Munchkin F9 faults, propane tanks, pressure

Marc_19

I have a Munchkin 199M installed in 2003.  Worked like a champ for 9 years.  Now I have intermittent F9 shut-downs, perhaps twice a month.  I have checked drain line and ignition rod, both good.  This started happening in the fall when I let one of my two 1000 gallon propane tanks get under 10%.  Seems to happen at any pressure now, but most recently when my tank was at 18%.  Someone told me that high-efficiency boilers do not like low pressure, and that I should not let the tank get below 20%--carbon could build up in the heat exchanger.  I have the usual regulators on the tank and line.

When the unit was installed, there was sometimes a faint gas odor.  Installer checked connections and lowered gas pressure slightly.  This helped with odor. 

Your thoughts on F9 and my propane questions?

Thanks,

Marc

SWEI

when was the boiler last serviced?

Did they clean the HX?

Marc_19

HX

Full "service" was a couple of years ago.  Replaced cracked wall.  Nothing recently, although rod was pulled and it was clean.

TMorg

Munchkin

First of all Boiler needs a good cleaning with CLR and a stiff nylon toilet brush. Then flush a lot of water through the fire side of the heat exchanger. Then look inside to make sure the Target wall in the back of the heat exchanger is in good shape. Grab the burner can and shake it. If it is loose at all you need to remove it and clean under the burner flange and replace the burner gasket. Then check out the gaskets on the air/gas tube that goes from the blower to the burner. These were originally a cardboard type and dried out quickly. The newer style is a gel type. Once these things are checked and reassembled. Put the boiler into high fire and with a combustion analyzer adjust your co2 to 9.1 fir Nat. gas or 10.1 for LP.