Hired-Hand Farm Hand Series: SCS w/Back-Up - Manual (Page 4)

Part No. 4801-5117 Rev. 8-01 Farm Hand SCS 2
4. Introduction to the SCS™(Smart Contactor System)
The SCS™ (Smart Contactor System), in its simplest definition, is an output drive system that is used
along with an environmental control. This drive system is capable of driving inductive loads of up to
1 hp. But, as the name implies, this system is much more than a normal mechanical relay system.
This section will introduce you to most of the important functions of the SCS™ panel. The following
lists the SCS™ panels that are currently available:
•
16 Stage SCS™ w/Back-Up System
•
16 Stage SCS™ Expansion System
•
8 Stage SCS™ Expansion System
•
24 Stage SCS™ w/Back-Up System*
* This system is not shown in this manual. It is used exclusively with the Farm Hand Vent Master 24.
Refer to Part No. 4802-5124, “Farm Hand Vent Master 24”, for specific information on the 24 Stage
SCS™.
The SCS™ name is derived from the intelligence and flexibility that the drive system possesses. Its
flexibility is displayed by the systems ability to be expanded at any time. It is built in 16 stage blocks
so the user can choose how many outputs stages are satisfactory. Depending on the environmental
controller that is used, up to eight 16 Stage SCS™ panels can be attached to the controller. That
allows an almost unlimited number of stages to be utilized. Inside the SCS™, outputs are grouped
together using relay strips. There are four relays on each strip. These strips are easily removed in the
event of a failure. You no longer have to worry about replacing an entire PC board every time one
mechanical relay fails. In addition, there is no rewiring involved.
The SCS™ panel’s intelligence is displayed in many ways. First, it only requires a twisted pair wire
to be connected from the master controller to itself. Additional stages are added by a “daisy-chain”
connection from one SCS™ to the next. In addition, the SCS™ is capable of relaying information
back the master controller that indicates the status of the stages. For example, it can detect if a stage is
not being allowed to operate due to the “Auto-Off-Manual” switch. This information can be used to
determine if an emergency situation has arisen. If so, the master controller can use the SCS™ Back-
Up System to override. This brings us to the most important feature of the SCS™ panel, the Back-Up
System.
An integrated Back-Up System accompanies the SCS™. This Back-Up System is like none before.
The SCS™ still exists as a stand-alone Back-Up System with its own temperature sensors. The
SCS™ still allows the user to set a “High Limit” and a “Low Limit” in which the system will maintain
by using three back-up cooling stages and one back-up heating stage. In addition, the SCS™ has
constant communication with the master controller. The importance of this communication will
become clear when you read the Back-Up System section of the manual, Section 7. This additional
communication means an added layer of protection for your important investment.
The SCS™ also contains an important fail-safe relay function. Should the SCS™ become inoperative,
such as loosing its power source, one relay strip (4 stages) will fail in a safe condition. This will cause
the ventilators connected to the selected relay strip to be switched on. See Section 8.4 for more
information about the fail-safe relay function.