Merco DHC 24-CE User Manual

SERVICE & TROUBLESHOOTING MANUAL

FOR

DISPLAY HOLD CABINETS

DHC SERIES

REV: 1/28/09

ELECTRICAL SPECIFICATIONS

Domestic DHC 24H

Domestic DHC 24

Internaitonal

International DHC 24-CE

Item # Description Voltage Hz. Watts Amps Cord/Plug Dimensions

DHC 24H­CE

Display Hold
Cabinet w/hum

Display Hold
Cabinet w/o hum

Display Hold
Cabinet w/ hum

Display Hold
Cabinet w/o hum

120 VAC 60 1500 12.5 6’, NEMA 5-15P 24” W x 36” H x 24” D

120 VAC 60 1175 9.8 6’, NEMA 5-15P 24” W x 36” H x 24” D

230 VAC 50 1500 7 2 M, CEE 7/7

230VAC 50 1175 5.5 2 M, CEE 7/7

610mm W x 915mm H
x 610mm D

610mm W x 915mm H
x 610mm D

OPERATION

• The DHC is designed to display and hold up to 4 – 18” pizzas for one hour.

• Set Main Power switch to the “ON” position.

• Pre-heat the unit for 20 minutes.

• Set the temperature control at desired temperature for your product. Factory recommendations are setting 6 on
the temperature dial (175° F, 80° C). The temperature range is 125° F (52° C) to 205° F (96° C).

• The red “Add Water” light will start blinking when water is needed. Fill the water tank with distilled water in
preparation to start the humidity cycle. The water tank will hold 1 gallon (3.75 liters) of water. Be careful not to
overfill. If the tank is overfilled water will exit back out of the fill cup. An audible alarm will sound prior to
overfilling of the tank. If the alarm is heard the operator is to cease filling the water tank.

• Set humidity. Factory recommendations are setting to “medium.”

• Open the access door(s) and load the product onto the shelves of the rotating rack. The rack will stop rotating
when the door(s) are opened.

• The DHC will keep your product hot and fresh for serving. The digital display will monitor the cabinet
temperature. The alarm will sound when the tank needs to be refilled.

CONTROL PANEL FEATURES

Main Power On/Off Switch – This switch controls power to the unit.
Temperature Display – Shows cabinet temperature in °F or °C.
Heat Control – This control regulates the cabinet temperature. The settings range from low to high.
Humidity Control – This control regulates the amount of cabinet humidity. The settings range from low to high.
Heat / On Light – This green light illuminates when the heat control is energized.
Add Water Light – This red light illuminates when additional water is required.

CHANGING MERCHANDISING DISPLAY PANELS

The merchandising panels supplied by Merco Savory are easily changed by removing the four (4) mounting screws
located on the top and back side of the unit (2 on each side).

WATER RESERVOIR FILLING INSTRUCTIONS

INITIAL FILLING
IMPORTANT: To prevent excess mineral build-up, which could affect the operation of this unit, only use low
mineral or distilled water. Service required due to excessive mineral build-up WILL NOT be covered under
warranty.

1. Set main power switch to the “ON” position.

2. Open the water reservoir cover (located on the left side of the control panel). Using the measu ring cup

provided, start filling the tank.

3. Fill the tank until the beeping sound is heard. This indicates the tank is filled to capacity. Do not overfill or

water will overflow from the water reservoir.

4. Close water tank reservoir.

5. Filling the water reservoir to capacity will allow for approximately 6 to 8 hours, depending on the type of food

displayed, control settings, frequency of door openings, etc.

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DHC Series Service Manual

WATER RESERVOIR FILLING INSTRUCTIONS (CONT’D)

RE-FILLING

1. The red “Add Water” light will illuminate when additional water is required.

2. IMPORTANT: DO NOT add water until this light is illuminated. The add water alarm will not sound unless t he

light is on.

3. Fill the tank until the beeping sound starts.

CLEANING INSTRUCTIONS

!

The DHC Display and Hold Cabinets are designed for easy cleaning. Remove the interior rack and wash in hot
sudsy water. The interior and exterior surfaces need nothing more than a daily wiping with a soft, damp cloth. Do
not use abrasive cleaners on any part of the unit. This will cause damage to the unit. This appliance shall not be
cleaned with high-pressure water jets.

