Pure Sine Wave vs Modified Sine & Refrigerators

[sundancev]

Wow, the forum responders on FMCA are simply spectacular.

 Reason for me writing is I realize after some 5 years with a Dometic 4 door refrigerator, I will have to replace some time perhaps sooner rather than later.  One of our friends went through this a couple of years ago and opted for a Residential fridge.  Due to high cost of Dometic's largest fridge, we are going to opt for a residential fridge also.

 I had talked with our friend about possibly using a separate pure sine wave inverter only for the fridge or perhaps replacing  the now 13 year old Xantrex modified sine wave inverter.  He was told in order to replace his current modified sine wave inverter (identical to ours) he would need to have his coach rewired at cost of at least $1,000 (which I thought would be remarkably cheap.)

 He and I were both concerned about the possible problems of having a separate pure sine wave inverter wired directly to the "house batteries" and serving only the electric plug for the new fridge.  He finally opted to plug in the new residential fridge in the old ice maker plug which is what I had considered doing when I ultimately had to make the decision on a new residential fridge.  

Question 1 is does anyone know if the suggestion about possible re-wiring if I change to a pure sine wave inverter in lieu of the current Xantrex modified sine wave is a reasonable requirement? 

Question 2 is would a supplemental 1500 watt pure sine wave for the proposed new residential refrigerator be a good option if it could somehow be wired into the automatic system that turns off the inverter when we have 110V shore power (including the 7500 watt generator.)  

My friend is currently running his new residential fridge using the old ice maker plug without a problem for more than a year so I know that is an option.  He does have two more heavy duty golf cart batteries than we have and I realize that is potentially an option we may need to explore.  We have 6 -6v Golf Cart Batteries.  I realize I have put forth a number of scenarios for our readers to consider and obviously allow my ignorance of most things electrical to show and simply ask your indulgence.  

 

For those who wonder why we do not want to stay with the current LP/Gas-110V combination that we currently have we offer the following  thoughts.  The Norcold and Dometic fridges of the large size we require simply have lots of problems that are not easily fixed.  Two years after spending almost $4,000 on our current 4 door Dometic, the heating unit failed.  The first words out of the tech's mouth when he saw the green dust in the bottom of the back portion of the fridge was "heck, there goes $2,000.)   I then said, well I did pay for an additional 3 years warranty which he suggested was excellent foresight on my part. i thought at the time, this is madness to think of something costing $4,000 not lasting more than two years.

 I then begin to think about the residential option.  My friend mentioned earlier had the big Norcold version and had continuous problems with his never keeping food cold enough or frozen properly in his fridge.  Paying that kind of money every few years is not good and we have heard so many good things from acquaintances who made the switch to residential.  

 

We have been full timing for some 7 years now in a 39' 2004 Fleetwood Providence, 350 HP ISC Cummins.  We now have 160,000 miles and hopefully will have 160,000 more before we have to hang it up.  We have worn out a Honda CRV and switched to a Ford Explorer with more storage room for a toad.  We think FMCA is simply the finest organization of its kind anywhere thanks to the wonderful Forum contributors.  For whatever it is worth, we fully concur with and hope the other members will vote for the recommended change to allow other types of RV users to join this wonderful group.  

[hermanmullins]

Sundance,

When our Never Cool die 2 years ago I installed a residential refrigerator. I installed a "Samsung RF-18". It is a 17.6 cubic feet unit and it has run for the entire time on on our Trace RV 2012 Modified Sane Wave Inverter with no issues.I had one issue when I installed the unit. It would not make ice. I pulled the unit out far enough to take off the inspection cover. I found that the two wire to the ice maker solenoid were just dangling there. The water is supplied through a clear plastic tube. The minute i plugged the wires in I saw the water flow. Never another problem. The reason I told this is to let folks know that before they install the unit check to see if the wires are connected.   

Herman

[desertdeals69]

There shouldn't be any need to rewired the coach to change from modified sine wave to pure sine wave.  If you go to a larger inverter you may have to increase the size of the battery cables but the ac wiring should be ok.  Some refrigerators won't run on modified sine wave, you may have to test it before installation.

