Ingersoll-Rand ReliaTel, Manual, Page: 128 / 176

128 RT-SVD03L-EN
Figure 77. ReliaTel ™ ™ economizer terminals
N No otte e:: Used on electromechanical Foundation ™ and
Precedent ™ .
VAV Economizer Cooling Operation
A similar method of determining and adjusting the
economizer setpoint as described in CV operation will
be used in VAV Cooling operation with the additional
VAV requirements below.
• Economizer Setpoint = SA Temp Control Point - 2°F.
• Economizer Cooling is only allowed when
economizing is enabled and SA temp is greater
than Economizer Setpoint - 1.5°F.
• If conditions allow enabling of economizer cooling
after a compressor is active, the economizer
damper is forced to 100% open until all
compressors are deactivated or conditions change
to disable economizing.
• If economizer cooling is active prior to mechanical
cooing, compressor operation will be inhibited until
the economizer damper reaches 100%. Once the
economizer reaches 100%, mechanical cooling will
be enabled without delay.
• During VAV Unoccupied operation economizer
cooling will operate as it does in CV Unoccupied.
Economizer Operation with Zone Sensor,
Programmable Zone Sensor or ICS
When economizing is enabled and the unit is operating
in the cooling mode with a zone sensor, the
economizer damper is modulated between its
minimum position and 100% to maintain the zone
temperature at the economizer setpoint.
When the unit is applied with a zone sensor,
programmable sensor or ICS, the economizer setpoint
(ESP) is derived from the Cooling and Heating
setpoints (CSP and HSP) so that ESP is the higher of 1)
CSP – 1.5°F or 2) HSP + 1.5°F.
When enabled, the economizer will modulate between
minimum position and 100% to maintain the mixed air
temperature to the calculated mixed air setpoint (53°F
minimum). If the mixed air temperature starts to fall
below the mixed air setpoint, the economizer starts
closing. If the mixed air temperature falls to 50°F or
below, the damper will close to the minimum position.
If the economizer is not able to satisfy the cooling
setpoint, 1
st
stage cooling will be energized. Should the
cooling setpoint not be satisfied with 1
st
stage cooling,
2
nd
stage cooling will be energized. Most often, the
economizer and 1
st
stage cooling will be adequate to
satisfy the load. 1
st
stage cooling will not start until the
economizer has been full open for five minutes on a
non-V3 (3 minutes if the unit is a V3) and the zone
temperature error has not been reduced quickly
enough.
Economizer Operation with
Conventional Thermostat (CV Only)
When the unit is operating from a conventional
thermostat or other binary input, the economizer
setpoint feature, relative to the cooling and heating
setpoints, is lost.
The economizer control is based strictly on a signal
from the thermostat, but still maintains mixed air
temperature control of 53° ±3°F when in the
economizer mode. The economizer enable and disable
function is still determined by the outside air sensor
through the RTRM.
If a single-stage thermostat is used, only the
economizer (if enabled) or the compressor (if
economizer is disabled) will operate on a call for
cooling. A two-stage thermostat is required to achieve
economizer operation and compressor operation at the
same time.
With economizer enabled, a Y1 call for 1
st
stage
cooling will be the economizer. The damper will
modulate between minimum position and 100% to
maintain mixed air temperature at 53° ±3°. At 50°F the
damper will be at minimum position. If the economizer
is enabled, a Y2 call for 2nd stage cooling will start the
first compressor only if the economizer damper is at
100% open continuously for 5 minutes on a non-V3 (3
minutes if the unit is a V3).
If the economizer is disabled, 1st stage (Y1) will be the
first compressor. If the unit has two compressors, a call
for 2
nd
stage cooling (Y2) will start the second
compressor.
When using a conventional thermostat, or other binary
input, the ReliaTel™ controls will only allow two stages
of cooling.
E Ecco on no om miizze err