Reply
 
Thread Tools Display Modes
Old 09-16-2015, 11:31 AM   #1
Senior Member
 
Sagecoachdriver's Avatar
 
Join Date: Jun 2015
Location: Southern California
Posts: 1,466
Using inverter for Fridge at high Altitude

Not exactly sure where to post this topic. We usually dry camp and from sea level to 10,000 feet. Had little problems with our Norcold N611 in our Winnebago. Wondering what surprises our new Forester with the Dometic will hold. In reading other topics, some have encountered issues with pilot not lighting at higher altitudes because of lack of oxygen. Has anyone every tried using an inverter rigged between the battery bank to the 110v wire for the fridge? If so, how many amps does the fridge draw and what size inverter would be needed? My batteries are 2 group 27s and I can easily recharge it with the generator during genny hours or use my Renogy 130 watt solar. This setup would only be used for 2-3 days at most.
__________________

__________________
2004 Winnebago Minnie 22e(went to a nice family Oct 3, 2015)
2016 Forester 2701DS (Aug 31, 2015)
2017 Camping 10 trips 32 nights
Sagecoachdriver is offline   Reply With Quote
Old 09-16-2015, 12:07 PM   #2
Senior Member
 
Join Date: Dec 2009
Location: Napa Valley, CA
Posts: 413
Mine uses about 5-6 amps on electric. An inverter of 1000watt output constant would be a good choice to run the frig and TV on 120v. If you figure using about 130-150 amps in 24 hours for all sources, you will only last 1-1.5 days with two batteries before needing to recharge. Best not to let batteries go below 50% charge before recharging.
__________________

__________________
2015 Rockwood A128S
2010 Rockwood 2604
2014 Ford F-250 CC SB 2WD
2008 Toyota Sequoia 2WD
Big Vic is offline   Reply With Quote
Old 09-16-2015, 12:22 PM   #3
Senior Member
 
Sagecoachdriver's Avatar
 
Join Date: Jun 2015
Location: Southern California
Posts: 1,466
Big Vic, the fridge will already be cold and running for days, so it won't be running continuously, but cycling. I figure about 100 amps per day then and running the generator for a few hours plus the solar should give me about 3 days then.
I am going to unplug the fridge and use my Kilawatt to see what the 110v amps are. I have a 400 watt inverter and perhaps if that works I can get the amp draw with my meter to see exactly what the 12v amp draw is. May need to buy a bigger inverter then. Wonder if that Harbor Freight one would do the trick. Nothing else would be on the circuit.
__________________
2004 Winnebago Minnie 22e(went to a nice family Oct 3, 2015)
2016 Forester 2701DS (Aug 31, 2015)
2017 Camping 10 trips 32 nights
Sagecoachdriver is offline   Reply With Quote
Old 09-16-2015, 02:05 PM   #4
Senior Member
 
Sagecoachdriver's Avatar
 
Join Date: Jun 2015
Location: Southern California
Posts: 1,466
Checked 110v amps and watts, 2.7 amps and 324 watts. So an 800 or 1000 watt inverter should do the job. Can always buy 2more batteries also.
__________________
2004 Winnebago Minnie 22e(went to a nice family Oct 3, 2015)
2016 Forester 2701DS (Aug 31, 2015)
2017 Camping 10 trips 32 nights
Sagecoachdriver is offline   Reply With Quote
Old 09-17-2015, 03:54 PM   #5
Senior Member
 
