We should talk about RV Refrigerators while we can.... (PART 1)

Greywolf · #1 (**permalink**) 05-29-2007, 10:25 PM

And here I am counting on inputs from other rv techs who also post here for inputs, or corrections if I goof anywhere in this.

For one thing - an RV fridge is not like a SONY MINI box, or the reefer in your home. It has a slow cooling process because it is designed to use a lot less energy to do it's job.

If you have a BIC lighter, pick it up and light it. THAT is the size of the flame that keeps an RV refrigerator running when it is undocked and going to the next campsite on the LPG system. How much energy is that? Not much...

When you open the door of an RV fridge, it takes about ten minutes for every minute it is open to cool back down. Some say twenty - some say thirty minutes.

If you have a lot of beverages and are going to a place where you can plug in appliances to house current - you are much better off toting a small conventional reefer that you can go in and out of for common drinks a lot (especially for "adult" beverages!).

RV refrigerators are designed for one and only one thing: STORAGE.

That's all! Get in, get out, plan what you need to get from it. They take a long time to cool back down.

The reason for all of this is that they are intended to make the most of whatever sources of energy are available to run them. In the case of LPG (LIQUID PETROLEUM GAS) they are deliberately designed to use the absolute minimum of it that is POSSIBLE... In the case of ELECTRICITY - you may be running on a generator, and thus burning fuel of some kind.

Someone I worked with recently estimated that an RV fridge could run on two seven gallon tanks of LPG with that tiny pencil flame for close to a year if the battery did not give out (it requires twelve volts to control the gas valve solenoid). Plugged in to a 115 volt source - the twelve volts would always be there, but a smart cookie would be running the fridge on electric to spare the $3.99 per gallon LPG price (or whatever it is locally).

Who's idea was all of this? Like everything else in an RV it evolved over time as the best solution to a lot of needs...

So right away we see that an RV refrigerator is going to need two out of three things in order to function:

1) 12 Volts
2) LPG
3) A 115 Volt AC housecurrent source

REGARDLESS if you are running the reefer on a 115 VAC shore cable plug-in, you have to have twelve volts available to the control circuits. It is used for switch selections and other functions. This is normally supplied by the coaches "CONVERTOR" (turns 115 AC into 12VDC).

NOTE: I'm going to bring home a pair of wire diagrams tomorrow and post them as references. I think if I do this thread well it will be something of a "SWAN SONG" for me...

Control selections are usually:

1) AUTO
2) LP
3) AC

What do these mean?

First lets talk about LP.

In the LP mode, the reefer is going to try to run on LPG exclusively, and if you are out of gas - it will call a failure AND NOT TRY TO COOL WITH ELECTRICITY.

In the A/C mode - you are telling the reefer to run on A/C line voltage only - and leave the LPG alone

In AUTO:

With AUTO selected on the refrigerator the reefer has a primary purpose - COOL IT'S INSIDES!

It will do this with LPG, but as soon as it detects an A/C housecurrent hookup it will switch to it as the least expensive, and also the best available source of input power.

NOTE: Even on A/C, the amount of energy used to cool is very small. We will get to that in part two, where I will disect the working principles of an RV refigerator "cooling unit". That won't be tonight.

Tomorrow or the next evening you will learn why it is important for your coach to be level with respect to your refrigerator.

How to tell if your reefer COOLING UNIT is bad, and why.

The reason it takes so long to cool.

How come BUGS are the worst thing on earth for your reefer.

And proper orientation of a reefer in it's compartment.

~Wolfie

PS: In fact... Let's hash over what I have posted on this so far, in case there are any questions on it, or if there are any inputs from other techs.

PPS: This will be a series because a lot of things come into play. You may not understand why I say some things at first - but over time you will. It's a big topic

95van · #2 (**permalink**) 05-30-2007, 05:01 PM

Interesting - you seem to imply it is okay to pull the camper with the fridge powered by LPG. Is this correct ? I've felt it was alright, since there is a solenoid that should shut off the gas flow if the heat from the flame is absent; but freinds have advised against it.

mechmagcn · #3 (**permalink**) 05-30-2007, 06:27 PM

Wolfie, I agree with everything posted so far, except, there are still many manual refers out there that use no 12V power at all. This thread could and will clear up a lot of the myths about RV absorption refrigerators. Keep it coming, I'm studying for my RVIA certification exam, never know what questions will be asked.
95van, the argument about running with or without propane valves on is an ageold issue. Some will declare that you are endangering the whole population by doing so, and others will say that they have done it for years without mishap. I myself leave the refer running on propane while traveling.
The biggest concern has always been a major leak of LP gas in an accident, but with the advent of modern excess flow valves built into the pigtails, it is unlikely that there will be a large discharge of gas.

