April Lutheran
Overview
This template generates a multi-zone VAV system served by a rooftop Air Handling Unit that provides ventilation and cooling. Each zone contains a VAV box which varies the flow of air for zone-level cooling and/or heats the air to provide heating. There is a central chilled water plant that provides cooling to the air handling unit.
Application
This system is used for two system options within Sefaira:
- VAV with Central Plant (using return air)
- VAV with 100% Outside Air
The template was designed to set up a VAV with Central plant system that uses return air.
yg-font-size-large wysiwyg-color-green120">Air Handling Unit (AHU) – Return Air
The table below describes the key properties of the AHU for this system where there is return air:
|
AHU Feature |
Default |
Extent of user-control |
|
Supply Air Temperature |
Constant (13C/55F) |
Can change constant value |
|
Supply Air Temperature Reset Controls |
None |
None |
|
Supply Air Pressure Reset Controls |
None |
None |
|
Peak Fan Power |
3.5 W/(L/s) or 1.65 W/cfm |
Can control peak load |
|
Fan Curve |
Standard ASHRAE. Click to see fan curve |
No control |
|
Economiser Cycle |
Dry-bulb Control with 19C threshold |
Can disable or change to enthalpy control (xx) |
|
Minimum Outside Air |
Sum of all zones minimum ventilation air |
Can change ventilation requirements in internal conditions |
|
Heating Coil |
Hot water from gas boiler |
Can change to electric coil or direct gas |
|
Heat Recovery |
Via return air only (not indirect) |
None |
|
Cooling Source |
Chilled Water |
No |
Air Handling Unit (AHU) – 100% outside air
The table below describes the key properties of the AHU for this system where there is return air:
|
AHU Feature |
Default |
Extent of user-control |
|
Supply Air Temperature |
Constant (13C/55F) |
Can change constant value |
|
Supply Air Temperature Reset Controls |
None |
None |
|
Supply Air Pressure Reset Controls |
None |
None |
|
Peak Fan Power |
Can control peak load |
|
|
Fan Curve |
Standard ASHRAE. Click to see fan curve |
No control |
|
Outside air configuration |
100% outside air |
No control |
|
Return Air Rate |
100% of air assumed to be returned for heat recovery |
No control |
|
Heat Recovery Efficiency |
Sensible and Latent effectiveness available. Default is 50% sensible and 0% Latent. |
User can change sensible and latent effectiveness |
|
Heating Coil |
Hot water from gas boiler |
Can change to electric coil or direct gas |
|
Cooling Source |
Chilled Water |
No |
Zone VAV boxes
The table below describes the key properties of the zone level VAV boxes for this system:
|
VAV Box Feature |
Default |
Extent of user-control |
|
Heating Coil Type |
Hot water (from Gas Boiler) |
Can change to electric coil |
|
Minimum Turndown Ratio |
Constant for all zones - 0.3 |
Constant rate is variable. No individual zone control |
|
VAV Box type |
Standard (damper only) |
User can choose fan powered terminal unit instead |
|
Peak Fan Power (Fan Powered Terminal Unit) |
0.10 W/(L/s) or 0.05 W/cfm |
Can control peak load |
|
Fan Curve |
Constant Volume Fan |
No control |
|
Supply Air Temperature |
Constant for all zones (36C / 95F) |
User can change constant |
|
Demand Control Ventilation |
None |
None |
The base case option is assumed to have a central plant that provides heating hot water to the AHU and VAV boxes and a chilled water system that provides chilled water to the central AHU.
|
Central Plant Feature |
Default |
Extent of user-control |
|
Heating Hot Water Source |
Natural Gas |
Can change to electric boiler |
|
Boiler Peak Efficiency |
Assumed to be 0.9 |
Value can be changed |
|
Boiler Performance Curve |
Curve shown here |
No Control |
|
Supply and Return Temperatures – hot water |
80/70 C or 176/158 F |
User can control |
|
System losses |
Constant efficiency of 15% |
User can control loss rate only. |
|
Peak Pumping Energy |
1.32 W/(L/s) or 21 W/gpm |
No control |
|
Pump Efficiency Controls |
Variable Speed Drives |
No control |
|
Efficiency Curve for Variable Pumping |
No control |
|
|
Pumping Configuration |
Primary Only |
No control |
|
Chilled Water Source |
Water-cooled Chiller |
Can change to air-cooled |
|
Chiller Peak Load Efficiency |
5 |
Value can be changed |
|
Chiller Performance Curve |
No control |
|
|
Supply and Return Temperatures – chilled water |
7/12 C or 44.6/53.6 F |
User can control |
|
System losses |
Constant efficiency of 10% |
User can control loss rate only. |
|
Peak Pumping Energy |
1.32 W/(L/s) or 21 W/gpm |
No control |
|
Pump Efficiency Controls |
Variable Speed Drives |
No control |
|
Efficiency Curve for Variable Pumping |
No control |
|
|
Pumping Configuration |
Primary Only |
No control |
|
Condenser Water Source |
Cooling Tower |
No extra options |
|
Cooling Tower Efficiency |
245.7 W/(L/s) or 15.5 W/gpm |
No control |
|
Supply and Return Temperatures – condenser water |
29/35 C or 84.2/95 F |
User can control |
|
System losses |
Constant efficiency at 95% |
User can control loss rate only. |
|
Peak Pumping Energy |
0.44 W/(L/s) or 7 W/gpm |
No control |
|
Pump Efficiency Controls |
Variable Speed Drives |
No control |
|
Efficiency Curve for Variable Pumping |
No control |
|
|
Pumping Configuration |
Primary Only |
No control |
Notes on modifications to the template
The heat recovery component of the 100% outside air VAV system is added by Sefaira after the expand objects script is run.
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