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dc73 · 01-21-2021, 10:45 PM

Installed two small inverters in my 2005 Winnie. One next to the bed in the back for CPAP for dry camping, phone charging for passenger while driving, etc.
Another one is installed in the living room mainly for device charging while driving. If we dry camp and need 110 AC we will just run the generator. These are just light duty inverters. The bedroom one is an Everstart 400w (800w max surge). The living room one is a Wagan Tech 500w (1000w max surge). I did lots of research but found conflicting information about wire sizing. I ended up going with what I felt was safe - 10awg directly to batteries.

For the bedroom inverter I ran the positive wire in a split loom under the rv, along the frame, back to the propane tank bay, where I drilled a hole to allow the wiring to pass by the gray water tank and enter the coach under the bathroom vanity. This is right next to the bedroom, so I was able to mount the inverter to the wall there. This run was approximately 30 feet one way. The Everstart has a 35amp blade fuse built in.

For the living room, I ran the wires into the bay next to the battery bank, up through the floor and mounted the inverter to the wall behind the swivel chair. I wired in a 10awg inline blade fuse holder with a 40amp fuse.

Neither of these are going to be heavily taxed. Some online sources would recommend much heavier cables. I found others that verify what I did is fine. Attached is a picture of one chart found at www.theinverterstore.com.
What do you all think?

Another question - the Wagan 500w inverter has an additional chassis grounding screw. How critical would this be to connect? For now I left it open, but it wouldn't be hard to run a grounding wire.

twinboat · 01-22-2021, 04:50 AM

My question is, did you place fuses on the end of the wires where they connect to the battery or higher power source.

Fuses protect the wiring from shorting out or overload, not the device it powers.

Any lighter gauge circuit needs to have a fuse or breaker at its source.

It's just like a home breaker panel. The breakers are near the meter and incoming electric, not near the outlets.

As far as using 10 guage wiring, if its not heavy enough, the inverters themselfs will let you know by sounding alarms or shutting down.

Psneeld · 01-22-2021, 05:07 AM

Agree with twin boat...

Should be fused at the battery ends...the wiring seems entirely too light (especially the 30 foot run) based on my wiring tables but yes you may get routine shutdowns/alarms.

As to the grounds...not sure why there is 2, would have to see what the manuals say....or call the manufacturer.

I am unfamiliar with that wiring chart, but I am assuming it agrees that your wiring is way too light.

twinboat · 01-22-2021, 06:23 AM

I took a look at the website you referenced.

The example and chart is all based on a 24 volt battery and inverter system.

Our RV are 12 volt systems. When you 1/2 the volts, you must double the amps.

With the present wiring, you will be ok with drawing about 1/2 the wattage of the inverter.

Psneeld · 01-22-2021, 07:40 AM

I would still check a 12V wiring guide...not sure DC wiring is rated linear to amperage...but it could be...I am not sure.

And if only drawing 1/2 the load to protect the wiring...it must be fused at that amperage or it is a probable hazard.

dc73 · 01-22-2021, 08:14 AM

Quote:

Originally Posted by Psneeld

Agree with twin boat...

Should be fused at the battery ends...the wiring seems entirely too light (especially the 30 foot run) based on my wiring tables but yes you may get routine shutdowns/alarms.

Yes I wired and inline fuse near the battery on the 500w inverter. All I had for now was a 40amp fuse, but could add a larger one later. The 400w inverter has a 35amp replaceable fuse built into it, so that's a long ways from the battery. Maybe I should add another one near the battery.

As to the grounds...not sure why there is 2, would have to see what the manuals say....or call the manufacturer.

The second ground is a chassis ground (chassis of the inverter itself), to ground it to the chassis of the coach.

I am unfamiliar with that wiring chart, but I am assuming it agrees that your wiring is way too light.

The 500w inverter - 500w/12v=42amp. Chart shows that a 10awg cable supports up to 55amp, and again, I won't be maxing it out.

dc73 · 01-22-2021, 08:18 AM

Quote:

Originally Posted by twinboat

I took a look at the website you referenced.

The example and chart is all based on a 24 volt battery and inverter system.

Our RV are 12 volt systems. When you 1/2 the volts, you must double the amps.

With the present wiring, you will be ok with drawing about 1/2 the wattage of the inverter.

