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Old 03-21-2018, 07:48 AM   #1
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How long will fridge keep food cold on battery

Hi, I have the 31L5 with the 18plus cubic fridge that runs on electric and gas. I have a 7 to 8 hour ferry ride planned where they will not allow the LPG to be on, so the fridge will need to be off or on electric.

1) Anyone know if the electrical outlet is inverted?

2) If inverted, will the house batteries run the fridge for 8 hours?

3) Should I just run my generator?

Thanks
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Old 03-21-2018, 07:58 AM   #2
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I am guessing you do not have a 3 way fridge that runs off 12 volt and are talking about running the fridge of an invertor? If the fridge was cooled down well and you kept the door closed I wouldn't think you would have a problem. I would have a hard time believing that they would have a problem with a propane fridge but would let you run a generator.
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Old 03-21-2018, 07:58 AM   #3
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What Ferry are you taking? Most will NOT let you run a Genny either! Some will NOT let you be Inside your unit also! Youroo!!
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Old 03-21-2018, 08:01 AM   #4
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The ferry is from Sydney to Newfoundland, and they want the LPG turned off at the tank. You do not have access to the unit for the duration of the trip.
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Old 03-21-2018, 08:32 AM   #5
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since you won't be opening/closing the fridge during transit, fill some extra milk jugs and freeze them. That will help keep your stuff cool enough without having to run anything.
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Old 03-21-2018, 08:37 AM   #6
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If some of the items you will be carrying in the fridge can be frozen, ( ie meat, water, ) freeze them before adding to fridge. The more cold items in the fridge the longer it will last. If it is not opened and everything is cold you should be OK.
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Old 03-21-2018, 08:45 AM   #7
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My residential fridge will run for a couple days on battery power(4x6v), if not opened and nothing else on. You should be fine for 7-8 hours.
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Old 03-21-2018, 09:01 AM   #8
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since you won't be opening/closing the fridge during transit, fill some extra milk jugs and freeze them. That will help keep your stuff cool enough without having to run anything.
x2
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Old 03-21-2018, 09:12 AM   #9
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I was discussing the merits of a residential fridge VS the RV fridge with two fellow campers last year. One was service manager for an RV dealer in MI the other camper owned an RV fridge and my unit had a residential fridge. He stated that a residential fridge without any power and with cold food in the unit will keep food for up to 3 or 4 days depending on how often the door is opened. Were as a RV fridge would only keep food cold for 2 days at the most. Why less insulation in the RV fridge and the efficiency of the cooling process that is use to operate the refrigeration for the cooling.

This was his reasoning for this statement.

I have driven for and up to 8 hours with the inverter off and no power to the residential fridge. The food was still cold and the temperature gage was still under 40F in the fridge. This occurred a couple of times when we started using the trailer for the first year. Turning on the inverter is now on our check list to insure that this is turned on when we break down for travel.
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Old 03-21-2018, 12:29 PM   #10
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Ferry Crosing

We have crossed the ferry and know others we have just shut the propane off turned the fridge off and never had a problem. Fridge was still cold when we got to NFL. Also enjoy your selves there, it is a great place to visit, and we ar planning on going back in 19.
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Old 03-21-2018, 12:57 PM   #11
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I am guessing you do not have a 3 way fridge that runs off 12 volt and are talking about running the fridge of an invertor? If the fridge was cooled down well and you kept the door closed I wouldn't think you would have a problem. I would have a hard time believing that they would have a problem with a propane fridge but would let you run a generator.
Propane is taboo on boats generally, because it is much heavier than air and settles right in to the lowest place in the hull and lays there until it gets a chance to blow. Gas fumes are evidently lighter or just more volatile and dissapate.

