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YORK INTERNATIONAL
93
FORM 150.62-NM1
EMS-PWM REMOTE TEMPERATURE RESET
EMS-PWM Remote Temperature Reset is a value that
resets the Chilled Liquid Setpoint based on a PWM in-
put (timed contact closure) to the microboard. This PWM
input would typically be supplied by an Energy Man-
agement System.
A contact closure on the PWM Temp Reset input at
CTB 1 terminals 13 - 20, will reset the chilled liquid
setpoint based on the length of time the contacts re-
main closed. The maximum temperature reset is
achieved at a contact closure of 11 seconds. This is the
longest contact closure time allowed. One second is
the shortest time allowed and causes the Chilled Liquid
Setpoint to revert back to the Local programmed value.
The reset value is always added to the Chilled Liquid
Setpoint, meaning that this function never lowers the
Chilled Liquid Setpoint below the locally programmed
value, it can only reset to a higher value. The micro-
board must be refreshed between 30 seconds and 30
minutes. Any contact closure occurring sooner than 30
seconds will be ignored. If more than 30 minutes elapse
before the next contact closure, the setpoint will revert
back to the locally programmed value. The new chilled
liquid setpoint is calculated by the following equations:
setpoint = local chilled liquid setpoint + °reset
°reset = (Contact Closure - 1) x
(*Max. Reset Value)
10
Example:
Local Chilled Liquid Setpoint = 45°F (7.22°C).
*Max Reset Value = 10°F (5.56°C)
Contact Closure Time = 6 Seconds.
(English)
(6 sec. - 1) (10°F/10) = 5°F Reset
So...the new chilled liquid setpoint = 45°F + 5°F= 50°F.
This can be viewed by pressing the Cooling Setpoints
key twice. The new value will be displayed as “REM SETP
= 50.0°F.”
(Metric)
(6 sec - 1) * (5.56°C/10) = 2.78°C
Reset Cooling Setpoint = 7.22°C + 2.78°C = 10.0°C
So...the new reset Cooling Setpoint = 7.22 °C + 2.78°C =
10°C. This can be viewed by pressing the Cooling Setpoints
key twice. The new value will be displayed as “REM SETP =
10.0°C.”
BAS/EMS TEMPERATURE RESET OPTION
The Remote Reset Option allows the Control Center of
the unit to reset the chilled liquid setpoint using a 0 - 10
VDC input, a 4-20mA input, or a contact closure input.
The Remote Reset circuit board converts the signals
mentioned above into pulse width modulated (PWM)
signals which the microprocessor can understand.
Whenever a reset is called for, the change may be noted
by pressing the Cooling Setpoints key twice. The new
value will be displayed as “REM SETP = XXX°F”
The optional Remote Reset option would be used when
reset of the chilled liquid setpoint is required and a PWM
signal (timed contact closure) cannot be supplied by an
Energy Management System. The Remote Temp. Re-
set Board will convert a voltage, current, or contact sig-
nal that is available from an EMS to a PWM signal, and
every 80 seconds provide a PWM input to the micro-
board. Figure 3 shows a diagram of the field and fac-
tory electrical connections.
If a 0 - 10VDC signal is available, it is applied to termi-
nals A+ and A-, and jumpers are applied to JU4 and
JU2 on the reset board. This dc signal is conditioned to
a 1 - 11 second PWM output and supplied to the PWM
input on the microboard at CTB 1 terminals 13 - 20. To
calculate the reset chilled liquid setpoint for values be-
tween 0VDC and 10VDC use the following formula:
setpoint = local chilled liquid setpoint + °reset
°reset = (dc voltage signal) x (*Max Reset Value)
10
Example:
Local Chilled Liquid Setpoint = 45°F (7.22°C)
*Max Reset Value = 20°F (11.11°C)
Input Signal = 6 VDC
(English)
°reset = 6VDC x 20°F = 12°F reset
10
setpoint = 45 °F + 12 °F = 57°F
(Metric)
°reset = 6VDC x 11. 11°C = 6.67°C reset
10
setpoint = 7.22°C + 6.67°C = 13.89°C
*
Max Reset Value is the “Max EMS-PWM Remote Temp. Reset” setpoint value described in the programming section under Cooling
Setpoints. Programmable values are from 2°F to 40°F (1.11°C to 22.22°C).
2