Correct me if I'm wrong, but look at that website again - The example is a 24v system, but once you do the math and arrive at an amperage value, the chart doesn't care what voltage it was. The chart is just showing amperage.

dc73 · 01-22-2021, 08:20 AM

Quote:

Originally Posted by twinboat

My question is, did you place fuses on the end of the wires where they connect to the battery or higher power source.

Fuses protect the wiring from shorting out or overload, not the device it powers.

Any lighter gauge circuit needs to have a fuse or breaker at its source.

It's just like a home breaker panel. The breakers are near the meter and incoming electric, not near the outlets.

As far as using 10 guage wiring, if its not heavy enough, the inverters themselfs will let you know by sounding alarms or shutting down.

The 500w inverter (5 foot run) has a 40amp fuse at the battery. The 400w inverter (30 foot run) has a 35amp replaceable blade fuse built into the inverter itself, so it seems like I should wire in a fuse at the battery.

Sbrownstein · 01-22-2021, 08:24 AM

Agree fuses belong at the batteries, just like all of those "independent" loads like CO detectors, steps, etc. You could put a 35 amps fuse on each of your #10 runs. At 35 amps you can draw 300 watts or so from each inverter. Your 30 foot run will drop a lot of voltage at 35 amps...more than 2 volts and I bet the inverter would complain at that but you probably don't ever draw that much.

The separate ground on many inverters is because the DC connections are + and -, not ground. Makes the GFI work if there is one.

Bet you never have a problem unless your batteries are low!!!!!!

Move the fuses though.

twinboat · 01-22-2021, 09:01 AM

Quote:

Originally Posted by dc73

Correct me if I'm wrong, but look at that website again - The example is a 24v system, but once you do the math and arrive at an amperage value, the chart doesn't care what voltage it was. The chart is just showing amperage.

You may be right, but you didn't calculate voltage drop in the wire runs.

You draw 55 amps on a 10 gauge X 2 ( There and back ) wire run, and there will be a 3% volt drop.
With a 12 volt system, 3% volt drop will shut down the inverter.

So, yes it can carry the amps and not melt down but the inverter will shut down.

A wire gauge calculator will figure that for you.

It's also the reason inverters are often kept close to the battery and 120 volts is run the long distances. 1/10th the amps, so 16 gauge wire can be used. Even loaded up, 3% voltage drop of 120 volts won't hurt anything.

Persistent · 01-22-2021, 09:28 AM

Since the wire run is much longer than 2 feet, the fuse or circuit breaker near the battery is required. Fuse or breaker for long runs come from ampacity charts. My 1975 code book shows a 30 amps fuse or beaker for 10 awg wire. There is a separate chart in my book showing larger gauges for longer distances.

Look at the installation instructions for the inverters. They probably have a wire size and distance chart. Check manufactures website if instructions are not in the box. The wire size required for efficient use is dependent on the design of the inverter. The manufacturer is probably the only one who knows the design parameters.

Larger gauge wire is required for longer runs. However, Twinboat has it correct. The inverters will probably alarm or disconnect if 12 volt supply voltages drops below minimum due to line voltage loss or low battery voltage.

My 400 watt inverter quits and requires reset. I run it on 14 gauge wire with a 15 amp fuse for lower watt appliances like a CPAP without the humidifier heater.

I wish you good luck and happy trails ahead!

bakedalaskan · 01-22-2021, 12:30 PM

Everything you installed the inverters for you can do with just 12 volt dc. Your CPAP is a 12 volt machine. All you need is the 12dc cord for it. Take out the inverter and install a 12 volt cigarette receptacle. Your other charging needs can be done with a simple 12 volt usb port. The inverters are inefficient and will waste precious battery capacity.
https://www.campingworld.com/triple-...lt-102456.html
Go to Amazon and look up dual car charger socket.
Look up the car adapter cord for your CPAP.
Good luck

dc73 · 01-23-2021, 01:23 PM

Thanks to all who commented, your input is invaluable. Most likely will use and experiment with this setup for awhile, and when I am ready to mess with it again I will probably upgrade to a single large inverter for the whole coach, either with a couple of dedicated 110v runs or actually connect it in with the switching system.

These threads, this input from all of you is always very helpful. I would not know who else to ask for these questions! The learning that happens from here is amazing also.

Thanks again!