11
During normal operation of zoning equipment, the amount of air passing through the air conditioning coil
or over the heat exchanger may be reduced to a point that undesirable air temperatures may develop in
the duct system (too cold or too hot). The Leaving Air Temperature (LAT) system is used to cycle the AC
compressor or heating system to prevent evaporator coil freeze-up or overheating of the heat exchanger.
Install the Sensor into the supply duct just around the corner from the Plenium and connect to the “LAT
Sensor” terminals (Fig. 10b). Connect the Green grounding lead to the ground terminal at the 24 VAC
terminals (Fig. 5a) along with the mechanical ground wire. Add no more than 25 ft. of wire to LAT Sensor.
NOTE: All LAT limit controls must be used as secondary controls only.
The LAT control setting must be above/below your primary factory protection level.
LAT SYSTEM SET-UP
Set both rotary switches(Heating LAT and Cooling LAT) to the desired heating and cooling limits
(Fig.10a).
Heating LAT settings range from 100° F to 180° F and OFF.
Cooling LAT settings range from 40° F to 56° F and OFF.
If you do not wish to use either or both, place the unused rotary switch pointer to the Off position.
You must install the sensor or place both rotary switches to the Off position.
Self Test: The Arzel Panel automatically detects an open or shorted LAT sensor and locks out the
equipment accordingly.
· Both Red LED’S at Heating LAT flashing indicates a shorted sensor wire or probe.
· Both Yellow LED’S at Cooling LAT flashing indicates an open sensor wire or probe.
High LAT: The temperature setting cycles the first-stage heating at set point temperature. Second-stage
heating is automatically cycled 10° lower than high temperature setting. Both stages will re-connect after
a 15° temperature drop.
Low LAT: The temperature setting cycles the first-stage cooling at set point temperature. Second-stage
cool- ing is automatically cycled 5° higher than set point temperature. Y1 will reconnect after a 4-minute
time delay if the duct temperature is above set point. Y2 will reconnect after a 4-minute time delay, if the
duct temperature is 5° above set point.
NOTE: All LAT limit controls are to be used as secondary controls only.
The LAT control setting must be above/below your primary factory protection level.
Rev. 5/01/01
MASTER ZONE CONTROL (MZC
®
)
Moving this switch to the ON position or closing a circuit across the “Set-Back” terminals, establishing
Zone 1 as the “Master Zone” and allows automatic (occupied/ unoccupied) set-back or set-up control. The
“Master Zone Control” mode operates as a single zone system: all zone dampers open and the
equipment is cycled based on Zone 1 thermostat settings. Master Zone operation may be initiated by
manual operation of the switch or it may be operated by a time clock or programmable thermostat with
dry contacts that close in the unoccupied mode (wired across the MZC Remote terminals). The switch
and the remote terminal are electrically parallel. You may use either one or both (Fig. 10b).
LAT™ (Leaving Air Temperature) Limit Controls for Heating and Cooling
(Fig. 10a)
(Fig. 10b)
U.S. and Foreign Patents & patents pending. © copyright 2004 by Arzel Zoning Technology, Inc.
