Section 1 - Ventilation
Honeywell Economizers 63-8594-02 20
Economizer Cycle Definition
On a First Call for Cooling From
Commercial Thermostat (Y1)
Controller signal is routed to the economizer
logic module.
IF THE OUTDOOR AIR IS SUITABLE FOR
FREE COOLING:
With analog economizers the actuator
modulates the outdoor damper open until the
room temperature is cool enough to satisfy the
call for cooling and maintain the mixed or
discharge air between 50 and 55°F (10 and
13°C). With the JADE
TM
controller the actuator
modulates the OA damper open to maintain
the MAT setpoint. The MAT default is 53F with
a 2F differential. The MAT setpoint can be
changed in the menu using the up and down
arrows on the JADE
TM
.
When the mixed or discharge air is between
50 and 55°F (10 and 13°C) the actuator will
hold damper position with analog
economizers, with JADE
TM
the actuator will
hold the temperature between -1F and +1F of
the MAT setpoint. For example if the MAT is
set to 53F, the damper will hold between 52F
and 54F.
When the mixed or supply air goes below 50°F
(10°C) the damper is modulated towards
closed (52°F for JADE
TM
in our example).
When the mixed or supply air goes above
56°F (13°C) the damper is modulated towards
open (54°F for JADE
TM
in our example).
For the analog economizers the MAT setpoint
is not adjustable, the range can be changed
using external resistance. For the JADE
TM
, the
MAT is adjustable between 38°F and 70°F.
IF THE OUTDOOR AIR IS NOT SUITABLE
FOR FREE COOLING:
The first stage of the cooling compressor is
turned on and the dampers are set to
minimum for occupancy requirements (V
at
if
using DCV, V
OT
if no DCV).
COMMERCIAL THERMOSTAT
Y2
Y1
SECOND
STAGE COOL
FIRST
STAGE COOL
OUTSIDE
AIR COOL?
ECONOMIZER CONTROLLER
YES
NO
OPEN OUTSIDE
AIR DAMPER
COMPRESSOR
MECHANICAL
COOL 1
M13816A
SINGLE STAGE COOLING
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