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Servicing should only be performed by a Qualied Service Agent
BLOWER SPEED CONTROL SUF 199 AND 250
The input of the SUF 199 and SUF 250 is determined by blower. The input of the water heater may be
determined by clocking the meter as shown on page 5 or by making sure the blower is receiving the proper
signal. The blower rpm is controlled by the Central Control Board (CCB). The rpm of the blower may be
measured by attaching a MULTIMETER that has a Hertz (Hz) setting as shown in the illustration below. If
the Hz signal is within +/-5% of the numbers in the chart below the reading is normal.
Model High Speed Hz Low Speed Hz
199 N 133 87
250 N 133 87
199 LP 200 156
250 LP 266 96
Note: Removing the plug shown in the illustration will cause the blower to accelerate and the input of the
water heater to increase to a much higher rate. This may cause damage to the water heater.
Meter black lead is connected to ground (not shown) and the red lead is connected to an open terminal on
blower speed control connection.
Meter red probe
connected to open
terminal on plug