Hansen FROST MASTER PLUS

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Specifications, Applications,

Service Instructions & Parts

FROST MASTER

PLUS

DEFROST CONTROLLERS

Bulletin F100d

JAN 2011

for Industrial/Commercial

Evaporator Defrosting

FM-71 Defrost Controller

INTRODUCTION

The Hansen Frost Master

is an easy-to-use defrost

controller for efficient removal of frost accumulation

on evaporator coil surfaces. This controller uses

simple, reliable solid-state electronics with a precision

quartz time clock and time adjusting slide knobs to

sequentially operate through logical defrost steps for

smooth but complete and effective defrosting. The

SPDT relays facilitate flexible connection of solenoid

valves and control relays. Defrost mode and step

times are easily viewed through the clear cover of the

NEMA 4 enclosure. Typically, one controller is used

per defrost control valve group.

KEY FEATURES

User friendly

SPDT relays, 10 amp switch rating

Entire program always visible

Battery back-up

Terminals for optional sensor defrost initiation

Terminals for optional sensor defrost termination

Staggered defrosting is simple

24 hour or 7-day scheduling

Precision quartz time clock

Remote Initiate only models available

APPLICATIONS

Designed specifically for defrosting industrial and

large commercial refrigeration systems, the Frost

Master

sequences solenoid valves and relays to

provide quick and efficient defrosting of evaporator

coils. Because of its SPDT relays and time adjustable

defrost steps, this controller is suitable for almost

every defrost application including: top and bottom

feed unit coolers, blast freezer evaporators, and

ice makers. Whether the evaporator uses hot gas,

electricity, or water to defrost, this controller makes

setting or changing defrost periods simple and easy.

A very precise quartz time clock facilitates accurate

setting of defrost start times. Time clocks include

battery back-up in case of short term power failure to

avoid any nuisance re-setting of clocks after power

interruptions.

Demand initiate and coil temperature terminate devices

may be directly connected to the Frost Master

when

something other than conventional time-only defrosting

is appropriate. The Frost Master

Plus models offer

a built-in temperature terminate feature as well as an

additional defrost step, SOFT GAS, which can help

minimize pressure shock to the evaporator during

defrosting.

TABLE OF CONTENTS

Specifications, Advantages, Installation ........................ 2,3

Initiation, Termination, Wiring ........................................ 4,5

Frost Master

Plus (SOFT GAS) ...................................... 6,7

Typical Defrost Applications ........................................... 8,9

Control Valve Selection ...............................................10,11

Remote Initiate Models, Order Info. ................................ 12

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Summary

FROST MASTER PLUS INTRODUCTION

TERMINATE (PLUS MODELS)

Explanation of the built-in temperature terminate feature for the Plus models.

TERMINATE TEMPERATURE SENSOR

Details on locating and connecting the temperature sensor for the Plus models.

FROST MASTER PLUS RELAY OPERATION

WIRING DIAGRAM

Wiring diagram specific to the Frost Master® Plus controller.

INTRODUCTION TO DEFROSTING

SOFT GAS VALVE

Purpose and application of the soft gas valve for pressure management.

EQUALIZE VALVE

Function and sizing considerations for the equalize valve.

TYPICAL DEFROST APPLICATIONS

BOTTOM FEED EVAPORATOR

Illustrates a control valve scheme for bottom feed evaporators.

TOP FEED EVAPORATOR

Illustrates a control valve scheme for top feed evaporators.

HOT GAS DEFROST NOMINAL VALVE SIZING (TONS)

VALVE SELECTION

Guide to selecting appropriate valve sizes based on refrigerant and capacity.

Summary

FROST MASTER PLUS INTRODUCTION

TERMINATE (PLUS MODELS)

Explanation of the built-in temperature terminate feature for the Plus models.

TERMINATE TEMPERATURE SENSOR

Details on locating and connecting the temperature sensor for the Plus models.

FROST MASTER PLUS RELAY OPERATION

WIRING DIAGRAM

Wiring diagram specific to the Frost Master® Plus controller.

INTRODUCTION TO DEFROSTING

SOFT GAS VALVE

Purpose and application of the soft gas valve for pressure management.

EQUALIZE VALVE

Function and sizing considerations for the equalize valve.

TYPICAL DEFROST APPLICATIONS

BOTTOM FEED EVAPORATOR

Illustrates a control valve scheme for bottom feed evaporators.

TOP FEED EVAPORATOR

Illustrates a control valve scheme for top feed evaporators.

HOT GAS DEFROST NOMINAL VALVE SIZING (TONS)

VALVE SELECTION

Guide to selecting appropriate valve sizes based on refrigerant and capacity.

The Hansen Frost Master® is a user-friendly defrost controller designed for efficient removal of frost accumulation on evaporator coil surfaces in industrial and large commercial refrigeration systems. It utilizes reliable solid-state electronics and a precision quartz time clock with time-adjusting slide knobs to sequentially operate through logical defrost steps, ensuring smooth, complete, and effective defrosting. Typically, one controller is used per defrost control valve group.

Function Description

The Frost Master® sequences solenoid valves and relays to provide quick and efficient defrosting. The defrost process begins with the PUMPOUT step (0-15 minutes), which removes liquid refrigerant from the evaporator, reducing the load from cold residual liquid and exposing more internal surface area to hot gas. This also minimizes the amount of liquid accommodated by the system during defrost.

