Whistling In Dixie
Dear RV Doctor:
We turn on the water heater only when we need hot water. However, when we do, within a couple of minutes we can hear a whining sound, which seems to come from the propane tank area. Our water heater is gas only, so we don’t have the option of using electrical power. We don’t have this problem when the furnace is running or the refrigerator is operating on gas. Is this something we need to be worried about? Is there something we can do to stop the noise?
Carolyn Kranz, Milton, Florida
In situations when there is low fuel demand, it’s common for the propane system regulator to emit a humming type of noise. Some have said it chirps. Here’s what I think is causing the sound you are hearing.
Under low propane flow, such as operating a single appliance on gas, one or both of the rubber diaphragms inside the propane regulator may vibrate to a certain frequency. This diaphragm vibration can cause an audible noise. Here’s how to determine whether the sound is being generated by a low-flow/low-demand issue. When you hear the whining begin, immediately light all the cooktop burners and switch the refrigerator to propane power. If the noise diminishes or stops under this higher demand for fuel, the problem is not really a problem, just a nuisance. If, on the other hand, the noise is exacerbated or does not lessen or disappear, there could be debris stuck at or near the orifices inside the body of the regulator or near the vent portion of the second stage on the regulator. Be sure to clean that vent periodically. It may be necessary to replace the regulator, especially if it is older than, say, 6 or 7 years, as they do wear out over time.
Another cause of the vibration-like noise could be the flexible connector that runs from the end of the regulator to the hard piping manifold. See whether that rubber hose is vibrating when the whining occurs. An overfilled container of gas is the third possibility. Pay attention to whether the noise diminishes as the fuel inside the container is used up. The whining may simply go away.
Stump The Docs
Dear RV Doctor:
Here is one that may stump you. I have a 2007 Fleetwood Pace Arrow with vacuum-flush toilets and a SHURflo water pump. I installed a Xantrex RS400 inverter to power the 32-inch LCD TV that we use while dry camping, and it works well. The problem is that when we flush the toilet, the water pump and the toilet vacuum pump start up. Actually, the water pump starts a second before the vacuum pump. The inverter senses low voltage for that split second, and it shuts down. I can reset the inverter and all is well. The kids who have the high-power car stereos install a 2- to 3-farad capacitor bank to prevent the car lights from dimming during high amplifier demand. Could this type of capacitor setup solve my problem so I can allow my wife to use the rest room? If so, where do I put it — at the battery, at one of the pumps, or at the inverter? I have the inverter within a few feet of the 6-volt batteries. Any thoughts?
Kevin Wilmouth, Greenwood, Indiana
Well, you did stump the RV Doc, so I turned to another Doc, my buddy Don Wilson at Xantrex, who is known as the Tech Doctor. Here’s what he had to say:
“The issue is voltage drop. Under heavy loads the DC voltage will drop where the current demand is higher than the conductor will allow. So, there are many possibilities and there is a solution, but finding it will depend on how the system was wired. Since the inverter was installed aftermarket, I would assume that it was tapped onto the existing converter wiring (which would be the largest wire). With that assumption in mind, the problem is that the wire feeds the DC load center AND the inverter. Without the inverter, the wire was sized properly for the DC load, but then a much larger load was added on with the inverter installation.
“First, verify my assumption by finding out whether the voltage drops at the inverter when flushing the vacuum toilet. Second, see if the voltage drops AT THE BATTERY when flushing. If both are true, the battery just can’t handle the sudden current demand. If the first is true but the second is not, then it’s a drop across the cable.
“The solution is to run new cable from the inverter directly to the battery, with a small pit stop through a fuse, and all will be well. Another solution is to add a capacitor, or battery, near the inverter, to maintain inverter DC voltage when the system demand is high — an electrical reservoir, if you will. A small AGM battery, which can be found at RadioShack, has way more capacitance than a capacitor, and is likely less expensive.
“Without knowing the real cause, I can’t guarantee the above results, but with some thought and knowledge, a solution can be found, even if it’s only flushing the toilet when you’re plugged into shore power!”
GARY’S NOTE: The small, dedicated, AGM battery that Don mentioned is simply wired in parallel with the main battery cables from the coach bank to the inverter.
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