Product Overview

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103859-12 - 8/19
MPO-IQ
Installation & Service Manual
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
8 System Start-Up (continued)
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