MHG Heating Ltd ©
MHG Heating Ltd Unit 4 Epsom Downs Metro Centre Waterfield Tadworth Surrey KT20 5LR
Phone: 0845 6448802 Fax: 0845 6448803 Email: info@mhgheating.co.uk
010911
Enhanced Fault Diagnosis Codes (LMU Internal Software Diagnostic Codes)
If required a more detailed fault diagnosis code can be viewed. This will assist where a definitive
cause for a repeated operational error cannot be found.
The enhanced fault diagnosis code is displayed at b0 within the second INFO level.
Access to this level can is detailed on page three of this guide.
The table below indicates a limited number of enhanced fault codes. If the exact number indicated
by the appliance is not detailed below please call our Technical Department or guidance.
Fault Code Fault Description
83 Combustion Fan Not Reaching Ignition Speed
87 Combustion Fan Operating Beneath Minimum Setting
90 Combustion Fan Not Reaching Pre Purge Speed
96 Flame Rectification Signal Detected When Burner Off
97 Flame Rectification Signal Detected When Burner Off
98 Flame Signal Lost During Operation
99 Flame Signal Lost During Operation
100 Flame Signal Lost During Operation
101 Flame Signal Not Detected Following Last Ignition Attempt
102 Flame Signal Not Detected Following Last Ignition Attempt
170 The Reset Button is being Continually Depressed. (Possible Display Module Mounting Error.)
259 The Reset Button Has Been Pressed When No Error Has Been Displayed (E153 Generator.)
282 Combustion Fan Not Reaching Correct Speed
400 System Hydraulic Error. Return Temperature > Flow Temperature. (Repeatedly.)
401 System Hydraulic Error. Return Temperature > Flow Temperature. (Repeatedly.)
402 System Hydraulic Error. Return Temperature > Flow Temperature. (Repeatedly.)
403 System Hydraulic Error. Return Temperature > Flow Temperature. (Repeatedly.)
404 System Hydraulic Error. Return Temperature > Flow Temperature. (Repeatedly.)
406 Boiler Flow Temperature Rising to Above Maximum Limit Temperature When Burner Is On.
422 Boiler Flow Temperature Rising to Above Maximum Limit Temperature When Burner Is Off.
433 System Hydraulic Error. ΔT between Flow and Return Too High. (Repeatedly.)
434 System Hydraulic Error. ΔT between Flow and Return Too High. (Repeatedly.)
435 System Hydraulic Error. ΔT between Flow and Return Too High. (Repeatedly.)
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