[obedb]

My guess is that most residential refrigerators will run on a modified sine wave inverter. That is, until the models that are not compatible have compressor burnout.😡  Herman and Joe Leamont have Smasung units that are compatible with the modified inverters. They have had good results and are happy with the change. Pure sine wave inverters have seen significant price drops in the last few years. My guess is that the pure sine wave inverter/ chargers have dropped also. If I was going to make the change to a residential refrigerator I would have to consider a new inverter/charger as well. You would then be able take your pick of refrigerator models.

 

 

 

 

[hermanmullins]

John,  Sorry, "To Whom It May Concern"

I will partly agree with you. The Pure Same Wave inverter would allow for more choices, but one of the biggest considerations is size. You must consider the space were the refrigerator will go. The Samsung RF-18 will fit width wise where the Never Cool 1200 goes the height is the issue.

We didn't have a heater below our 1200, just drawers. I was able to sit it on the floor and put a door above it.

Herman 

Edited September 18, 2017 by Hermanmullins
My Bad.

[wolfe10]

Conservative answer is that a pure sine wave inverter will either be the same or BETTER than the MSW for running a refrigerator.  Some do run successfully on MSW, but that may limit you on your choice of residential refrigerators.  Check with the refrigerator manufacturer before ASSUMING.  Not sure I would mention either way that it is for an RV, but there are a number of homes "off the grid" that use inverters to power household appliances.

As far as rewiring, the only reason for doing anything other than a direct sway:

If the new inverter is a higher amp model, requiring larger gauge wire and/or the remote panel and perhaps wiring from inverter to panel re different.

I would favor one good quality PSW inverter to too.  And the size a 1500/2000 watt inverter will generally have a built in ATS so it automatically switches over to an external power source from either shore power or generator.

[sundancev]

We did cross the GW Bridge on Monday trying to head back to Florida to help family.  What a fiasco.  We had always crossed on a Sunday but could not this past week, hence the awful two hour ordeal to drive 2 miles.  Wonder why my friend was told he had to re-wire in order to go to a pure sine wave.  He has had wonderful luck with his old modified sine wave and a Whirlpool residential fridge

[obedb]

Who is John??

There are routes around the George Washington Bridge. Never cross it unless you enjoy swearing at yourself. 

😄😂

[hermanmullins]

Sorry my bad.😔

Herman 

[BillAdams]

Just to be clear, if you replace 2000W modified sine wave inverter with a 2000W sine wave inverter you would not need ANY wiring upgrades and the only cost would be the new inverter.  If the old inverter was 1500W and you want to move to a 3000W then the wiring between the battery and the inverter may need to be replaced with larger wires.

[tbutler]

We replaced our Norcold with a residential refrigerator.  I wrote the process up and posted with pictures here on the forum.  You can find the post and following discussion at this link. 

Our coach was originally wired for a 1500 Watt inverter.  When we purchased the coach the inverter didn't work so it was replaced with a 2000 Watt inverter.  No change in wiring was made at that time.  Later we replaced the 2000 Watt modified sine wave inverter with a 3000 Watt pure sine wave inverter.  Again no rewiring was done between the battery supply and the inverter. 

There is a fuse to protect the wiring and we've never had a problem blowing a fuse on the inverter circuit.  Check the fuse on the inverter circuit.  If the replacement inverter uses more amps than the fuse is rated for then you would need to replace wiring.  If not, you would be able to use the wiring that is already there.

[obedb]

Guess that about sums it up for all possibilities. I like that. No doubt about choices. Love it when a good plan comes together.😉

 

[desertdeals69]

I would check with the mfg  to see if they would warranty when installed in an RV.  On my last coach I installed a Haier and fortunately I had made a phone call to tech service and they did not tell me that there was no warranty in a RV.  In 7 months the compressor failed running on a psw 3000 watt Xantrex.  They said no warranty so I told them to listen to the recording of our service phone call and they decided to cover it.  I got my money back at Lowe's.

[obedb]

We all love call centers don't we!😜  Imagine finding a fridge that will fit in the allowable space and contacting a call center that  is, who knows where to, find out if the unit will work with a modified sine wave  inverter ( cane we say square wave ) ?  May have no idea what you even talking about? In our case, we would have to move the 120volt circuit breaker panel that also has all of the 12volt coach related blade fuses in the same location  below the Dometic for the coach, and that is just to be able to fit a Res fridge into that spot. I will guarantee you that if all of that was done, the inverter would be a true sine wave inverter. Would love to have a residential fridge in our Phaeton for many reasons. It is in our bucket list , but younger we are not getting.

