Inverter AC output on the existing camper power sockets

[Herve]

Hi,

Has anybody tried to wire an inverter so that the AC current is on the existing camper AC sockets?

It seems possible with a device like this:

PROwatt SW Inline Transfer Relay

www.xantrex.com

The FWC is 30 amps DC but only 7.3 amps AC as far as I understand:
they use the DLS-30: Page Not Found
So it should be possible to use this one isn't it?

Is it doable? Do you know how to wire it? Would it work only with their inverter, or any inverter?

Thanks,

Herve

 

[K7MDL]

It is doable. Easiest if you have a breaker or fuse panel (you should). Find the breaker/fuse that feeds your AC outlet and route it to the device input. The device output goes on to the AC outlet. Wire the inverter AC output to the device. This should be a fixed wired connection and not an AC plug. Not all inverters have fixed AC output wire terminals.

15 amps x 120VAC = 1800W before inverter efficiency losses. Assume maybe 85% efficiency and you are good for a 1500W output inverter size.

The DLS-30 AC current does not matter here since it will come from the breaker panel in parallel with the relay device. When shore power is on, the inverter output is bypassed (if the AC outlet is the only load) and all shore power goes to the AC outlet, breaker/fuse panel and battery charger as before. When shore power is off, the inverter supplies the AC power to only the AC outlet, and the DC charger is off (no AC input to run it).

If you insert the device on the wire coming into the camper before the breaker panel, then you will have a loop. When shore power is removed, the battery charger runs the AC inverter which runs the breaker panel which runs the battery charger, so it is trying to charge itself, but with efficiency losses, it is a losing game .

 

[pods8]

K7MDL hit it for you.

My biggest question is how much AC do you want to run? If it's a small/occasional load most of use fine a simple cig plug in inverter suits us just fine. If you're going to have a larger hard wired inverter then I could see trying something like this, but you'll need the battery bank to back it...

 

[Herve]

Thanks for the detailed explanation K7MDL! Yes, I have the breaker / fuse panel.

Pods8: I was thinking of putting a 1000w inverter. I have dual batteries.

I might try this and report back. Could take a few months, it is not at the top of my (very long) camper todo list!

On this topic, I also have the air conditioner installed by FWC. It is 515 watts, which not that much more than the AC only fridge I also have. I've always heard people say you can't run it on the battery. Can someone explain to me why? Could I at least run it for a short while just to get a blast of fresh air in my face, not to cool down the whole camper for a whole day in the desert? If that matter, I also have 85 watt solar panel on top of camper and can attach an additional 60 watt outside panel from plug on the back of the camper.

Thanks,

Herve

 

[K7MDL]

515 Watts? That seems rather small for an AC unit. A 9.2BTU unit run maybe 10 amps on 120VAC.

In any case to run it off the inverter it will draw a lot of current the entire time it is cycled on. At 515 Watts that is 4.3amps at 120VAC and about 43 amps at 12.0VDC. That is a lot of current drain for your batteries to do for any length of time. With 2 batteries of 100 amphrs of usable capacity each, you would get 4-5 hours run time, stretched a solar panel and the cycling rate. With strong sun and the extra solar panel and allowing for your DC fridge you might make it work for a couple hours per day certainly for minutes at a time to give you your cool air in the face effect . How fast you can recharge your batteries is the limit here, since by the time you want the AC off, the sun will likely be low or gone and you will not be able to recharge the batteries from a deep discharge. Running short periods of time will compensate for this.

You must also be certain your choice of inverter is rated for motor start and run currents, not just rated for running small appliances and chargers. Your compressor motors may have a high start current.

 

[Herve]

Yes, that's a lot of current! It's 4.9 amps at 115V so 47 amps at 12V.
But if I run the truck engine at the same time, then I would be able to use the inverter to power the AC without draining the batteries, isn't it?

I'm thinking of getting a 1000W inverter that is rated 2000W surge. The AC unit (see picture attached) is the one FWC installed states 515 watts and they told me "it will run on a 1000W generator but it's better to use a 2000W generator so it can run in eco mode (quieter)". So I think this will work, isn't it?

Thanks for the feedback,

Herve

 

[leadsled9]

I have the factory FWC air conditioner in my Hawk. I would not recommend running it off of an inverter with your engine running as that is very inefficient. You are far better off running it off of a Honda 2000 generator.

