STULZ E
2
SERIES CONTROLLER FOR PERIMETER SYSTEMS OPERATION MANUAL
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speed algorithm based on static pressure, return temperature,
or dehumidifi cation fan speed. If suction pressure rises above
the high suction pressure limit, the fan speed decreases,
reducing airfl ow to the evaporator coil to decrease the suction
pressure. If the suction pressure falls below the low suction
pressure limit, the fan speed increases to increase suction
pressure. A message Suct Press Limit Active will
appear in the Info>Fans and CW menu screen.
On dual compressor systems, a suction pressure transducer is
utilized for each circuit. In this case the controller will respond
to the lower suction pressure value to increase fan speed and
to the higher suction pressure value to decrease fan speed.
4.7 Communication With the Controller
It is possible for the controller to communicate in a variety of
ways. Multiple A/C unit controllers may be connected together
using a pLAN. This enables the operation of multiple A/C units
to be managed from a lead controller's interface display panel
(see Section 7.0).
Using a comm card, the controller(s) may also be connected to
a BMS for monitoring and control of data points using a choice
of available serial communication protocols.
In the event of a BMS monitoring/control signal failure, the E²
controller will default to local operation at the current setpoints
for the fan, external economizer damper and chilled water
control valve. The local sensors have priority over the BMS
system.
4.8 Remote On/Off
Terminal positions are provided to connect a remotely located,
On/Off switching control device for Remote On/Off operation. If
the A/C unit is turned on and the E² controller receives a remote
24V input signal via the remote switching device, the system will
operate. If the switching device opens, removing the 24V input
to turn off the A/C unit, the controller disables all control outputs
and a message "Off by Remote Shutdown" appears in the main
display screen. The A/C system will automatically be re-enabled
when the 24V Remote On/Off signal is restored for the A/C unit
to turn back on.
As an example, the control device may be an On/Off switch,
thermostat or a humidistat. If customer provided, the remote
On/Off control contacts must be sized appropriately. The
Remote On/Off contacts must have a rating of 15 mA @24
VAC. Refer to the electrical drawing included with the A/C unit
for the wiring details.
4.9 Weekly Timer
The weekly timer may be used to set up an operating schedule
to automatically scale back or shut down the air conditioner
during low demand or unoccupied periods. This is an energy
saving feature offering the ability to create up to seven operating
schedules tailored to the needs of the building. For example
a fi ve day (Monday-Friday) weekday and two day (Saturday
and Sunday) weekend operating schedule may be set-up.
Each operating schedule may be set-up with its own setpoints
for temperature and humidity and offsets which will replace
the current temperature and humidity setpoints during that
operating schedule's time period. An evening (night-setback)
schedule may also be set allowing the A/C unit to operate at
night with relaxed temperature/humidity setpoints and offsets.
See Section 5.3.4 for detailed instructions on setting-up an
operating schedule.
4.10 Dual Power Transfer Switching
Dual power transfer switching is optionally available for critical
operations. With this option, two power service disconnect
switches are provided to connect two independent power
sources. Each power source is monitored by a phase monitoring
relay. If the user selectable primary power source is interrupted
or, if a phase loss or imbalance occurs, the power transfer
circuitry switches operation of the A/C system to a secondary
power source. Switching is accomplished using open transition,
break-before-make contactors.
The dual power transfer switching sequence may be controlled
by one of two methods: 1) The phase monitor relays in the air
conditioner manage the power transfer sequence and provide
input signals to the system controller for monitoring purposes
or, 2) the phase monitor relays provide input signals to the
system controller which manages the power transfer sequence
and sends control signals to the switching relays in the air
conditioner.
4.10.1 Power Transfer Performed by Phase
Monitors
Each power source is monitored by a phase monitor relay, one
output of which goes to the power switching circuit and the other
output sent to the system controller for monitoring purposes.
Upon an interruption to the user selectable primary power
source, the system controller de-energizes along with the fans
and compressor and/or chilled water valve, and the alternate
power phase monitor relay starts a built-in timer (adjustable).
After an auto transfer sequence delay period which ensures the
“switch to” power source is stable, the air conditioner is switched
to the alternate power source.
When power is transferred, the system controller re-boots and
after approximately 30 seconds, it provides an alarm signal.
The controller also displays an alarm message indicating which
power source failed. This alarm message may be conveyed
through an optional BMS serial communications link. When the
controller reboots, it re-establishes the control sensor inputs
and restarts the operating sequence it was in at the time of
the switch over as described in Section 3.3. If the AC system
utilizes a compressor, and it was running at the time power is
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