Greywolf · #4 (**permalink**) 05-30-2007, 10:12 PM

For one thing (and I will rob this statement wholesale when we get around to propane (ALIAS: LPG) systems) - there are TWO STAGE regulators on todays systems to prevent major leaks. In the Air Force and NASA community this is called "Redundant Fail-Safes".

For those of you who have used compressors or compressed gasses a lot, you are used to seeing forty to one hundred ten PSI pressures.

Now imagine ONE PSI...

Let's take it further, eh?

SIXTEEN INCHES of "Water Column" is equal to one PSI.

The maximum allowable pressure for an LPG system is 11 to 12 inches of water column....

Appliances using LPG are tested for leaks at 8.5 inches of water column with the gas turned off at the tank, and must hold this pressure for at least three to six minutes.

THAT is how seriously it is taken. ONE HALF of 1 PSI is the measure.

1 full PSI out of a regulator is an instant FAIL for a gas system.

There is an additive mixed into LPG (which is normally colorless, and oderless) that makes it reek worse than a dead body. It is called "ETHYL MERCAPTAN" and is added in a strength of one or more pounds of Ethyl Mercaptan to 10,000 gallons of LPG (TEST QUESTION!!!), this is sufficient to make the slightest leak instantly noticeable. Put plainly - it smells horribly GROSS! This is done deliberately so that if there is any significant leak at all, you WILL notice something.

Curiously: The latest version of the Guinness Book of World Records lists Ethyl Mercaptan as: "THE SMELLIEST SUBSTANCE ON EARTH".

There is also a recent recall on some RV refrigerators that makes them about as fireproof as they can get. There is a thread here concerning that.

If you are at all worried about running propane for the reefer on the road, you can always crack a roof vent just a tiny bit to draw air out without having it wide open.

~Wolfie

BPofMD · #5 (**permalink**) 05-30-2007, 10:19 PM

"POTATO"
-is not spelled with an "E"... No, but it has an EYE!! Sorry Wolfie..I just HAD to do it!

Greywolf · #6 (**permalink**) 05-30-2007, 10:20 PM

Your new knick-name is SPUD!

-Deal with it...

IDMooseMan · #7 (**permalink**) 05-30-2007, 10:38 PM

Wolfie,

This info is great. I can't wait for more. If the doctor gives me the OK, I'll be going to CA to pick up a travel trailer my mom bought us for our 20th anniversary. I'll be bringing the TT back to ID.

I would like to make a request though. When you "finish" with the fridge thread, would you or someone consider a microwave info thread.

My mom had the TT tested and the microwave seems to be causing a short somehow. She sent me the printout of the technicians notes, so I'll have an RV shop in ID check it out further when I get it back here.

Greywolf · #8 (**permalink**) 05-30-2007, 10:50 PM

The microwave 115 VAC circuit is a seperate line out of the convertor from the AC breakers. It is for the microwave outlet only (the plug-in on the wall of it's compartment).

The main cause of a short circuit in THAT is either a bad MIKE Unit (rare, but possible), breaker without enough capability to handle it, OLD WORN OUT breaker, or...

There is always a chance that a screw or a staple was shot into the wiring for it after it was installed.

If there are traces of mouse droppings in the trailer anything is possible...

You can get a GFCI tester for about five dollars at any good home improvement store (such as Lowes, or Home Despot) (NOT A PLUG for either of them), and you can also check the dedicated MIKE outlet for a short with a meter.

In keeping with the "PRINCIPLE OF DETERMINING KNOWN GOOD UNITS" I would first pull the MIKE out of the trailer and try it on a house outlet. If it works, that much is good to go. There should only be about six obvious screws holding it in place.

It could also be that it draws more amps than the breaker it is on. The MAX breaker should only be about 30 amps. If it pulls that, and is a TT - it is likely using the full input to the trailer, and that isn't right.

