Hoshizaki KM-100A [31/65] Minute diagnostic procedure

IV. SERVICE DIAGNOSIS

1. 10-MINUTE DIAGNOSTIC PROCEDURE

The10minutecheckoutprocedureisbasicallyasequencecheckwhichcanbeused

atunitstart-uporforsystemdiagnosis.Using this check out procedure will allow you

to diagnose electrical system and component failures in approximately 10 minutes

under normal operating conditions of 21°C or warmer air and 10°C or warmer water

temperatures. Before conducting a 10 minute checkout, check for correct installation,

propervoltage per unit nameplate and adequate water supply.Asyou go through the

procedure,checktoassurethecomponentsenergizeandde-energizecorrectly.Ifnot,

thosecomponentsandcontrolsaresuspect.

1) Turnpoweroffandaccessthecontrolbox.Clearanyicefromthebincontrolactuator

locatedinthebin.

2) Turnpoweronandplacethecontrolswitchinthe"ICE"position.A5seconddelay

occurs. The "POWER OK" LED on the control board comes on. If the "POWER

OK"LED isashing (indicatingafullbin),check thebincontrol.See"II. 5.[b] BIN

CONTROLCHECKPROCEDURE."

3)OneMinuteFillCycle–Theinletwatervalveisenergized.After1minute,thecontrol

boardcheckstheoatswitch.Iftheoatswitchisclosed,theunitcyclestoharvest.

Ifclosed,continuetostep4.Iftheoatswitchisopen,theunitrepeatsthe1minute

ll cycle until water enters and the oat switch closes (low water safety protection

duringinitialstartupandattheendofeachharvest).Diagnosis:Ifthewatervalve

does not open, check for no supply voltage at water valve terminals, bad coil, or

pluggedscreenorexternallter(nowaterow).Ifunitfailstostartharvest,checkfor

openoatswitchorbad1minutetimerinboard.

4) Initial Harvest Cycle – The inlet water valve remains energized, contactor coil

energizes to start the compressor (and fan motor on a remote condenser unit),

andthehotgasvalveenergizes.Theevaporatorwarmsandthethermistorsenses

48°F (9°C). The control board then receives the thermistor's 3.9 kΩ signal and

turns operation of harvest over to the harvest timer.The timer completes counting

(1 to 3 minutes). The unit then cycles to freeze. Diagnosis: Check if compressor

is running, hot gas valve is open, water valve still open.Average harvest cycle at

factorysettingis2to3minutes.Howlongdoesinitialharvestlast?1.5minutesafter

initial harvest begins, touch the compressor discharge line. Is it hot?  If not check

refrigerantpressuresandcompressoroperation.Ifitishot,touchtheinletlinetothe

evaporator.Isithot?Ifitishotandthefreezecycleisnotstarting,checktheharvest

timer adjustment, the thermistor for open circuit, the discharge line temperature,

compressorefciency,andifthehotgasvalveisfullyopen.

5) Freeze Cycle – The compressor remains energized, pump motor, (line valve if

applicable), and fan motor energize. The inlet water valve and hot gas valve de-

energize.Theunitisheldinfreezebya5minuteshortcycleprotectiontimerwhich