Rinnai FUA-E, Service Manual

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D. Solenoid Valves.
There are 3 solenoid valves and one modulating valve. Two of the solenoids are burner
sectional solenoids, and the third is the main, safety solenoid.
The easiest way to check the gas valve is by putting the manometer on the test point on
the gas valve and cycling the unit. If the solenoids are working correctly the burner
pressure when it lights should be around 8mbar. If the pressure stays at 0 mbar (or
goes up slightly, to about 1 mbar) the safety solenoid is not opening; this is only a true
test if the sparker is definitely sparking. If the pressure goes up to 21 mbar the sectional
solenoid is not opening. Once the suspect solenoid valve has been determined you can
determine the faulty component (solenoid valve or pcb.)
The solenoids should be tested for voltage and resistance at pcb connector F from the
wiring diagram. The resistance is measured with the unit electrically isolated and the
connector unplugged. Put the meter leads on the connections and measure through the
solenoid. The voltage is tested while the unit is running and the connections are made.
While the unit is lit put the leads into the plug and measure the voltage (DC.) Only the
Main SV and SV1 will open upon ignition. SV2 will not have voltage unless the unit is on
medium to high fire.
Main SV Pink – Black
200 – 240 Vdc appx 6.5 k Ohms
SV1 Black – Blue 200 – 240 Vdc appx 8.0 k Ohms
SV2 Black – Yellow 200 – 240 Vdc appx 8.0 k Ohms
Modu SV Pink – Pink 2 – 15 Vdc 67 – 83 Ohms
If the voltage is incorrect replace the pcb.
If the resistance is incorrect replace the solenoid valve. It should be noted that
sometimes solenoids jam and are faulty even though the resistance is correct. If there is
voltage to it, and there is no gas getting past it, then it is a faulty solenoid, assuming you
have confirmed the incoming pressure. (High gas pressure will prevent a solenoid from
opening, for example, if a second stage LPG regulator has not been used.)
The voltage should be present after the spark ignitor has begun to tick. If the unit does
not begin to do anything check the Thermal Fuse Circuit (E.)
If the resistances and voltages are correct continue.
Check the secondary gas pressure change when the set temperature is changed from
55 to 37°C.
The secondary pressure should change. If it does, go to the water flow servo circuit (G.)
If the pressure does not change replace the modulating valve.
Diagnostic Checks