TEMPMASTER
48
FORM TPM3-EG1 (518)
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 (SA) set-
point. In the event temperatures off the hydronic coil are below 34.0°F, the fans will shut
down and the hydronic valve will open 100%. This function is an automatic reset, so as
the temperature 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 calculated 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 shall stage up compressors, one at a time, to meet de-
mand.
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 tem-
perature (OAT) only and compares it to a reference temperature setting. Outside air is
deemed suitable for economizing when the OAT is determined to be less than the refer-
ence temperature setting. This method of economizing is effective, but it is prone to some
changeover inefficiencies due to the fact that this method is based on sensible tempera-
tures 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 temperature 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 reference temperature setting. This method of econo-
mizing allows the reference temperature setting to be set higher than the dry bulb econo-
mizer and is consequently a more efficient single package unit economizer.
Dual Enthalpy Economizer: With the optional dual enthalpy economizer, the unit control-
ler monitors and compares the OA and RA enthalpies in addition to comparing the OAT to
the reference temperature setting. Outside air is deemed suitable for economizing when
the OA enthalpy is determined to be less than the RA enthalpy and the OAT is less than
the reference temperature setting. This method of economizing is the most accurate and
provides the highest degree of energy efficiency for a single package unit economizer.
Controls (Cont'd)
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