Liebert TM-10098 User Manual

Large Systems

iCOM

Environmental Training and Service Manual

Microprocessor

TM-10098: Rev. 02/06

Training & Service

iCOM

Control Training and Service Manual

iCOM

Manual

iCOM

Controls Training and Service Manual

Disclaimer of Warranties and Limitations of Liabilities

The authors and editors have taken every precaution to ensure accuracy and completeness in this manual. The authors and editors make no expressed or implied warranty of any kind with regard to the documentation in this manual. Liebert Corporation assumes no responsibility, and disclaims all liability for incidental or consequential damages resulting from the use of this information or from errors or omissions. Liebert Corporation may make improvements and/or changes in the product(s) described in this manual at any time. Information in this manual is subject to change at any time and does not represent a commitment on the part of Liebert Corporation.

Liebert® and the Liebert logo are registered trademarks of Liebert Corporation. Emerson® and the Emerson logo are registered trademarks of Emerson Electric Co.

Specifications subject to change without notice.

Printed in the United States of America

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Table of Contents

Chapter 1: Temperature/ Humidity Control 6

Temperature Control Types Intelligent Control Proportional Control Proportional + Integral (PI) Control Proportional + Integral + Derivative (PID) Control Temperature Control Operations and Charts 2 Stage Compressorized 4 Stage Compressorized Cooling Dual Compressor Digital Scroll Operation Glycool Cooling Dual Source Cooling Staged Reheat Humidity Control Absolute (Predictive) Humidity Control Relative Humidity Control Humidifier Operation Autoflush Control for Infrared Dehumidification Operation 1 Stage Dehumidification, Compressorized Operation 2 Stage Dehumidification, Compressorized Operation Reheat During Dehumidification Additional Programs Next Maintenance Calculation Shared Parameters an Understanding Networking and Functions Teamwork Unit Lead/ Lag or Running/ Standby Fuctions

6 6 8 8

9 11 11 11 13 18 18 20 21 25 25 27 27 29 31 31 32 33 35 38 40 41 48 49

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Chapter 2: Programming Functions 52

Programming Functions

iCOM Display Components and Functions iCOM Keypad Layout Descriptions iCOM Display Symbols/ Icons

Programming Functions Status Display Screens Menu Screens – Icons/ Parameter Names User Menu Icons and Descriptions Service Menu Icons and Descriptions Advanced Menu Icons and Descriptions User Menu Parameters Service Menu Parameters Advanced Menu Parameters Event Notifications Parameters Event ID Number, Description and Function

52 53 54 55 56 56 57 58 59 60 60 67 84 90 92

Chapter 3: iCOM Hardware Connections 100

Introduction Display Boards Unit Control Board Switches and Jumpers Large Display Switches and Jumpers Small Display Switches and Jumpers Temperature/ Humidity Board Switches and Jumpers Unit Control Board Plug Connectors Fuse Board Connectors Temperature/ Humidity Board Connectors

100 101 102 104 105 106 107 111 112

Chapter 4: General Troubleshooting Data 114

Introduction Isolation Basic Operation of the Triac Basic Operation of the Opto-Isolator Troubleshooting the Opto-Isolator

114 115 116 118 119

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Unit Control Board: Opto-Isolator/ Triac Legends iCOM Diagnostics/ Service Mode Programs

Basic Troubleshooting Steps Moisture Content Charts Suction Transducer Information Digital Scroll High Temperature Sensor Chart Unit Code Description Troubleshooting Checklist Glossary of Unit/ Systems Parameters

121 123 124 126 143 144 145 146 147

Glossary of Terms 156 Computer and Network Terms 160 Network Information 165 How To Use The Schematics 169 Electrical Schematics 170

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Chapter 1

Temperature and Humidity

Control Programs

This section provides details on how your Liebert iCOM control responds to the user programmed inputs values and room conditions. Refer to this section when you need specific information control operation. This section includes details on four (4) user selectable temperature control programs and two (2) user selectable and humidity control programs.

Cooling and/ or Heating Required, in Percent (%)

The temperature control programs for the iCOM microprocessor is based on a calculated percent (%) requirement for cooling and/ or heating. This percent (%) requirement is determined by the control type (algorithm) selected by the user.

