036-21539-003-B-0305
16 Unitary Products Group
• Electric Heat Operation - All electric heat models (fac-
tory installed only) are wired for a single power source
and include a bank of nickel chromium elements
mounted at the discharge of the supply air blower to pro-
vide a high velocity and uniform distribution of air across
the heating elements. Every element is fully protected
against excessive current and temperature by fuses and
two thermal limit switches.
The power supply wiring can be routed into the control
box through a threaded pipe connection in the base pan
of the unit or through a knockout in the wiring panel on
the front of the unit.
• BAS Controls - York’s Magnum series units offer factory
mounted BAS controls such as Novar, Honeywell,
Johnson, and CPC.
REHEAT MODE SEQUENCE OF OPERATION
The reheat control board allows the user to select two differ-
ent modes of operation via a jumper connection on the board.
(See Figure 2.) Each mode is described below. Refer to Fig-
ures 2 - 4 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 cool-
ing mode operation.
When the room thermostat calls for second stage cool-
ing, 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.
FIGURE 1 - UNIT CUTAWAY
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