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wiring details of ground-mount system w/ string inverter, plus generator backup

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  • #16
    Thanks for chiming in ...

    Originally posted by Ampster View Post
    My understanding is most line side taps are done because of buss capacity issue. Either the calculation about the buss Amperage capacity or just no more room for an additional breaker. Clearly adding a breaker is simpler with no downtime or need to coordinate.
    I'm not worried about the down time, esp. since trying to minimize that is something the bldg inspector is being proactive about. And yeah, my panel is pretty full. OTOH, when/if I implement the critical-loads subpanel (in my drawing), that'll free up lots of room.

    I understand now. Those are a cost effective solution to the issue of power outages.
    Well, the cost is low but I'm not sure how high the effective is; only works when the sun shines, and I've got shading issues, so maybe I'll get close to the 2kW 3-4 hours per sunny day, if I'm lucky. But in an extended outage, that should be enough to juice up the Leaf's battery a little (the Leaf then powering some critical loads).

    My separate inverter is a way to provide some portable backup to my relatives in case of an emergency. In the process I discovered the capacity of the DC to DC converter that allows me to pull over 100 Amps at 12 volts that running 1500 Watts of power would require. I currently can connect the inverter with jumper cables to my 12v battery. Long term want to set up Anderson connectors to make it easier and safer. It is only intended to be used on an 120 volt extension cord and I have no plans to connect it to to an Generator input for a critical loads panel. In my case my critical load panel would require 240 volts anyway.
    The Leaf's DC-to-DC is reputed to be able to source 135 amps (at 12vdc), but I decided to be conservative (and not risk damaging anything) by sticking with a 1kW inverter. It can power my fridge, the modem/router/phone, and a light circuit (LEDs, of course) in the living area (for a few days, I estimate).

    Also, this is cute, it allows me to cook with gas. Our dual-fuel range (electric oven, gas cooktop) will not allow the gas to flow if there's no electricity. But it has a 3-wire connection, IOW a neutral in addition the the 240vac hots. So if I connect a that 120vac inverter to both poles, then the 240vac part of the range sees zero volts (and of course, it wouldn't have enough amperage to run the oven anyhow). But the 120vac circuits, running off one hot and the neutral, work fine and don't draw much juice; and they let all the "logic" work, so the gas flows ! Will still work when I install a real generator inlet, I just wire the 120vac "hot" to both hots at the connector.

    You might be interested in this thread (, and I did something very similar: replaced the 12v battery hold-down with a custom connector which includes a big ANL fuse and an Anderson connector.

    One issue I've run into, the inverter has a GFCI outlet and an undefeatable ground-neutral bond. When I connected it to the main panel (in a very ad-hoc way when I tested it), the GFCI saw the bond and tripped (apparently they will do this, even though the neutral and hot currents aren't necessarily unbalanced). So if I expect my critical-loads subpanel to work with the Leaf/inverter, I need to be able to switch the neutral, which is non-trivial; or spring big bucks for a real transfer switch.
    Last edited by RShackleford; 02-27-2020, 03:53 PM.