EGC? OCPDs? Charge regulator?
Click to expand...
I'm dodging your questions 😇, but just wire it for AC. DC is not worth the hassle. If it's a super small system use a Morningstar SureSine inverter.
 
tom baker

tom baker

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Art 720 dates from the 1930s and is for dc wiring, when farms had dc lighting plants. Do a google for delco lighting plants.
Its the shortest article in the nec.
 
tortuga

tortuga

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Oregon
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mbrooke your doing some interesting projects these days.
The old delco systems are very interesting, they were 32 Volt nominal. My first house I bought was built (in Oregon) around 1901 before grid power here. It had some strange knob and tube, like 8 awg and 10 awg to lights only, I later concluded it was for a 32 VDC system.

I have a design I have been working on for a remote barn on a produce farm, It will be based on a 127 volt DC battery bank with BMS (used Leaf EV).
Then it wall have a 120 DC panel for DC water pumping, other motors in the barn, and lighting loads.
And a 120 DC / 120 AC inverter.
120Vdc bus is a standard for "industrial" UPS's, called a "low bus", also marine (Navy) and rail, so there is surplus equipment to be had in that rating.
The one hiccup with it is there is no 120 VDC charge controller for the PV supply.
 
romex jockey

romex jockey

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Vermont
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electrician
MBrooke
take a gander @ >>>

Part II. System Grounding
250.20 Alternating-Current Systems to Be Grounded.


<<<<<<snip>>>>>>>>>

(A) Alternating-Current Systems of Less Than 50 Volts.

~RJ~
 
S

suemarkp

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Location
Kent, WA
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I think SquareD QO breakers are one of the few rated to interrupt DC loads. We tend to distribute 28 VDC in some of our facilities. A 5-30 receptacle is a common choice, as we don't use thsoe for 120VAC circuits (they'd get the locking L5-30 instead).
 
mbrooke

mbrooke

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Location
United States
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Technician
tortuga said:
mbrooke your doing some interesting projects these days.
The old delco systems are very interesting, they were 32 Volt nominal. My first house I bought was built (in Oregon) around 1901 before grid power here. It had some strange knob and tube, like 8 awg and 10 awg to lights only, I later concluded it was for a 32 VDC system.

I have a design I have been working on for a remote barn on a produce farm, It will be based on a 127 volt DC battery bank with BMS (used Leaf EV).
Then it wall have a 120 DC panel for DC water pumping, other motors in the barn, and lighting loads.
And a 120 DC / 120 AC inverter.
120Vdc bus is a standard for "industrial" UPS's, called a "low bus", also marine (Navy) and rail, so there is surplus equipment to be had in that rating.
The one hiccup with it is there is no 120 VDC charge controller for the PV supply.
Click to expand...


Do you really need a charge control? 😀

I'm still debating if I should sub-dived the batteries into smaller fuse protected groups. As well as the panels.

And idea of I need an EGC to all the metal parts?
 
Fred B

Fred B

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Location
Upstate, NY
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Electrician
Might want to check out Article 690 (NEC 2017), it has a lot of requirements.
690.41 covers grounding and bonding. Of interest there is requirements for ground fault protection.
Also of note 690.11 (will make some irritated) requirements for AFC Protection.
Charge controller is good idea regardless (some small systems it's integral to units) as the solar will keep generating and sending charge to the batteries and potentially overcharge (can have catastrophic consequences) without some form of regulation.
mbrooke said:
I need a few pointers. Solar panels + storage batteries. 12/24 volt DC to lights and outlets.

What does code require in summary? Anything special? Yes
How do I ground the system? Article 250, Article 690.41
Do I need an EGC? Maybe, most likely Yes, Article 690.41(A) Article 690.43 to 690.50
OCPDs? Yes, maybe, Article 690.9
Charge regulator? Yes, Article 690.71 & 690.72, also reference because of storage batteries Articles 706 and 705 applies
Click to expand...
Would recommend full review of Article 690, 705, & 706 as depending on your configurations different sections apply differently.
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
mbrooke said:
Do you really need a charge control?
Click to expand...
Yes, for the use case I am working on of ultra rural water pumping & farm related, the solar stings can be 480 VDC, plus you want to use MPPT Technology.
There are 120 DC charge controllers out there on the international market.
I was hoping midnight solars new controllers would fill that niche, but sadly not.
 
tortuga

tortuga

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Location
Oregon
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Electrical Design
LarryFine said:
I believe Edison was for DC, but Westinghouse went with Tesla's AC.
Click to expand...
Thats how I understand it, Edison had a hold on NYC with DC, Westinghouse and Tesla setup Philly with two phase AC.
As the storey goes Tesla ended up living his last years in one of the last hotels in NYC that was 110/220 DC.
 
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