Universal Programmable Controller

CEMP-E

TI 811-12

18 August 1998

modems, line drivers or LAN. The remote terminal unit contains I/O functions to handle digital and

analog data, digital data error detection, and message transmission. Failure of a remote terminal unit

must set each piece of controlled equipment to a predetermined failure mode. Remote terminal units will

have an uninterruptible power system to sustain operation during a power failure in those situations

where their associated smart field panels also require an uninterruptible power system.

4. UNIVERSAL PROGRAMMABLE CONTROLLER. Universal programmable controllers are field

programmable stand-alone controllers which are used to control HVAC systems, central plant equipment,

or entire small buildings. The universal programmable controller contains a seven-day calendar and a

real-time clock so that building, equipment, and system operations are maintained independent of

communication with the smart field panel and island or central station. Universal programmable

controllers are less costly than smart field panels, but have limited I/O point capacities. Because of the

potential cost benefits of universal programmable controllers, the designer will consider their use in stand-

alone buildings requiring only a few points. The relationships between smart field panels and universal

programmable controllers are shown in Figures 4-4 and 4-5.

Data Transmission Circuit

to Central/Island Station

Modem or

Line Driver

Smart

Universal Programmable

Field

Controller Communication Bus

Panel

I/O Interface

Universal

To Utility

Programmable

Systems

Controller

I/O Interface

To Utility

Systems

Figure 4-4. Smart Field Panel and Universal Programmable Controllers (System with Multiple Data

Transmission Channels)

4-4