Installation manual

035-16682-000-E-0303
Unitary Products Group 69
Example: By actual measurement, it takes 7 seconds for the
hand on the one cubic foot dial to make a revolution with just
a 570,000 Btuh furnace running. Read across to the column
in Table 24, headed 1 Cubic Foot where you will determine
that 525 cubic feet of gas per hour are consumed by the fur-
nace at that rate. Multiply 525 x 1050 (the Btu rating of the
gas obtained from the local gas company). The result of
551,000 Btuh is within 5% of the 570,000 Btuh rating of the
furnace.
ELECTRIC HEATING
The electric furnace is operational as shipped from the fac-
tory and does not receive any field adjustments.
COOLING OPERATING INSTRUCTIONS
COMPRESSOR
Compressors are factory mounted ready for operation (See
page 61 Compressor Rotation).
OIL LEVEL - All compressors are factory charged with oil.
Each compressor is equipped with an oil level sight glass.
Check for proper oil level which is approximately to the center
of the sight glass. Recheck oil level at startup.
INTERNAL WIRING
Check all electrical connections in the unit control box;
tighten as required.
CONDENSER FANS
Check for proper condenser fan rotation; clockwise facing the
air discharge. If condenser fans are rotating backwards, line
voltage to unit single point power connection is misphased
(See page 61 Compressor Rotation).
SEQUENCE OF OPERATION
CONSTANT VOLUME UNIT
OVERVIEW
The main control of the constant volume units is the program-
mable thermostat. The thermostat provides occupied / unoc-
cupied scheduling, heating / cooling minimum stage ON /
stage OFF times, automatic switching from heating to cooling
modes, fan delay on power failure, and an economizer
enable contact that disables the economizer in the unoccu-
pied modes. Additionally, the thermostat is designed to ramp
the space temperature from the unoccupied setpoints to the
occupied setpoints. The thermostat determines when to start
this morning warm-up / cool-down based upon the deviation
from the occupied setpoints and the rate of temperature
change.
To follow the sequence of operation, the thermostat cannot
determine if an output function is available. For example, if
the belt on the supply fan were to break, the thermostat will
still call for the fan to operate and if space conditions require,
heating or cooling calls will also be made. Separate relay
logic is used to prevent undesired operation of heating and
cooling stages. Our logic is designed such that airflow must
be proven before any heating or cooling stage can operate
and mechanical cooling is locked out below 40°F for all units
without head pressure control. The thermostat provides con-
tact closures to control the isolation relays for supply fan,
each cooling stage, each heating stage, and the economizer
availability. The thermostat is responsible for determining
when calls for cooling and heating are given, while the isola-
tion relays are responsible for executing these calls and pro-
tecting the unit through appropriate safety devices. The
thermostat controls the supply fan and cooling stages by
closing a relay contact between terminals RC and:
G - Supply Fan
Y1-1st Stage Cooling
Y2-2nd Stage Cooling
Y3-3rd Stage Cooling
Y4-4th Stage Cooling
Heating stages are controlled by a contact closure between
terminals RH and:
W1-1st Stage Heating
W2-2nd Stage Heating
The economizer is enabled through the auxiliary economizer
relay by contact closure between terminals A2 and A1. (The
auxiliary economizer relay is a SPDT relay, so the contact
between terminals A2 and A3 is simultaneously broken.)
FIGURE 30 - TYPICAL FLAME APPEARANCE
GAS
SUPPLY
PIPE
BURNER
BURNER BRACKET
IG N IT O R
BURNER FLAME
(B LU E O N LY )
HEAT EXCHANGER TUBE