View Full Version : Pure Sine Wave Inverter

06-05-2011, 01:10 AM
Been thinkin. Dangerous. We have a power pig in our Newell and it called an Amana Refrigerator. We also have a 458 modified sine wave inverter. The Amana is great when we are plugged in and terrible when on the inverter.

Been doing a little research and have discovered that a refrigerator will use 20% more power on modified sine wave vs. pure sign wave.

So with $150 1500 watt pure sine wave inverters now available, I am thinking of rewiring and running the frig 100% of the time on a pure sine wave. Leave the rest of the coach alone. Trying to figure the down side.

06-05-2011, 02:20 PM
I take it that you will be charging the Batteries with the previous system? Sorry I don't have much experience with this, our Refrigerator is LPG/Electric.
I can advise you to use a Source Isolation Switch if you do install one.

Richard and Rhonda
06-07-2011, 12:57 AM

You are right the frig is a hog. You can disconnect the defrost circuits, and heated seals on the door to cut some of the power use. Turn off the ice maker, if boon docking.

06-13-2011, 05:24 PM
I think you will need to spend more then $150 on an inverter to run your refrigerator. The initial surge needed to start the compressor will more then likely destroy your refrigerator and/or the inverter due to high amperage/low voltage conditions on startup

06-14-2011, 12:24 AM
hi gary, i gotta agree with john. there are two reasons the rv inverters are so expensive (AND HEAVY). 1. the ability to handle surge wattage requirements while still delivering high quality power (steady voltage, phase and current). 2. the charging system that they are as well.

i am an EE, and my son in law is a phd in power engineering and he had the same thoughts. that the cheapo inverter will likely not be of enough size to handle a compressor startup (the locked rotor amps or LRA) and still deliver the quality of power required to not dramatically shorten the life of the compressor.

when i rebuilt my freedom 458, i also re-wired it correctly (common for aftermarket installs). it is the same modified sine wave inverter you have. i put in a circuit to run my microwave. the microwave works, but dreadfully. meaning it sounds strange and is not at full power, but it does work. some microwaves klystrons require high quality power more than others and the sharp convection microwaves we have are one of those.

i don't use it that way very often, but if i did and had to replace he microwave that is a little easier than he fridge to replace....

so, i would spend some time with any non rv inverter making sure it will really do the job.

the other thing is that i am not sure you can use the same batteries to power a second inverter. so you would need to check that out. or you would need another bank of batteries.

you can calculate how long your batteries will power an invertor with specific current draws. a fridge compressor really sucks the power...

so, caution rules on this.


06-14-2011, 10:24 PM
I try to stay with high end equipment on our '82 and this would leave out an entry level inverter. The way that I look at it is that NEWELL used high end equipment and I am going to keep it that way. I believe that is why our older coaches are still in such good condition and I surely am not going to shorten the life by saving a couple of bucks.
Sorry, not trying to offend anyone just my thoughts.

06-15-2011, 12:05 AM
Amana Refrig = 11amp max (placarded) =1320 watts

Low end inverter 1500 watts continuese, 3000 surge = equals plenty of power.

Since this is inverter only, there would be no problem running it off the same house battery bank. I would let the 458 handle the charging problems.