Alternative Energy Class Room Automation Control System Lighting and Temperature Control By: Al Woodward EET-2011

Description Of Operation The Alternative energy room has four packaged console heat pumps. Two units are for first stage and two are for second stage. A set of units will consist of unit 1 and unit 3. Another set of units will consist of unit 2 and unit 4. Operation will consist as follows: First stage will consist of one set of units. Second stage will consist of the other set of units. The sets of units will alternate as first or second stage through a flip-flop in the plc program. Upon power up there will be a one-shot in plc program that will activate a two-minute on-delay timer for two-minutes to prevent compressor operation for two minutes. The staging of units will be based on input from the room temperature sensor. When compressor operation is initiated there is an off-delay for two minutes to insure operation for two minutes. Upon completion of compressor operation there will be a two-minute on-delay timer to prevent compressor short cycling. Occupied and unoccupied time periods will be controlled through a time schedule in the plc program. The lighting momentary toggle switches are inputs to the PLC. The two room motion sensors are input to the PLC for night time operation of lighting system.

A Heat Pump Loop System

Terms Ambient temperature is the temperature of the medium surrounding a body, for example, the room air temperature. Sensible heat is the heat which results in a temperature change only when a transfer takes place. It is sensible heat that is produced by a heating system, is lost through a building wall, or is removed by a refrigeration system. Latent heat is absorbed or released when a material changes phase without a change in temperature. The three phases are solid, liquid, and gas.

Terms Thermal capacity is the amount of heat required to raise the temperature of a unit of mass of a material one degree. Quantity of heat: Btu or British thermal unit is the unit of measure of quantity of heat in the IP system and is the heat required to raise the temperature of one pound of water one degree Fahrenheit. This is approximately the amount of heat given off by burning one kitchen (wood) match. The term therm is often used as a measure of heating fuel. A therm is equal to 100,000 Ton of refrigeration is used to size air condition or refrigeration units. The term was developed when ice was used to provide refrigeration. It is equal to the cooling effect (heat removal) that would be developed by melting a ton of ice over a 24 hour period. Since the latent heat of fusion for ice is 144 Btu/lb, we have: 2000 lb x 144 Btu/lb/24 he = Btu/h Mechanical equivalent of heat 1 hp = 2545 Btu/h 1 kW = 3413 Btu/h

Automation Direct PLC DL06 PLC Units The DL06 micro PLC line has nine base units to choose from, each has 20 built-in inputs and 16 built-in outputs. The DL06 is a great fit for high voltage, VAC applications or remote 12 VDC applications, and everything in between. The DL06 line of modular micro PLCs offers an inexpensive solution for small to medium size I/O applications with features such as: 20 built-in inputs and 16 built-in outputs, expandable to 100 I/O total Nine combinations of AC or DC powered PLC units with AC, DC and relay I/O 14.8 KB of total memory 229 instructions, including 8 PID loops Built-in real-time clock/calendar Two communication ports, including RS232/ 422/ 485 capability Supports networking for MODBUS RTU, Ethernet, DeviceNET, Profibus, and ASCII in/out Integrated high-speed inputs and pulse output 12 discrete I/O option modules 7 analog I/O option modules 7 communications and specialty option modules Thermocouple and RTD temperature inputs Removable terminal blocks ZIPLink compatibility with 16-point discrete I/O option cards Optional LCD display for operator interface or maintenance troubleshooting

Block Diagram For PLC Temperature Control System

Transfer Function

A Typical Console Heat Pump

One of the four heat pumps.

Automation Direct PLC

F0-04RTD 4-Channel Resistive Temperature Input Module

An RTD is a temperature device made from platinum, copper, or nickel.

RTD = Resistive Temperature Device

PLC is controlling room within 0.1 degrees Fahrenheit 72.3 vs

Inside the control cabinet the plc and electronics are housed.

Control cabinet and associated conduit.

An electrical safety switch was installed for lockout / tagout.

Fluorescent Lighting System Is Controlled Through The PLC.

Momentary Wall Toggle Switches Are Used For Input To The PLC To Operate Lighting

Standard toggle switches were removed and momentary toggle switches were installed for input to the plc

Lighting Control In The Evening Is Operated Through A Motion Detector.

Opt isolator Is Used For An Interface between 277V and 110V PLC Input.

In the future classroom PLC’s can be networked with RS-485