Which is better: 48vdc or 110vac from source to multiple units

risingtiger

New Member
Joined
Mar 23, 2021
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2
Which is better: running 48vdc or 110ac from solar/battery shed to multiple points of load?

I will have the solar/battery unit about 100 feet from the house and about 75 feet from an Airbnb unit. Both locations will be primarily drawing AC power, but also some DC: I’m assuming about a 80%/20% split. The home will likely need roughly 2-3KW and the Airbnb would likely need about 1K.

It annoys me that, if I supply 110VAC to the units, I would be running through an extra DC->AC->DC hop for 20% of the load. But, then again, I would still have to convert 48VDC to 24/12VDC for final use anyways, so it might be a illogical concern.

Is it standard practice for solar system designers to run one inverter at the batteries so that power is traveling as AC to multiple units (over less expensive wire)? Or is there an argument to run 48VDC to the units (over more expensive wire) and have an inverter at each unit?
 

Alphacarina

Solar Enthusiast
Joined
Feb 22, 2021
Messages
215
Assuming you don't want to run both AC and DC power to both places, IMO you really only have one choice - Put the inverter in the shed with the batteries and run AC power to both buildings and then convert back to DC as necessary. But, if the DC loads are small, you could run both AC and DC feeds - Small DC loads wouldn't require big cables

A 100 foot run of 48 volts DC to power a 3KW inverter in the house would require LARGE battery cables to deal with the voltage drop, where 3KW of 120 volt AC could probably be handled by 10 gauge Romex - The current in a DC feed to an inverter in the house would be more than twice as much and require large wire sizes to keep the voltage drop manageable

Don
 

risingtiger

New Member
Joined
Mar 23, 2021
Messages
2
@Alphacarina. I think you're right. 110VAC seems to be the best option. I think 48V is about where I'd want to be. I suppose if someone wanted a larger battery bank in series they could pull 120VDC direct from the batteries and then just zip DC power to the house on affordable cables.
 
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