Anyway, pretty hard to run a vehicle Ferry without gasoline engines running on the boat.
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Old 03-21-2018, 12:58 PM   #12
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I've done the Newfoundland ferry several times and have never had a problem. I've read that an RV fridge just loses about 1 degree an hour and I've never had an issue with defrosting or food spoilage. You won't be allowed to access your rig, so you won't be opening the fridge door while on board. BTW, If you're going to the west side of Newfie there's a very nice RV park not too far north of the ferry dock. I don't recall the name of it, but it has full hookups and nice sites.
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Old 03-21-2018, 01:00 PM   #13
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Originally Posted by Jim34RL View Post
I was discussing the merits of a residential fridge VS the RV fridge with two fellow campers last year. One was service manager for an RV dealer in MI the other camper owned an RV fridge and my unit had a residential fridge. He stated that a residential fridge without any power and with cold food in the unit will keep food for up to 3 or 4 days depending on how often the door is opened. Were as a RV fridge would only keep food cold for 2 days at the most. Why less insulation in the RV fridge and the efficiency of the cooling process that is use to operate the refrigeration for the cooling.

This was his reasoning for this statement.

I have driven for and up to 8 hours with the inverter off and no power to the residential fridge. The food was still cold and the temperature gage was still under 40F in the fridge. This occurred a couple of times when we started using the trailer for the first year. Turning on the inverter is now on our check list to insure that this is turned on when we break down for travel.
That is generally true. The better Norcold or Dometic 12v/110v compressor fridges are light years ahead of their gas/electric brethren. And they fit the identical same dimension spots. A Norcold 12v/110v will only use about 3 amps on DC and about 4/10th amp on 110v. That is pretty darn efficient.
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Old 03-21-2018, 01:31 PM   #14
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Thanks to all that responded. Looks like I will simply shut everything down. I also like the idea of adding a couple of gallon jugs of frozen water, just for insurance.

We plan to be on the Island for a month, it will be our second time there, first time with an RV. We are going before the kids get out of school, so we will not have to plan anything.
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Old 03-21-2018, 01:34 PM   #15
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We went to Newfoundland in our 2015FR3 on the North Sydney to Port-aux-Basques ferry. All of the food in the freezer was still frozen solid and the food in the fridge was ice cold upon arrival. The refrigerator was a propane/electric model so there was no power to the fridge on the 7 hour trip to Port-aux-Basques or the 6 hour trip back.

As for the nice campground near the Newfoundland ferry terminus, we found the .grandcodroy.com campground to be one of the best we’ve found anywhere. Nice sized sites, good showers, the friendliest owners/operators anywhere, great hiking trails, and all in an amazingly charming area of Newfoundland. We spent our first night in Newfoundland there and spent another 5 days there before leaving Newfoundland. Very close to the ferry so no rushing, no worries. As a matter of fact, we’re going back to Newfoundland for 3 weeks later this year and are very much looking forward to the Grand Codroy Campground and the entire Grand Codroy area.

Enjoy your trip!
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Old 03-21-2018, 01:35 PM   #16
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Quote:
Originally Posted by sleepybadger View Post
since you won't be opening/closing the fridge during transit, fill some extra milk jugs and freeze them. That will help keep your stuff cool enough without having to run anything.
x2
X3 (best answer!)

A full fridge holds cold better than an empty one (thermal mass plays a role in this). Air doesn't store much thermal energy (or lack thereof), but a pound of butter at 35 degrees or so is a pretty good thermal storage device. A bottle of orange juice is also effective as a thermal storage device. Bread, frozen french fries, frozen vegetables, and other light, airy items, not so much. Stock up on steaks.

Consider your home fridge during a power outage. Leave the door closed, and the contents will survive for far more than 8 hours. Open the door, however, and the cold air literally falls out onto the floor. That's why a chest freezer is vastly superior to an upright, and why supermarkets can have frozen items in an open-top chest freezer. The cold air sinks and settles into the freezer.

Variables in refrigerator insulation will also make a difference (RV sales people notwithstanding). Perhaps a "residential" fridge (120 volts via inverter at all times) is better insulated, but I think that's more a matter of the individual fridge and its manufacturing and design than it is the cooling source. In fact, a residential fridge has a much more efficient cooling "engine" than an RV fridge, so it could easily cheat on insulation. That may not be the case, but cooling "engine" and insulation have no mandatory correlation.