The four (4) user selectable temperature control programs are:

• Intelligent

• Proportional (P)

• Proportional + Integral (PI)

• Proportional + Integral + Derivative (PID)

Temperature Control Program Types

Intelligent Control – Factory Default Setting

The Intelligent Control operates from a set of general rules that defines how the control output should be adjusted for different system conditions. The rules are designed to duplicate the actions that an experienced human operator would take if manually controlling the system.

Basically, this is done in a three-function process that differs from earlier mathematically defined strict type data, hence, fuzzy logic. The on and off, true or

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untrue type of statement is not used. The consideration now is how to set the input value into a membership set, qualify this membership with rules, then decide on the output consequence for action. It is not really that simple, but it is basically how it works. The process:

Membership

• Measure value of input variables

• Map and transfer data into range of set domain

• Assign input membership into sets

Knowledge Base/Decision Making

• Provide a data base of definitions for rules base

• Provide a rules base and define function and domain

• Simulate human decision making based on concepts and actions

defined by implications and rules

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Consequence

• Convert defined range of knowledge to a corresponding output variable

• Define a non-intelligent action from a deduced intelligent action

Just as an operator might take several things into consideration before making a temperature control decision, the intelligent control can be programmed to do likewise. For example, not only is the current temperature used in making temperature control decisions, but also conditions such as:

• How fast is the temperature changing?

• What direction is the temperature changing?

• What is the cooling output now?

• What was the cooling output in the past?

• How long ago was the cooling output changed?

• Other factors

Any number of rules can be used in an intelligent control to define the controls operation under various operating conditions. Hence, several advantages are gained from this type of control over a more standard control approach that uses a fixed mathematical equation to define the operation of the control for all conditions (such as a Proportional or PID Control). You can expect Intelligent Control to be

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more efficient and precise for most applications, but system performance based on room conditions is not as predictable as standard approaches that use a fixed equation.

The Liebert Intelligent Control includes rules that significantly enhance the performance of the system, both from a standpoint of precision control and system reliability.

Rules are included that:

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• Cause the control to ignore very small or temporary temperature/ humidity deviations. This eliminates unnecessary control adjustments that contribute to control instability.

• Help limit the frequency of control adjustments thus extending the life of system components that are susceptible to mechanical wear or cycling.

• Recognize undesired modes of control operation such as hunting, and make adjustments to the control response to eliminate them.

• Estimate the present load on the system and then tend to force the control output to the appropriate state.

• Recognizes conditions, which indicate a large load change and allows the control to temporarily respond more quickly than normal.

• Cause the control to anticipate the need for reheat during dehumidification and activates reheats when overcooling occurs.

Proportional (P) Control

The proportional control is the standard control method that maintains the room at a temperature proportional to the load. The temperature maintained increases as the room load increases. At full load the room would be controlled at a temperature equal to the temperature set point (TSP) plus ½ of the temperature proportional band (PB). The operator programmed inputs are the temperature set point (TSP) and temperature proportional band (PB) adjustments. The operator may also program a temperature dead band (DB) adjustment.

Proportional + Integral (PI) Control

The PI control combines two (2) individual terms to determine the control output for a given set of conditions. Note that PI control is used only for temperature. If PI control is selected, the humidity control will be in percent relative humidity (%RH).

The proportional (P) term is determined by the difference between the current temperature and the control set point. This term is expressed in % cooling (heating desired for each degree above (below) the set point. It is adjustable from 0% to 100% per degree. The purpose of this term is to adjust the control output for any deviation between the current temperature and the control set point.

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The integral (I) term is determined by two things: the difference between the return air temperature and control set point and the amount of time this difference has existed. This term is expressed in % cooling (heating) desired for each minute and degree above (below) the set point. It is adjustable from 0% - 100% per degree/minute. The purpose of this term is to force the control to maintain the temperature around the set point by slowly but continuously adding (subtracting) a small amount of cooling (heating) to the total control output until the temperature is at the set point.

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Proportional + Integral + Derivative (PID) Control

The PID control combines three (3) individual terms to determine the control output for a given set of conditions. Note that PID control is used only for temperature. If PID control is selected, the humidity control will be in percent relative humidity (%RH).

The derivative (D) term is determined by the rate of change of temperature. This term is expressed in % cooling (heating) desired for each degree per minute rise (fall) in temperature. It is adjustable from 0% to 100% per degree/minute. The purpose of this term is to adjust the control output for quickly changing temperatures, thus providing an anticipation control.

