Saturday, September 7, 2013

RV Maintenance - Propane System

My whole life I have been afraid of propane.  I wouldn't even light a propane barbecue.  However since we got the Scamper I had to overcome that fear because every appliance in the camper runs on propane.  I have read so much about propane systems, how to maintain them, test them, etc. I can honestly say I no longer fear propane.  I certainly highly respect it, which is why I have been quite anal about testing for leaks.  I purchased a propane leak detector, or "sniffer", for about $25.00.  It's quite simple and works.  You push the button to turn it on, and the green light flashes for about 30 seconds while it heats up.  Then when the green light is on solid, it's ready for testing.  Just put it near any connections you want to test.  If it detects a leak, the red light starts flashing and an audible alarm sounds.  I always check it first to make sure it's functioning properly before doing a leak test by holding it near a stove burner and turning on the gas for a few seconds.  If it goes off I know it is functioning properly and the batteries are good.


So as mentioned in a prior post we upgraded our propane regulator this year to an auto-changeover regulator.  I also decided to buy a couple of tank gauges to monitor propane levels.  The regulator doesn't tell you how much gas you have left, just that there is gas or that one tank has run out and it's running off the reserve tank.  The gauges also provide a quick way to leak test the system.  With the system pressurized and all the appliances turned off, turn off both tank valves.  Watch the gauges for 3 minutes.  If the needle in the gauge drops at all, there is a leak.


As part of routine maintenance of the propane system it is good to run the following tests once yearly, or whenever the system has been opened up for any reason.  The three tests that should be performed are: 

1.  Operating pressure test; 
2.  Regulator lock-up pressure test; and 
3.  Timed pressure-drop test.

In order to complete these tests you will need a manometer.  There is a tutorial on YouTube (http://www.youtube.com/watch?v=QnlfQK-8qy4) where a gentleman shows you how to make a home-made manometer, and that is what I did.  It was quite simple actually.  All it required were two pieces of wood, 7' of clear plastic tubing, some water with food coloring and a drill. Below is the finished product:


1.      Operating Pressure Test

The ideal operating pressure for the propane system in an RV is 11 inches of water column.  An RV's appliances are designed to operate between 10 and 14 inches of water column, so 11 is the ideal pressure and are what all new regulators are set to.  But over time, the springs can get weak and the regulator may need adjustment or replacement.  Since our regulator is new, it should test at 11 inches of water column.  

To test your operating pressure, you need to hook up the manometer to a test port downstream of the regulator. Our new regulator has a test port on it but I do not have a test port fitting for it.  The simplest place to connect the manometer hose was to a burner valve on the stove.  Newer RVs have a secondary regulator in the stove, so operating pressure would show around 9 to 10 inches of water column if it has one. Our stove is 42 years old and does not have a stove regulator, so it should read 11 inches of water column directly from a burner valve.

I first turned the propane tanks off, removed the burner valve and connected the hose.  I used a hose clamp to ensure a tight connection.  Then I turned the propane tanks back on, and then slowly turned on the burner that my manometer was connected to.  It read 11 inches of water column, right where it's supposed to be.


Then I turned on some other propane appliances to put a load on the system.  The level of the manometer dropped to about 10 1/2 with other appliances running.   Acceptable pressure is 10 to 11 inches of water column so the pressure was good.  When I turned on another burner on the stove the water level in the manometer bobbed up and down a lot.  Not sure if there is something up with the burner valves in the stove or not, but this was the only appliance that affected it that way.  It remained steady with all other appliances except the stove.  On doing some research about this, I discovered this symptom could mean that there is oil in the lines (a normal byproduct of propane).  It has probably accumulated in these 42-year-old lines.  Jeff's Jeep is off being repaired right now but when he gets it back I'll use the air compressor on it to blow the lines out.  This will involve disconnecting the main propane feed line to the stove, and the line at the regulator. Then I will blow compressed air through the line to clear out any accumulated oil.

2.      Regulator Lock-Up Pressure Test

Lock-up pressure is the pressure contained in an RV gas system that has an open valve on the propane container, and all the appliances turned off.  So there is pressure in the system, but no flow of propane. In a properly adjusted system, the lock-up pressure, that pressure required in a gas system to close the seats inside a two-stage regulator and stop the flow of gas, is typically 1.0 water column inch above the set pressure.

The maximum allowable lock-up pressure is 14.0 inches of water column. Typically the pressure will only rise one-inch under a regulator lock-up condition. It should certainly stop at no higher than 14.0 water column inches. If it continues to creep upward after about three minutes, the regulator is faulty and should immediately be replaced.

Our lock-up pressure test passed, with the water column only rising about an inch.

3.     Timed Pressure Drop Test

The next thing I did was use the manometer to do a timed pressure drop test to test the propane system for leaks.  First, I turned off both propane tanks.  Then I turned on one of the burners to release some propane from the system to bring it down to 8 inches of water column.  Reducing the pressure to 8.0 inches of water column removes the lockout condition of the propane regulator.


On our stove this was tricky - it keeps bobbing back up, and then you have to release more, and then sometimes you release too much and have to start over.  I suspect it may be related to the oil in the lines. Once you finally get it to 8 inches of water column and it stays at 8 inches, you time it for 3 minutes and watch the water level in the manometer.  If the level drops, you have a leak somewhere in the system.  My level did not drop at all after 10 minutes so the system is tight.