 

[wildebill308]

6 hours ago, obedb said:

Who is John??

There are routes around the George Washington Bridge. Never cross it unless you enjoy swearing at yourself. 

😄😂

Crossed South bound on the Tappan Z about 4 hours ago and my little Kenmore was making ice all the way pluged into my modified sine wave inverter.

Bill

[manholt]

I'm confused again!   What does the GW and John have to do with any answer to OP?  Does "John" have the same make, year, model of coach? 

[jleamont]

I actually inquired about this with Xantrex prior to our residential conversion. I was told to swap the unit was simple, the only difference was our remote control panel inside was not compatible with the newer inverter and had to be replaced also. No rewiring required.

I have heard of a few installing a 2nd inverter by itself dedicated the refrigerator, that a different game all together that would require some wiring.

As far as the calling customer support . I called them with questions, they read from a screen and had no idea how to answer my questions, I gave up.

I installed a GE in our coach, its a 15.5CUft, I went with this unit for a few reasons,

1, almost no cabinet modification necessary to make it fit. Just a notch up top for the upper hinge to clear the cabinet opening inside.

2, I saw the same model in a new Fleetwood Excursion that came from the factory, I figured someone at Fleetwood and GE determined it would be ok in a motorhome environment.

I had no idea if it would run on MSW inverter, the Fleetwood coach had a PSW inverter.

I bought it, took it home, ran a cord from the coach to the refrigerator siting in the garage, powered it up via inverter and shore power, listening for a sound difference in the motor, none noted. I let it cool down on the inverter, checked the motor temperature, wrote it down. Did the same plugged into shore power, no difference in noise or temperatures. I installed it the next day.

[obedb]

Joe/ I thought that you replaced your nocold with a Samsung.

[obedb]

In my next to last truck, I installed a dorm or office fridge. Bought it at Walleys World. It was a name brand that escapes me at present. Had a big MSW inverter that powered a hotplate, coffee maker, microwave, coffee grinder, rice cooker, Sat receiver and TV, you name it.....

Not all at the same time of course, but the fridge beat the thermo-electric cooler that runs all of the time and keeps food fresh, but no freezer. The small freezer was nice to have. The dorm unit lasted maybe 4 months before failure. Had a friend with pretty much the same set up. His made it not quite a year before failure. If either unit lived that short life in an office or dorm, imagine the grumbling.

I still believe that it was the MSW inverter that was the caused the failure.

[manholt]

Joe.  What happened to the Samsung?

[jleamont]

Never had a Samsung, it required to many modifications to the cabinet to make it fit. DW told me any CUFT close to the NoCold 1200LRIM or better was adequate. Ours is 15.5 the Nocold was 12.0 (or close to it). It slid in like it belonged, plus Fleetwood was using the same model as factory optional equipment, I figured someone tested it in a coach environment, what the heck, the last huge plus.....$585.00 price tag. I figured if it only lasted 5 years I wasn't out much $$$. Ending year 3, no regrets!

 

[manholt]

Joe.  Sorry, my bad.  Got you confused with Herman!   Guess ObedB did also!

[jleamont]

2 hours ago, manholt said:

Joe.  Sorry, my bad.  Got you confused with Herman!   Guess ObedB did also!

[kaypsmith]

I have one thing to add to the OP, while shopping for a residential fridge, be sure to pay close attention to the information sticker on the inside of the fridge, looking for the lowest amperage available in the fridge of your choice, the lower the better because it will allow for the least usage of electricity, meaning of course longer time of run on the batteries.

Also a newer technology is inverter technology, it does work better on PSW and probably will not run on MSW. This is one of the best improvements in the refrigerator industry, it allows the fridge to stay at the programmed temperature without the compressor cycling off and on (one of the most inefficient ways to run a fridge), start up of any motor is the the most costly part of running it.

The inverter technology does not mean that it is designed to be run on an inverter, but that the motors uses the ability to slow down or run faster due to cycle change to keep up with the need to cool more or less.

Good luck hunting! Kay

[wayne77590]

On 9/20/2017 at 4:50 AM, manholt said:

Joe.  Sorry, my bad.  Got you confused with Herman!   Guess ObedB did also!

Oh the humanity! Sorry for Joe!

Kay, thanks for the information. I'm going to try and get one of the little men running around in my head to remember it.