Tom48's Avatar
 
Join Date: Apr 2015
Location: Ontario, California
Posts: 1,007
Quote:
Originally Posted by Sagecoachdriver View Post
Not exactly sure where to post this topic. We usually dry camp and from sea level to 10,000 feet. Had little problems with our Norcold N611 in our Winnebago. Wondering what surprises our new Forester with the Dometic will hold. In reading other topics, some have encountered issues with pilot not lighting at higher altitudes because of lack of oxygen. Has anyone every tried using an inverter rigged between the battery bank to the 110v wire for the fridge? If so, how many amps does the fridge draw and what size inverter would be needed? My batteries are 2 group 27s and I can easily recharge it with the generator during genny hours or use my Renogy 130 watt solar. This setup would only be used for 2-3 days at most.
That might be a backup plan, but when I accidentally ran my refrigerator on the inverter I suddenly realized it was pulling about 400 watts and with our big 2000 watt pure sine wave inverter, I think that translates to about 40 amps 12 volt. My solar charging system is good for about six and a half apps or so per hour on an average day so I'm thinking that might not be so good by the end of the day. Unlike a residential refrigerator that only draws with the motors running, the heating element in an ammonia base refrigerator seems to run continuously. Seems like maybe you would need more batteries and more solar to run continuously on 120 volt.
__________________
Tom48 is offline   Reply With Quote
Old 09-17-2015, 03:57 PM   #6
Senior Member
 
Tom48's Avatar
 
Join Date: Apr 2015
Location: Ontario, California
Posts: 1,007
Quote:
Originally Posted by Big Vic View Post
Mine uses about 5-6 amps on electric. An inverter of 1000watt output constant would be a good choice to run the frig and TV on 120v. If you figure using about 130-150 amps in 24 hours for all sources, you will only last 1-1.5 days with two batteries before needing to recharge. Best not to let batteries go below 50% charge before recharging.
That sounds about right, but I think overlooks the fact that a four amp draw @ 120 volt is more like a 40 amp draw at 12 volts, where in there may be a problem. The modified sine wave inverters are little more efficient than the pure sine wave and should be okay for a heating element where as not so good for sensitive electronics or electric motors. But still I think calculating the draw will suggest the need for more batteries. And maybe more solar.
__________________
Tom48 is offline   Reply With Quote
Old 09-17-2015, 04:09 PM   #7
Senior Member
 
Tom48's Avatar
 
Join Date: Apr 2015
Location: Ontario, California
Posts: 1,007
[QUOTE=Sagecoachdriver;985424]Checked 110v amps and watts, 2.7 amps and 324 watts. So an 800 or 1000 watt inverter should do the job. Can always buy 2more batteries also.[/QUOT

So here it is on these numbers. 324 watts will pull about 32 amps 12v so times 24 hours divided by 105 reserve amps or about 7 group 27 batteries dead in 24 hours.

May be I am wrong and the refrigerator does not draw continuously when on 120v. I caught mine after an hour of running steadily at almost 400 watts and never repeated it for testing purposes. Anyway, I understand they don't build too many refrigerators to run volt, maybe for that reason, it would only be feasible of the automotive alternator or the generator is running. Good luck

I bet you could run it through the kilowatt meter for 24 hours and register the cumulative usage, just as a test while you are still at home
__________________
Tom48 is offline   Reply With Quote
Old 09-18-2015, 12:32 PM   #8
Senior Member
 
Join Date: May 2012
Posts: 513
I installed an 1K modified sine wave inverter in my 2011 Georgetown 327DS when I purchased it. The inverter was wired to provide power only to the Dometic fridge and the original AC power line for the fridge was rerouted to the inverter as its shore power feed. The inverter has its own internal transfer switch so it self disconnects whenever AC power is available from the generator or a campground's power outlet. The inverter's control panel is mounted remote from the inverter, just below the sink where it's easy to see and use.

When running on AC, the Dometic fridge draws around 300W. The fridge does cycle the AC power draw, using it only when needed to keep the fridge cold, the same way it does when running it on propane. The 300W draw pulls around 24A from the battery. Two deep cycle 100AH batteries will provide 100A of power (drawing them down to 50% of capacity) which is around 4 hours of cooling for the fridge. I figure that worst case, the fridge will be actively cooling 50% of the time which means that I can run the fridge for 8 hours on batteries before venturing into the "how low can you go without damaging the battery" zone. Don't forget that discharged batteries need to be recharged to prevent sulfation of the plates. If you're running the fridge on batteries, how will you recharge them?

Your batteries also power your interior lights, propane detector, furnace fan, water heater controls, and a host of other small things you didn't know were connected to the battery. Running the fridge on batteries sounds like a good idea but, in the long run, doesn't appear to be a good choice for dry camping unless you have at least 500W of solar power available or are planning on running the generator for at least 4-5 hours a day.