All three terms are adjusted by selecting the “Setpoints” icon in either the USER or SERVICE Menu screen. If PID control is selected, the temperature proportional band value (and optional temperature dead band value) is not used by the control. For optimum performance, a PID control must be adjusted or tuned according to the characteristics of the particular space and load to be controlled. Improper tuning can cause the control to exhibit poor response and/ or hunting. The characteristics of the space and load may change seasonally, so occasional returning is required for optimum performance.

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A suggested tuning procedure is as follows:

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1. Initially adjust the integral and derivative settings to 0% / degree-min and 0% / degree / min..

2. Starting with 20% / degree, adjust the proportional setting in small increments (10% steps) until the control sustains a constant hunting action (the temperature swings are approximately the same amplitude from one peak to the next).

3. Note the time in minutes between peaks of adjacent temperature swings and the amplitude of the temperature swing (degrees above the set point).

4. Adjust the proportional control setting to about l/2 the value obtained in Step 2.

5. Adjust the integral setting to a value calculated by the following equation: approximate room load (in % full load) time between peaks x peak amplitude x 4.

Note: If calculation results in a value of less than 1%, then set the integral to 1%.

6. Adjust the derivative to a value calculated by the following equation: time between peaks x 5%.

The above tuning procedure is only an approximation for an initial set of adjustments and are based on the "average" room characteristics. Your particular settings may need to be further adjusted for optimum PID control performance.

Some suggestions for additional tuning are as follows:

• If cooling output overshoot is occurring on load changes, decrease the proportional setting or the derivative setting.

• If system hunting occurs with constant room load, decrease the integral setting.

• If the control responds too slowly, resulting in large temperature excursions on a load change, increase the proportional setting or the derivative setting.

• If a constant temperature deviation exists between the temperature and set point, increase the integral setting.

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Temperature Control

Operations and Charts

The temperature proportional control band value is divided into two parts: the temperature set point plus ½ of the temperature proportional band for cooling operation and the temperature set point minus ½ of the temperature proportional band for heating operation. A temperature dead band can also be programmed into the control to shift the cooling and/ or heating on/ off operations away from the temperature set point.

This programmed temperature dead band value is divided into two parts: the temperature set point plus ½ of the dead band – no cooling operation and the temperature set point minus ½ of the band – no heating operation.

The temperature set point range is adjustable from 41 - 104°F in increments of 1°F. The temperature proportional band range is adjustable from 2 - 54°F in increments of 1°F. The temperature dead band range is adjustable from 0 - 36°F in increments of 1°F.

Standard 2 Stage Compressorized Cooling

The basic temperature cooling control band is established at the temperature set point with the length equal to ½ of the programmed temperature proportional band divided by the number of cooling stages.

The Liebert DS units are supplied with two (2) compressors, each compressor is rated at ½ of the unit capacity. The two (2) compressors will be either the semi-hermetic or scroll type and will operate in an on/ off configuration to cool the space.

The temperature controller activates the first cooling stage (lead compressor) when the return air temperature increases to 50% of the cooling proportional band and the second cooling stage (lag compressor) at 100% of the cooling proportional band. The optional hot gas bypass solenoid valve, supplied with each compressor when ordered, is also energized on a call for cooling.

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The temperature controller deactivates the second stage of cooling (lag compressor) when the return air temperature decreases to 50% of the cooling proportional control band value. The first cooling stage (lead compressor) is deactivated when the return air temperature decreases to the temperature set point value or 0% of the cooling proportional control band value.

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2 Stage Compressorized Cooling – No Dead Band

Note: in the above example that the control band begins at the 70°F temperature set point and has a length of 4°F, which is ½ of the programmed temperature proportional band value.

As the return air temperature increases Cooling 1 (lead compressor) is activated at 72°F or 50% of the cooling control band. If the return air temperature continues to increase Cooling 2 (lag compressor) will activate at 74°F or 100% of the cooling control band.

When the return air temperature starts to decrease, Cooling 2 (lag compressor) is deactivated at 72°F or 50% of the cooling control band and Cooling 1 (lead compressor) is deactivated at the temperature set point of 70°F or 0% of the cooling control band.

Temp Set Point: 70°F Proportional Band: 8°F

Temp Set Point + (1/2 Proportional Band)

Cool 1 On

70 71 72 73 74 75

Cool 1 Off

Cool 2 Off

Cool 2 On

Increasing Temperature

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2 Stage Compressorized Cooling – With Dead Band

Note: in the above example that the control band begins at the 70°F temperature set point and has a length of 5°F, which is ½ of the programmed temperature dead band value plus ½ of the programmed temperature proportional band value.

