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Freshman Series - Owner's Manual - Installation, Operation, and Service Instruction - Version 1.1 EN
opens at 150°F and resets automatically, and a line voltage
fuse at the element which opens at 219°F and will not
automatically reset, consult a service technician to replace
these fuses.
Hydronic Coil
There is one temperature disc sensing the air temperature
entering the hydronic coil. A temperature of 37°F will open
either circuit. A low entering temperature will close the
damper to all outside air, remove power to all fans and open
the hot water valve. The disc automatically resets when the
temperature rises above 59°F.
Changeair is not responsible for injury to untrained or unauthorized personnel who
attempt to do repairs based on the trouble shooting procedures outlined in this section.
8.5 General Unit Sequence of Operations
The following is a suggested sequence of operations, which
is determined by the control thermostat. All units supplied by
Changeair, arrive with a standard control terminal strip to inter-
face with a thermostat. Consultation with the design engineer
will determine the exact sequence required for your applica-
tion, which may vary from the example given.
Occupied Mode
Unit operation is energized by an occupied signal and provides
fresh air as per ASHRAE code 62-89. While occupied, the sup-
ply fan runs continuously. Heat and Cool functions would cycle
as needed with the high speed supply fan and occupied set
points from the thermostat. Temperature protections move the
fresh air damper to a minimum position when the mixed air
temperature falls below 50°F.
Unoccupied Mode
Fresh air damper is disabled. Unit will operate on Heat/Cool
function, cycling the high speed fan as required to meet unoc-
cupied set points determined by the thermostat.
Cool
When cooling is required, an economizer circuit will process
the signal. This is a multi-function board, controlling the cool
signal to the compressor (optional) and damper positioning.
On models with mechanical air conditioning, it will lock out the
mechanical cool below 60°F outside temperature and intro-
duce 80% fresh air to achieve cooling. On models without me-
chanical air conditioning, free air-cooling is the only function.
Heat
Hydronic/Steam
The type of valve (modulated or on/off) dictates the type of
control required: the on/off type requires a 24vac signal to ac-
tivate it from closed to full open. The modulated type requires
a 0-10vdc signal. To operate it from closed to any point up to
full open (10vdc). The thermostat /controller must be capable
of providing a modulated heat signal.
Electric
Electric resistance elements in numerous voltages and Kilowatt
(KW) capacities are available. Most elements (except very
low KW capacity units) come in two banks: For Example: 10KW
= 2banks X 5KW each. The thermostat /controller must be
capable of providing staged heat signals.
Damper Control During The Occupied Mode
The damper actuator is controlled by one of the following four
methods:
1. Preset Potentiometer - An onboard potentiometer, adjust-
able to a xed voltage is enabled during the occupied
mode.
2. Air Quality Monitor (Optional) - This device controls fresh
air based on air pollution levels in the occupied mode. The
damper will modulate based on preset sensitivity and mini-
mum to maximum voltage outputs. Consult your Changeair
product catalog for more information on this product.
3. Remote Control - An external controller may supply a DC
voltage signal to control the damper actuator based on its
system sequence of operations.
4. CO2 Ventilation Controller (Optional) - This sensor accurate-
ly monitors occupancy levels based upon CO2 levels within
the room. The corresponding modulating output signal is
used to regulate the fresh air damper to provide ventilation
based upon the actual occupancy levels of the space.
Troubleshooting Guide
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