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6.6.3 Terminal Heating

This group of building descriptors applies to proposed design systems that have reheat coils at the zone level. The building descriptors are applicable for baseline building systems 5 through 8.

Terminal Heat Type
Applicability Systems that have reheat coils at the zone level
Definition

The heating source for the terminal unit. This includes:

  • Electric resistance
  • Gas furnace
  • Oil furnace
  • Hot water
  • Steam
Units List (see above)
Input Restrictions As designed.
Baseline Rules Table 6.6.3-1 shows the terminal heat type for each baseline building system.

Table 6.6.3-1: "Baseline Building Terminal Heat Type"

Baseline building System Terminal Heat Type
System 1 – PTAC None
System 2 – PTHP None
System 3 – PSZ-AC None
System 4 – PSZ-HP None
System 5 – Packaged VAV with Reheat Hot Water
System 6 – Packaged VAV with PFP boxes Electric Resistance
System 7 – VAV with Reheat Hot Water
System 8 – VAV with PFP boxes Electric Resistance
Terminal Heat Capacity
Applicability Systems that have reheat coils at the zone level
Definition The heating capacity of the terminal heating source
Units Btu/h
Input Restrictions As designed. However, if the unmet load hours exceed 300, the energy analyst and design team may have to increase the size of the equipment so that the unmet load hours are less than 300. See Figure 6.1.2-1 and Figure 6.7.2-1.
Baseline Rules The software shall automatically size the terminal heating capacity to be 25% greater than the design loads. However, the equipment may need to be reduced in size such that the unmet load hours of the proposed design does not exceed the baseline building by more than 50. See Figure 6.7.2-1.
Reheat Delta T
Applicability Systems that have reheat coils at the zone level
Definition

This is an alternate method to enter the terminal heat capacity. It can be calculated as follows:

(6.6.3-1)

$$ \Delta T_{reheat} = T_{reheat} - T_{cool\_supply} $$

$$ \Delta T_{reheat} = Q_{coil} / \left ( 1.1 * C\!F\!M \right )$$

where

$ \Delta $Treheat
heat rise across the terminal unit heating coil (°F)
Treheat heating air temperature at design (°F)
Tcool_supply supply air temperature at the heating coil (°F)
Qcoil heating coil load (Btu/h)
CFM airflow (cfm)
Units Degrees Fahrenheit (°F)
Input Restrictions As designed, but may need to be increased if unmet load hours are greater than 300
Baseline Rules Method not used for baseline building. See Heat Capacity above.