Section 17 - Retrofit and Upgrades
185 Honeywell Economizers 63-8594-02
Before: W859 Economizer With H205
The W859 and W957 are combinations of multiple control devices that were designed to be
installed directly on top of a Mod III or IV Honeywell damper actuator. Included was a mixed air
controller, transformer, relays for high limit switchover, minimum damper position and
connections for a SPST outside air high limit.
The mixed air controller capillary extended from the case of the units to the mixed air section.
The setpoint for the mixed air temperature was on the case.
The outside air changeover control was added during installation and could be either dry bulb or
enthalpy depending on the application. Many of these were installed on rooftop units with the
schematic illustrated above using a H205 enthalpy control as the switchover device. The H205
was an electromechanical enthalpy control with a nylon humidity element.
The W859, W957 and H205 are no longer available for purchase and need to be replaced with a
JADE
TM
controller and new Modutrol Motor.
Replace the W859 or W957 with a JADE
TM
controller and a M7285A1045 Modutrol motor.
TRANSFORMER
H205
M945 DAMPER MOTOR
MIXED AIR
TEMPERATURE
CONTROLLER
W2
B
G
W1
Y1
Y2
1
W R B
BW R
T1
T2
L2
L1
(HOT)
M13848A
W859D ECONOMIZER ASSEMBLY
1K1 1K2
2K1
W R B
MINIMUM POSITION
CONTROL
2 3
O
R
SYSTEM
SWITCH
COOL
AUTO
HEAT
FAN
SWITCH
ON
AUTO
T874/Q674 THERMOSTAT/SUBBASE
2ND STAGE HEAT
1ST STAGE HEAT
FAN
HIGH
SPEED
FAN STARTER
AUXILIARY CONTACT
COOLING
RELAY COILS
2K
1K
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