[JRTJH]

Bob, There's enough pressure but not enough volume of propane. Try it sometime when you are installing a new tank. Connect the pigtail (with no propane in the trailer lines) and turn on the tank valve quickly. The system will purge and one (maybe 2) stove burners will light and function. Turn on the HWH and it will light, the "auto changeover regulator" between the tanks will turn red and the HWH will "fizzle out".... There have been two or three posts about this on our forum in the past couple of months. The "remedy" to furnaces or HWH's that won't work has been to turn off the propane tanks, remove the pigtails (this resets the limiters) and then reattaching them and SLOWLY opening the tanks. I've had the same thing happen on our big grill at home. I installed a new regulator and "fussed through" a Saturday of no outdoor cooking only to find out that the pigtail limiter wasn't working. I could light one burner, but as soon as I lit the second one, they would both fizzle out and barely maintain a flame. The propane dealer (not the kid at the hardware store propane fill station) explained it to me much as I explained it here...

If the flow limiter is activated, very little propane (at 11" WC) will flow through the lines, It will maintain enough flow to run a low use burner, but it won't be enough volume to run the two "big users" (the HWH and the furnace).