Quiz 4 Flashcards
(23 cards)
Define Unit Ventilator
-Often in classrooms mounted along exterior walls
-May provide DX or CHW cooling and electric or HW heating
-Designed to bring in outside air for ventilation via OA grille
Define Chilled Water Coil
-Consists of several rows of copper tubing attached to fins similar to a car radiator that increase the surface are cooled by the coil
-Chilled water from chiller is pumped through tubing and cools the fins
-Room air then blown through the coil where room heat is absorbed into the chilled water, producing cool SA
-Valve is generally used to vary the temp of air leaving the coil
Define Hot Water Coil
-Constructed basically the same as the chilled water coil
-Hot water from boiler is circulated by pump through the tubing causing the coil tubes and fins to become hot
-Room air circulated through coil, air absorbs heat form the fins and sends the heated air back to the space.
-Hot water valve is generally used to vary temp of air sent back to space
Define Steam Heat Coil
-Steam heating, steam travels through insulated piping to the steam coil.
-Heat transferred to the air passing through the coil causing steam to condense back to a liquid
-Condensate is returned to boiler to be reheated producing more steam
-Steam and water coils are not interchangeable
Define Steam Trap
-Allows the liquid condensate to pass from steam coil and return to boiler by way of a sump but also block flow of live steam to the sump
-Vented to outside in many systems
-Live steam in condensate piping would be vented outside and wasted
Define Steam Boiler
-Boils water for steam heating systems
-Two basic forms: firetube and watertube
-Low pressure steam with max pressure 15 psig
-Natural gas most common fuel, oil and electric also found
-Less piping than a HW system but harder steam volume control
Define Firetube Steam Boiler
Define Watertube Steam Boiler
-Boiler blows burning fuel around the tubes which contain water
Define Condensate Return System
-System used for steam heating of air handler or radiator
-Steam vapor changes state to liquid, releasing heat into coil or radiator
-Condensate returned to boiler to be used as make-up water
-May be vented or pressurized which does not vent to atmosphere
Define Two-Way Valve
-Any type of valve with two ports: inlet and outlet
-Typically labeled “A” and AB” respectively
-Used in many applications from basic on/off to more complex variable flow applications
Define Three-Way Valve
-Any type of valve with three ports
-Can have mixing or bypass valve
-Mixing valves mix to sources hot water from boiler - (A) and cooler return water (B) to get to proper temp supply water from port AB
-Bypass valves divert a portion of supply in either of two directions: Water from boiler enters “O”. If room needs full heating all the water flows from port “X” through heating coil. Room is too warm? Valve diverts portion through port “Z”.
Define Check Valve
-Two port valve allowing fluid to flow in only one direction
Define Valve Reheat
1) VAV box attempts to warm space if it falls below set point by reducing SA entering room by CLOSING the VAV box damper to minimum position.
2) Happens when set point is STILL not satisfied by SA limiting. VAV reheat box reopens damper to allow RA from unit to turn on auxiliary heat (electric or hot water)
Define Electric Controls
-Electricity is medium used to send signals and control equipment
-Energizes burners, controls electric heat, operates two-position valves and dampers or turn off/on fans and pumps among other things.
-Example: relay or contactor which controls high voltage equipment with low voltage control signal.
-Limited to providing two-position control but in certain cases they can offer modulating control
Define Electronic Controls
-Advanced form of electric controls
-Solid-state components on controllers can receive and process multiple input signals or overrides
-Either two-position or modulating
-Accept variety of inputs and accommodate complex control and override schemes
Can be enhanced with visual systems (LCD or LED display screens) that show system status and operation
-NO microprocessor
Define Pneumatic Controls
-Compressed air is the medium used to send signals and control equipment.
-Supplies 20 psi of compressed air to pneumatic stats (controllers)
-Stat then regulates input pressure to directly open valves, close dampers and energize other equipment based on room needs.
-Inherently proportional
Define EER
-Energy Efficiency Ratio: Measure of efficiency of cooling equipment
-How much cooling for amount of energy being used
-(BTU/Hour of Cooling Output) ÷ (Watts of Electric Input)
Name 3 reason’s why EER is not accurate.
1- Tested in a lab situation where there is a perfect unchanging environment giving little indication of what unit might do in occupied space
2- Assume ramp time is 0 because they are running the units in a constant run environment
3- Lab assuming every zone is occupied and equally loaded all the time but in real life this is never true.
Define Free Programmable
-Two different types: application specific and freely programmable
-Freely programmable is a DDC controller that’s completely accessible and changeable. Programming can be set up in any way the user would like within the system limits
-Freely programmable: Direct control also possible. i3 installs Distech at clients receiving a new or upgraded EMS
Define Unitary Controller
-Directly controls one particular piece of equipment such as an AHU
-It serves under a supervisory controller
Wiresheet
- Type of programming logic in which logic blocks are visually connected together with inputs, outputs and variables.
-Controller translates the physical connections into machine code
-Visual way to program , but can be harder to achieve the outcome you want from that program.
-Examples or logic blocks are AND, OR, and LESS THAN: most common Tridium EMS program
Line Coding
-Type of programming logic in which all programming is written out line by line in basic language.
-Less visual and more wordy
-Allows programmer to be more creative as they are not limited to available logic blocks in wiresheet
-Common is RC Studio
Application Specific Controller
- Two different types: application specific and freely programmable
-Application specific controller (ASC) is a DDC controller where programming can’t be altered and outputs can’t be directly controlled
-Each ASC controller is set up for specific application or configuration that it will run
-Small list of things that can be changed including some variables (set points)
