15
Fig. 16 - Single Enthalpy Curve boundaries
Table 6 - California Title 24 Regional High Limit Dry Bulb Temperature Settings
Fig. 15 - Dry Bulb
and Mixed Air Sensor
Dry Bulb Sensor
Economizers are shipped standard with an outside air dry bulb
sensor. System default setting (high temp limit) is 63°F, and has
a range of 48° to 80°F. Sensor is factory installed on economizer
(note: a 2nd sensor is provided for mixed air temperature).
Note: California high temperature setting requirements by region
are shown below in Table 6.
TABLE 140.4-B AIR ECONOMIZER HIGH LIMIT SHUT OFF CONTROL REQUIREMENTS
Device Type
a
Climate Zones
Required High Limit (Economizer Off When):
Description
Fixed Dry Bulb
1, 3, 5, 11-16
Outdoor air temperature exceeds 75°F
2, 4, 10
Outside air temperature exceeds 73°F
6, 8, 9
Outdoor air temperature exceeds 71°F
7
Outdoor air temperature exceeds 69°F
Differential Dry Bulb
1, 3, 5, 11-16
Outdoor air temperature exceeds return air temperature
2, 4, 10
Outdoor air temperature exceeds return air temperature minus 2°F
6, 8, 9
Outdoor air temperature exceeds return air temperature minus 4°F
7
Outdoor air temperature exceeds return air temperature minus 6°F
Fixed Enthalpy
b
+ Fixed
Dry Bulb
All
Outdoor air enthalpy exceeds 28 Btu/lb of dry air
b
or
Outdoor air temperature exceeds 75°F
a
Only the high limit control devices listed are allowed to be used and at the setpoints listed. Others such as Dew Point, Fixed
Enthalpy, Electronic Enthalpy, and Differential Enthalpy Controls, may not be used in any climate zone for compliance with
Section 140.4(e)1 unless approval for use is provided by the Energy Commission Executive Director.
b
At altitudes substantially different than sea level, the Fixed Enthalpy limit value shall be set to the enthalpy value at 75°F and
50%
relative humidity. As an example, at approximately 6,000 foot elevation, the fixed enthalpy limit is approximately 30.7 Btu/lb.
