EarthLinked Prime Series, Quick Start Instructions

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PSC-QS (10/16) Page 60
Appendix: Functions of the Nano-PLC (for Air-only
models)
Programmable Logic Controllers (Nano-PLC) come standard in all Prime Series units as well as in
the Classic SDH, SCW and SCWD. The Nano-PLC is programmed to ensure different functions
depending on the units, you can find a detailed description of these functions below.
I. Vocabulary:

Air Zoning
: “Sectioning a space into zones which are controlled independently of each other.”
II. Functions of PSC/PSD units equipped with the Nano-PLC (Air Only
Models)
1) Efficient Two-Stage Operation: PSC/PSD units are true two-stage, two air speed machines.
They have three dedicated terminal strips for Thermostat/Zone Board input, Air
Handler/Furnace output as well as a Aux heat source/Damper override terminal strip with
terminals labeled “A”, “S” and “D”. Thermostats and Zone Board outputs must always terminate
on the Thermostat/Zone Board terminal strip. Air handler and Furnace outputs must always
terminate on the Air Handler/Furnace terminal strip, inside the compressor unit.
2) Comfort Control:
A “Y1” call starts first stage heating/cooling which will run for 20 minutes.
Should the 20 minutes elapse without satisfying the call and without the thermostat calling “Y2”,
second stage heating/cooling will be tri
ggered. If the unit is in heating mode (“O” not energized
on the Thermostat terminal strip), second stage will trigger a 20-minute Auxiliary heat timer.
Should the 20 minutes elapse without satisfying the heating call and without the thermostat
calling for Auxiliary heat,
“W” and “E” terminals will be energized to trigger the Auxiliary heat.
This feature can take place of any balance point control such as an outdoor thermostat or
temperature sensor.
3) Comfort Assurance:
In the event that a “Y2” call takes place without a “Y1” call (for example in
the case of a thermostat fault), the unit will operate in second stage until the fault is corrected
anytime a “Y2” call occurs. The Auxiliary heat timer is still active and starts on the “Y2” call as
well if the unit
is in heating mode, “O” not energized.
4) Performance Assurance:
If more than two consecutive “Y1” calls take place without the
thermostat calling for “Y2” or, before the 20-minute second stage timer runs out during each
call, on the third “Y1” call, a maintenance cycle will be triggered which will hold and lock the
system into second stage for 5 minutes to ensure proper oil return to the compressor. The
maintenance cycle locks out any other call or mode until completion. After the maintenance
cycle complet
es, or if a “Y2” call is made before the maintenance cycle occurs, the counter
resets back to zero.