By Gary Bunzer
Four For Two-Fer
Dear RV Doctor:
If both of my air conditioners can run with the generator, doesn’t that mean the wiring can handle them both? Why can’t I just replace the 30-amp cord with a 50-amp and run both A/Cs from the shore power also?
Marcia Hicks, Fort Walton Beach, Florida
Dear RV Doctor:
In an earlier column you talked about the 30-/50-amp shore power option, but you didn’t explain why an RV that can run two air conditioners on generator power cannot run both when on shore power.
Larry McCann, Victorville, California
Dear RV Doctor:
I have a 1994 Coachmen with a 30-amp cord. I have a 7-kw generator with two air-conditioning units. With the generator on, I can use both A/C units. With the coach plugged into a 30-amp outlet, I can use only one air conditioner at a time. Can my power cord be changed to a 50-amp cord?
Mark Millen, Hollywood, Maryland
Dear RV Doctor:
I have a type A motorhome that has two roof air conditioners and is wired for 30-amp service. When we go to campgrounds and plug in, only the front A/C will operate. The rear one will not come on. I also wired a 30-amp circuit at my house, and it will run only the front A/C. Why will they not both run together when plugged into shore power? They both run on the generator.
Rodney Pace, Arlington, Texas
Okay, gang, even though logic says it should be possible to just install a 50-amp cord in place of a stock 30-amp cord and run two air conditioners simultaneously, the issue is circuit protection. To comply with RV codes and standards, each roof air conditioner must be wired through its own dedicated 20-amp circuit breaker. In a typical 30-amp system, when on shore power, there is only one 20-amp air-conditioning circuit available. Some RVs are equipped with a switch (either manual or automatic) that will allow a choice as to which air conditioner is to run off that shore power. But with only one 20-amp breaker available via shore power, only one air conditioner can be safely operated at a time. Properly sized generators, however, can power both A/Cs simultaneously, because the generator has an output above the required 40 amps. In some installations, the second circuit breaker is located on the generator itself.
With each air conditioner being protected by its own 20-amp breaker, it would be a mathematical impossibility to use a 30-amp shoreline cord. Two times 20 is 40, right? It’s only a 30-amp main circuit on the panelboard.
Replacing the 30-amp with a 50-amp cord is simply not feasible, either. The 50-amp cord has four conductors, since it’s bringing in two separate legs of 120 volts AC from the campground pedestal (not 240 volts). A 50-amp RV has two legs of 120 volts each powering the various circuits, plus a neutral and a ground conductor. The 120-volt appliances and circuits inside the coach are split between each leg of 120 volts along with their respective circuit breakers. One A/C is wired to one leg, and the other A/C is wired to the other leg of incoming voltage.
It is possible, though it’s probably cost-prohibitive, to have the coach retrofitted and rewired properly and converted to a “legal” 50-amp system. But what about adding a second shoreline cord rated at 20 amps and wiring one of the air conditioners to that second power cord? Most campgrounds have a 30-amp and a 20-amp receptacle in the same pedestal, right? Such a setup would not be code-compliant. In years past, it was permissible for an RV to have two power cords, provided each had its own panelboard distribution box and was electrically isolated from the other. But this changed with the 1996 National Electric Code.
However, aftermarket products are available that will allow you to run both A/Cs automatically but still only one at a time. One cycles, then the other. They are never running at the same time, but they alternate to keep the motorhome evenly cooled. Such a product is probably the wiser alternative. In some coaches, it’s also possible to run the gen set while plugged into shore power, which should allow you to operate both air conditioners simultaneously.
Elevated Fridge
Dear RV Doctor:
I have a Norcold refrigerator that came standard with my 2006 Holiday Rambler. From the get-go, while running on LP gas, the refrigerator will turn off and flash (indicating electric service or issues with the LP-gas system). This usually happens in elevations above 7,000 feet and in the early morning hours after midnight. The dealer tells me that this is normal; however, I don’t think this is the case, since other campers around me don’t have this issue. Can you tell me how much of an issue barometric pressure may be playing on this unit? Can you give me advice as to what I can do to fix/repair this issue?
Adrian Valencia, Albuquerque, New Mexico
Adrian, the first step: make sure the batteries are in good condition and fully charged. Many symptoms found in today’s appliances are due to faulty or undercharged batteries. I suspect you do have a propane problem, but we need to eliminate the electrical component first. I recommend having the batteries fully charged and analyzed with a carbon-pile battery load tester to ensure their integrity.
Turning to liquid propane, realize that, as a fuel, it is affected by both temperature and pressure. At higher elevations, the air is at lower pressure, making it more difficult to achieve “perfect” or “acceptable” combustion in any of the LP-gas-burning appliances. The same goes for lower temperatures. Pure propane gas vaporizes at -44 degrees Fahrenheit, but there is the possibility you have a mixture of butane and propane in the container. Butane is often used in the southern portions of the country, and it is a member of the LP-gas family, but it vaporizes at 32 degrees Fahrenheit. At or below these temperatures, the gases will not vaporize, because it is simply too cold. Near these temperatures, combustion problems can develop.
When a problem develops with the LP-gas system in an RV, the refrigerator is oftentimes the first appliance affected. Your situation, however, may be further influenced by an incorrectly adjusted LP-gas system. Have your local dealer perform an operating pressure test on your coach to make sure the regulator is set correctly. I expect the real problem, however, lies with the environment; specifically, when the air temperature in the early morning is near freezing. Try to find out whether your LP-gas vendor uses butane or propane or a mixture. If it is butane, switch to propane if possible.
Slide “˜N Stop
Dear RV Doctor:
I have a 2004 motorhome with a slideout problem. The slide will only travel 1/2 to 2/3 of the way and stop. It doesn’t matter whether it’s traveling in or out. The panel will indicate a problem, but the manual doesn’t tell me how to fix it. I need to back up the slide a few times for a second or two, then I’m able to finish the slide travel. I have used slide lube, with no change.
Robert Shorter, Brazil, Indiana
Robert, in thinking your problem through, the most likely cause is the control board itself or possibly the motor for that slide, but I would recommend you contact the dealer and have them decipher the error code to be sure. Also, check to be sure the slideout is not binding or seizing, and inspect the mechanism itself for signs of damage or abrasion. Inspect the underbelly of the slideout for damage, as something could be wedged between the coach frame and the slideout floor. Make sure the slide is properly aligned and square when it is extended and retracted, as well as during its travel in and out. If the slide is out of alignment or binding, the motor may be drawing too much current trying to move the slide, and the controller is sensing this overload and shutting down. The error code will provide the answer.
If the slideout is indeed out of alignment or binding, have a qualified RV service center make the adjustments, as they can be tricky and should not be attempted by a do-it-yourselfer. If the slideout is in correct adjustment, then I would suspect a faulty control board, worn motor, or bad clutch.
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