Reznor OH Unit Installation Manual - Manual (Page 17)

Form I-OH, PN 120390 R5, Page 17
Primary Control System
The primary control, mounted on a 4x4 outlet box on the burner is responsible for start-
ing the burner, supervising a safety operating cycle, shutting the burner off at the end
of the call for heat, and locking out "on safety" if there is a flame failure beyond the
safety timing.
The primary control system has a cadmium sulfide cell that responds to light intensity
to sense the presence or absence of flame. The ignition system is comprised of an
ignition transformer and two electrodes that deliver a concentrated spark across a fixed
gap to ignite the oil droplets in the nozzle spray. If the spark is inadequate, the cad-
mium sulfide cell will not sense the presence of flame and the primary control system
will lock out.
Blocked Vent Switch (CSA only)
The blocked vent switch is mounted on a bracket on the control side of the heater. It is
a manually reset, temperature sensitive switch designed to shut down the burner when
there is a positive pressure in the combustion chamber.
Before attempting to restart a heater that has been shut down by the blocked vent
switch, find and remove the blockage causing the positive pressure. After correcting
the problem, reset the switch.
7.5 Control Wiring
Thermostat
Use either an optional thermostat supplied with the heater or a field-supplied thermo-
stat. A 24-volt thermostat is required to actuate the low voltage controls on this heater.
A line voltage thermostat can be used when wired for low voltage use. Do not attempt
to wire relays or other accessories to the thermostat connections as these are
not load terminals.
The thermostat should be located five feet above the floor on an inside wall, not in the
path of warm or cold air currents, nor in corners where air may be pocketed. DO NOT
install on or directly suspend from the heater. DO NOT install the thermostat on a cold,
outside wall. For specific connection details and instructions on setting the heat antici-
pator, refer to manufacturer's instructions provided with the thermostat.
8. Commissioning
and Startup
8.1 Checklist Prior to Startup
□
Check clearances. Be certain that the clearances listed in Paragraph 4.1 have
been observed.
□
Check hangers. Be certain that all hangers are adequately anchored and that all
unions or threaded fittings are snug and do not rotate under conditions of vibration.
Heater must be level.
□
Check electrical supply. Be sure that wire gauges are as recommended and
that the voltage is as stated on the furnace. A service disconnect switch should be
used. Also determine that fusing or circuit breakers are adequate for the load use.
□
Check oil supply.
□
Check piping. After installation and before being covered, piping should be tested
for leaks. Before testing, disconnect supply piping at the burner and cap. Test pip-
ing hydrostatically, or with equivalent air pressure, not less than 1-1/2 times the
maximum working pressure but not less than 5 pounds per square inch at the
highest point of the system. The test shall be made so as not to impose a pressure
The circulating air high limit switch has a nonadjustable setting of 145°F for a Size 95
heater and 160°F for Sizes 140 and 190. The limit control automatically cycles when
the internal temperature exceeds those setpoints. For the heater to operate properly
and safely, the cause for the temperature exceeding the high limit setpoint must be
determined and corrected.
The super high limit switch provides redundant safety control and is calibrated to open
at a much higher temperature (350°F) than the standard automatic reset limit switch.
An interruption of the circuit by the super high limit switch indicates a major failure
caused by a malfunction of the primary safety controls or mis-wiring. Before attempt-
ing to re-start the heater, the cause must be corrected and the fan and limit assembly
replaced.
CAUTION: Make
sure the thermostat
has an adequate
VA rating for the
total requirements.