Inverter feeding main panel-why not? - Montana Owners Club

Ozz · 03-24-2011, 01:59 AM

I don’t want a sub-panel. I want the OPTION to have all (120 volt) circuits hot if I wish to plug something in, or turn something on.
If I want to plug a device somewhere that I wouldn’t have planned on with a sub-panel, I can use that outlet, or circuit.
I know the limitations of an Inverter on a battery bank, so I must be selective on individual, and multiple power loads.
I know there is a limited amount of battery power available as well.
The reasons I chose the Magnum MS2812 Pure Sine wave, is that it is a ‘Hoss’
It is 2800 VA continuous power (23 amps) 3900 surge for 5 seconds, 3200 watts for 5 minutes and a smokin’ 30 minutes of 3,000 watts surge.
All this at 90% efficiency with a small no load 30 watts stand-by.
I am using 6 Golf cart batteries.
The charging and Inverting aspect is an obstacle I am addressing.
As you know, you can’t charge the battery bank when you are Inverting.
I think I can use two relays, a 40 amp contact rating two-pole 120 volt coil for the Inverter charger power supply, then a small 120 volt coil N.C. relay to open the circuit to the 40 amp relay when it senses the power output from the Inverter supply.
The Inverter/charger on ‘Charge’ mode would have the 40 amp contacts closed, on ‘Invert’ mode, the contacts open.
All this would be automatic, a Ozz-transfer switch.
I could do this simply by flipping off the two-pole 30 amp switch I installed, or tripping the 30 amp supply breaker, but I want it to be automatic.
So, the only user select action would be the line voltage load management, I don’t think we would have any trouble with that, I have 3 wall-mounted displays that would be displaying the amp draw from the battery bank.
SO, why won’t this work? Am I missing something?

Ozz · 03-24-2011, 04:13 AM

Here are the controls: Works good on test bench.

firetrucker · 03-24-2011, 04:54 AM

Ozz, you're using the terms inverter and charger (and not converter) in a way that's left my head spinning. Since it ought to work (and I trust you've got it right), my only question is, is there a possible failure mode that will get the charger in trouble?

Bob

drknapp · 03-24-2011, 05:14 AM

I think you have a good idea.

Sounds like you are setting up a circuit similar to the Uninterruptable power supply in our computer room at work. Ours does charge the batteries while inverting. In our case this arrangement provides continous power in case of outages and also provides noise and voltage spike immunity for the equipment. There is also a circuit that bypasses the charger/inverter circuitry so that you can work on the system while providing power to the circuits.

I'm not an expert, but I think that the biggest thing you will have to watch for is to make sure that if you switch to "house" power you do break the circuit. You don't hit anything out of phase (if there are any motors on the circuits) as the inverter won't be synchronized to your house power.

Ozz · 03-24-2011, 09:41 AM

Quote:

quote:Originally posted by firetrucker

Ozz, you're using the terms inverter and charger (and not converter) in a way that's left my head spinning. Since it ought to work (and I trust you've got it right), my only question is, is there a possible failure mode that will get the charger in trouble?

Bob

Hi Bob,
It is confusing when you first talk about it, and in the details I presented, it gets really confusing.
Basically what we have is just an Inverter that gives 120 volt power when we camp 'off grid' from the batteries.
When we go to the campground to do laundry and dump the tanks, we are charging batteries and getting 12 volts just like the converter system many have. The campground gives us 120 volts; 30 amps or 50 amps.
The reason people use sub-panels when camping 'Off grid' and having Inverters power the 120 volts is that if you don't use a sub-panel, you are getting 120 volts, and also at the same time trying to charge the batteries. (Unless you flip off the breaker.)
In this case, the Inverter would be constantly switching back and forth internally, causing damage to the Inverter.
Another reason is that the Inverter will not power everything in the trailer, it has it's limits. Unless you have two wired together, you only get 120- no 220. Many folks would POSSIBLY overload the Inverter by having it power the main panel.
I will monitor my power usage, not running resistive loads (Heater, water heater elements)
My Half-time oven would probably only be used on the Microwave side of it, also the Coffee machine would be used in the morning when we are on Generator, charging batteries, like most folks do.
The key is to have automation. Automatic transfer switches, only one power source at a time. Generator, OR Inverter, OR 'Park power'
I have those automatic switches.
My automatic Inverter/Charger switch will take care of the 'Loop' problem.
Firetrucker and drknapp, as to the possible failure mode, I think I have protection in place for that. I work with these relays and contactors, they cycle millions of times and rarely fail. The controls pictured are what is in the transfer switches that are in all RV's with Generators.

