York YCAS0295EB, Installation Operation & Maintenance

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17 YORK INTERNATIONAL
FORM 201.19-NM7 (804)
Thermal Overload
Three PTC (positive temperature co ef fi cient) ther mistors
in the motor windings provides thermal pro tec tion. The
sensor re sis tance stays rel a tive ly con stant at 1k
Ω
until
a tem per a ture of 266°F (130°C) is sensed. The sensor
ex pe ri enc es a rapid rise in re sis tance be yond this tem-
per a ture. When ev er the re sis tance of one of the sen sors
reach es 13k
Ω, +/−
3k
Ω
, the 2ACE module trips, which
ul ti mate ly de-energizes the mo tor’s pi lot cir cuit. Re set
is manual after the mo tor cools and the sen sor re sis tance
drops to 3.25k
Ω, +/−
0.5k
Ω
.
Current Imbalance (Loaded & Unloaded)/
Loss of Phase
A 2 second delay at start-up allows for any imbalances
resulting during normal starting conditions. After this
ini tial delay, the 2ACE module compares the “Op er -
at ing Current” to the measured half line current. The
“Op er at ing Current” is given by 0.65 X factory overload
cur rent setting.
An unloaded compressor condition occurs when any
measured half line current is less than the “Operating
Current.” A current imbalance exceeding an unloaded
level of 25% will result in the motor pilot circuit being
de-energized.
A loaded compressor condition occurs when any mea-
sured half line current is great er than or equal to the
“Operating Current.” A cur rent imbalance exceeding a
loaded level of 17% will result in the motor pilot cir cuit
being de-energized.
Imbalance is defi ned as
(High Phase - Low Phase)/High Phase
Improper Phase Sequence
The 2ACE module calculates the phase sequence at
start-up using the three cur rent transformers to de-
ter mine wheth er the three phase sequence on the load
side of the main contactor is miswired. Upon de tec tion
of a miswired motor load, the mod ule will de-energize
the main contactor pi lot circuit within 50 millisecond
re sponse time.
Additional information on the 2ACE MP module may
be found on page 119.
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