Next, the HOT GAS step (0-45 minutes) introduces hot gas (or another frost-melting medium) to the evaporator. The duration of this step depends on factors like evaporator design, frost accumulation, hot gas supply quality and quantity, and valve size. It is crucial for the HOT GAS step to be long enough to completely remove all frost; partial removal can lead to increased frost/ice problems over time. A 5-second delay is incorporated before the "H" relay switches to its position, allowing the suction solenoid valve to close before the hot gas solenoid valve opens.

The EQUALIZE step (0-5 minutes) follows, gradually reducing the pressure inside the newly defrosted evaporator to near suction pressure. This is achieved by either a bleed-down solenoid valve bypassing the suction shut-off valve or by allowing the surrounding ambient temperature to cool the evaporator. This step minimizes sudden surges in suction pressure and reduces the impact of pressure changes on the suction accumulator, preventing unnecessary loading/unloading of compressors and pump cavitation.

Finally, the FAN DELAY step (0-5 minutes) resumes normal refrigeration but delays evaporator fan operation for the set time. This allows remaining water droplets from melted frost to freeze onto the evaporator surface, preventing them from being blown into the refrigerated space when air circulation resumes. Usage of all steps is optional and any step can be skipped by setting its time adjustment to zero.

The Frost Master® Plus models offer additional features, including a fifth defrost step called SOFT GAS (0-5 minutes) and a built-in adjustable Temperature Terminate feature. The SOFT GAS step gradually increases pressure inside the evaporator by opening a small soft gas solenoid valve prior to the main hot gas valve, priming the evaporator for full hot gas flow and minimizing pressure shock. The soft gas solenoid valve remains open throughout the SOFT GAS and HOT GAS steps.

Important Technical Specifications

Defrost Steps:
- PUMPOUT: 0 to 15 minutes (0 to 45 minutes for Plus models)
- SOFT GAS: 0 to 5 minutes (Plus models only)
- HOT GAS: 0 to 45 minutes
- EQUALIZE: 0 to 5 minutes (0 to 10 minutes for Plus models)
- FAN DELAY: 0 to 5 minutes
Relays: SPDT, 10 amp switch rating each.
Defrost Interval:
- 24-hour clock: 96 settings (15-minute increments)
- 7-day clock: 84 settings (2-hour increments)
Battery Back-Up: 90 hours for quartz time clock.
Power: 115V 50/60Hz; 230V 50/60Hz.
Terminal Strip: Accepts 14-22 AWG wire sizes.
Controller Temperature Range: -20°F to 120°F (-29°C to 50°C) ambient.
Enclosure: NEMA 4, high-impact polycarbonate clear cover, gasketed.
Auxiliary Terminals: 1/4" spade terminals for optional defrost initiate or temperature terminate.
Terminate Temperature Range (Plus models): 30°F to 65°F (-1°C to +18°C), typically set around 40°F (4°C). Sensor wire leads can be up to 500 ft (152 m) long, at least 20 AWG (0.5 mm2).

Usage Features

User Friendly: Control settings are in refrigeration terms ("defrost steps"), making setup and adjustment straightforward.
Program Visibility: The entire defrost program is always visible through the clear cover.
Battery Back-Up: Ensures accurate timekeeping during short-term power failures, avoiding nuisance re-setting.
Optional Sensor Defrost Initiation/Termination: Terminals are provided for connecting demand initiate devices (e.g., frost sensors, computers, PLCs, push buttons) or temperature terminate devices (e.g., thermostats).
Staggered Defrosting: Simple to implement for multiple evaporators, preventing too many units from defrosting simultaneously.
Scheduling: Offers 24-hour or 7-day scheduling options.
Precision Quartz Time Clock: Facilitates accurate setting of defrost start times.
Remote Initiate Models: Clockless models (FM-01, FM-02, FMP-01) are available for initiation via external, momentary dry contact closure, offering flexibility for computer-controlled systems.
Defrost Step and Mode Lights: Green LED indicates normal refrigeration; red LEDs indicate defrost mode and current step, providing clear operational status.
Manual Stepping: A button allows for manual initiation and advancement through defrost steps, useful for testing or unusual frost accumulation.
Demand Initiate: The defrost initiate feature (N.O. 1/4" spade terminals) requires closure of these terminals and a tripped time clock tab for defrost to begin in clock-equipped models. Remote Initiate models can initiate defrost any time the device closes the terminals. A factory-installed jumper closes the initiate terminals for time-only defrost; this can be removed for demand initiate.
Terminate Feature (Plus Models): The built-in temperature terminate feature allows easy adjustment of the terminate temperature directly on the controller face. When the set temperature is reached during the HOT GAS step, defrost ceases, and the EQUALIZE step begins, ensuring quick and efficient defrosting. The sensor should be located at the last place on the evaporator coil where frost or ice remains.

Maintenance Features

Minimal Service Required: These controllers require practically no service or maintenance.
Field Replaceable Components: The only field-replaceable components are the time clocks (24-hour or 7-day) and the terminate temperature sensor (for Frost Master® Plus models).
Clock Replacement: To replace the clock, disconnect power, remove three 5/32" socket cap screws, carefully pry the clock away, insert the new clock's spade terminals into the clamp connectors, replace screws, restore power, and set time-of-day and defrost start times.