MFTCW and MFTHW- Error 40

MFTCW and MFTHW- Error 40

Error 40 is a HARD LOCKOUT when a gas leak is detected in or around the cabinet for greater than 5 seconds OR 3 times in 10 minutes.

FYI - THE NUMBERED BLUE BOXES BELOW CORRELATE TO A SPOT ON THE FLOW CHART ABOVE

(1) Explanation of Error 40-Hard Lockout - POTENTIAL GAS LEAK !

IMPORTANT !  If you smell gas, STOP!  A potential gas leak is best left to a qualified, licensed and insured, properly trained technician! 


It is strongly suggested that an ELECTRONIC GAS LEAK DETECTOR be used to detect gas leaks in and around the cabinet of the appliance. 

A "soapy" solution can be used BUT not as effective as an electronic gas leak detector. 

Fluorescent solutions are slightly more effective than a soapy solution, but again,  not as effective as an electronic gas leak detector ! 

  1. Turn off all electric to the boiler for safety ! 
  2. Check for potential gas leaks on all gas piping near and around the boiler.  Pay specific attention to all fittings ,unions, gas cocks. If any gas leaks are found , make proper repairs/replacement to gas piping, fittings, unions, gas cocks as "proper" plumbing practice and local codes require and mandate. 
  3. Check for potential gas leaks inside of the boilers cabinet , paying specific attention to where the gas supply connects to the boilers incoming gas line. (a gas supply connected and tightened to the boilers gas connection can be disturbed when not "backing" up the fitting with a second wrench) ! 
  4. Turn electric to the boiler back on. 
  5. Reset the error by pressing the boilers DISPLAY power button.

  6. A video is included and attached below
  7. Assure there is a call for heat (CH or DHW). 
  8. CAREFULLY continue to check for gas leaks along all of the boilers gas lines and connections paying specific attention to the boilers gas valve connections and the orifice connection. 
  9. Further check the boilers intake and exhaust (an electronic gas leak detector MUST be utilized to do this) entering the blower and exiting the blower as well as ALL rubber boots and flue exhaust connections. Make any and all necessary repairs/replacements if a gas leak is found. 
  10. If all gas piping, fittings, valves, unions are FULLY PROVEN TO BE FREE OF GAS LEAKS AND THIS IS A NEW INSTALLATION,  it is possible that "off gassing of the adhesives, sealants, etc." is occurring and this condition will rectify itself within a few run cycles. 

* IT IS NEVER RECOMMENDED TO OPERATE THE BOILER WITH THE GAS LEAK "SNIFFER" REMOVED FROM THE CIRCUIT BOARD FOR AN EXTENDED TIME !




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