Scholar V Installation & Startup Manual 07/2016 New
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E. Thermocouple Module
The Thermocouple Module has 4 channels. Type K thermocouples are used.
• Channel 0 –
Supply Air (treated air discharged from unit to the room)
• Channel 1 –
Outdoor Air (ambient outdoor air entering condenser compartment)
• Channel 2 –
Outdoor Coil #1: T
his thermocouple is located in the distributor tube
bundle for Coil #1 and measures refrigerant temperature. It is used for defrost
control.
• Channel 3 –
Outdoor Coil #2:
This thermocouple is located in the distributor tube
bundle for Coil #2 and measures refrigerant temperature. It is used for defrost
control.
F. Variable Speed Control Methodology
The variable speed compressor is capable of operating at speed from 1200 rpm
to 3600 rpm in cooling and 4800 rpm in heating. Cooling or heating capacity is
basically proportional to the compressor speed.
A control band is established by assigning a differential (+ or -) to the cooling set
point or heating set point. This differential is adjustable but comes factory set at
0.25°F. For example, if the cooling setpoint is 75°F, the differential establishes a
“deadband” from 74.75°F to 75.25 °F. If the heating setpoint is 65°F, the “deadband”
would be 64.75 °F to 65.25 °F.
In Cooling, if the room temperature is outside of this deadband on the high side,
the compressor speed (and cooling capacity) slowly ramps up. This cools the room
more and lowers the room temperature. When the room temperatures enters the
“deadband”, the compressor speed and capacity stop modulating and hold constant
at their current values. If the room temperature falls below the “deadband” on the
low side, the compressor speed and capacity slowly ramp down until the room
temperature climbs and re-enters the “deadband”, at which point the compressor
speed and capacity stop modulating and hold constant at their current values. The
following drawing shows this process in graphical form.
