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Author Topic: Question about a 3 way Refrigerator  (Read 4546 times)
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« on: September 05, 2010, 06:30:43 AM »

I've got a big nice 3 way RV refrigerator with oak panel doors that match my cabinets that I was thinking about installing in the MC-9. I had intended on just using a standard 110V apartment size refrigerator until I got this one. My question is, If I use the 3 way refrigerator, can I hook up only the 110V part of the 3 way and leave the 12v and LP unhooked? I only plan on using the refrigerator under generator power or shore power and don't really want to cut any extra gas vent holes in the bus.
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« Reply #1 on: September 05, 2010, 06:40:05 AM »

you can run your 3 way on electric only, but u need to hook up 12v to power  the 3 way control panel. good luck, ron
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JackConrad
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« Reply #2 on: September 05, 2010, 07:07:25 AM »

RV refrigerators require an air vents for proper (and effecient) operatoin, no matter which source of power you use. They need a vent in the side of the coach nesar the bottom of the refrigerator for air intake and a vent in the roof for the hot air to exhaust. This "chimney effect" is what removes the heat and allows th refrigerator to cool.  Jack
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« Reply #3 on: September 05, 2010, 07:19:56 AM »

RV refrigerators require an air vents for proper (and effecient) operatoin, no matter which source of power you use. They need a vent in the side of the coach nesar the bottom of the refrigerator for air intake and a vent in the roof for the hot air to exhaust. This "chimney effect" is what removes the heat and allows th refrigerator to cool.  Jack

Does the 110V side of the RV refrigerate produce a lot more heat than a standard household refrigerator??? I was wondering if the refrigerator could be vented inside the bus as opposed to the outside. The enclosement that the refrigerator sits in could have a simple vent grill installed in the bottom and another vent at the top to allow air to move throughout behind it. I just wouldn't want to dump an excessive amount of heat back into the bus.
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« Reply #4 on: September 05, 2010, 10:24:52 AM »

I know next to nothing about RV fridges but...as far as I'm concerned residential fridges are often installed without enough venting/space for air to flow.  Since a bus is so small, and you will be using AC etc...it would be pretty counter productive not to allow for the heat of the  fridge to vent outside. 
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« Reply #5 on: September 05, 2010, 12:05:20 PM »

Yes, an RV frig produces a lot more heat than a household frig.  They work on different technologies.  The household frig uses a compressor.  The RV frig uses what is called "absorption" to cool.  It uses heat instead of a compression cycle.  It is equivalent to running an electric heater.  It must be vented to the outside.  This is also for safety since it uses ammonia gas which you would want to vent outside also if it leaked.
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« Reply #6 on: September 05, 2010, 12:14:50 PM »

i was going to say it's about the equivalent of a 350 watt space heater, since they use around 3 amps at 120 VAC.  Not that much, but some.  I think the venting of the ammonia gas in a failure is a very real reason to have the fridge installed with the required sealed vents top and bottom.  If you don't want the vents, then I would advise against having the RV type fridge.  Not totally kosher, but my bottom vent is into a luggage bay which is itself vented to outside, so I did not cut a hole in the side of the bus.  PITA for regular maintenance, though.

Brian
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« Reply #7 on: September 05, 2010, 03:27:30 PM »

I just pulled the Hot Water Heater out of the 1998 Gulf Stream donor RV figuring it was just a propane water heater. After unhooking everything and pulling it out, I found out it is also a 3 way unit too. I didn't even know you could heat water with 12 volts. I'm happy though that it will run off shore power besides only LP Gas.
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« Reply #8 on: September 06, 2010, 04:49:37 AM »

The 12 volt on the water heater is probably to power the "brain" and the ignitor for the LP.  Jack
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« Reply #9 on: September 06, 2010, 06:33:23 AM »

You can run the RV fridge on 120 with no problem, 12 volt is for the controls. You do need to vent it like others have suggested though. If you have the manual it will tell you what you need to do. They do produce lots of heat and in order for it to work properly/safely they need to be vented.

We had a Norcold and ran it on 120 volt, for about one year. It started to leak ammonia so we pulled it out and installed an apartment size Whirlpool. I like it much better as we are always hooked up to a pole. The cost of the fridge was cheaper than the cost of a new cooling/heating unit for the Norcold.

I installed it in the same place so the fridge has breathing room.

It all depends on how you use your coach, and if you want to punch holes in the side and roof.

Paul
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« Reply #10 on: September 06, 2010, 03:21:39 PM »

An RV frige cools by boiling an ammonia mixture, it actually has a boiler.

When you use AC it uses heating coils, this heat needs to vent and it can vent inside as long as there is no ammonia leak.

When you use LP it also vents carbon monoxide, which, of course is a killer.

DC only works for a short time in moderate weather, it is not good. As already posted, DC is necessary to operate frige panels/controls.

The clearance specs between frige coils and vent  (I think it is called a chimney, for good reason) walls are critical for proper operation. So you need the installation manual and need to follow it closely. Most are available online.
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« Reply #11 on: September 06, 2010, 07:11:22 PM »

A lot of the older 3-way units didn't require 12V control voltage.   No matter, as everyone has indicated, the answer to your question is yes.     
If it requires 12V control voltage, the DC "cool" circuits should be interlocked (or disconnected) so that they cannot operate unless the ignition is 'ON'...a "DC" fridge on a 3 way system is a dead cranking battery waiting to happen.  Any time the AC goes out, the fridge will try to switch over to 12V.  That ain't good...unless the engine is running. 

JR

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« Reply #12 on: September 06, 2010, 07:20:09 PM »

Our frig in automatic mode defaults to AC.  If there is no AC, it goes to LPG, and if there ain't none of that it goes to DC.  However, if you choose the mode--say put it in AC, it will not automatically switch fuels.  It will complain instead.  Hence, to avoid the problem JR referred to, don't use the auto mode unless you know you want it.
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« Reply #13 on: September 07, 2010, 07:53:29 PM »

I run my Norcold on "Auto" when it is on AC, that is the only way it will run on AC. If AC fails it switches to Gas.

It does have a "Gas" position and a "DC" position, but not an "AC" position.

I don't think it will ever revert to DC under any conditions, but it may. It never has.
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« Reply #14 on: September 07, 2010, 09:24:54 PM »

I have the Dometic Sidewise and I installed it last year. The vents in the side and roof were already there so I only had to place the fridge according to specs, this said you must understand that an RV fridge MUST be vented outside, if not you run the risk of poisonous ammonia gas being (if ever a leak should occur) vented into you living space which is an immediate death sentence if the volume is sufficient as the ammonia both blinds you AND closes your wind pipe. I have worked deck hand onboard ship storing supplies etc into the huge ammonia deep freezers and had leaks from time to time. Ammonia when intermixed in your breathing space is almost always fatal and very rarely not. you take a huge risk not venting an RV fridge on manufacture specs.
You can put a solar run roof vent W/ fan that will not tax your batteries at all an it cost around $100 it also turns on by temp of the fridge's rear fins. For the side vent you should use the standard model that passes RV safety code.

You want to really insulate that box the fridge sits in, real well, especially the wall of the bus. if you don't your fridge will always have cooling and regulating problems. When you are done you want a completely air tight and super insulated encasement separating the house from the box surrounding the fridge, the spray foam in the can works really well for sealing crevices and spaces regular insulation doesn't reach and is air tight.
Your "chimney should be as direct and unobstructed as you can make it.
and installing additional 2 temp controlled RV fridge exhaust fans mounted in the chimney and aimed to blow up to push air out the roof vent is also a good idea as these buses tend to heat up in the sun.

been there done that have the T-Shirt.
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