Welcome to the Ice-O-Matic on-line training modules. Ice. Pure and Simple

Welcome to the Ice-O-Matic on-line training modules. Ice. Pure and Simple

DIAGSING FREEZE-UP ISSUES This module will help in diagnosis of a freeze up should it occur on various models of ICE Series Cubers. This module defines a freeze up as the unit never entering defrost, stays too long in the freeze cycle creating blocks of ice or enters defrost then leaves without harvesting the ice.

R-1 Relay Coil Timer Initiate Control Solid State Timer Delay First, let s do a brief review of the sequence of operation for the 150 pound through 1000 pound production units. The Low Pressure Timer Initiate controls the untimed portion of the freeze cycle. The LPTI closes on pressure drop, energizing the Timer. The Timer will continue the freeze cycle for the length of time it is set for, controlling the bridge thickness, then closes. This energizes the Relay, sending the unit into a defrost cycle.

In the under counter units, there is only one relay. In modular units there are 2 relays, the top of which ( Relay 1) energizes the defrost components.

Once the relay energizes the defrost components, the Harvest Assist Assembly controls the length of the defrost cycle. The assembly pushes the ice off of the Evaporator, then retracts to it s original position, terminating the defrost cycle and the unit re-enters freeze.

When diagnosing a freeze-up, it is best to start the diagnosis while the unit is still having the issue. By clearing the Evaporator, you may be hiding one of the symptoms of the problem, thereby delaying the diagnosis.

How to check LP Control with Ice on the Evaporator Ice. Pure and Simple The diagnosis would start by checking the status of the LPTI. The LPTI can be checked while the unit is in freeze by placing your meter across the terminals of the control. If line voltage is displayed on your meter, the control is open. If no voltage is displayed, the control is closed or no voltage is applied to it. The Timer can also be checked in the same manner once the LPTI closes.

How to check LP Control with No Ice on the Evaporator Ice. Pure and Simple To check the set point of the LPTI, start by turning the unit off after a harvest. Unplug the Water Pump and set the Timer to 1 second. Now turn the selector switch to ICE. With no load on the Evaporator the suction pressure will drop quickly. Watch your suction gauge. When the LPTI reaches it s set point, it will close, energizing the Timer for only one second. The Timer will then close, starting the defrost. With the opening of the Hot Gas Valve the suction pressure will begin to rise. The lowest pressure shown on your gauge before the suction rises IS the set point of the LPTI. Verify this set point with the chart in the Technical Service Manual.

The following slides will examine freeze up issues related to the control circuit.

1 Evap Modular Units LPTI WON T CLOSE The unit is unable to enter defrost. Relay 2 Coil WASH Water Pump ICE Cam SW Relay 1-A Purge Valve Contactor Harvest Motor Purge SW Hot Gas Relay 1-B LP Control Timer Relay 1 Coil Relay 1-B Fan Bin Fill Switch ICE Fan Cycle Control Relay-2 HP Control High Temperature Safety Contactor Coil POWER SUPPLY

1 Evap Modular Units TIMER WON T CLOSE The unit is unable to enter defrost. Relay 2 Coil WASH Water Pump ICE Cam SW Relay 1-A Purge Valve Contactor Harvest Motor Purge SW Hot Gas Relay 1-B LP Control Timer Relay 1 Coil Relay 1-B Fan Bin Fill Switch ICE Fan Cycle Control Relay-2 HP Control High Temperature Safety Contactor Coil POWER SUPPLY

1 Evap Modular Units OPEN COIL ON RELAY 1 Relay 2 Coil The Purge Valve will open, but the unit will not energize the Hot Gas Valve or the Harvest Assist Assembly. The unit will not harvest the ice. WASH ICE Cam SW Water Pump Relay 1-A Purge Valve Contactor Harvest Motor Purge SW Hot Gas Relay 1-B LP Control Timer Relay 1 Coil Relay 1-B Fan Bin Fill Switch ICE Fan Cycle Control Relay-2 HP Control High Temperature Safety Contactor Coil POWER SUPPLY

