Rheem 834 Series Service Instructions Manual page 12

9c. A critical fault is detected: SV2 (6) and SV3 (7) are de-energised which results in a
main burner (5) shut down, the ignition module (8) is de-energised, battery (17)
recharge and water throttle valve (18) functions are terminated if on (these will be
explained later in this section), and fault indication is provided. If the battery voltage is
> 3.1 VDC the MASV (4) is driven to the minimum opened (minimum gas) position.
SV1 (12) is also de-energised if on. The heater will not operate until it has been reset
(hot tap turned off and then turned back on) at which time the heater will restart from
step 1.
Note: The heater has an overheat switch (19) that will open circuit if it detects a
temperature of 95°C ± 4.5°C. If activated, the overheat switch must be manually reset
by pressing and releasing the reset button on the switch after temperatures have fallen
to a safe level (≤ 90°C).
Cold Start Function (Water Throttle Valve): When performing a cold start, which is
usually the first start up in the morning or after the water heater has been idle for
considerable time, the temperature controller (3) may activate the cold start function to
conserve water and gas.
During initial operation (on first opening of a hot tap) and if the hot water outlet
temperature is < 20°C as detected by the hot water outlet temperature sensor (16), the
cold start function is activated and the water throttle valve (18) is energised to reduce the
water flow rate through the heater by 33 ~ 55%. The water throttle valve has two positions;
fully open (de-energised) and partially closed (energised), therefore the percentage
reduction in water flow rate is dependent on initial water flow rate and inlet water pressure.
The water throttle valve is de-energised when the hot water outlet temperature sensor
detects ≥ 20°C or 12.5 seconds has expired.
Note: This function will only be activated provided the heater setpoint temperature is 60°C,
battery voltage is > 3.1 VDC and the flow rate through the heater is > 6 L/m.
Seasonal Adjustment Valve Operation: A manually adjustable valve is located at the
cold water inlet that provides the customer with the option of reducing the water flow rate
through the heater in colder weather to avoid insufficient heating. When in the summer
position the valve lever points down (valve fully open).
Battery Recharge Function: During normal burner operation, if the battery (17) voltage is
> 2.8 VDC and < 3.5 VDC, the battery recharge function is automatically activated and the
battery is recharged by the hydroelectric generator (1) until the battery attains a voltage of
3.5 VDC or the heater ceases to operate due to cessation of water flow.
The rechargeable battery is utilised to power the water throttle valve (18) and reset the
MASV (4) to low fire position during shut down when there is no water flow through the
heater. Note: If the rechargeable battery voltage is < 3.1 VDC, the MASV reset will be
performed during start-up of the water heater.
Ignition Module Flame Rectification Operation: An AC voltage is passed from the
ignition module (8) to the flame sensor (9) during the ignition sequence and during normal
burner (5) operation. When the pilot (11) or main burner is alight, the AC voltage passes
from the flame sensor through the pilot or burner flame to earth and is converted to a DC
voltage as it passes through the flame (this is known as flame rectification). The DC
voltage is detected by the ignition module via the ignition module earth connection. Flame
detection is in micro amps (µA) and the ignition module determines that a flame is present
if the detected flame signal is > 0.5 µA. Normal flame generation is 2 ~ 10 µA (2 µA @ min
fire, 10 µA @ max fire).
TM081 Rheem 834 Series Hydroelectric CFGWH Service Instructions
REV: AA Issued: 22/02/17
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