York ZJ R-410A - Manual (Page 12)

251934-YTG-G-0708
12 Johnson Controls Unitary Products
• BAS Ready Economizer (2-10 V.D.C. Actuator Without a
Controller)
• Hinged Filter Door Access And Tool Free Access
Panels
• Hinged Tool Free Blower, Blower Motor, Filter And
Electrical Access Panels
• High Static Drive
• Low Static Drive (ZJ/ZR/ZF300 only)
• 2" Pleated Filters
• 4" Throw Away Filters
• Disconnect Switch
• Supply Air Smoke Detector
• Return Air Smoke Detector
Reheat Mode Sequence Of Operation
The reheat control board allows the user to select two different
modes of operation via a jumper connection on the board. (See
Reheat Control Board.) Each mode is described below. Refer to
Reheat Controls - Part 1 and Part 2 when reading this section.
“Normal” Mode
When the reheat control board (RCB) detects a need for
dehumidification (24VAC) at "HUM" via the field supplied
dehumidistat connected to RHTB-1 and RHTB-2 and there is
not a call for cooling, it energizes the hot gas relay (HGR),
which energizes the 3-way valve (SOL 3), the condenser coil
valve (SOL 2), and de-energizes the reheat coil bleed valve
(SOL 1). The Y1 signal is passed to the unit control board
(UCB), which engages circuit # 1, resulting in circuit #1 reheat
mode operation.
When the room thermostat calls for first stage cooling, with or
without a call for dehumidification, the RCB senses a signal
through "Y1", de-energizing the HGR, which de-energizes SOL
3 and SOL 2, and energizes SOL 1, engaging circuit # 1,
resulting in circuit #1 cooling mode operation.
When the room thermostat calls for second stage cooling, the
RCB senses a signal through "Y1" & "Y2" and engages circuit
#1 and circuit #2 in the cooling mode.
Indoor blower operation is initiated upon a call for first stage
cooling, second stage cooling or dehumidification.
Anytime there is a call for 2 stages of cooling, the unit will not
operate in the reheat mode, even if there is a call for
dehumidification at "HUM".
The unit will not operate in the reheat mode if there is any call
for heating.
On units with economizers, the unit will not operate in the
reheat mode if there is a call for cooling and the economizer is
operating as first stage of cooling.
All safety devices function as previously described.
"Alternate” Mode
When the RCB detects a need for dehumidification (24VAC) at
"HUM" via the field supplied dehumidistat connected to RHTB-1
and RHTB-2, and there is not a call for cooling, it energizes the
HGR, which energizes the SOL 3, SOL 2, and de-energizes
SOL 1. The unit then operates with circuit #1 in reheat mode
and circuit #2 in cooling mode.
When the room thermostat calls for first stage cooling while
there is still a call for dehumidification, no operational change is
made. The call for cooling is ignored and the unit continues to
operate with circuit #1 in reheat mode and circuit #2 in cooling
mode.
When the room thermostat calls for second stage cooling, the
RCB senses a signal through "Y1" & "Y2" and de-energizes the
HGR, which de-energizes SOL 3 and SOL 2, and energizes
SOL 1. Both circuits operate in the cooling mode.
Indoor blower operation is initiated upon a call for first stage
cooling, second stage cooling or dehumidification.
Anytime there is a call for 2 stages of cooling, the unit will not
operate in the reheat mode, even if there is still a call for
dehumidification at "HUM".
The unit will not operate in the reheat mode if there is any call
for heating.
All safety devices function as previously described.