York MILLENNIUM Y22, Installation Manual

Page: 72 / 140

102777-YIM-E-0206
72 Unitary Products Group
the supply fan. Operation of heating is dependent upon
the APS closure.
When all run rules are satisfied, cooling stages are avail-
able. A call for first stage cooling, Y1, initiates the control
rules for cooling. When the control is satisfied [tempera-
ture, short cycling timing, safety circuits, etc.], it sends
voltage out terminal C1 to contactor 1M for compressor
1. If compressor 1 is not available, the control will start
compressor 2 via C2 / 2M.
In Occupied mode, the economizer is enabled [if
installed and the parameter set in the control]; if free
cooling is available, the economizer will energize in
place of the first cooling stage.
A thermostat call for second stage cooling powers termi-
nal Y2, third stage powers Y3 (30 and 40 ton) and fourth
stage powers Y4 (40 ton only). These thermostat calls
are entered into the control’s logic, and available cooling
stages brought on to meet the demand.
NOTE: The economizer may function when all mechanical
cooling stages are locked out on low ambient.
3. When the control calls for Compressor 1 (25 ton), or
Compressor 1 or 2 (30 and 40 ton), it will also call con-
denser fan stage 1 through terminal CF1, powering the
coil of contactor 6M (condenser fan 1). On 25 ton units,
condenser fan 2 (contactor 7M) is brought on by PS5 if
discharge pressure on compressor 1 exceeds 280 psi.
Fan 2 drops out if discharge pressure drops below 180
psi; condenser fan 4 (contactor 8M) is brought on by PS6
monitoring discharge pressure on compressor 2.
4. A control call for Compressor 2 powers contactor 2M
through terminal C2, and CF2 (fan 3) on 25 ton units. On
30 and 40 ton units, because fans 1 and 2 pull through
coils for both circuit 1 and circuit 2, the coil of contactor
7M (condenser fan 2) is powered in turn through either of
condenser fan cycling switches PS5 or PS6, which
enables condenser fan 2 operation if the discharge pres-
sure of Compressor 1
or Compressor 2 exceeds 280 psi.
5. 30 and 40 ton only: A call for Compressor 3 powers con-
tactor 3M (contactor, compressor 3) from terminal C3. A
call for Compressor 3 or 4 also powers terminal CF2,
second stage condenser fans (contactor 8M, condenser
fan 3, and also contactor 9M, condenser fan 4 - 40 ton
only).
6. 40 Ton Only: A call for Compressor 4 powers the coil of
contactor 4M from terminal C4.
7. Gas Heat Option, Stage 1: a W1 call locks out cooling
and initiates the control logic for Heat 1. The supply fan
is engaged, at full speed if VAV-equipped. Once APS (air
proving switch) closes to acknowledge supply airflow,
power is supplied from terminal H1, which engages Igni-
tion Control 1 (IC1) at heat module terminal W/TH. 24V
is supplied to IC1 at terminal R/24V, and to the overtemp
limit switch LS1, which opens only with excessive heat
exchanger temperature, on each gas heat module. That
switch is monitored by connecting each limit switch to
the LIM1, 2, or 3 terminal at the Simplicity board. IC1
closes contacts between terminals L1 and IND to
engage Draft Motor 1. The 24V signal downstream from
the overtemp limit switch goes through the vent motor air
proving switch circuit to the PSW terminal on IC1.
With LS1 and PS1 closed, IC1 will attempt ignition. IC1
provides direct spark ignition with flame verification, and
controls the GV1 gas valve through manual reset switch
RS1 (rollout switch). If RS1 has tripped, GV1 is locked
out and IC1 will electronically lockout after three failed
ignition attempts. The Simplicity control monitors voltage
to the gas valves through terminals GV1-3.
When the W1 call is canceled, power is removed from
IC1 terminal TH, which directs IC1 to close GV1. As long
as APS continues to prove supply fan airflow, IC1
remains powered and keeps the L1 to IND contacts
closed for 45 {60??} seconds to maintain the operation of
Draft Motor 1 for a postpurge of the heat exchanger.
8. Gas Heat Option, Stages 2 and 3: the Millennium Sim-
plicity responds to W2 and W3 similarly to W1, if the unit
is equipped with second and third heat modules.
9. Electric Heat Option: the Millennium Simplicity control
allows staging electric heat. On units with the Electric
Heat Option, a call for heat (W1) will initiate the main
supply fan. When the Simplicity control is satisfied by the
APS, it will complete the circuit to the first stage of elec-
tric heat by energizing terminal H1. If additional heat is
required, H2 will energize the second stage of electric
heat [if the unit is so equipped], and H3 the third stage [if
the unit is so equipped].
All electric heat modules have an auto-reset primary
limit, monitored by the control, and non-restartable back-
up limits. Dirty filters, broken belts, fan motor burn-out or
running this unit below 6,000 CFM will cause the limit to
trip on the auto-reset primary limit. In addition to the pri-
mary limit, back-up limits may trip under these condi-
tions. The backup limits are one-trip devices and will
have to be replaced should they trip.
When a call for heat has been satisfied, the highest
stage running will be de-energized until all are de-ener-
gized.
10. Hot Water Heat Option: the unit will send a 2-10 VDC
signal to drive a hot water valve.
Disconnect all power supplies before checking or
servicing the electric heat section.