Champion usn-72 User Guide

Part 5: BASIC SERVICE

The 1" valve is controlled by the final rinse control thermostat, (See 5.3.9), 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 sche-

matic 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 disas-

semble the valve by removing the four bolts in the valve bonnet.  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.

1/2" NPT thermodynamic steam traps are installed in the condensate lines

for the steam booster and tank heat steam coils.  All condensate lines for the

USN-72 must be gravity drain with no back pressure in order for the steam

trap to function correctly.

To test the operation of a steam trap:  Turn off the steam and water

supplies.  Turn off the power at the dishwasher control cabinet.  Bleed any

steam pressure from the lines.  Disconnect the condensate return line downstream from the steam

trap.  Return the dishwasher to normal operation and observe the discharge coming from the

steam trap.  If you do not observe small amounts of water periodically discharged then the stream

trap is most likely defective.

To clean a steam trap: Turn off the steam and water supplies.  Turn off the power at the dish-

washer control cabinet.  Bleed any steam pressure from the lines.  Remove the large hex cap in

the center of the steam trap. Remove the disc and inspect the steam trap orifice below.

Clean the orifice with a paper clip or other smooth tool.  Reassemble the trap in reverse order.

To replace a steam trap: Turn off the steam and water supplies.  Turn off the power at the

dishwasher control cabinet.  Bleed any steam pressure from the lines.  Break the union in the

condensate line before the steam trap. Remove the trap.  Install a replacement trap  in reverse

order making sure to apply pipe sealant to threads.  Return the dishwasher to normal operation

and test the trap as described above.

Refer to Fig. 6.16, Part 6, Replacement Parts, for a detailed drawing of the steam booster assem-

bly.  The steam booster consists of three pieces as shown on the next page:  the shell casting into

which the straight seamless copper tubes are fitted, the rear header, and the flow header with two

tappings for tank connections.  Headers are bolted to the shell casting and sealed against leaks by

heavy gaskets.  Where soft water or low percentage of mineral deposits is used, it should only be

necessary to clean the heater tubes annually.  No acids are needed to clean the heater tubes.