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The second new safety feature is called a "flow-limiting-device" it's purpose is to restrict the flow of escaping gas if there is an excessive leak in the RV's gas system. It's this second "flow-limiting-device" feature and how it works, that forms the core of the secret! Almost every time the cylinder valve is opened, a small ball in the center of the brass nipple (inside the green nut) is pushed forward into a brass seat. This seat doesn't totally shut off the gas. By design, it allows a small amount of gas (by-pass flow) to go into the RV's gas system. If everything in the gas system is closed and in the off position and there are no leaks, the by-pass flow builds up a back pressure that equalizes the pressure in the system with the cylinder pressure and with the help of a small spring pushes the ball back off the seat and allows unrestricted flow through the system. All this happens in about five seconds and the owner doesn't even know it's happening, appliance light, furnaces and water heaters run and everything is normal. Now lets look at the same system but with a burner left on at the range top. Again the cylinder valve is opened, the ball is pushed into the seat, the by-pass flow goes out though the system but this time it can't equalize because the flow continues out through the open range top. The owner goes inside and starts to cook dinner. He lights two burners on the range top and everything seems OK until the furnace comes on. At that point, the flames on the range top are drawn way down and the furnace won't ignite, everything seems starved out. The reason? We don’t have full un-restricted cylinder flow to run our system, we only have the small by-pass flow which is far too small to feed the appliances in our gas train. |
