Lennox Mini-Split Service Manual / Page 229
P1 Flow Chart
Voltage protection
Check the voltage of outdoor unit power
supply, the voltage between
L(L1) and N (L2) range min. 187~ max
253VAC
Yes
Check whether the voltage of IPM board
P and N is normal? DC277-356V for
18-27KBtu/h; DC277-410V for 36KBtu/h.
No
Replace bridge rectifi ers, and then
check whether the system can run
normally(Only for 4-zone)
No
Replace IPM board, and then check
for normal unit operation
No
Replace outdoor main board.
Problem Solved.
Yes
Yes
Check the primary power supply.
No