Mitsubishi PEH series User Manual page 66

[6] Emergency operation
1) When the following check displays occur at the outdoor unit, or when the wired remote controller or indoor unit
microcomputer fails, if there are no other defects, emergency operation is possible by shorting the connector (CN31)
on the outdoor controller board.
• Abnormalities that allow emergency operation
Display
Liquid temp thermistor (TH1) open or shorted
U4
Condenser/evaporater temp thermistor (TH3) open or shorted
E8 Indoor-outdoor communication receive abnormal (outdoor unit)
E9 Indoor-outdoor communication send abnormal (outdoor unit)
E0 - E7 Communication other than outdoor unit abnormal
2) Check items and precautions when performing emergency operation
1 In addition to the abnormalities above, check the outdoor unit for any abnormalities. (When there is an abnor-
mality other than the above, emergency operation is impossible.)
2 Check the operating range. (For U4 display)
Since the outdoor fan always operates at full speed at emergency operation, do not operate the air conditioner
outside the range shown below.
Operation range (outdoor unit intake temperature)
Cooling
Heating
3 When performing emergency operation, set the outdoor unit after setting the emergency operation switch (SWE)
on the indoor controller board. For the indoor emergency operation method, refer to the indoor unit wiring
diagram.
4 A power failure causes emergency operation to become continuous operation. ON/OFF, temperature adjust-
ment and other operations cannot be performed from the remote controller.
(When a PEH-P8YE or P10YE indoor unit is connected, check that the special indoor unit power is turned on,
then start emergency operation.)
5 Since cool air is discharged from the indoor unit, when the outdoor unit starts the defrosting operation during
heating emergency operation, do not operate the air conditioner for a long time.
6 You can perform cooling emergency operation up to 10 hours. The indoor unit heat exchanger may freeze.
7 At the end of emergency operation, always return the switch settings, etc. to their original state.
3) Emergency operation contents
1 The operation mode operates according to the contents set (cooling or heating) by SW4-2.
2 The fan operation condition is always 100 % operation.
3 The operation mode display flashes every other second.
Check contents
geater than 20 C
less than 10 C
- 64 -
Operation outside this range may cause com-
pressor trouble.