Toshiba MMY-MUP0801HT8P-TR Service Manual page 257

(8) Set Bits 1 and 2 of SW100 on the interface P.C. board same as that of the failed header unit (terminator
resistance setting).
[Wiring changes to communication line]
(9) Redirect the indoor-outdoor communication line connected to the failed header unit [Uv (U1/U2)] to the unit
selected as the header unit [Uv (U1/U2)].
(10) If a central control device is connected, connect the central control communication line [Uh (U3/U4)] to the
communication line terminal of the unit selected as the new header unit [Uh (U3/U4)], and connect up the
tie connector between the [Uv (U1/U2)] and [Uh (U3/U4)] terminals.
Failed header unit
(11) Turn on the power supply to all the units connected to the system other than the failed unit.
Determine what to do with the power supply to the failed unit in the following manner.
<In case of failure in compressor, electrical part, P.C. board>
Leave the power supply off.
<In case of failure in refrigerating circuit or related part (pressure sensor, temperature sensor,
refrigerating cycle part, or fan system part)>
Turn on the power supply to protect the compressor (by turning on the case heater).
(When the power supply to the unit is turned on, [E19] (failure in the number of outdoor header units) will
be displayed on the 7-segment display. However, this will not cause any problems.)
This is the end of header outdoor unit backup operation setting. Check the operation.
(6)
Set SW101 and SW102
identically to failed header
SW101 SW102
ON ON
1 2 3 4 1 2 3 4
SW104 SW105
ON ON
1 2 3 4 1 2 3 4
Set Bits 1 and 2 of SW100
identically to failed header
SW100
ON
1 2
Unit selected as new header unit
(previously follower unit No. 1)
Indoor-outdoor communication line
(Uv (U1/U2) terminal)
Redirect the indoor-outdoor communication
line from failed header unit to unit selected
as header unit [Uv (U1/U2)].
(7)
Turn on Bit 3 of SW103.
SW103
ON
1 2 3 4
SW107
ON
1 2
(8)
Central control communication line
(Uh (U3/U4) terminal)
(9)
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Follower unit No. 2
(10)
If central control device is connected,
redirect central control communication
line from failed header unit to unit
selected as new header unit [Uh (U3/U4)].