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Old 06-30-2016, 09:48 PM   #1
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Stumped on Rooftop AC

My powering system is:
A 2000 watt, 6000 watt surge for up to 20 seconds AIMs inverter with 70 amp charger built in.
A 140 amp battery isolator between start battery and house batteries with a 225 AH bank at 50%.
300 watts of solar power with smart charge controller.
A 30 amp inlet for shore power on the exterior

What is your guys best way to avoid running my rooftop AC into my breaker box for that system? Or avoiding it's draw going through the inverter?
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Old 06-30-2016, 10:17 PM   #2
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I would plan on letting the AC draw go through the Inverter if at all possible. Some Inverters can sense load current during such things as a compressor starting up and share or balance the load to the batteries from generator if the generator or land-line can't feed load adequately. (Or even be programmed to limit current from AC input and disable/transfer functions when necessary.)

Or... if you have no plans to let AC run from anything but a generator/land-line I would isolate the circuits entirely. You could add a set of automatic transfer switches and configure them to switch loads depending on your needs of multiple load feeds.

...

After re-reading your question; Automatic Transfer Switches from land-line and your Inverter to two separate distribution panels/circuits would be best in your current situation.
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Old 06-30-2016, 10:39 PM   #3
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I'll look into the auto transfer switch. The thing is I thought a 2000 watt inverter with that good of surge should handle the rooftop AC. Start up was fine, but the inverter couldn't handle the cycle after a few minutes.

My theory on seperating the AC entirely is that even on the Airconditoning would be running close to my 2000 watt inverter maximum and would leave little room to use more electronics.

I plan on only using the AC from gen or shore connect. I was going to run the AC line to a 30 amp receptacle box but that would require a "suicide cord" to plug into the gen or shore power. what should I do to run the gen to the AC solely?
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Old 06-30-2016, 11:36 PM   #4
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Use an appropriate extension cord and just plug it into the genny directly?
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Old 06-30-2016, 11:49 PM   #5
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Why do you want to avoid wiring the AC into the breaker box?
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Old 07-01-2016, 12:02 AM   #6
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Because my inverters wired into the breaker box, and at 2000 watts the AC's draw would make it hard to use anything else with air conditioning.
Is there a way to bypass the inverter?
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Old 07-01-2016, 12:05 AM   #7
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Use an appropriate extension cord and just plug it into the genny directly?
I'd like to but I had purchased this as to solely run the Air conditioning to.


Wiring this would require a double male end cord.
Should I just do a seperate breaker box?
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Old 07-01-2016, 07:52 AM   #8
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im lost.. you want t orun the A/C only on shore power or the generator, correct?

why would the 12 volt inverter even be providing power if the genny is on or the bus is plugged into shore power?

during shore or genny power wouldnt the 120 volt transfer switched have alleviated the inverter so its now just sitting idle? and if your genny isnt running or shore power isnt connected then there is nowhere else to get power for the Air unit But the inverter so it has to go through it then..
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Old 07-01-2016, 12:24 PM   #9
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I'm in the same camp with cadillackid. Unless you want to run the AC off of batteries, then hooking it to the inverter would seem to be a waste.

What kind of AC do you have? You can also look into getting a "soft start" system for the AC that will drop that initial surge down if you want to run it off of the batteries.

Also, 300W and 225aH won't cut it for powering an AC through an inverter.
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Old 07-01-2016, 03:03 PM   #10
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Let me check whether I'm following along: there's a rooftop AC which needs to be hard-wired to somewhere. There's a circuit breaker panel feeding circuits to receptacles and what-not. There's an inverter supplying power to that breaker panel. It's undesirable to wire the AC into the breaker panel because the inverter can't carry that load. Am I on track so far?

First thing that comes to mind is wire the AC into that panel and just don't turn it on while the inverter is supplying the power. If that's inadequate, the next step could be to automate: when the inverter is running, interrupt the thermostat control or power to the AC so that it cannot be turned on (ie install a relay; the more sensible thing would be to have shore power close the relay so that the AC can operate only when shore power is supplied).

For the cord-and-socket style of transfer switch what you need is called a "power inlet." They're used on boats, transfer switches where a portable generator would be temporarily connected, etc. It has male pins instead of a female receptacle; it's the opposite of the RV outlet you pictured above. Return that outlet or install it at the house as a place to plug your shore power cord in.

Here's one other option. Connect the AC directly to the shore power cord. Also connect a transfer switch to the shore power cord; this would provide the link so that the breaker panel can be connected to inverter or shore source.
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Old 07-01-2016, 08:04 PM   #11
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Automatic transfer switches and/or completely isolated manual transfer type circuits are still the way to go unless you want to add more batteries and copper coils to that Inverter.

(That Inverter can't handle the amperage for long enough to start the surge on most compressors; although maybe with higher AWG AC lines.)

...weight of the transformers is key in evaluating a heavy-surge capable Inverter.
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Old 07-01-2016, 08:09 PM   #12
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In my experience the best rule for Inverters/Chargers: If you can pick it up and mount it without a jack or another person it's not meant for running heavy loads continuously and reliably.
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Old 07-03-2016, 12:00 PM   #13
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Boy... My memory is not what it use to be....

I addressed the exact same issue when I did my last bus (20+years ago).