CAUTION: UNPLUG UNIT AND ALLOW IT TO COOL BEFORE CLEANING.

WARNINGS

!
!
!

!

To prevent electric shock, always unplug the unit before performing cleaning, maintenance or repair.

Plug the cabinet into a properly grounded electrical outlet of the correct voltage, size and plug
configuration. If the plug and receptacle do not match, contact a qualified electrician to determine
proper voltage and size and install the proper electrical outlet.

Do not attempt to clean the water tank system with chemical agents.

Only use GE F13T5CW Teflon coated fluorescent bulbs or equivalent for replacement.

CAUTIONS

!
!
!

Some exterior surfaces on the Display Cabinet will get hot. Use caution when touching these areas
to avoid injury.

The unit must be transported in an upright position. If transported on its side, all glass surfaces must
be secured with tape and the water must be drained.

Never use anything but water in the tank system.

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3

SEQUENCE OF OPERATIONS

DHC-24 120VAC Single Phase
Power is permanently supplied to the normally open on/off switch. Closing the on/off switch supplies 120VAC to

the display, fan motor, and two 60 Watt back lights through the normally closed hi-limit to the normally open heating
thermostat. Power is also supplied to the relay, float switches (located in the water tank), and the fluorescent lights.
The relay supplies 120VAC to the normally open humidity thermostat. When the humidity thermostat closes,
120VAC is supplied to the water heating element and to the humidity indicator light. When the float switch detects
a low water condition, the relay switches power from the humidity thermostat to the low water indicator light. When
the door is closed, the proximity switch closes and the display board will supply 120VAC to the rack motor. The
display uses a RTD probe to sense and show cabinet air temperature.

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DHC Series Service Manual

SCHEMATIC

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5

TROUBLESHOOTING GUIDE

CONDITION POSSIBLE CAUSES SUGGESTED SOLUTIONS

No Steam

No Heat

Water leaking in
control area

Rack will not rotate 1. Defective proximity switch

Rack continues to
rotate when door is
open

Fluorescent lights do
not illuminate

Light doesn’t
illuminate when tank
is low

No temperature
display

Sign lights do not
illuminate

Water inside cabinet

1. No water in tank

2. Lime/mineral build-up

3. Closed Hi-Limit

4. Defective Thermostat (humidity)

5. Defective Relay

6. Defective Floats

7. Defective Element

1. Defective Hi-Limit

2. Defective Heati ng Thermostat

3. Defective Element

4. Defective Motor

1. Water tank overfilled

2. Defective water line

2. Defective Displ ay Board

3. Defective Motor

4. Missing Roll P in(s)

5. Defective Clutch

1. Defective Proxi m ity Switch

2. Defective Board

1. Lights burned out

2. Improper socket connections

3. Defective Ballast

1. Defective or Li med F loats

2. Bad Light

3. Bad Relay

1. Defective RTD

2. Defective Displ ay Board

1. Burned out bulbs

2. Improper Socket Connections

1. Defective Drain Valve

2. Humidity too high

1. Check to see if water tank is filled

2. Clean or replace affected parts

3. Check continuity. 200 Ohms. Replace as needed.

4. Check for cycle by increasing. Replace as needed.

5. Replace as needed

6. Long float is normally open. Replace as needed.

7. Check continuity.
120V=44 Ohms + 10%, -5%. 230V=160 Ohms.
Replace as needed.

1. Replace as needed.

2. Replace as needed.

3. Check continuity. (13 Ohms) Replace as needed.

4. Check coil for continuity. Replace as needed.

1. Check for proper water level.

2. Repair as needed.

1. Check continuity or missing magnet. Replace as

needed.

2. Check connections, replace as needed.

3. Replace as needed.

4. Reinstall roll pin(s)

5. Replace as needed.

1. Check continuity. Replace as needed.

2. Replace as needed.

1. If light flickers, check grounding. Replace as needed.

2. Check connections, replace as needed.

3. Replace as needed.

1. Replace as needed.

2. Replace as needed.

3. Check signal to coil. Verify wiper trips. Replace as

needed.

