U.S. Boiler Company MPO - IQ, Service Instructions Manual

Page: 49 / 92

49
Ix. SYSTEM START-UP (continued)
WARNING
Before installation of the boiler is considered
complete, the operation of all boiler controls must
be checked, particularly the primary control and
high limit control.
J. VERIFY HONEYWELL OIL PRIMARY FEATURES
using procedures outlined in Instructions furnished with
control or instructions as follows:
1. R7284 FEATURES AND CONTROLS
a. The Oil Primary is a microprocessor-based control.
The indicator light provides diagnostic information
for lockout, recycling and patented cad cell status.
There is a manual reset button to exit the Lockout
Mode and enter the Idle Mode (see Figure 31).
b. Pump Priming Cycle: To facilitate purging air from
the oil lines and filters. The R7284 can be placed
in a purge routine by pressing and releasing the up
arrow button during the Trial For Ignition. “Pump
Prime” is shown on the oil primary display along
with the time left on the Trial for Ignition (TFI).
Pressing the up arrow button adds a minute to the
TFI time for a maximum of 10 additional minutes.
(press the up arrow button 10 times). Pressing the
down arrow subtracts a minute from the TFI time
(see Figure 31).
c . Limited Recycle: This feature limits the number of
recycle trials (for each call for heat) to a maximum
of three trials. If the flame is lost three times and
does not successfully satisfy a call for heat, the Oil
Primary locks out.
d. Limited Reset (Restricted Mode): In order to limit
the accumulation of unburned oil in the combustion
area, the control can only be reset three times. The
reset count returns to zero each time a call for heat
is successfully completed.
e. T-T Jumper: All R7284 models have internal "TT
Configured ON" parameters set to "ON".
The R7284 has an LCD display and simply displays
lockout and flame status on it.
f Cad Cell Resistance Check : For proper operation
it is important that the cad cell resistance is below
1600 ohms.
Cad Cell Resistance (ohms) is measured by the oil
primary. The thresholds are:
< 1600 Ohms Normal operation
> 1600 Ohms Service burner soon
> 6100 Ohms Flame loss, burner shuts down
> 9999 Ohms Check for broken cell or wire.
R7284 displays resistance in ohms during Running
Mode.
2. CHECK OIL PRIMARY CONTROL
CAUTION
Due to the potential hazard of line voltage, only
a trained, experienced service technician should
perform the following safety checks.
This control contains no field-serviceable parts.
Do not attempt to take it apart. Replace entire
control if operation is not as described.
a. Preliminary Steps
•
Check wiring connections and power
supply.
•
Make sure power is on to the controls.
•
Make sure limit control is closed.
•
Check contacts between ignitor and the
electrodes.
•
Check the oil pump pressure.
•
Check the piping to the oil tank.
•
Check the oil nozzle, oil supply and oil
filter.
b. Check Safety Features
Safe Start:
•
Place a jumper across cad cell terminals.
•
Follow procedure to turn on burner.
Burner must not start, indicator light turns on and
control remains in Idle Mode.
•
Remove jumper.
c. Simulate Ignition or Flame Failure:
•
Follow procedure to turn on burner.
•
Check cad cell resistance. If resistance is below
1600 OHMS and burner runs beyond safety
cut-out time, cad cell is good.
Figure 31: R7284 Oil Primary Terminals,
Display and Function Buttons