As I recall, I placed all of the "inverter" loads on sub panel and placed the inverter inline on the circuit that fed the sub from the main panel.

Upon the loss of shore or genny power the inverter (with transfer) would kick in and support the loads fed from the sub panel.

I am re-reading my own description and I am not sure that I am being clear. Let me see if I can place a picture. It was really a simple installation.
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Old 07-03-2016, 12:06 PM   #14
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Boy... My memory is not what it use to be....

I addressed the exact same issue when I did my last bus (20+years ago).

As I recall, I placed all of the "inverter" loads on sub panel and placed the inverter inline on the circuit that fed the sub from the main panel.

Upon the loss of shore or genny power the inverter (with transfer) would kick in and support the loads fed from the sub panel.

I am re-reading my own description and I am not sure that I am being clear. Let me see if I can place a picture. It was really a simple installation.
That's what I was trying to go for thank you!
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Old 07-03-2016, 12:28 PM   #15
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Thank you everybody for your help. Y'all ever have the experiences where you over think something so much that any solutions become Cloudy? Bingo right here

I ended up with this set up: two seperate panels seperating the Air conditioning load!

My first set up is like this. Since this picture I've added two more 225 AH batteries to the equation giving myself 500AH bank.
I've also got 1/0 gauge cables from batteries to inverter. As well as ran a 140 amp smart isolator from start to house batteries. This system will be powered by isolator/solar down the road and will mostly just be charging phones/laptops or George foreman.


I mounted the inlet on the outside for shore power/ genny connect if batteries get low.


I ran 10 gauge Romex from rooftop AC to my back storage area and to a seperate panel box like this:




The storage are will house my cbr600, fishing stuff, and a small woodworking shop for my girls etsy shop. I just got a champion 3100 inverter genny that will be housed back there down the road to run the AC. I was worried about vapor coming through the back into the interior. But after insulating with vapor barrier, spray foamed the cracks, batting insulation and sound deadening board. Plenty of space back there and Windows for ventilation. I did take the advice and put a lawn mower back there and drove down the road.

Heres a picture of the kitchen I'm building since I have posted in awhile. Thank you guys!
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Old 07-03-2016, 12:34 PM   #16
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Sounds like you did a good job of isolating the area but I would still recommend at least a powered exhaust vent (12v) that is wired to run any time the genny is turning. I just hate waking up dead.
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Old 07-03-2016, 12:42 PM   #17
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Sounds like you did a good job of isolating the area but I would still recommend at least a powered exhaust vent (12v) that is wired to run any time the genny is turning. I just hate waking up dead.
Like a fantastic vent in the back?
My two ideas where to mount the genny on a shelf next to the window with exhaust pointing out.
Or to weld up a cage on a cart and wheel the genny outside and lock it to the bus at nights.

I did put a C02 alarm inside the bus and inside the storage area too.
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Old 07-03-2016, 12:54 PM   #18
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Anything (like a fantastic vent) that will create negative pressure in that area and vented outdoors will help but directing the exhaust outside is definitely better. And if you intend to run it while going down the road...that can create a whole nuther set of issues. Aerodynamics could easily overcome a vent. And if going the re-directed exhaust route, you still need to have it positioned so that it won't get sucked right back inside.

I am putting mine on a small rear deck with an exhaust extension going up just above the rear roof line.

There have been way too many RV deaths associated with both genny & engine exhaust fumes, even in high end, factory built units, so just try to play it as safe as possible.

And the CO2 alarms are a must have. A propane alarm is a good idea too.
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Old 07-03-2016, 04:32 PM   #19
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Anything (like a fantastic vent) that will create negative pressure in that area and vented outdoors will help but directing the exhaust outside is definitely better. And if you intend to run it while going down the road...that can create a whole nuther set of issues. Aerodynamics could easily overcome a vent. And if going the re-directed exhaust route, you still need to have it positioned so that it won't get sucked right back inside.

I am putting mine on a small rear deck with an exhaust extension going up just above the rear roof line.

There have been way too many RV deaths associated with both genny & engine exhaust fumes, even in high end, factory built units, so just try to play it as safe as possible.

And the CO2 alarms are a must have. A propane alarm is a good idea too.
+1

Serious Stuff!! Carbon Monoxide is really a silent killer.

I personally recommend placing the generator outside the living space. I have done a couple of these where we extended the rear bumper and installed something similar to the APU boxes on semi trucks. Or, on the Eagles we place the genny in the engine compartment (rear) and ran the exhaust out next to the bus exhaust.

In all cases exhaust was run well outside of the exterior of the bus and exited to the rear.

I, with very rare exception, do not run the genny while sleeping. Just my cautious nature.

I do recommend an alarm as well. I would suggest a CO monitor as opposed to a CO2 monitor. The first goes off in the presence of Carbon Monoxide as is found in exhaust gasses. The second goes off in the presence of Carbon Dioxide as is found in...... Beer....

I make a little joke but don't be mistaken, CO poisoning is really a serious concern. In lethal concentrations it can still be undetectable.

Be Safe.

S.
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Old 07-04-2016, 11:50 PM   #20
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Tango would this out the window be sufficient? Same precautions as before plus this. I'd make my own but on a time crunch before s trip from FL to Texas.
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