As the return air temperature increases Cooling 1 (lead compressor) is activated at 73°F or ½ of the dead band value plus 50% of the cooling control band. If the return air temperature continues to increase Cooling 2 (lag compressor) will activate at 75°F or ½ of the dead band value plus 100% of the cooling control band.

When the return air temperature starts to decrease, Cooling 2 (lag compressor) is deactivated at 73°F or ½ of the dead band value plus 50% of the cooling control band and Cooling 1 (lead compressor) is deactivated at 71°F or ½ of the dead band value plus 0% of the cooling control band.

Remember the temperature dead band value is used by the control to shift the cooling on/ off operations away from the temperature set point.

Temp Set Point + (1/2 Dead Band + 1/2 Proportional Band)

Temp Set Point: 70°F Proportional Band: 8°F Dead Band: 2°F

Cool 1 On

70 71 72 73 74 75

Cool 1 Off

Cool 2 Off

Increasing Temperature

Cool 2 On

Optional 4 - Stage Cooling, Two (2) Compressors with Unloaders

The Liebert DS units are supplied with two (2) compressors, each compressor is rated at ½ of the unit capacity. Each compressor will be the semi-hermetic type

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and will be supplied with an electrical cylinder unloader valve. The electrical solenoid valve used to unload or reduce the cooling capacity of the compressor. The compressors will operate in an on/ off - loaded/ unloaded configuration method to cool the space. The hot gas bypass solenoid valve option is not available on 4 stage systems.

The temperature controller activates the first cooling stage, lead compressor unloaded, when the return air temperature increases to 25% of the cooling proportional band. The second cooling stage, lag compressor unloaded, is activated when the return air temperature increases to 50% of the cooling proportional band.

The temperature controller activates the third cooling stage, the lead compressor loaded, when the return air temperature increases to 75% of the cooling proportional band. The fourth cooling stage, the lag compressor loaded, is activated when the return air temperature increases to 100% of the cooling proportional band.

The temperature controller deactivates the fourth cooling stage, lag compressor loaded, when the return air temperature decreases to 75% of the cooling proportional control band value. The third cooling stage, lead compressor loaded, is deactivated when the return air temperature decreases to 50% of the cooling proportional control band value.

The temperature controller deactivates the second cooling stage, lag compressor unloaded, when the return air temperature decreases to 25% of the cooling proportional control band value. The first cooling stage, lead compressor unloaded, is deactivated when the return air temperature decreases to the temperature set point value or 0% of the cooling proportional control band value.

The table below shows the devices activated by each of the four cooling stages.

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STAGE COMPRESSORS, UNLOADER STATE

Compressor 1 On, Unloader On (Energized) Compressor 2 Off, Unloader Off (De-Energized)

Compressor 1 On, Unloader On (Energized) Compressor 2 Off, Unloader On (Energized)

Compressor 1 On, Unloader Off (De-Energized) Compressor 2 On, Unloader On (Energized)

Compressor 1 On, Unloader Off (De-Energized) Compressor 2 On, Unloader Off (De-Energized)

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4 Stage Compressorized Cooling – No Dead Band

Note: in the above example that the control band begins at the 70°F temperature set point and has a length of 4°F, which is ½ of the programmed temperature proportional band value.

As the return air temperature increases Cooling 1, the lead compressor unloaded, is activated at 71°F or 25% of the cooling control band. If the return air temperature continues to increase Cooling 2, the lag compressor unloaded is activated at 72°F or 50% of the cooling control band. If the return air temperature continues to increase Cooling 3, the lead compressor is loaded at 73°F or 75% of the cooling control band. If the return air temperature continues to increase Cooling 4, the lag compressor is loaded at 74°F or 100% of the cooling control band.

When the return air temperature starts to decrease, Cooling 4 is deactivated at 73°F or 75% of the cooling control band. If the return air temperature continues to decrease Cooling 3 is deactivate at 72°F or 50% of the cooling control band. If the return air temperature continues to decrease Cooling 2 is deactivate at 71°F or 25% of the cooling control band and Cooling 1 is deactivated at the temperature set point of 70°F or 0% of the cooling control band.

Temp Set Point: 70°F Proportional Band: 8°F

Temp Set Point + (1/2 Proportional Band)

Cool 2 On

Cool 1 On

70 71 72 73 74 75

Cool 1 Off

Cool 3 Off

Cool 3 On

Cool 4 OffCool 2 Off

Cool 4 On

Increasing Temperature

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The example below is based on a temperature set point of 70°F with a control band length of 4°F, which is ½ of the programmed temperature proportional band value.

