CHAMPION USN72 - Manual (Page 62)

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Part 5: BASIC SERVICE
5.3.9 Final Rinse (Steam) Thermostat Adjustment and Replacement (Cont.)
To adjust the final rinse thermostat: Turn power off to the dishwasher at the dishwasher control
cabinet. Block the final rinse activator so the final rinse runs constantly. Return the dishwasher to
normal operation. Remove the protective cap from the center of the final rinse thermostat enclosure
to expose the adjusting screw. Turn the adjusting screw incrementally 1/16 of a turn clockwise to
increase the final rinse temperature. Turn the screw counterclockwise to reduce the final rinse
temperature. Monitor the final temperature thermometer after each adjustment until temperature
maintains a minimum of 182-185 ° F.
NOTE:
The normally open contacts of the low temperature cutoff thermostat must close whenever the
final rinse temperature falls below 180 ° F.
To adjust the low temperature cutoff thermostat: First perform the final rinse thermostat procedure
described above. Turn the steam supply off to the booster assembly so the final rinse temperature falls
below 180 ° F. Remove the protective cap from the center of the cutoff thermostat enclosure to expose the
adjusting screw. Turn the adjusting screw incrementally 1/16 of a turn clockwise to increase the cutoff
temperature. Turn the screw counterclockwise to reduce the cutoff temperature. In other words, if the
final rinse water temperature is 182 ° F. and the low cutoff thermostat activated the chemical sanitizing
system (supplied by others), then it would be necessary to turn the screw counterclockwise to reduce
the cutoff temperature to 178-180 ° F.
To replace the final rinse or cutoff thermostat: Turn off the water and steam supplies to the booster.
Place a rack in the dishwasher to operate the final rinse and bleed off any water pressure from the line.
Turn power off to the dishwasher at the dishwasher control. Remove the protective cap and round cover
from the thermostat body. Note the location of the wires and disconnect. Disconnect the conduit.
Remove the thermostat from the booster piping. Install the replacement in reverse order. Return the
dishwasher to normal operation and perform the adjustment procedures described above.
For machines S/N J1698 and after: To replace the control thermostat see the Special Bulletin Section
on page 111 at the end of this manual for instructions on the replacement of the thermostat.
5.3.10 Steam Solenoid Valve Repair
The USN-72 dishwasher uses a 3/4" steam solenoid valve on each tank
steam supply line. The 3/4" steam valves are identical in appearance to the
3/4" water valves, (See 5.3.4). The steam booster uses a 1" steam solenoid
valve on the inlet of the booster steam supply line, (See picture at right).
The 3/4" valves are controlled by a tank heat thermostat, (See 5.3.8), which
connects 120VAC to the valve coil during a call for heat. If the valve fails to
operate, first check that 120VAC is supplied to the valve coil. If voltage is not
present, then refer to the electrical schematic and troubleshoot the circuit. If
voltage is present then the valve may require a rebuild kit or replacement coil.
Turn off power at the dishwasher power switch and main disconnect. Turn off
main incoming steam supply and bleed off any steam pressure in the line. Check the coil for continuity
with a VOM set at the highest resistance range. If the coil checks good then disassemble the valve by
unscrewing the threaded bonnet with a strap or spanner wrench. Remove and inspect the valve piston and
diaphragm. Inspect the valve seat for mineral deposits and pitting. (Replace the complete valve assembly
if pitting is severe). Reassemble the valve in reverse order. Turn on steam and power supplies and check
for leaks.