inverter to panel wiring

[jerry f]

How do you wire an inverter (not a charging combo unit) to a panel so only 2 breakers are powered by the inverter but on shore all are powered. I understand you can cut or seperate the bus for the 2 breakers but then shore will only power the others not isolated. I thought of a wire from the load side of shore breaker to each bus but then the inverter will follow that path to also feed both buses. Expertise wanted.....

[Alan Wheeler]

Well firstly you must have both shore power and Inverter power isolated. To say that another way, the shore power must be isolated from the AC circuits when the inverter is running and when the Shore power is running, the inverter must be the one isolated. Both Phase and Neutral lines must isolate. A two position switch can be used, but a three position with centre OFF is a better choice. This is for two reasons. Positive isolation of both circuits during switching and the fact that I can isolate the AC circuitry by selecting the OFF position. I use a rotary type on my panel.
It needs to be a multi pole with probably four or six poles. This part gets a little hairy to explain and you may be best to get the aid of a sparky to draw a simple circuit.
But effectively, one pole set will switch phase and neutral between Shore and Inverter and the other pole set will be wired in such a way so as to bridge and unbridge the two circuit breakers from the shore feed and to the inverter feed.
Hope that helped

[Rick]

Right! You need to "split the bus" of your ac breaker panel. If the breakers that you wish to serve with the inverter output are identified you must cut loose the hot wires from the breaker panel that goes to them.

What is often more difficult is to identify the neutral wires which serve those breaker outputs. Most often these neutral wires are all bussed together with no identifying markers. One way to identify them is to plug a lamp into the outlets served by the breaker and one-by-one remove neutral wires from the bus until the lamp goes out and mark the wire.

You then can use an automatic transfer switch or a manual one to switch the breaker hot and neutral wires (you therefore need a "two-pole single-throw" switch) between the two sources (shore power main breaker output or the inverter output). The switch will have six terminals (or more).

An automatic transfer switch uses a relay whose coil is wired to shore power (usually with a short time delay to prevent relay chattering should a shore connection be not always solid) so that when shore power is present the relay contacts deliver power to the desired breakers from shore power. When shore power drops out the relay makes a connection to the inverter output.

Rick

[Alan Wheeler]

Oooh, I like that relay idea Rick. I never thought of that. Hmmm, yet another project put onto the list

[GordMay]

Jerry:
You might begin by telling what inverter (make & model) you are installing.
As previously noted, many inverters have an integral transfer switch (or relay), sometimes tagged "automatic bypass (idle mode).

[davemaskell]

if the inverter is an automatic transfer all you do is feed the inverter from a spare breaker, pick up a neutral, go to the inverter, and bring the load side back to the panel. cut the bus so you isolate the breakers you want to feed,put the hot from the inverter on them, and take those feed neutrals to a seperate bus and put your inverter neutral on with those neutrals.

[jerry f]

Gord, I was planning on instaliing a xantrex prowatt 1750 and I like Wheelers plan of a multi-pole switch.What do you think and does anyone have a company and model of such a switch.This inverter does not have automatic switching.

[GordMay]

Jerry:
You are contemplating a relatively simple modification (utilizing the “Prowatt”), which is difficult (for me) to describe in words.
E-mail [or PM, or tel: (807) 622-3600] me a FAX number, and I’ll fax you a simple wiring diagram.

You don’t need any Neutral to Ground Switching. The Prowatt could be wired to always feed the (cut & isolated) “Essential” circuits off battery power without any switching at all ...

or the preferred method, where

The (isolated) “Essential” circuits could be wired to a double pole - double throw (DPDT) switch, wherein they are powered from either the AC Shore Power Panel, or the Inverter.

Added Later:
This system can always power the "Essential" loads, but requires that you manually switch the "Essential" loads to Inverter Power (When Shore Power Unavailable).

Regards,
Gord

[jerry f]

Gord, my fax is 952-322-1295.Thanks for the help. Jerry