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Old 06-27-2016, 03:14 PM   #15
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The problem you will have is if the additional refrigerator draw creates an overload on your whole system so that your net charge level drops as you drive. You can either add a fairly pricey power monitoring system or just an inexpensive voltmeter to watch your system voltage. I'd be looking at something like this: https://www.amazon.com/Cllena-Waterp...ital+voltmeter Connect it to the house battery and check it when you start and after a few hours. As long as it is stable or increasing you are fine. If it steadily drops you need to bulk charge with the generator for an hour or two as you drive. Your biggest problem will probably be stopping for most of a day to play tourist. With the battery voltage monitored and a voltage state of charge chart you can build a bit of history so you can judge how long it takes to get in trouble. As long as the engine battery is kept isolated you can alway shut off the refrigerator inverter while you drive and let the house battery recharge while the closed refrigerator coasts on it's insulation as another option. Note: I would probably not do what you are doing but that is what you can do and how you can make that choice work with the limitations you have.
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Old 06-27-2016, 03:15 PM   #16
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Frigs are computed on running 1/4 of the time or 6 hours a day with an indoor temp of 76 degrees. An 11 cuft Whirlpool will use 5.7 amps to run and about 14 amps to start at 120 volts on a pure sign wave inverter. Figure about a 20% increase in amperage use if it is powered by a modified sine wave.
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Old 06-27-2016, 05:33 PM   #17
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FWIW That is why I am saying to go for it. A pure sine will be less efficient that a modified sine in the conversion because of the filtering losses in the "pure sine". Another problem is cyclic loads like the defrost heater schedule is not generally known by the user so cannot be accommodated or adjusted.
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Old 06-27-2016, 06:05 PM   #18
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I Run my absorbsion refrigerator on a 1000 watt sine wave inverter.

It draws 350 watts which is, more then most residential units.

I have 1, gp27 and 2, cg2 batteries equaling about 290 AH, charged thru a 100 amp Cyrix battery combiner, hooked to the chassis battery.

The alternator is a factory 120 amp?, unit that comes on a 1999 E450 cutaway chassis.

I traveled from FL to NY monitoring my volts with a Scangauge II. It never dipped below 13.4, anytime, on the trip.

What you are suggesting will work.
The amp draw will be less and only about 1/3 the time.
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Old 06-27-2016, 09:45 PM   #19
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I am running a Samsung RF18 with two 12V Interstate 4D batteries and a Xantrex 458 2500W MSW inverter, and my Delco 28Si alternator has no problem keeping up.

Paul
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Old 06-27-2016, 09:57 PM   #20
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Residential fridges in RVs are all the rage these days, and for good reason with all of the advantages they have over gas absorption. If you have a good pure sine inverter that can handle the draw, which it looks like you have, and at least 2 house batteries, you are good to go. The systems are well proven and work perfectly. You will not need to run the generator, your alternator will keep up.

I would suggest you look at a counter depth model, they are shallower and won't stick out as much. I would also suggest a French door model. The 2 short doors have more clearance than the one big door. It was very important to me to be able to fully access the fridge for food prep while travelling long distances. The bottom freezer configuration puts your most used food items at eye level and is also supposed to be more efficient. I bought my first bottom freezer unit 15 years ago and will never go back to a top freezer.

I have a Frigidaire French door counter depth model that comes standard in Georgetowns. I absolutely love it although I don't think the in door water and ice are worth it. I strongly recommend you add the secondary ice maker in the freezer, it's only $60 from Amazon, takes 15 minutes to install, and produces tons of glorious ice.

It has an amazing space saving LED lighting system and a really flexible interior that accommodates large plates and tall items. It really kicks the Samsung French door model I have in my house in just about every way. I also love the in door display, it is easy to configure and works very well. I have 4 house batteries and can go 4 to 5 days so 2 batteries should be ok for your stated use.

Believe me when I tell you that a good luxury 3 door fridge will transform your camping experience while adding a significant amount of high end feel to your coach.

