Rinnai REU-KA2530FFUD-US Service Manual page 14

Heat Exchanger, Outgoing Water Temperature and
Inlet Thermistors:
Check all thermistors by inserting meter leads into each
end of the thermistor plug. Set your meter to the 20 K
scale and read resistance. Applying heat to the
thermistor bulb should decrease the resistance. Apply-
ing ice to the thermistor bulb should increase the
resistance. See below for examples of typical
temperatures and resistance readings.
*Example:
140°F = 2.2 ~ 2.7K
221°F = 0.6 ~ 0.8K
59°F = 11.4 ~ 14K
86°F = 6.4 ~ 7.8K
113°F = 3.6 ~ 4.5K
(SV1, SV2, SV3 and POV) Gas valve and Modulating solenoids: (Set meter below 2K)
Wire Color
(Main) Black - Pink
(SV1) Black - Blue
(SV2) Black - Yellow
(SV3) Black - Red
(POV) Yellow - Yellow
(M) Water Flow Control Device Servo or Geared Motor:
Red - Pink
White - Blue
Grey - Brown
Grey - Orange
NOTE: The grey wire listed above turns to black at G connector on the PCB.
Condensing Water Heater Service Manual
KB Series Electrical Diagnostic Points
Voltage Resistance
11 ~ 13 VDC 24 ~ 28 ohms
11 ~ 13 VDC 35 ~ 41 ohms
11 ~ 13 VDC 35 ~ 41 ohms
11 ~ 13 VDC 39 ~ 42 ohms
2 ~ 15 VDC 67 ~ 81 ohms
5 ~ 8 VDC 24 ~ 28 ohms
5 ~ 8 VDC 35 ~ 41 ohms
N/A N/A
N/A N/A
Flame Rod:
Place one lead of your meter to the flame rod and the
other to ground. With the unit running you should read
between 5-150 VAC. Set your meter to the μ amp scale
and series your meter in line with the flame rod. You
should read 1 μ amp or greater for proper flame circuit.
In the event of low flame circuit remove the flame rod
and check for carbon or damage.
Frost Protection:
This unit has frost protection heaters mounted at
different points to protect the water heater from freezing.
All of them should show a positive resistance reading.
Amp Fuses:
This unit has one inline (10) amp glass fuse. Remove
the fuse and\ check continuity through it. If you have
continuity through the fuse then it is good. Otherwise the
fuse is blown and must be replaced.
Connector # Pin #'s
B1 3 - 4
B3 4 - 6
B2 4 - 7
B4 4 - 5
D4 1 - 2
G2 3 - 4
G2 1 - 2
G2 5 - 7
G2 6 - 7
14
RU80i/e, RU98i/e
100000354