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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8767
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Munchkin 199MASME R1 boiler. The boiler shut down

Customer Question

I have a Munchkin 199MASME R1 boiler. The boiler shut down with a F02 fault code. I hit the reset button and it ran for a day then it shut down again after a few more shutdowns and resets I checked the voltage on the molex connector to the outlet thermistor and it was 5 volts DC, I also replaced the thermistor, the boiler ran for 40 hrs and it shut down with an F02 fault code again this time I could not reset it , if I hit the reset button the fault code will not clear and the boiler will not start. Voltage at thermistor connector is 5 Volts DC. Any suggestions how to fix the problem I need heat I live at 6200 ft.
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: 3 thermostats are calling for heat, there are no filters its radiant heat, are you familiar with munchkin boilers
JA: Do you plan on doing the work yourself?
Customer: yes if I can I installed the boiler 10 years ago and it ran fine
JA: Anything else we should know to help you best?
Customer: No I described the problem as well as I can
Submitted: 1 year ago.
Category: HVAC
Expert:  Gaztech replied 1 year ago.

Hi! not many tech's on line tonight, I will try to help as much as I can.

Customer: replied 1 year ago.
well it only helps me if you are familiar with my munchkin boiler
Customer: replied 1 year ago.
no i dont want to talk at this point
Expert:  Gaztech replied 1 year ago.

As a tech I am used to adapt to many situations,

I would try to find the OHM chart for that thermistor and check it even if it's new I always check them first.

for now you could try measuring both old and new one to compare..

Customer: replied 1 year ago.
ok will do that get back to later
Expert:  Gaztech replied 1 year ago.

Up to you!!?

Expert:  Gaztech replied 1 year ago.

THE FO2 IS RESPONDING TO THE SUPPLY WATER TEMP. BE SURE YOU HAVE PROPER FLOW THROUGH THE PRIMARY PIPING.

YOU SHOULD HAVE A PRIMARY PUMP THAT IS OPERATING ANYTIME THERE IS A CALL FOR HTG. OPERATION. THIS IS ACCOMPLISHED THROUGH THE TT CIRCUIT.

THE SUPPLY AND RETURN TEMP SENSORS ARE THE SAME PART JUST HAVE A DIFFERENT COLOR WIRE CONNECTION. YOU CAN MAYBE SWAP THE TWO SENSORS AND SEE IF THE CODE GOES TO F03, IF SO YOU WILL KNOW IT IS THE SENSOR, I HAVE HAD WHERE THE PRIMARY PUMP AND THERMISTOR WERE BOTH A PROBLEM.

ALSO AS A REGULAR MAINTENANCE THE HEAT EXCHANGER NEEDS TO BE CLEANED YEARLY ESPECIALLY IF USED TO HEAT DOMESTIC HOT WATER AND HOME HEATING THE MORE OPERATING HRS.

THIS BOILER SEES THE INCREASED BUILD UP IN THE HEAT EXCHANGER WHICH WILL EVENTUALLY LEAD TO BUCKING THE HIGH LIMIT

Customer: replied 1 year ago.
put brand new thermistor in same thing f02 code on can not reset it
Expert:  Gaztech replied 1 year ago.

I will let another colleague try to help you with your issue

Customer: replied 1 year ago.
ok thanks
Expert:  Phil replied 1 year ago.

Hello, you have my sympathy ...although I do not always agree with other experts in this case I thing Gaztech was on the right track his advice is worth review.

As you may or may not be aware, Munchkin had a relatively short run and are now out of business, with only scant parts support if you are lucky...

They had less than 0.01% of the market before going out of business, very few boiler men as a percentage have ever worked on these, then given the many failure modes, even if they had worked on one or two... the particular problem is unlikely to have been the same as yours.

The average life span of boilers in that class runs roughly 10 years, give or take, beyond that point any time or money spent in repairs is likely be met with follow on problems. If this boiler is over 5 years old, and given Munchkins history and parts problems (Munchkin was innovative, very few of their parts were off the shelf so that generic parts seen on many other boilers and commonly available are not available for Munchkin.... you might be well advised to replace it most especially if it is over 10 years old or had been used to heat domestic hot water as Gaztech mentioned.

Let me know if you would like to discuss this broader situation with me or Gaztech further... meantime I will opt out so others here can see your questions.

Customer: replied 1 year ago.
ok i will call the place i bought the unit from and see if they still carry any spare parts and find out if there is a service technician in my area
Expert:  Phil replied 1 year ago.

Good idea!