installing a 2000w power inverter

[chevyluver]

Hi, I have a 2000w power inverter I pulled out of my semi truck. I used it in there to run my fridge and microwave. I was planning on installing it under the seat behind the driver area, over the battery box. My question is, if I make a power cord to plug  into the inverter, and into a 120v outlet, would it backfeed properly to supply the motorhome with 120v? I replaced the fridge with the 120v fridge I had in my truck, so I need to power it when I'm off the grid, and it would be nice to have power to the outlets as well. Thanks for any advice. It's a 1973 d-22 Winnebago. 

[DaveVA78Chieftain]

First you need to figure out your daily requirements.

Example of how to estimate DC usage

Device        Number     Rating          Daily Hrs       Daily Total
                                 in amps           Used          In Amp-Hrs
Lights               8    X      1.5       X       0.5       =        6
Stereo              1            2.0                4.0                 8
Water Pump     1            4.0                0.25               1
DC TV               1            5.0                4.0                 20

Minimum Daily DC Total                                            35 Amp-hr

Furnace           1            7.0                3.0                 21

Maximum Daily DC Total                                           56 Amp-hr

Now you get to figure out your AC requirements:
Device        Number     Watts          Daily Hrs              Daily Total
                                                      Used                 Watts used
Fridge             1    X      132     X      (24 x .2)    =           634
Microwave       1    X      900     X      0.25          =           300

Daily AC Watts Total                                                      934
Daily AC Amp hours (934 Watts / 12 VDC)                        79  Amp-hr
Correction for inverter efficiency (79 x 1.)                        87  Amp-hr

Minimum daily AH Requirement (35AH (DC) + 87AH (AC) = 122AH
Maximum daily AH Requirement (56AH (DC) + 87AH (AC) = 143AH

You should never deplete a battery lower than 50% so I would have at least 350AH battery bank (safety margin).  400AH would be preferred for this case (4 Trojan T125 6VDC Deep Cycle batteries). 

Note: Variable usage for appliances like a furnace that cycles on and off.
Number of hours turned ON = 24.  % of time ON per hour 25%.  24 X 25% = 6 Amp-hrs
% ON depends on outside temp and heat loss of rig.

A 2000ah inverter is not big enough for a air conditioner.  Even so, because of the huge 15 amp AC compressor draw (15 amps X 120 VAC = 1800 Watts) an AC would require a huge battery bank.

Dave

[moonlitcoyote]

My question is, if I make a power cord to plug  into the inverter, and into a 120v outlet, would it backfeed properly to supply the motorhome with 120v?

Did you miss his question Dave?

[DaveVA78Chieftain]

Actually no.  Before one even thinks about using a 2000W inverter, one needs to see if he has enough energy to use it.  That requires looking at the whole setup, not just one piece of it.  Notice the high draw of the AC household fridge he moved from truck to RV (700 Watts after correction).  I used a 1.1 amp apartment fridge that runs 15 min / hr example. If you do not have a large enough battery bank you will be very unhappy come morning.  The semi truck has a large bank of multiple 6VDC batteries which most RV's do not.  So, think about the whole system, not just a piece of it.  If he only has the typical 200ah system (2 12VDC batteries in parallel), he will run it down to 40% charge  (78ah) in one day for even the minimum requirement  (122ah) .

Dave

[moonlitcoyote]

I realize he may not have enough power but I was looking forward to the answer to his actual question.

[DaveVA78Chieftain]

I have a 1500W inverter I use for an apartment fridge, microwave, tv and computer.  Given I have a 400ah battery bank it works fine.  If I have to use the furnace though, I really need to keep an eye on usage.  As I said before, AC operation is not even a question.  Just takes far to big of a battery bank.

Dave

[007]

the answer is yes , if he makes a double ended cord plugs one end into the inverter and the other into an outlet  it will put power into the system just like a string of outlets on an extion cord with outlets at both ends and 2.3,4,5 in the middle lay it on the ground, put power in any one of them and they all have power

[DaveVA78Chieftain]

WARNING   WARNING  WARNING

the answer is yes , if he makes a double ended cord plugs one end into the inverter and the other into an outlet  it will put power into the system just like a string of outlets on an extion cord with outlets at both ends and 2.3,4,5 in the middle lay it on the ground, put power in any one of them and they all have power

Unsafe as hell! 

When cable unplugged from receptacle there will be exposed live 110VAC on male pins of connector.

When plugged into receptacle there will be exposed live 110VAC on male pins of SHORE POWER connector.

WARNING   WARNING  WARNING

Dave

[007]

correct , question was can power be put into an outlet,  so i.m guessing he knows that bare wires or plug ends will be hot! but good point ,

[tntwardell]

Can you just plug the shore power plug into inverter. I have been wondering this for a while. Hook inverter to battery bank then an extension cord to the shore power plug. not running ac or heaters just a tv dvd and laptop.

[newrvguy]

Would the best way be to take some romex and go from the inverter to the circuit breakers directly on the converter to just the breakers you want power at?  Example the TV breakers?

[chevyluver]

Thanks, I thought it would work, it's just temporary idea to get me to shorepower. I was going to cap the shorepower connection while I'm driving/using the inverter. Another question, does the sealed batteries still emit gasses while they charge/discharge? I was thinking of putting a set of extra sealed batteries under the seat with the power inverter. I just don't want to kill myself doing it.

[DaveVA78Chieftain]

does the sealed batteries still emit gasses while they charge/discharge?