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STAGE TEMPERATURE

Cool 1 ON Cool 2 ON Cool 3 ON

Cool 4 ON Cool 4 OFF Cool 3 OFF Cool 2 OFF Cool 1 OFF Set point

Set point plus 1°F Set point plus 2°F Set point plus 3°F Set point plus 4°F Set point plus 3°F Set point plus 2°F Set point plus 1°F

4 Stage Compressorized Cooling – With Dead Band

Temp Set Point + (1/2 Dead Band + 1/2 Proportional Band)

Temp Set Point: 70°F Proportional Band: 8°F Dead Band: 2°F

70 71 72 73 74 75

Cool 1 Off

Cool 2 On

Cool 1 On Cool 3 On

Cool 2 Off

Cool 3 Off

Cool 4 Off

Increasing Temperature

Cool 4 On

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As the return air temperature increases Cooling 1, lead compressor unloaded, is activated at 72°F or ½ of the dead band value plus 25% of the cooling control band. If the return air temperature continues to increase Cooling 2, lag compressor unloaded, will activate at 73°F or ½ of the dead band value plus 50% of the cooling control band. If the return air temperature continues to increase Cooling 3, lead compressor unloaded, is activated at 74°F or ½ of the dead band value plus 75% of the cooling control band. If the return air temperature continues to increase Cooling 4, lag compressor loaded, will activate at 75°F or ½ of the dead band value plus 100% of the cooling control band.

When the return air temperature starts to decrease, Cooling 4 is deactivated at 74°F or ½ of the dead band value plus 75% of the cooling control band. If the return air temperature continues to decrease Cooling 3 will be deactivate at 73°F or ½ of the dead band value plus 50% of the cooling control band. If the return air temperature continues to decrease Cooling 2 will be deactivate at 72°F or ½ of the dead band value plus 25% of the cooling control band and Cooling 1 is deactivated at 71°F or 1/2 the dead band value plus 0% of the cooling control band.

Remember the temperature dead band value is used by the control to shift the cooling on/ off operations away from the temperature set point.

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Optional Dual Compressor Digital Scroll Operation

100

1 compressor operation

Switch 2

70 50

PWM

35 20

2 compressor operation

ressor ONSwitch 1 com

Off

Start/ sto

35 700%

In the chart above we are defining the Digital Compressor start and stop at the capacity need and how the compressors load and unload with the PWM from the controller and the unit setting for temperature control.

Note that the Digital Scroll will run continuously while the head is raised and lowered as the need for cooling is required from 10% to 100% and vise versa.

Optional Glycool (Econ-O-Cycle) Cooling

When supplied with the Glycool option, the basic unit is supplied with an additional coil, piping, valve and a Glycol Fluid Sensor (AQ), which is mounted to the unit supply fluid line and serves as control interface in determining the system operation. Selection of the glycool or compressorized operation is controlled by microprocessor using this aquastat to sense the glycol temperature.

The Glycool (Econ-O-Cycle) Cooling program establishes two distinct control bands for cooling control operation. The first band controls the operation of the chilled glycol valve and the second controls the operation of the compressors, either 2-stage or 4-stage.

The microprocessor checks the return air temperature and the entering glycol fluid temperature to determine a cooling capacity. In order to reduce compressor cycling and to prevent chilled glycol valve hunting, Glycool (Econ-o-Cycle) cooling capacity does not become available until the entering chilled glycol fluid

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temperature is at least 8°F below the return air temperature, or 3°F lower than the return air temperature for two consecutive hours.

When the microprocessor decides that the return glycol fluid temperature is cold enough the first cooling band is the modulating valve control method, and the second band, added to the first band, is for the compressors as in the normal 2-Stage or 4-Stage control method. If the chilled glycol fluid temperature is not cold enough the valve control band is replaced by the compressor band. If the chilled glycol cooling capacity is reduced by a rise in the glycol fluid temperature, the control band shrinks proportionally. This allows the compressor band to move down as well. The following shows the Glycool operation at 100% capacity and the Glycool at 50% capacity.

