Emerson E2 User Manual download pdf (Page 191)

Pulse Accumulation Software Overview • 11-49

drop leg temperature rises above this setpoint, the con-

denser fans are cycled ON regardless of the value of the

TD.

The Drop Leg Offset setpoint is an adjustment

entered, if needed, after measuring liquid subcooling dur-

ing operation of an individual condensing unit.

The TD setpoint is the optimal difference between the

refrigerant drop leg temperature and the ambient (plenum)

temperature. When the TD (i.e., drop leg temp + drop leg

offset - plenum temp) begins to climb above this setpoint,

fans will be cycled ON to bring down the drop leg temper-

ature, thus lowering the TD measurement.

The TD deadband setpoint is a range of values around

the TD Setpoint within which the value of the TD calcula-

tion is acceptable. When the TD rises above the setpoint

plus 1/2 the deadband value, fans will begin cycling ON.

When the TD falls below the setpoint minus 1/2 the dead-

band value, fans will cycle OFF.

For the Condenser Fan On Delay setpoint, fans are

cycled ON when the TD is above the setpoint at the rate

set for Condenser Fan On Delay. For example, if this field

is set to 30 seconds, each fan is staged ON in 30-second

intervals until all fans are ON, or until the TD falls back

below the setpoint.

For the Condenser Fan Off Delay setpoint, fans are

cycled OFF when the TD is below the setpoint at the rate

set for Condenser Fan Off Delay. In other words, if this

field is set to 30 seconds, each fan is staged OFF in 30-sec-

ond intervals until all fans are OFF, or until the TD rises

back above the setpoint.

11.19.6 Inputs

The Drop Leg Temperature input is the current drop

leg temperature used for TD control.

The Plenum Temperature input provides the current

value of the ambient temperature used for TD calculation.

11.19.7 Alarms

For Drop Leg High alarm, the alarm setpoint is the

drop leg temperature that, if exceeded, will cause an alarm

to be generated. If you wish to generate an alarm for high

drop leg temperature, enter the desired setpoint. Other-

wise, to disable this alarm, leave the value set to NONE.

For Drop Leg Delay, if the drop leg alarming feature

is used, enter the amount of time the drop leg temperature

must be higher than the setpoint before an alarm will be

generated (HHH:MM).

For TD High alarm, the TD alarm setpoint is the value

of the TD calculation that, if exceeded, will cause an alarm

to be generated. If you wish to generate an alarm for high

TD, enter the desired setpoint. Otherwise, to disable this

alarm, leave the value set to NONE.

For TD Delay, if the TD alarming feature is used,

enter the amount of time the TD must be higher than the

setpoint before an alarm will be generated (HHH:MM)

11.20 Pulse Accumulation

11.20.1 Overview

The Pulse Accumulation application counts incoming

pulses and converts that consumption value into a rate

value once per minute. Pulses are user-specified by the

Input Type parameter (power, gas, liquid, or volume) to

represent what is being measured.

The Pulse Accumulator input can support many types

of pulse counting applications, such as flow meters for

water and gas applications. In addition, application-spe-

cific logging, such as hourly, daily and monthly usages are

supported for pulse type inputs.

11.20.2 Configuration

Set the Input Type parameter to the desired measure-

ment (power, gas, liquid, or volume).

The analog input connected to the board and point

number must be configured as a Pulse Accumulator Type

input. The engineering unit of the analog input must match

the engineering unit that is being used in the Pulse Accu-

mulation application.

11.20.3 Outputs

All output information is available from the main Sta-

tus screen or from under the Outputs tab in application

Setup. Current output status, average output, high trip,

NOTE: The engineering unit for the Pulse

Accumulator Type Input is specified by the

active EU parameter. This parameter is located

in the General Controller Information screen under

the Engineering Units tab and determines what unit of

measure will be used when the Input Type is set.

TIP: The engineering unit that is active in the

Pulse Accumulation application can be deter-

mined by viewing the Total Accumulation out-

put on the application Status screen.

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