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H−Pressure Switch Checkout (Heat Pump
Systems Only)
The high pressure switch is a normally closed (N.C.) auto-re-
set high pressure limit located in the compressor discharge
line. The switch is factory set to open when operating pres-
sures rise above 375psig and close when the pressure drops
below 300psig. The intent of the switch is to protect the out-
door unit from abnormally high operating pressures during
mild weather heating days.
1
Connect refrigerant gauges to the outdoor unit vapor
line.
2
Establish a compressor heating demand and allow
system to begin operating (see heating checkout sec-
tion if you need help with this).
3
Allow system to operate several minutes so refriger-
ant pressures can balance.
4
Momentarily block return air opening and carefully
watch high pressure gauge. When hot gas line pres-
sure reaches approximately 375psig, an error code will
be set in the control center, DIAGS 1,2,3 and 4 will turn
on, and outdoor unit will turn off.
5
Remove the restriction. When hot gas pressure drops
below 300psig, all DIAGs should turn off.
I−Blower Speed Checkout
The indoor blower speed should vary as zone demand
changes. Blower speed can be viewed by attaching an
electronic voltmeter between DS and any C terminal on the
control center. This is not a precise measure. It is just a
visual indicator that speed is changing.
1
Connect electronic voltmeter between DS and any C
terminal on the control center. Leave all field wiring in
place.
2
Select DC volts scale.
3
Start zone heating or cooling checkout procedure.
4
25 volts DC = high speed. Varies depending on input
voltage at primary transformer.
10 volts DC (approx.) = medium speed or 55 % of
blower.
0 volts DC = low speed or off.
All speeds in between are a percentage of 25VDC.
Troubleshooting
A−Zone Control Diagnostics
(Diagnostic LEDs)
®
When the Harmony
II zone control system finds a prob-
lem (error condition), it will turn on one or more of the diag-
nostic LEDs in the zone control center and may flash the
service alert LED in the zone control panel.
Decoding the Light Patterns
The LEDs can be lit in several different patterns, each pat-
tern corresponding to a different error condition. See
tables 7, 8, and 9. These tables show each possible display
pattern, a description of the error, and ways to correct the
error.
Some of the errors found in tables 7, 8, and 9 will cause a
fail-safe or shut-down condition. The system will shut-
down after the error is present for about five seconds. Dur-
ing a shut-down condition, all dampers will open, there is
no demand to the condensing unit or furnace, and the
blower can not be controlled from the control panel. Nor-
mal operation will resume five seconds after the error has
been corrected.
The blower may run during a fail-safe condition after a
heating demand. This is due to the operation of the blower
control board inside the furnace.
If a shut-down condition occurs while there is a call for cool-
ing, a five minute time-out is initiated before cooling can be
called for again. The time-out begins at the time of the shut-
down condition and does not affect the response to nor is
affected by a heating demand.
The meaning of the DIAG light combination may be
different depending on whether or not the service
alert light is flashing when the code is set (table 9 on
Page 37). With this in mind, it is important to remem-
ber that when the service alert LED is flashing, it only
flashes for an error condition currently in progress.
When previously set error codes are read, the ser-
vice alert LED has no meaning. The service LED was
flashing when the stored error occurred, even if it is
not currently flashing.
Only codes that have resulted in the control panel flashing
the service LED get stored. A code that will not flash the
service LED, or one that has not been present long enough
to flash the service LED (about 5 seconds), will not be
stored.
Page 34
IMPORTANT
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