Glycool at 100% Capacity – No Dead Band

Temp Set Point + (1/2 Proportional Band + 1/2 Proportional Band)

Temp Set Point: 70° Proportional Band: 8°

Valve Closed

70 71 72 73 74 75 76 77 78 79

Band 1 Glycool Valve Band 2 Compressors

100% Open

Cool 1 On

Cool 2 On

Increasing Temperature

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Glycool at 50% Capacity – No Dead Band

Temp Set Point + (1/2 Proportional Band + 1/2 Proportional Band)

Temp Set Point: 70° Proportional Band: 8°

Valve Closed

100% Open

Cool 1 On

Cool 2 On

70 71 72 73 74 75 76 77 78 79

Band 1

Band 2 Compressors

Glycool

Valve

Increasing Temperature

Dual Source Cooling

When supplied with the Dual Cooling option, the basic unit is supplied with an additional coil, piping, valve and a Glycol Fluid Sensor (AQ), which is mounted to the unit supply fluid line and serves as control interface in determining the system operation. Selection of the chilled water or compressorized operation is controlled by microprocessor using this aquastat to sense the water temperature.

The Dual Source Cooling program establishes two distinct control bands for cooling control operation in the same method as Glycool. The first band controls the operation of the chilled water valve and the second controls the operation of the compressors, either 2-stage or 4-stage.

The microprocessor checks the return air temperature and the entering chilled water fluid temperature to determine a cooling capacity. The chilled water cooling capacity is considered to be 100% if the entering Chilled Water fluid temperature is 8°F lower than the return air temperature.

When the microprocessor decides that the return chilled water temperature is cold enough the first cooling band is the modulating valve control method, and the second band, added to the first band, is for the compressors as in the normal

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2-Stage or 4-Stage control method. If the chilled water temperature is not cold enough the valve control band is replaced by the compressor band.

Dual Cooling at 100% Capacity – No Dead Band

Temp Set Point + (1/2 Proportional Band + 1/2 Proportional Band)

Temp Set Point: 70° Proportional Band: 8°

Valve Closed

100% Open

Cool 1 On

Cool 2 On

70 71 72 73 74 75 76 77 78 79

Band 1 Chilled Water

Valvel

Band 2 Compressors

Increasing Temperature

An addition program available with the Dual Cooling option is called Minimum Chilled Water Temperature. This program allows the end user to select the minimum chilled water temperature that permits simultaneous operation of the chilled water control and compressor control. When the supply chilled water temperature decreases to this programmed value ONLY the chilled water valve control is operational, the compressors are locked out.

Staged Electric Reheat

The basic temperature heating control band is established at the temperature set point with the length equal to ½ of the programmed temperature proportional band divided by the number of reheat stages.

The Liebert DS units are supplied with three (3) reheat stages (elements), each stage is rated at 1/3 of the unit capacity. The three (3) stages will operate in an on/ off configuration to reheat the unit discharge air as it enters the space.

The temperature controller activates the first electric heating stage when the return air temperature decreases to 33% of the heating proportional band. The second electric heating stage activates when the return air temperature decreases to 66%

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of the heating proportional band. The third electric heating stage activates when the return air temperature decreases to 100% of the heating proportional band.

The temperature controller deactivates the third heating stage when the return air temperature increases to 66% of the heating proportional control band value. The second heating is deactivated when the return air temperature increases to 33% of the heating proportional control band value. The first heating stage is deactivated when the return air temperature increases to the temperature set point value or 0% of the heating proportional control band value.

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3 Stage Electric Reheat – No Dead Band

Note: in the above example that the control band begins at the 70°F temperature set point and has a length of 4°F, which is ½ of the programmed temperature proportional band value.

As the return air temperature decreases Reheat 1 is activated at 68.7°F or 33% of the heating control band. If the return air temperature continues to decrease Reheat 2 will activate at 67.4°F or 66% of the heating control band. If the return air temperature continues to decrease Reheat 3 will activate at 66°F or 100% of the heating control band.

When the return air temperature starts to increase, Reheat 3 is deactivated at

67.4°F or 66% of the heating control band, Reheat 2 is deactivated at 68.7°F or 33% of the heating control band and Reheat 1 is deactivated at the temperature set point of 70°F or 0% of the heating control band.