Happy fridge shopping!
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Old 06-27-2016, 10:45 PM   #21
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The problem you will have is if the additional refrigerator draw creates an overload on your whole system so that your net charge level drops as you drive. You can either add a fairly pricey power monitoring system or just an inexpensive voltmeter to watch your system voltage..
He has a Magnum Energy inverter. I believe his model includes the fancy control panel that features a shunt to measure power from the batteries, which is hands down the best way to see actual power use and ascertain battery state.
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Old 06-28-2016, 06:09 AM   #22
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If he has the instrumentation that works. The point is to keep an eye on one's house voltage. It used to be a pricey chore. A couple of years ago very low cost decent digital meters started coming out of China so we can now update the 3 or 4 lights to a meaningful number for $10 or so. As I said, I don't know his specific unit. It does sound like a gasser so normal battery capacity is generally not high and increasing it is not a simple drop in. Given what he wants capacity is sort of moot. For anyone who expects to dry camp on a regular basis residential refrigerators are a bad joke for most of the motor homes sold. They do not have battery trays and will not handle large storage batteries or more than 2 batteries without a lot of additional work not done by the factory.
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Old 06-28-2016, 07:12 AM   #23
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My RR draws 1 amp 120VAC when compressor running and cooling, 0 when at temperature, and 8 amps when going thru defrost cycle (there's a big resistive load which heats up and melts the ice).

Easy way to remember to convert to DC usage is just multiple the amps x 10. (Doesn't account for conversion loses, but good enough for rough order of magnitudes).

1 amp @120VAC would be 10 amp draw @ 12VDC. Even during the defrost cycle you'd be drawing 80 amps DC, so you should be fine.

Refrigerator current consumptions are obviously device specific, but new refrigs are quite efficient compared to yesteryears.

We have a 2000 watt inverter, and regularly drive with the RR and crockpot going (draws 3 amps@120VAC). My alternator is 160amp DC.
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Old 06-28-2016, 07:37 AM   #24
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... It does sound like a gasser so normal battery capacity is generally not high and increasing it is not a simple drop in. Given what he wants capacity is sort of moot. For anyone who expects to dry camp on a regular basis residential refrigerators are a bad joke for most of the motor homes sold. They do not have battery trays and will not handle large storage batteries or more than 2 batteries without a lot of additional work not done by the factory.
My 'gasser' has 4 house batteries and place for more. Most people are getting 4 days and some 5 when dry camping, which is most of what I do but the point is moot becasue I will run out of water by the begining of the 3rd day.

The only bad joke here is gas absorption technology with their limited cooling ability and small capacity. I don't think it will be long before both Attwood and Norcold will start offering standard refrigeration technology to stop the sudden drop in sales.

Well Attwood anyway, Norcold still needs to dig out of their class action suit loss.
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Old 06-28-2016, 08:03 AM   #25
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I think 2 batteries and your inverter should be able to handle this very specific need very easily. You have made it clear that you are only concerned about keeping the fridge running during TRAVEL only. The alternator from your vehicle should be plenty fine for keeping the batteries charged for the little bit of usage from the fridge while driving. But, even if not using the alternator, the inverter and batteries themselves should be enough while only going from shore power to shore power.

no worries, cheers!
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Old 06-28-2016, 08:23 AM   #26
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FWIW the only bad joke I see is the assumption that there is something inherently wrong with a gas absorption refrigerator.
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Old 06-28-2016, 04:36 PM   #27
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That's because I forgot the punch line. Gas absorption fridges become less Efficient as the outside temperature climbs. This seems to be an exceptionally big issue these last few years.

Residential fridges are not as adversely affected because they have a proper compressor to chill the air.

Gas absorption fridges Usually have much less space and can be dangerous, as was proven with the successful class action suit:

Norcold gas absorption refrigerators, typically installed in RVs and boats, have a cooling unit issue which may cause the boiler tubes to corrode and leak flammable gas which could increase the risk of a fire.

See how funny the joke is now? Ok well maybe not.
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Old 06-28-2016, 06:57 PM   #28
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so we put a simple inverter in our unit to handle some additional needs which included a heated mattress pad.. but we found that the mattress pad and something else wouldn't function... an email to the mattress manufacture got a call back from their engineer who politely told me that my inverter was not good enough to support the electric circuit board in the mattress pad... and he sent me to a guy in southern OR who offers the best price and quality of full wave sine inverters.... we ended up buying and installing that... and that one alone now powers all the electronics that have circuit boards that don't have an external power supply (computers etc.)

with a modern refrigerator having extensive circuit boards I'd want to know if the inverter is a full sine wave unit and if it will support the START LOAD of the AC Motor.... that would be the high rating on the unit.. it will ALWAYS draw that to start and usually run at 50% of that once the motor starts....

Just my thoughts... can I put a web site here... donrowe.com
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