1. Check continuity (see chart). Replace as needed.

2. Replace as needed.

1. GE F13T5CW. 18-20 Ohms across pins on same

end. Replace bulbs as needed.

2. Check connections, replace as needed.

1. Replace as needed.

2. Turn down humidity.

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PARTS LIST – DHC-24 CABINET

KEY NUMBER PART NUMBER DESCRIPTION QTY USED

1 Trim 2
2 Slide Glass L & R 2
3 46206SP Rear Door Assembly 24” Cabinet 1

- Door Hinge (Part of Door Assembly) 3

- Rear Door Glass 1

- Rear Seal Door Stop 1

- Door Handle Assembly 1
4 Power Cord 1
5 Top Cover 1
6 46201SP Light Assembly Complete 2

- 4-40 x ¼” Pan Screw 4

46214SP Fluorescent Bulb, F13T5 1
46215SP T5 Lampholder 2

7 46301SP Pizza Rack 24” 1

7A 46305SP Pretzel Rack 24” 1
7B 46306SP Sandwich Rack 24” 1

8 46257SP Trim 1
9 46258SP Clutch 1

10 46259SP Cotter Pin 1

11 46314SP Sign – Pizza 24” 1
11B 46315SP Sign – Pretzel 24” 1
11C 46316SP Sign – Sandwich 24” 1

12 46218SP Front Curved Glass 1
12A 46219SP Front Door Left and Right* 1

* Must be purchased as set
13 46220SP Top Seal 1
14 46221SP Bottom Seal 1
15 46222SP Louver Panel Left 1

15A 46223SP Louver Panel Right 1

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EXPLODED VIEW ILLUSTRATION – DHC-24 CABINET

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PARTS LIST – DHC-24 ELECTRICAL COMPONENTS

KEY NUMBER PART NUMBER DESCRIPTION QTY USED

2 369805 Rocker Switch 1
3 46225SP Knob 2
4 46226SP Green Pilot Light 1
5 M51052SP Red Pilot Light 1
6 46227SP Label Water Fill Hum. 1
7 46228SP Panel, Left Hand Top Rear 1
8 46229SP Control Panel 1

8a 46204SP Control Panel Assembly 1

9 46230SP Label, Control, Hum. 1
10 46231SP Panel, Right Hand Top Rear 1
11 46232SP Latching Relay 1
12 46233SP Temp/Hum. Control with Probe 1
13 46234SP Digital Display Unit 1
14 46235SP Cover, Heat/Hum. Chamber 1
15 46236SP Water Fill Assembly

15a 46237SP Elbow, ¾ NPT x ¾ Slip 1
15b 46238SP Bulkhead Fitting 1
15c 46239SP Nut, Bulkhead 1
15d 46240SP 90° Elbow ¾ NPT / Slip 1
15e 46241SP Tubing, Tygon ¾” ID

16 46242SP Heater, Air, 120V 1
17 15856SP Thermocouple, Air Inlet 1
18 46243SP Hi Limit Thermostat 1
19 46244SP Water Tank 1
20 46245SP Heater, Immersion 120V 1
21 46246SP Pipe Coupling 1
22 46247SP Socket, Quick Connect 1
23 46248SP Plate, Water Cover 1
24 46209SP Water Tank 1
25 46249SP Gearmotor 115V .2a 1
26 46250SP Water Tank Top 1
27 46251SP Switch, Float Lo Limit Assembly 1
28 46252SP Switch, Float Hi Limit Assembly 1

Switch, Float

29 369124 Cooling Fan 1

29a 46254SP Cooling Fan Shroud 1

30 46255SP Bulkhead 1
31 46256SP Ballast 1
32 000678SP Lamp Socket 1
33 000370SP Light Bulbs 1

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EXPLODED VIEW ILLUSTRATION – DHC-24 ELECTRICAL COMPONENTS

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Merco Savory, LLC

1111 North Hadley Road

Fort Wayne, Indiana 46804

United States of America

Telephone: [phone]

U.S. Fax: [phone]

Int’l Fax: [phone]

Service Hotline: [phone]

www.mercosavory.com

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DHC Series Service Manual