Temp Set Point: 70°F Proportional Band: 8°F

Decreasing Temperature

Temp Set Point - (1/2 Proportional Band)

Reheat 1 On

Reheat 2 On

Reheat 3 On

65 66 67 68 69 70

Reheat 3 Off

Reheat 2 Off

Reheat 1 Off

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3 Stage Electric Reheat – With Dead Band

As the return air temperature decreases Reheat 1 is activated at 67.7°F or ½ of the dead band value plus 33% of the heating control band. If the return air temperature continues to decrease Reheat 2 will activate at 66.4°F or ½ of the dead band value plus 66% of the heating control band. If the return air temperature continues to decrease Reheat 3 will activate at 65°F or ½ of the dead band value plus 100% of the heating control band.

When the return air temperature starts to increase, Reheat 3 is deactivated at

66.4°F or ½ of the dead band value plus 66% of the heating control band. Reheat 2 is deactivated at 67.7°F or ½ of the dead band value plus 33% of the heating control band. Reheat 1 is deactivated at 69°F or ½ of the dead band value plus 0% of the heating control band.

Remember the temperature dead band value is used by the control to shift the cooling on/ off operations away from the temperature set point.

Temp Set Point - (1/2 Dead Band + 1/2 Proportional Band)

Temp Set Point: 70°F Proportional Band: 8°F Dead Band: 2°F

Reheat 2 On

Reheat 3 On

65 66 67 68 69 70

Reheat 3 Off

Decreasing Temperature

Reheat 1 On

Reheat 2 Off

Reheat 1 Off

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Humidity Control

Humidification and/ or Dehumidification Required, in Percent (%)

The humidity control programs for the iCOM microprocessor is based on a calculated percent (%RH) requirement for humidification and/ or dehumidification. This percent (%RH) requirement is determined by the control type (algorithm) selected by the user.

The two (2) user selectable humidity control programs are:

• Absolute Humidity, grains of moisture in the air

• Relative Humidity (%RH)

Humidity Control Program Types

Absolute (predictive) Humidity Control – Factory Default Setting

Absolute (predictive) humidity control is based on the moisture content in the return air. The iCOM microprocessor control automatically adjusts the humidity

control as the return air temperature deviates from the programmed temperature set point. This calculation converts the return temperature and humidity values to a moisture content value defined as either grains per cubic foot or grains per pound. This recalculated content value is compared to the content control band that is determined by the:

• Programmed temperature set point

• Programmed humidity set point in %RH

• Programmed humidity proportional band in %RH

This automatic adjustment results in a predictive humidity control response. With absolute humidity control, the humidity control program is automatically adjusted approximately 2% RH for each degree difference between the return air temperature and the temperature set point. Note the following example:

Temperature

Set Point

Humidity Set Point

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Proportional

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Humidity

Band = 6%

Content Level

Grains per LB.

75°F 75°F

The Absolute (Predictive) Humidity Control Flowchart shows what the program is doing and why.

Programmed Values Temp Set Point Humidity Set Point Humidit

The program can be analyzed using the Moisture Content Charts supplied in a later chapter of this manual. It is important to remember that the display provides the humidity value in %RH, not moisture content. The moisture content (grains) values are used only in the internal control program calculation. The LCD display will indicate relative humidity percentage for both methods of control. If the absolute method of control is selected, the adjusted humidity reading will be shown.

When utilizing the absolute (predictive) humidity control program feature, the humidity level is automatically adjusted ~ 2% RH for each degree difference between the return air temperature and the temperature set point.

When absolute humidity control is used, over dehumidification is avoided in the space. When overcooling occurs, causing an increase in the relative humidity reading, the humidity control program “predicts” what the RH will be when the dehumidification cycle ends and the temperature returns to the programmed set point. This allows the dehumidification cycle to end at the proper time.

Proportional Band

Present Room Temperature Room Humidity

50% +3% 59.2 50% -3% 52.5

Calculates Band

Calculates Content

Humidif

Dehumidif

Compares Moisture Content to Band and Makes Decision

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Relative Humidity Control

Relative humidity control is based on the humidity content in the return air. The iCOM microprocessor control determines the unit humidification/ dehumidification

operation by comparing the return air humidity value to the control band that is determined by the:

• Programmed humidity set point in %RH

• Programmed humidity proportional band in %RH

Operations and Charts

The humidity proportional control band value is divided into two parts: the humidity set point plus ½ of the programmed humidity proportional band for dehumidification operation and the humidity set point minus ½ of the programmed humidity proportional band for humidification operation.

A humidity dead band can also be programmed into the control to shift the humidification and/ or dehumidification on/ off operations away from the humidity set point.

This programmed humidity dead band value is divided into two parts: the humidity set point plus ½ of the dead band – no dehumidification operation and the humidity set point minus ½ of the band – no humidification operation.

