CEMP-E
TI 810-11
30 November 1998
increase. In either case, there could be adverse effects on HVAC system performance. The designer
must evaluate and account for the new pressure drops in deciding whether to change the type of valve.
5. RETROFIT PROJECTS WHERE ONLY FINAL ELEMENTS MAY BE LEFT IN PLACE. Some HVAC
retrofit projects may involve new controls, but may not require replacement of existing primary elements
such as dampers, valves, sensing elements, or other measurement devices. In such instances, the
designer must insure that the control signals (both input and output) and actuators for the final elements
are in accordance with the design guidance provided in this manual.
6. RETROFITS INVOLVING ECONOMIZER CONTROL LOOPS. If an HVAC system with an
economizer mode of operation is to be retrofitted, or if an economizer mode is to be added to an existing
HVAC system, the economizer components must be in accordance with the guidance described in the
manual.
7. RETROFIT PROJECTS INVOLVING HVAC SYSTEMS NOT COVERED IN THIS MANUAL. When
an individual HVAC control system not shown in this manual requires upgrading, it may not be feasible
nor suitable to follow the guidance of this manual. It is most likely that maintaining consistency with the
remainder of the control system is of more value. It is the responsibility of the designer to evaluate
existing conditions to determine the suitability of following the guidance of this manual.
8. GENERAL CONSIDERATIONS FOR RETROFIT PROJECTS.
a. Only electric or electronic terminal unit controls, if serviceable, may be reused.
b. No existing pneumatic controls except pneumatic valve actuators and damper actuators, if
serviceable, may be reused.
c. If pneumatic actuators are to be reused and the designer finds that their use is justified on the
basis of life-cycle cost, the existing air compressors and related accessories, if serviceable, may be
reused.
d. Electric or electronic HVAC control systems with standard signal levels (i.e., 4-20 ma) if
serviceable, may be reused.
e. If existing HVAC systems are retrofitted with control systems designed in accordance with this
TI, extension of EMCS to such HVAC systems will interface with the control system as shown in this TI.
6-2
Previous Page