1 Evap Modular Units OPEN COIL ON HOT GAS VALVE The Hot Gas Valve will not open and with the opening of the contacts of Relay 1, the Fan Motor will shut off. The unit will eventually go off on high head pressure without harvesting the ice. WASH ICE Cam SW Relay 2 Coil Water Pump Relay 1-A Purge Valve Contactor Harvest Motor Purge SW Hot Relay 1-B Gas LP Control Timer Relay 1 Coil Relay 1-B Fan Bin Fill Switch ICE Fan Cycle Control Relay-2 HP Control High Temperature Safety Contactor Coil POWER SUPPLY

1 Evap Modular Units Contacts of Purge Sw. OPEN Relay 2 Coil If the Contacts of the Purge Sw. are opened during defrost, Relay 1 will lose power as soon as the LPTI opens, sending the unit back to freeze without harvesting. WASH ICE Cam SW Water Pump Relay 1-A Purge Valve Contactor Harvest Motor Purge SW Hot Gas Relay 1-B LP Control Timer Relay 1 Coil Relay 1-B Fan Bin Fill Switch ICE Fan Cycle Control Relay-2 HP Control High Temperature Safety Contactor Coil POWER SUPPLY

Intermittent Freeze Ups A possible cause of intermittent freeze ups can be the Harvest Assist Assembly motor Bumping. Inside the small motor is a ratchet that should allow the motor to turn clockwise only. If this ratchet wears or becomes displaced, the motor can turn either clockwise or counterclockwise at any time.

Harvest Assist Should the ratchet be worn, the motor could turn counterclockwise for a split second. The Cam Switch will ride out of the depression of the Clutch the wrong direction, closing the Normally Open contacts of the Cam Switch. The Water Pump and the Purge Valve will shut down with out purging the water. Then the ratchet could catch, forcing the motor to turn back clockwise.

Harvest Assist The motor will turn the Clutch back clockwise. The result will be the Cam Switch dropping back into the low side of the Clutch, re-opening the Normally Open contacts of the Cam Switch. The unit will return to the freeze cycle without harvesting the ice. The following cycles may harvest as normal. Should your unit occasionally create thick slabs of ice, replacing the Probe Motor may be in order.

Should the Harvest Assist Assembly become dislodged from its mounts or the Probe Shaft become disconnected from the swivel, the unit will go through a short defrost (about 30 seconds) while the Probe Motor rotates 360 degrees, then returns the unit to the freeze cycle without harvesting the ice slab.

The following slides will examine freeze up issues related to the refrigeration system.

Should a TXV fail to meter properly and is over feeding refrigerant, the suction pressure will remain elevated. This may cause the LPTI not to close if the set point can not be reached, causing a freeze up. The suction pressure should slowly, continuously and steadily drop during the freeze cycle as ice is formed on the Evaporator.

The same issue will be encountered if the is inefficient. The suction pressure may remain high enough that the LPTI can t close, but low enough to form ice, resulting in a freeze up. Check the s amp draw against the RLA listed on the data tag. Five minutes into the freeze cycle the amp draw should be within 10% of the RLA listed to be considered efficient.

A dirty or clogged Condenser or an inefficient Fan Motor can also contribute to freeze up issues by not allowing the heat exchange from the unit. Fan Motor amp draw should be verified to assure efficiency. Lack of liquid feeding the TXV can cause a freeze up. This can also be the case in an over charged system.

A dirty or damaged Evaporator can cause a freeze up by not allowing all the ice to be harvested from the plate. Examine the Evaporator for pitting or loose horizontal dividers, either of which can cause ice to remain on the plate. If part of the ice slab remains on the Evaporator when the unit re-enters the freeze cycle, a freeze up can be the result.

Should the Hot Gas Valve start leaking by, the result would be a higher suction pressure. Depending on the degree the valve is leaking, it can result in either no production of ice to slow production. If the leak is slight, it may keep the suction pressure above the set point of the LPTI, resulting in a freeze up. There should always be a marked temperature difference between the inlet and outlet of the Hot Gas Valve.

Diagnosing Freeze-ups Quiz