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Munchkin 80 / SS-45 Question

slade8200 Member Posts: 5
Just moved into a new place a few months back.  Previous owner took extremely good care of the house and was very meticulous on maintenance.  However I found that the hot water temp was a little too cold for my liking and the shower would run out of hot water after 13 mins or so.  I have a Munchkin 80 and SuperStor-45 setup.  I changed the SuperStor temperature value in the Muchkin from the default of 119 to 140 (did this last night).  This morning I had a 5 min hot shower then it went cold, also my heat was not working.  Checked the display and I had a F05 error code.  Reset it and the boiler fired back up.  I'm sure this error code has arisen due to my changing of the water tank temp.  I did a little reading and someone said increasing the post purge time might help?  I'm not sure... any ideas?  Thanks.


  • lchmb
    lchmb Member Posts: 2,997

    the munchkin manual..

    FO5:    Supply Temperature is too High (locks out at 230 degrees F). Make sure you have water flow. Does the Munchkin shake, make a gurgling sound, and then lock out? You have a water flow problem. First check the circulators to see if they are working. Check to make sure pumps and check valves are installed in the correct direction, not backwards. Make sure there are no obstructions in the plumbing such as ball valves turned off, or almost shut off. No three-way or two way valves should be used on the boiler primary loop without a pressure-by-pass valve. If you have a pressure by pass valve, check its setting, and check that it is not installed backwards.
  • slade8200
    slade8200 Member Posts: 5

    What temperature is it actually referring to?  Supply from what?
  • Jr_12
    Jr_12 Member Posts: 38

    He is referring to the supply from the boiler. Most likely when the unit fires up for domestic it is not flowing whether it be from a bad/plugged pump or obstruction in the boiler/piping. If you reset the unit and watch it you will probably notice the display temperature rise up significantly fast and then jump out on high limit. It will also sound like your boiler is making popcorn inside. If this is the case I would recommend calling a contractor in.

    There is also the small possibility that this could be a thermistor error. You will find an Ohm chart in your manual by the fault codes to check that direction.
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