95van · #9 (**permalink**) 05-31-2007, 06:09 PM

Thanks guys ! I didn't think it was too bad. Since the first time I accidentally left it lit and noticed it traveled fine like that, I've been hauling with it on and just not letting the nay sayers (including wife) know. What she doesn't know won't hurt me ;-)

Greywolf · #10 (**permalink**) 05-31-2007, 10:16 PM

"Hmm.... What smells like a dead carcass in here? Is it leaking propane?"

(opens fridge)

"NOPE.... It's the five pounds of Gulf Shrimp I bought in Corpus Christi... SHE TURNED OFF THE DAMNED REFRIGERATOR AGAIN!!!"

You ask, how can I visualise that so well....

Go figure.

IDMooseMan · #11 (**permalink**) 05-31-2007, 11:20 PM

Quote:

Originally Posted by Greywolf

The microwave 115 VAC circuit is a seperate line out of the convertor from the AC breakers. It is for the microwave outlet only (the plug-in on the wall of it's compartment).

The main cause of a short circuit in THAT is either a bad MIKE Unit (rare, but possible), breaker without enough capability to handle it, OLD WORN OUT breaker, or...

There is always a chance that a screw or a staple was shot into the wiring for it after it was installed.

If there are traces of mouse droppings in the trailer anything is possible...

You can get a GFCI tester for about five dollars at any good home improvement store (such as Lowes, or Home Despot) (NOT A PLUG for either of them), and you can also check the dedicated MIKE outlet for a short with a meter.

In keeping with the "PRINCIPLE OF DETERMINING KNOWN GOOD UNITS" I would first pull the MIKE out of the trailer and try it on a house outlet. If it works, that much is good to go. There should only be about six obvious screws holding it in place.

It could also be that it draws more amps than the breaker it is on. The MAX breaker should only be about 30 amps. If it pulls that, and is a TT - it is likely using the full input to the trailer, and that isn't right.

Thanks for the input on the microwave issue, Wolfie.

The MIKE is unplugged and out of the TT. The TT is in CA. My mom gets around on a walker, so I'll print this and take it with me. If she still has the TT MIKE in possession, I'll test it before the return trip.

I'm not real good with electrical troubleshooting, but if you could give me an idea on how to test the plug-in on the TT, I could give it a try. I'll look for a GFCI tester before I leave. I do have a multi-meter, but not a lot of experience using it. Is it as "simple" as plugging in the ground-lead to bottom hole on the plug and the positive-lead into one or both of the slots on the plug? If it is, I'm guessing I should be using the VAC 200 or VDC 200 scale? Am I close or did I just fry myself?

cmpd1781 · #12 (**permalink**) 05-31-2007, 11:26 PM

Good advice....I know I'm not a tech...and this is a tech thread....BUT...as a user....

You're absolutely right on the cooling properties of the frig.....We've got a Lance slide-in.......Run mostly on gas when we take to the outer banks (no A/C hookups out there sportsfans)....Works like a charm....But keeping the truck and camper level when parking is a must......And keeping the freakin' door closed is paramount...You know what you want when you open it...and I have a 10-second rule for opening and closing the frig.....

But the freezer works great (ice cube trays for the martinis are a NECESSITY!...haha), and make sure the birds nests are cleaned out of the pilot light housing, and the gas line is in good shape......and oh yeah...the gas bottle is full!.....

And knowing when to use the A/C setting...or the battery setting....or the LPG setting.....Read the damn manual!!!.....

Good read though, Wolf.....Are you the new FTE RV guru?.....(haha)

Greywolf · #13 (**permalink**) 05-31-2007, 11:37 PM

I'm just a guy in training that has to undo what well meaning but blatant fooles have done to other peoples toys.

It's an interesting occupation...

But I do pay attention and take notes.

MarkMoore · #14 (**permalink**) 06-01-2007, 08:48 AM

Thanks for the great post Wolfie - I've wondered for sometime now what was more efficent for the frige - gas or shorepower. I'll be watching for part 2.

rvpuller · #15 (**permalink**) 06-01-2007, 09:04 AM

Quote:

Originally Posted by Greywolf

If you are at all worried about running propane for the reefer on the road, you can always crack a roof vent just a tiny bit to draw air out without having it wide open.

~Wolfie

Running with the roof vent open even just a little will cause a negative pressure in your rig so it will draw dust and road dirt into the trailer around the slides will be the worst. I learned this the hard way.

Denny