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9 60-2285—7
R4795A
CHECKOUT
2. The flame current is at least two microamperes for
R7289A Rectification Amplifier (color-coded green), or at
least 1.5 microamperes for an R7290A Ultraviolet Amplifier
(color-coded violet).
IF A STEADY READING OF AT LEAST MINIMUM
STRENGTH CANNOT BE OBTAINED, ONE OR MORE
OF THE FOLLOWING CONDITIONS CAN EXIST:
• Improper supply voltage.
• Defective flame detector wiring including:
— Open circuits.
— Short circuits.
— High resistance shorts caused by moisture, accu-
mulated dirt, or an improper choice of detector lead-
wire for the particular installation.
• Improper sighting, improper viewing window, or dirty
viewing window for optical detectors.
• Improper application of a flame rod including:
— Insufficient ground area.
— Poor location of flame rod in flame.
— Excessive heat on flame rod insulator, greater than
600°F (316°C).
— Ignition interference.
• Improper application of a vacuum photocell including:
— Temperature over 165°F (74°C) at photocell.
— Dirty photocell envelope.
• Defective sensor.
PILOT TURNDOWN TEST
IMPORTANT: If the R4795 is used to prove a pilot flame,
perform the following Turndown Test to assure that
the main burner can be lit by the smallest pilot flame
that will hold in the 2K (flame) relay.
1. Shut off the fuel supply to the main burner only by
closing the manual main burner shutoff cock. Do not shut off
fuel supply to the pilot valve.
2. Start the system by raising the setpoint of the control-
ler (or pressing the START button). After prepurge is com-
pleted, the pilot will light and pull in the flame relay.
3. Reduce the size of the pilot flame to the turndown
condition by slowly closing the manual valve on the pilot gas
line. At the turndown condition, the pilot will be small
enough so it just barely holds in the flame relay (2K).
a. Slowly turn down the pilot until the flame relay drops
out.
b. Allow the control to complete prepurge.
c. As the control attempts to restart the pilot, turn the
pilot back up slowly just until relay 2K pulls back in.
You will have 15 seconds to complete this step before
lockout occurs.
d. Again turn the pilot down slightly but not enough so
the flame relay drops out. If the relay drops out, simply
allow the control to complete the purge period and
then turn the pilot back up to pull in the flame relay as
in step c. above. The closer the pilot is to the dropout
condition, the more conclusive the test will be.
FLAME CURRENT CHECK
The flame current check is the best indicator of proper
flame detector application. Perform the check at the time of
installation, and at any time service is done on the system,
and at least once a month, or more often, while the system is
in operation. This prevents shutdowns due to poor flame
signal.
Test by connecting a W136 (or equivalent) to the ampli-
fier and reading the flame current while the burner is operat-
ing. (Fig. 11).
Fig. 11—Connecting meter to read flame
current.
M8689
W136
117053 METER
CONNECTOR PLUG
(SUPPLIED WITH W136)
BLACK
BLACK
BLACK
RED
RED
FLAME
CURRENT
TEST JACK
PLUG-IN
AMPLIFIER
IF 117053 METER CONNECTOR PLUG IS NOT AVALIABLE
(R7289A RECTIFICATION AMPLIFER ONLY)
FLAME
DETECTOR
F LEAD
G LEAD
RED
F
G
W136
R4795
-
+
Insert a 117053 Meter Connector Plug, wired color-to-
color to the W136 leadwires, into the test jack on the ampli-
fier (Fig. 10). This automatically puts the microammeter in
series with the flame detector.
If an R7289A Rectification Type Amplifier is used and a
meter connector plug is not available, disconnect the flame
detector lead from the F terminal; then connect this lead to
the Black lead of the microammeter, and connect the Red
lead of the microammeter to the F terminal.
NOTE: If an R7290A Ultraviolet Type Amplifier is used, the
flame current cannot be read by connecting a micro-
ammeter in series with the F lead.
When reading the flame current, assure that the following
criteria are met:
1. The flame current is steady; meter does not vary more
than a needle width.