I have a 1000 watt inverter in my camper too, but would never consider wearing out my trucks motor running the AC for the camper. If you do the inverter installation yourself....you'd better be familiar with building heavy duty cables. I installed the Zantrex Prowatt SW1000, it has a surge capability of 2000 watts. Zantrex required that welding cable size 0 be used for the installation. That is large cable. See pictures.

 

[Herve]

Oh, I like where you put the awning crank handle and table leg.

I was thinking of putting the same inverter you have. Is there a reason you installed it outside and not inside the cabinets? Not enough room or for heat dissipation? I haven't looked at that yet.

Thanks,

Herve

 

[K7MDL]

A small generator is the way to go. Runs forever on a gallon of gas, and is as quiet if not quieter than your truck, especially if it is a diesel. Also good when your home pwoer goes out. If you have a gas home furnace and gas hot water and a microwave oven, it will run them easy and keep you in good warm and fed.

Run the AC off the generator direct. Can also be used to recharge your batteries after running the furnace on a cold night. Many can output 12VDC to charge a battery direct. hard part is storing it for travel some place and carrying the few gallons of gas. Carry a pump instead if you have a gas truck and pump fuel from your truck main gas tank.

 

[Stan@FourWheel]

I would recommend using the generator for the Air Conditioner.

Trying to use an inverter to run the air conditioner will put quite a load on things.

If you hook up the inverter, it would probably be best to hook it up directly to the battery/batteries with some big cables and a big in-line fuse.

Here are some sample pictures.

The smaller wiring in the cabinets in not designed for that amout of amps.

Hope this helps.



.

 

[MakersTeleMark]

Looks a lot like my setup. Really crappy blurry pic, but you get the idea.

 

[leadsled9]

I was thinking of putting the same inverter you have. Is there a reason you installed it outside and not inside the cabinets? Not enough room or for heat dissipation? I haven't looked at that yet.


I put it there both for heat dissapation and I didn't want to take up all of my cabinet storage with an inverter. The inverter has worked great, I highly recommend the brand and model.

Like Stan says....you need big cables. The manual calls for size 0. The last picture shows the size of the cables where they are attached to the 150A circuit breaker.

I no longer have a table leg to store as I have a Lagun Table Mount. Page 2 has pictures of my installation:
http://www.wanderthewest.com/forum/index.php?/topic/4643/page__st__10

 

[Herve]

Thanks for all the replies.

I have a 2000w generator so I'll keep using that for the air conditioner. I was just wondering if powering it using an inverter was a good idea or not for occasional use. It seems doable but not a good idea so I won't design my solution around that. I'm sure I'll end up trying it anyway, for science!

So I think I'm going to scale back a bit my plan. I'm thinking of getting this cheaper inverter:

http://www.amazon.com/Cobra-CPI-880-Inverter-output/dp/B001TE0IMG

And installing it under the cabinet, next to the main camper power on/off switch.
It's small enought to fit there, and I can just use the on/off switch on the inverter.

And I think I'll also get the Xantrex Relay to wire the camper 120V circuit to work with either shore power or inverter:

PROwatt SW Inline Transfer Relay

www.xantrex.com

Xantrex says only use it with their inverters but I don't see why it wouldn't work with this cheaper modified sine wave inverter...

I'll report back after I buy and install this.

Herve

 

[Herve]

So I finally installed my inverter.

I got this one:

http://www.amazon.com/Cobra-CPI-880-Inverter-output/dp/B001TE0IMG

I decided not to try to hook it to the camper AC circuit using a relay after reading this article. It looks like you can do so expensive (pure sine wave) inverters, but not with the cheaper one like the one I got.

I ended up with about 10 feet of cable between the battery and the inverter. It is more than what most manuals recommend. I went with gauge 4, which is big but not over the top. According to page 10 here, I should have about .3 volt drop, which I think I can live with.

It is working well. It even powers the air conditioner. I haven't tried for longer than an hour (it would empty both batteries in about 6 hours), but it's good to know I can use that in case I have to leave the little dog in the camper for a short while. Amazingly, the inverter fan was barely working after an hour of continuous high wattage use. This is one great little inverter.

I'm quite happy with where I put it, I think it will prevent me from tripping on cables, which I've been prone to do.

Here are some pictures.

Herve