Residential RV fridges use conventional compressors vs. the 'evaporative" cooling of the RV/dual or triple 'fuel' source fridges common in smaller RVs (the cooling engines). But that has zero to do with how the fridge performs when not running. It does impact recovery. The residential fridge will recover much more quickly than an evaporative RV fridge. Fire up the propane ASAP after docking.

Frozen stuff in the freezer will certainly help, but without power, even a residential fridge won't have fan circulation of air between compartments, so what's in the freezer is essentially isolated from the fridge compartment. A freezer full of frozen stuff won't do much to cool the contents of the fridge section. But a full freezer will stay frozen better than a partially empty one, even if some of what's in there is frozen peas. Peas are better energy storage devices than air.

The frozen milk jug of water in the fridge section is a great bit of insurance to turn your "fancy ice box" into an ice box that will easily preserve food for 8 hours or more without power. (There were days when this WAS refrigeration.)

Your frozen "jugs" can be anything that fits available space...water bottles, tupperware tubs, whatever. Water bottles, in particular, are good in-fill, because you can drink them on the other end, refill, stick them in the RV freezer, and have them ready for the ferry ride home. They also can fit on top of things, fit in drawers and on door shelves, and so on. Chances are that a gallon jug might be a snug fit in your freezer on a 2-way or 3-way RV evaporative fridge. But if it fits, that big, monolithic block of ice is ideal. Here the physics are linear. A gallon jug is 128 oz. It will take 8 x 16 oz. water bottles to equal 1 gallon jug.

Put your ice "high" in the compartment and let the cold "fall" to the lower areas. Cold air is heavier than warm air. A layer of frozen water bottles on their sides on top of the contents of the upper shelf will cool more effectively than ice on the bottom shelf.

Water ice has one huge advantage over most other "cold" objects. It takes a substantial amount of energy to transform ice at 32 degrees F into water at the same temperature. This melting is called "fusion" to achieve the "change of state." Frozen water requires the most energy of common elements to transform it from solid to liquid. It's not terribly important to know the physics other than to know that frozen water (and other water based liquids such as juices) are particularly good cold storage devices...and make a much better choice when trying to do the "ice box" effect on your fridge.

The ice box effect will be great for your peace of mind, and you'll have some extra water at your destination.
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Old 03-21-2018, 01:43 PM   #17
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Frig on inverter

Quote:
Originally Posted by jimmoore13 View Post
X3 (best answer!)

A full fridge holds cold better than an empty one (thermal mass plays a role in this). Air doesn't store much thermal energy (or lack thereof), but a pound of butter at 35 degrees or so is a pretty good thermal storage device. A bottle of orange juice is also effective as a thermal storage device. Bread, frozen french fries, frozen vegetables, and other light, airy items, not so much. Stock up on steaks.

Consider your home fridge during a power outage. Leave the door closed, and the contents will survive for far more than 8 hours. Open the door, however, and the cold air literally falls out onto the floor. That's why a chest freezer is vastly superior to an upright, and why supermarkets can have frozen items in an open-top chest freezer. The cold air sinks and settles into the freezer.

Variables in refrigerator insulation will also make a difference (RV sales people notwithstanding). Perhaps a "residential" fridge (120 volts via inverter at all times) is better insulated, but I think that's more a matter of the individual fridge and its manufacturing and design than it is the cooling source. In fact, a residential fridge has a much more efficient cooling "engine" than an RV fridge, so it could easily cheat on insulation. That may not be the case, but cooling "engine" and insulation have no mandatory correlation.

Residential RV fridges use conventional compressors vs. the 'evaporative" cooling of the RV/dual or triple 'fuel' source fridges common in smaller RVs (the cooling engines). But that has zero to do with how the fridge performs when not running. It does impact recovery. The residential fridge will recover much more quickly than an evaporative RV fridge. Fire up the propane ASAP after docking.

Frozen stuff in the freezer will certainly help, but without power, even a residential fridge won't have fan circulation of air between compartments, so what's in the freezer is essentially isolated from the fridge compartment. A freezer full of frozen stuff won't do much to cool the contents of the fridge section. But a full freezer will stay frozen better than a partially empty one, even if some of what's in there is frozen peas. Peas are better energy storage devices than air.