rollie41 · 03-24-2011, 10:43 AM

Ozz, I just completed an instillation similar to what you are talking about. I am using my main breaker panel to supply to the trailer. I have 4 sources, Front shoreline (I added a new receptacle), rear shoreline, inverter, and generator. I don’t want to worry about which source is in play so I removed the main cable from panel and moved it to the basement, installed a new line from the panel to basement with male plug, added a new 3 new lines to the basement and installed 4 Female receptacles for them. Now I just plug in the source I want to use and use breakers to select where it goes. I leave the autoformer and surge protector there for when deeded. I'd add a picture but can't figure out to do it.

firetrucker · 03-24-2011, 10:45 AM

Ozz, now that I've looked up the Magnum and realize that you have a dual purpose unit, everything makes sense.

I'm not sure why you're cascading relays, though. Don't you want to kill the ac input to the inverter when an ac output from the inverter is detected, just like flipping the breaker? Seems like if you don't break that line, then the inverter is still going to toggle.

Bob

Ozz · 03-24-2011, 10:54 AM

Rollie, that is a great idea, a little different than mine, but should work super! My friend if you are smart enough to do that, you can whip the old photo problem!

Bob, that is exactly what my two relays are doing, the N.C. contacts allow power to the charger in the Inverter, when voltage is detected from the Inverter side to the panel, the small coil is energized opening the contacts killing the power to the charger. Silly simple

rollie41 · 03-24-2011, 10:55 AM

got it I think

Ozz · 03-24-2011, 11:02 AM

Yes you did, looks as clear as can be. Neat work.
Is that male plug ever 'hot' when not plugged into it's mate?

7.3Ford · 03-24-2011, 11:26 AM

Ozz,

I also powered everything with my inverter. I have a 50Amp Transfer switch, which transfer shore power or inverter/generator. Output from transfer switch goes to EMS-HW50C Electrical Management System, which feeds main bus. I still have the original converter, but I installed a wall switch to turn it on/off. Another transfer switch would make it automatic, but I was cheap.

Most times I just let the solar panels charge the batteries, and leave the converter off when hooked up to shore power, but I can turn it on when hooked up to shore power or generator if batteries are way down, and it is a cloudy day (not often I have to do that).

Ozz · 03-24-2011, 11:54 AM

Good system, nothing wrong with a little 'switch flipping'
I really like the idea of the main panel feed, I like the option of having all outlets ready to use.
I like your solar option too

rollie41 · 03-24-2011, 12:13 PM

no is not hot, just the line from the 50A main breaker.

Ozz · 03-24-2011, 01:10 PM

Quote:

quote:Originally posted by rollie41

no is not hot, just the line from the 50A main breaker.

Rollie, would your panel feed be plugged into it when needed?
Would it be live if you were plugged into shore power and nothing plugged into the male outlet?

rollie41 · 03-24-2011, 01:56 PM

no, panel is isolated and feed by panel feed line, both shorelines terminate at female plugs along with generator and inverter in basement. only way to power trailer is threw panel feed line.

Ozz · 03-24-2011, 02:04 PM

Quote:

quote:Originally posted by rollie41

no, panel is isolated and feed by panel feed line, both shorelines terminate at female plugs along with generator and inverter in basement. only way to power trailer is threw panel feed line.

You did a really nice job on your set-up, very neat as well.

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