Yes.  Battery uses chemical conversion to produce energy with an explosive gas by product.  All batteries have to be ventilated to the outside.

Dave

[chevyluver]

Yes.  Battery uses chemical conversion to produce energy with an explosive gas by product.  All batteries have to be ventilated to the outside.
Dave

That's what I thought. I guess I'll make a big battery box instead

[Rickf1985]

There is another very unsafe problem here that nobody has touched on. You are backfeeding a circuit therefore you are bypassing any circuit breakers on that circuit. It is entirely possible to grossly overload that circuit and cause a fire. I don't know if you have ever seen the outlets on a motor home but they are the same as a mobile home and those have caused many fatal fires. I worry about mine all the time because on a motor home you are flexing them all the time. There are no screwed on connections, just wires pushed down between two sharp blades, that's it. Nothing to hold them there either. They come loose with a load on them and you have arcing. Inside of a motor home wall................... well, the end result is never good.

[pvoth1111]

Yes.  Battery uses chemical conversion to produce energy with an explosive gas by product.  All batteries have to be ventilated to the outside.


Hydrogen.......=======bomb

[Alaskan Itasca]

I have a 1000W (2000w spike) inverter in mine, I run a small 120v fridge and the tv/blue ray. I just wiired in an seperate outlet near the tv using household wire. I then ran an extention cord over to the fridge under the rear bench and around to the fridge and just plug it in to the inverter outlet while I'm driving and then plug into the shore power supplied outlet at the campground (I used to move the plug to the fridge between the built in out let and the extention cord and realized it was a pain in the rear). I can run my fridge (pulls 200 watts when running, but spikes up to about 1500 watts or so when starting, and the tv/blue ray pull about 20 watts running. I'm running two six volts and can last the night without depleting the batteries with the furnace on (It's in the  upper 40s low 50s here most nights in the summer), but then have to charge the batteries in the day time so I can make it through the next night, which requires running the 2k watts honda generator for 4 hours or better to get the batteries charged up with my external charger. I need a new power center mine no longer charges the batteries. MY inverter won't run the microwave the startup spike is to great even though it's only a 700 watt microwave. I can run some small coffee pots but most pull too much power to run the water heater inside the pot.

I really want a propane fridge or at the e minimum a more effiecent 110 fridge.

[xerofall]

I have a 1000W (2000w spike) inverter in mine. MY inverter won't run the microwave the startup spike is to great even though it's only a 700 watt microwave.

Thanks for posting this. I was about to purchase a 1000W inverter and a 700 watt microwave. So would I need to get at least a 1500W inverter to power a 700W microwave?  I heard before it needs to be at least double the required wattage? 

[DRMousseau]

I too have minimal needs, and I JUST installed a "Boondocker" converter/charger and will be setting in TWO new T-105's this weekend, to replace the old automotive 12V the PO has in this thing. I'm usually on shore power every night, and when I plug in, I also plug in the "Boondocker" to the outlet box on my power panel. Each morning, I unplug both, the shore cable from the post, and the "Boondocker" from the panel.

Now sometime soon, I'll be installin' a 2500w inverter on the panel. When I'm "offline", I'll jus plug the shore line into the inverter, leaving the "Boondocker" unplugged. My biggest issue is runnin' 4ga cables from the batteries to the "Boondocker" AND the inverter. The PO had 10ga and it was fine for the original basics. But upgrades like this are gonna need ALOT more.

[ibdilbert01]

I installed a marine grade 3000/6000 watt inverter in mine, coupled with an Iota 30amp transfer switch.    Kind nice to be able to run just about anything without turning on the genset. 

[eXodus]

yeah the bigger the inverter the more power you are wasting at low outputs.

They are getting better, but at the moment they are just burning about 1% of their rated power when idling. So you got 3000w about 20-30w  2A two amps are constantly sucked out of your batteries while doing nothing.

I did take a 1000w so I'm only wasting about 0.5-0.8A.

To make my system save I will wire an external outlet to the inverter where I can plug in the shore cord when I'm not running the genset or have external power.
So no backfeed and such interesting constructions.

Or I rewire everything and just run all my outlets always through the inverter. This is a solution for the bigger inverters, rewire-ring the power center so that only the A/C and the Charger is feed from external and the outlets are run by the inverter.
You are not loosing much power 10-15% when plugged in. 

Downside, when charging it takes a little longer to get the batteries up.

[gadgetman]

I ran a romex to my cord compartment to my inverter 1500w. I just plug in the whole coach and dont use the AC except with the gen. Also if you are going to wanting to use a microwave a pure sine wave inverter is much better. Microwaves dont like modified wave inverters.

One safety measure you should check  when using a inverter. You need to check the voltage from the neutral to the ground on any plug powered when the inverter is on. You should see almost ZERO voltage. If you have 25v to 75v your inverter is NOT bonded.RVs are NOT bonded at the breaker box because they know you will plug into a bonded shore power and only one spot can be bonded by code. A system that is NOT BONDED IS A ELECTRICAL HAZZARD .

If your inverter is not bonded all you have to do to bond it is make a bonding plug. You take a male cord plugin and join the ground and the neutral terms and simply plug it into the inverter  110 plugin. Now you are safe.
Be sure to put a switch on your converter so it is shut off when using the inverter Thats a battle the batteries cant win !!

Not being bonded is also why your ground fault plugs wont work while running a non bonded inverter.

Here is a nice link that explains it better 

http://www.noshockzone.org/generator-ground-neutral-bonding/