I use my inverter to power the fridge only when driving or making a short stop, usually less than one hour. With the motor running, I have a 175A alternator providing power to chassis and house batteries so the 24A draw for the inverter isn't an issue. This allows me to drive with the propane shut off, a good thing to do from a safety standpoint.

Phil
__________________
pmsherman is offline   Reply With Quote
Old 09-19-2015, 12:58 AM   #9
Senior Member
 
Tom48's Avatar
 
Join Date: Apr 2015
Location: Ontario, California
Posts: 1,007
Quote:
Originally Posted by pmsherman View Post
I installed an 1K modified sine wave inverter in my 2011 Georgetown 327DS when I purchased it. The inverter was wired to provide power only to the Dometic fridge and the original AC power line for the fridge was rerouted to the inverter as its shore power feed. The inverter has its own internal transfer switch so it self disconnects whenever AC power is available from the generator or a campground's power outlet. The inverter's control panel is mounted remote from the inverter, just below the sink where it's easy to see and use.

When running on AC, the Dometic fridge draws around 300W. The fridge does cycle the AC power draw, using it only when needed to keep the fridge cold, the same way it does when running it on propane. The 300W draw pulls around 24A from the battery. Two deep cycle 100AH batteries will provide 100A of power (drawing them down to 50% of capacity) which is around 4 hours of cooling for the fridge. I figure that worst case, the fridge will be actively cooling 50% of the time which means that I can run the fridge for 8 hours on batteries before venturing into the "how low can you go without damaging the battery" zone. Don't forget that discharged batteries need to be recharged to prevent sulfation of the plates. If you're running the fridge on batteries, how will you recharge them?

Your batteries also power your interior lights, propane detector, furnace fan, water heater controls, and a host of other small things you didn't know were connected to the battery. Running the fridge on batteries sounds like a good idea but, in the long run, doesn't appear to be a good choice for dry camping unless you have at least 500W of solar power available or are planning on running the generator for at least 4-5 hours a day.

I use my inverter to power the fridge only when driving or making a short stop, usually less than one hour. With the motor running, I have a 175A alternator providing power to chassis and house batteries so the 24A draw for the inverter isn't an issue. This allows me to drive with the propane shut off, a good thing to do from a safety standpoint.

Phil
I really like your analysis and can find absolutely no fault with it. So, that leaves only -- can you tell me the model of the inverter and or auto switch you are using. Also, the modified sine wave is considerably more efficient than Pure Sine which is probably not needed in this application.

I absolutely loved you description. Unlike many of mine, I UNDERSTOOD YOURS.

Tom
__________________
Tom48 is offline   Reply With Quote
Old 10-16-2015, 04:50 PM   #10
Senior Member
 
Join Date: May 2012
Posts: 513
Quote:
Originally Posted by Tom48 View Post
I really like your analysis and can find absolutely no fault with it. So, that leaves only -- can you tell me the model of the inverter and or auto switch you are using. Also, the modified sine wave is considerably more efficient than Pure Sine which is probably not needed in this application.

I absolutely loved you description. Unlike many of mine, I UNDERSTOOD YOURS.

Tom
I purchased a Xantrex XM1000. Less than $250 from Amazon.

A year after it was installed, I added, to the inverter, a GFCI protected outlet at the sink and another one below the sink in the plumbing compartment. The sink outlet is for a slow cooker (300W) when driving while the one in the plumbing compartment services the heating strip that keeps everything in there from freezing when we use the RV in the winter. I'm still under the 1kw rating of the inverter.

Don't forget that a device like this needs large cables from the battery. Mine is installed using 2/0 welding cable with a circuit breaker near the battery and a marine disconnect switch installed at the RV inside entrance steps. The remoted control panel uses standard telephone cable routed under the sink.

Phil
__________________

__________________
pmsherman is offline   Reply With Quote
Reply

Tags
fridge, inverter

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Virginia Campgrounds

Reviews provided by




ForestRiverForums.com is not in any way associated with Forest River, Inc. or its associated RV manufacturing divisions.


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 06:16 PM.