FORM 100.50-EG3 (802)
73
YORK INTERNATIONAL
POWER SUPPLY
Unit power supply shall be 460V 3-phase 60 Hz (208,
230 and 575V optional) single-point power connections
with terminal block connections.
GAS-FIRED HEATING SECTION
One or two (or three for the YPAL070-095) gas-fired
heating modules shall be installed to provide the heat-
ing requirements per the schedule shown on the plans.
The heat exchanger shall be of tubular design. Tubes
shall be 2-1/4" OD and constructed of minimum 20-
gauge, G160 aluminized steel (1.6 mil aluminum sili-
cone alloy) for corrosion resistance.
Each gas-fired heat module shall have an induced draft
combustion fan with reliable spark ignition and redun-
dant gas valves with pressure regulator.
An induced draft fan shall be provided to maintain a
positive flow of air through each tube, to expel the flue
gas and to maintain a negative pressure within the heat
exchanger relative to the conditioned space. Induced
draft fans shall be direct-drive.
Dual (2) high limit controllers per heating module, with
automatic reset to prevent the heat exchanger from
operating at an excessive temperature will be installed.
A safety pressure switch in the induced draft fan motor
circuit must be provided to prevent ignition until suffi-
cient air flow is established through the heat exchanger.
Airflow safety shall be provided by rollout switch pro-
tection and shall discontinue furnace operation if the
flue becomes restricted.
Units shall ship with an external flue to be shipped in
the unit and mounted on the job site. The flue shall
discharge products of combustion above the unit, pre-
venting recycling of corrosive combustion gases back
through the heat exchanger. Gas heating sections shall
be U.L./CSA certified to both US and Canadian safety
standards.
ELECTRIC HEAT SECTION
An electric slip-in heater shall be installed within the
rooftop unit to provide the heating requirements per the
schedule shown on the plans. The electric heater shall
be wired in such a manner as to provide multiple steps
of capacity.
The heater shall be an industrial grade design using an
open coil(s) made of the highest grade resistance wire
containing 80% nickel and 20% chromium. The resis-
tance coil(s) shall be adequately supported in the air
stream using ceramic bushings in the supporting frame-
work. Terminals of the coil(s) shall be stainless steel
with high temperature ceramic bushings.
The primary high temperature protection shall be an
automatic reset type thermal cut out. Secondary pro-
tection shall be an automatic reset type thermal cut out.
Secondary protection shall be a replaceable thermal
link.
The operation of the electric heater shall be an integral
part of the roof top control system. Power connection
to the strip heater shall be through the single power
point connection for the entire unit. Electric heat shall
be E.T.L. certified.
CONTROLS
A factory-mounted unit controller with a 4x20 character
alphanumeric display and one-touch keypad shall be
included as standard. The controller and keypad shall
be housed inside the low-voltage compartment of the
control/power panel. On units with supply or exhaust
VFDs, the VFD keypads shall be located inside the
same panel as the unit controller and interface keypad.
Control operating data, setpoints, unit setup, configu-
ration, service and history shall all be accessible via a
single key. A system alarm LED shall indicate failures
to the operator with more detail provide in the menu
screens. The user interface shall function with a simple
menu-driven display for easy access to unit data with
integral time clock for weekly and holiday scheduling.
The unit keypad shall include password protection to
prevent unauthorized access and tampering with unit
setpoints and configuration.
A single terminal strip shall be provided for all thermo-
stat and customer hard-wire connections.
Unit controls shall be completely factory packaged and
compatible with a room thermostat. Constant volume
units shall operate with a two (2) cool/two (2) heat ther-
mostat. Staging decisions shall be based upon the de-
viation of space temperature from set point and the rate
of change of the space temperature.
VAV units shall operate with a sensor in the supply air
stream for cooling operation. Staging decisions shall
be based upon the deviation of supply air temperature
from set point and the rate of change of the supply air
temperature.
Controllers shall have the following safeties (both VAV
and CV):
