Inverter Upgrade

[ckerrick]

The original inverter has failed on our 2013 25' RB International. Original inverter is an obsolete 600 watt unit, intended to power only a television, DVD player or other low power items. We are running two Trojan T105 6 volt batteries with 225 total amp hour capacity (112 useable) and have two 100 amp solar panels on top. After doing some research into inverters, I am considering upgrading to a 2000 watt pure sine wave inverter in order to be able to run the microwave (1350 watts) for short periods off the inverter/batteries. I understand that I'd have to install heavier 1/0 battery cables with a protection fuse, and that I'll need an inverter with a transfer switch to continue to use the existing Airstream setup which allows for use of either shore power circuits or inverter circuits. If I upgrade the inverter to run the microwave I assume the microwave must be plugged into an inverter outlet rather than the house/shore power 120V outlet it's plugged into now. Is there a wiring/connection solution that would allow me to run the microwave off the inverter circuit when dry camping or off a house/shore power circuit when connected to shore power? Is this feasible? Advice please? Thanks!

[uncle_bob]

Hi

Done properly, an inverter setup involves a transfer switch. In one position, the switch connects "stuff" to the shore power. In the other position it connects the same stuff to the inverter output. There are some subtle issues about neutral to ground bonding that need to be properly handled on both sides of the switch ( = you want a bond in the inverter mode and it can not be there in the shore power mode).

If you have a bunch of circuits that are on the "output" of the transfer switch, a separate box is often used to handle this or that. If the wiring is more simple, you might do with some fuses and a bit of this and that.

Battery wiring / fusing to the inverter needs to handle the maximum current the inverter can draw. Inverters have a bunch of ratings. An inverter that puts out 2KW constantly might well put out 4KW "peak". Is peak a second, a 1/60 second, or 2 minutes? It depends a lot on the exact inverter you bought. While the battery may be putting out 12.6 normally, the inverter may drop out at 9 or 10V. If you take 4KW at 9V, that's a *lot* of current.

All of that is very manufacturer specific. You can indeed find "2KW" inverters that get wired with 4/0 cable and 400A fuses. No, they don't all get set up that way. Yes some manufacturers are a bit "over the top" on their recommendations.

The only real point is that you need to do some digging on the model inverter you buy. You need to be sure it will handle the continuous duty loads you will be running. You need to make sure it has cables adequate for its needs.

Bob

[s1000pre]

I installed an additional 1,800 watt progressive dynamics pure sine inverter to power the microwave, galley outlets, or bath outlets. It works great and allows you to use the oem 14 awg wiring. A 2,000 watt will require you to re-wire the outlets using 12 awg. and upgrade breakers to 20amp. I kept my 1,000 watt inverter as well to keep from potentially overloading the circuit while running the TV’s and microwave simultaneously, you might want to do the same. It was a fairly easy install.

[1StreamDream]

Originally Posted by s1000pre

I installed an additional 1,800 watt progressive dynamics pure sine inverter to power the microwave, galley outlets, or bath outlets. It works great and allows you to use the oem 14 awg wiring. A 2,000 watt will require you to re-wire the outlets using 12 awg. and upgrade breakers to 20amp. I kept my 1,000 watt inverter as well to keep from potentially overloading the circuit while running the TV’s and microwave simultaneously, you might want to do the same. It was a fairly easy install.

Stewart, I had exactly this line of thought, can you share any additional specifics about how you did this wiring ? Did you move the 120VAC wall circuit that feeds the microwave outlet to the inverter, and thus now you always have to power the microwave from the second inverter ? Or do you have something different in your wiring scheme ? Also, did you add any battery capacity to support this (I currently have 200A of BB LioN, was thinking I might need to go 300A if I wanted to power the microwave that way). If you have any photos of where you placed the second inverter, that might help me visualize how I can do the same. I have a 25' RB(twin), the inverter is under my longer bench in the kitchen, I don't have much additional space in there. Thanks in advance for any other details you can offer.

[s1000pre]

Originally Posted by 1StreamDream

Stewart, I had exactly this line of thought, can you share any additional specifics about how you did this wiring ? Did you move the 120VAC wall circuit that feeds the microwave outlet to the inverter, and thus now you always have to power the microwave from the second inverter ? Or do you have something different in your wiring scheme ? Also, did you add any battery capacity to support this (I currently have 200A of BB LioN, was thinking I might need to go 300A if I wanted to power the microwave that way). If you have any photos of where you placed the second inverter, that might help me visualize how I can do the same. I have a 25' RB(twin), the inverter is under my longer bench in the kitchen, I don't have much additional space in there. Thanks in advance for any other details you can offer.

I added the bath outlet, and galley outlet to the 15amp microwave circuit. I then ran this through the 1,800 watt inverter. This way it runs as it does when plugged in to shore, or I can run it off the batteries.
I do have 3 100amp BB’s, I’m not sure if 200 will suffice, check with BB. My Victron shows a 160ish amp drain when the microwave is running off of the inverter.
My inverter is mounted on the inside wall of my front compartment opposite my oem inverter. I ran two 14awg wires. One back to my oem 15amp microwave fuse. The other to the microwave outlet. The inverter is powered by 4awg wires connected directly to my batteries.
Outlet Wiring: I found the oem 14 awg wire for the microwave under my cabinets. I cut it and connected to the 14awg wire from the inverter. I also found the wire powering the galley and bath outlet, I cut and connected to the same 14awg connected to the inverter as well.
Feel free to call with for specifics, some of this is easier explaining over the phone. 612-819-5593 PST.

[ckerrick]

Stewart, thanks for info regarding your installation. I'm not very knowledgeable nor experienced in electrical work, so anticipate having the local Airstream dealer do the inverter replacement installation and wiring for me. I want to be sure that the 2000W inverter is wired correctly/safely. From speaking to inverter sales people I have been informed that for sure I need to upgrade battery cables to 1/0 and to add at least a 200A inline fuse. The topic of inverter outlet wiring or circuit breaker wasn't discussed. You said Airstream put in 14 AWG when built, but that you upgraded to 12 AWG. Is this something I should ask Airstream to do... to rewire that inverter outlet with heavier wire? And is upgrade of the related circuit breaker to 20A a necessity for safety?

My thought on connecting the microwave is to simply run a heavy duty extension cord from the microwave (above the refrigerator) over to the wall where the TV is (between refrigerator and sofa/dinette seating) so it could be plugged in to the inverter outlet there when using battery power or plugged into the adjacent 120V outlet when using shore power. Otherwise, maybe the microwave could be plugged directly into the inverter itself? Please advise. Thx.

[s1000pre]

Sorry for the confusion. Some of this is easier discussed via the phone. I did not re-wire with 12awg. The Progressive Dynamics 1,800 watt inverter does not require 12awg which is the reason I went this direction. I was able to use the existing oem 14awg wiring. All I had to do was splice in here and there, eliminating the need to re-wire. I purchased all items necessary on Amazon. I added a 300 amp fuse between the 300 amp buss bars I installed. I then added breakers between all other connections. I’m not sure what your electrical or mechanical capabilities are. It’s not as complicated as it sounds. You connect all of the wires. The fuse was the last item I added on the positive leg. Once the fuse was installed, I set all of the breakers. I saved thousands doing it myself, though it did take a good three or four days to complete.