Johnson Controls 100 Series Engineering Guide

JOHNSON CONTROLS
62
FORM100.50-EG12 (918)
HYDRONIC HEAT
If the unit is configured with either of the wet heat options (steam or hot water) the single
package unit controls will modulate the hydronic valve to maintain a supply air set point.
In the event temperatures off the hydronic coil are below 34.0°F the fans will be shut down
and the hydronic valve will open 100%. This function is an automatic reset so as the tem-
perature rises above 36.0°F, the unit will automatically begin normal operation.
ELECTRIC HEATING OPERATION
For units equipped with electric heaters, the unit can control up to six stages of electric
heat which are staged on based on heating demand calculates by the IPU controller.
MORNING WARM-UP
Morning warm-up can be initialized by BAS or by the IPU controller if the internal schedul-
ing is used. If the internal scheduling is used, the morning warm-up start time is calculated
through an adaptive algorithm. When morning warm-up is required, the IPU controller
energizes the VAV heat relay, starts the supply fan and qualifies the return air tempera-
ture (RAT) for 5 minutes. The internal heat source (gas, hot water/steam, or electric) is
controlled to maintain the RAT to the return air (RA) heating setpoint, morning warm-up
ends when occupancy occurs (BAS, internal scheduling, or contact closure), or when the
maximum morning warm-up time has expired.
ECONOMIZER OPERATION
The unit can be equipped with one of three types of optional economizers, dry bulb, single
enthalpy, or comparative enthalpy. When the unit controller determines that outside air
is suitable for economizing, the unit controller will control the outside air (OA) damper(s)
open to provide economizer cooling. If economizer cooling alone is insufficient for the
cooling load, the unit controller will stage up compressors, one at a time, to meet demand.
The control logic for the three types of economizers is as follows:
Dry Bulb Economizer
The dry bulb economizer is the default economizer control scheme. With the dry bulb
economizer, the unit controller monitors the outside air temperature (OAT) only and com-
pares it to a reference temperature setting. Outside air is deemed suitable for economiz-
ing when the OAT is determined to be less than the reference temperature setting. This
method of economizing is effective, but is prone to some change-over inefficiencies due
to the fact that this method is based on sensible temperatures only and does not take
outside air moisture content into consideration.
Single Enthalpy Economizer
With the optional single enthalpy economizer, the unit controller monitors the OA enthalpy
in addition to the OAT and compares it to a reference enthalpy setting and a reference tem-
perature setting. Outside air is deemed suitable for economizing when the OA enthalpy is
determined to be less than the reference enthalpy setting and the OAT is less than the ref-
erence temperature setting. This method of economizing allows the reference temperature
setting to be set higher than the dry bulb economizer and is consequently a more efficient
single package unit economizer.
Controls (Cont'd)

Johnson Controls 100 Series Specifications

General

Brand	Johnson Controls
Model	100 Series
Category	Air Conditioner
Language	English