The humidity set point range is adjustable from 1 – 80% RH in increments of 1% RH. The humidity proportional band range is adjustable from 1 – 20% RH in increments of 1% RH. The humidity dead band range is adjustable from 0 – 50% RH in increments of 1% RH.

Humidifier Operation

The Relative Humidity control program is used to illustrate the humidification operation in the following examples. The basic humidification control band is established at the humidity set point with the length equal to ½ of the programmed humidity proportional band value. The Liebert DS units are supplied with an infrared humidifier rated at the unit capacity.

The humidity controller activates the infrared humidifier when the return air humidity level decreases to 100% of the humidity proportional band. The humidifier makeup water solenoid valve also operates during humidification operation based on a timing sequence.

The humidity controller deactivates the infrared humidifier and makeup water solenoid valve when the return air humidity level increases to 50% of the humidity proportional control band value.

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Control Training and Service Manual

Infrared Humidification – No Dead Band

Note: in the above example that the control band begins at the 50% humidity set point and has a length of 4%, which is ½ of the programmed humidity proportional band value.

As the return air humidity decreases the infrared humidifier is activated at 46%RH or 100% of the humidification control band. When the return air humidity starts to increase, the infrared humidifier is deactivated at 48%RH or 50% of the humidification control band.

Humid Set Point: 50% Proportional Band: 8%

Humidity Set Point - (1/2 Proportional Band)

Humidification On

45 46 47 48 49 50

Humidification Off

Decreasing Humidity

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Controls Training and Service Manual

Infrared Humidification – With Dead Band

Note: in the above example that the control band begins at the 50% humidity set point and has a length of 5%, which is ½ of the programmed dead band value plus ½ of the programmed humidity proportional band value.

As the return air humidity decreases the infrared humidifier is activated at 45%RH or ½ of the dead band value plus 100% of the humidification control band. When the return air humidity starts to increase, the infrared humidifier is deactivated at 47%RH or ½ of the dead band value plus 50% of the humidification control band.

Humidity Set Point - (1/2 Dead Band + 1/2 Proportional Band)

Humid Set Point: 50% Proportional Band: 8% Dead Band: 2%

Humidification On

45 46 47 48 49 50

Humidification Off

Increasing Temperature

Autoflush Control for Infrared Large (IFL) or Small (IFS) Pans

The Autoflush Water-Level Control software program is an integral part of the infrared humidifier system. The program automatically controls a water makeup valve to maintain the proper water level in the humidifier pan during operation. When a call for humidification exists, the program performs a series of checks.

The first check to see how long the infrared humidifier has been off. If the off time is equal to or greater than the programmed value (factory default is 15 hours), it is assumed that the pan is dry and a program called pre-fill is initiated to add water to the pan. During the pre-fill operation the infrared lamps are inactive. The pre-fill time is programmable with an adjustable range of 1 to 120 seconds for either pan size. The factory default for a large (IFL) pan is 60 seconds and for a small (IFS) pan is 30 seconds.

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If the off time is less than 15 hours (or user programmed value) the pre-fill program is bypassed and the infrared lamps and water valve are activated at the same time to fill the pan to the proper water level and initiate humidification.

During normal infrared humidification operation the water makeup valve is periodically closed (no pan fill) and opened (pan fill) based on a timing sequence to allow for the evaporation of water from the pan (see flow chart below).

With the humidifier water flush rate set at the factory default value of 150% the water makeup valve will open for 7 minutes of fill time with an off time of 45 seconds between fill cycles for a small pan. For a large pan water makeup valve will open for 10 minutes of fill time with an off time of 80 seconds between fill cycles. The user can modify the percentage from 110% to a maximum of 500% in 1% increments.

Autoflush Control Flow Chart

Control Training and Service Manual

Call for Humidification

On in last 15 Hours?

YES

HMV Pre-fill 30 sec – small pan 60 sec – large pan

HMV and Lamps on 4 min – small pan 7 min – large pan

Humidification Lamps only 8 min – small pan 10 min

large pan

Refill 110% to 500%

Notes:

1. IFL: Infra-red Large and IFS: Infra-red Small

2. Last 15 Hours is programmable from 1-120hours.

3. Pre-fill time is programmable from 1-120 seconds on Large or Small pans

4. Normal Fill is programmable from 1-120 seconds

5. Refill is programmable in 1% increments

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