The frozen milk jug of water in the fridge section is a great bit of insurance to turn your "fancy ice box" into an ice box that will easily preserve food for 8 hours or more without power. (There were days when this WAS refrigeration.)

Your frozen "jugs" can be anything that fits available space...water bottles, tupperware tubs, whatever. Water bottles, in particular, are good in-fill, because you can drink them on the other end, refill, stick them in the RV freezer, and have them ready for the ferry ride home. They also can fit on top of things, fit in drawers and on door shelves, and so on. Chances are that a gallon jug might be a snug fit in your freezer on a 2-way or 3-way RV evaporative fridge. But if it fits, that big, monolithic block of ice is ideal. Here the physics are linear. A gallon jug is 128 oz. It will take 8 x 16 oz. water bottles to equal 1 gallon jug.

Put your ice "high" in the compartment and let the cold "fall" to the lower areas. Cold air is heavier than warm air. A layer of frozen water bottles on their sides on top of the contents of the upper shelf will cool more effectively than ice on the bottom shelf.

Water ice has one huge advantage over most other "cold" objects. It takes a substantial amount of energy to transform ice at 32 degrees F into water at the same temperature. This melting is called "fusion" to achieve the "change of state." Frozen water requires the most energy of common elements to transform it from solid to liquid. It's not terribly important to know the physics other than to know that frozen water (and other water based liquids such as juices) are particularly good cold storage devices...and make a much better choice when trying to do the "ice box" effect on your fridge.

The ice box effect will be great for your peace of mind, and you'll have some extra water at your destination.
My frig stays cold for 3-4 days on the inverter. Mine is a 24.5 cu. ft. frig. I have never had a problem. I open and close it as normal.
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Old 03-21-2018, 02:03 PM   #18
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No problem from Sydney

We did exactly the same trip 2 year ago, and we have a regular Dometic fridge, and this not a problem. Keep in mind that the temperature on the dock is fairly cool on the sea, and this makes me believe that our fridge can stand a lot more than 8 hours on the battery. At the time we had a single 12 V battery.
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Old 03-21-2018, 03:09 PM   #19
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My residential fridge will run for a couple days on battery power(4x6v), if not opened and nothing else on. You should be fine for 7-8 hours.
He don’t got residential fridge
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Old 03-21-2018, 03:11 PM   #20
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My frig stays cold for 3-4 days on the inverter. Mine is a 24.5 cu. ft. frig. I have never had a problem. I open and close it as normal.
I believe the implication from the OP was that the fridge could run on propane. That suggests it's not a residential fridge. I think your fridge may be different (24.5 cu. ft. residential vs. an 18 (+/-) dual fuel RV fridge in the OP's unit.)

That said, it's possible - likely - that the OP's coach also has an inverter. If so, the fridge might be connected to the inverter full time, but that seems unlikely. More likely, since it also runs on propane, the 120 volt supply is connected via conventional circuits to the 120 volt circuits straight out of the RV's main Converter. Why "invert" 12 volts to 120 and consume half of a large inverter's capacity, and risk draining the batteries unintentionally, when one has propane as an alternate fuel source?

For a residential fridge, having a dedicated inverter to power the fridge would certainly make sense. For a multi-fuel fridge, many automatically hunt for power, with 120 volt power primary, and propane secondary. But all you need to do is pull the plug on shore power and the fridge automatically starts the igniter and hopes for propane. I have a 3-way fridge, and that's how it works. I can also manually override and run directly on 12 volts for a SHORT time. If the fridge was connected to 12 volts via an inverter, it would just draw on the battery and never look for propane...soon leading to a dead battery.

Perhaps it's possible to run an extension cord from the auxiliary inverter to the fridge in this situation. Setting aside the fact that a fridge that's closed up tight may not run often, it's important to take stock of the battery bank on a rig that's not setup to run a residential fridge. The standard batteries might have substantially less capacity than those in a coach built to run a residential fridge...less than enough for a sustained run of the fridge on 120 volts through the inverter--at least in regular, day-to-day use. Then again, if the fridge is stuffed and closed on the ferry, it probably won't run often...and all would be well.
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