Quiz 5 Flashcards
Define Water treatment in hydronic systems.
-Chilled water, condenser water and hot water systems all use chemical water treatment to minimize corrosion, scale buildup and biological growth to help assure optimum efficiency, long life and to minimize service costs for the HVAC equipment.
Define MEchanical and Electrical Safety Interlocks
-Devices to help prevent equipment operation in unsafe conditions.
-Examples: smoke detectors in air handler return and/or SA ducts to prevent spread of smoke in case of fire, water flow switches which prove water flow in chilled water and condenser water piping before the chiller will start, and air flow switches which prove flow before electric heat activates in a VAV reheat box.
Define Relays and Contractors
- Both electromagnetically operated switches and operate under similar principles.
-Difference comes from application perspective.
-Contractors used for high voltage/high power switching purposes whereas relays are used for low voltage/low power switching.
Define SEER
-Seasonal Energy Efficiency Ratio
-Higher SEER rating indicates better efficiency from that unit.
-Calculated similarly to EER by looking at the ratio of BTU output of heating or cooling to amount of energy it consumes.
-DIFFERENCE: SEER is measured at an average across 8 specific outside air temps to give a better representation of overall performance. Not accurate just like EER.
Define Heat Exchanger
-Stand-alone physical device for the specific use of exchanging heat between two loops (Steam, HW, or CHW) and creating supply water for building to which it is attached
-Takes in supply water from outside source such as chiller downtown. It exchanges heat with the return water coming from the building and creates supply water for the building.
-The two water loops are next to each other but never touch.
-Common in large building systems
Define Primary/Secondary Pumping
- Two pumping systems in a chiller and/or boiler system.
-Primary pumping loop circulates water within the chiller or boiler itself to maintain constant flow through equipment
-Secondary loop sends the chilled or heated water to the individual air handler coils throughout the building.
-Wasted energy is often found in a secondary pumping system that has been left on sending water throughout the building when it is not needed.
-Primary system may be off as indicated by the chiller but the secondary pumping system can run independently of it.
Define Central Plant
-Houses the chillers and boilers for abuilding or a group of buildings
Define Psychrometric Chart
-A chart that represents the behavior of mixtures of air and water vapor under varying conditions
Define Relative Humidity
-Actual amount of moisture in the air expressed as a percentage of the amount of moisture the air is capable of holding.
-Technical sense: amount of water vapor in the air divided by amount of water vapor the air can hold (at the same pressure and temp).
-Important because air can hold more moisture at higher temps than at lower temps which change its relative humidity
Define Enthalpy
-Total heat content of the air (sensibel + latent heat)
-Example: Air at 72° and 40% RH has a lower enthalpy than air at 72° and 60% RH
Define Dry Bulb Temperature
-Sensible temp reading you would find on a thermostat
-Measured in F° or C°
-Gives direct indication of the sensible heat content of the air
-Weather reports give dry bulb temp reading outside and a stat will give you dry bulb temp in a room
Define Wet Bubl Temperature
-Rought definition: coldest you can get something through evaporation given the existing relative humidity
-Exampe: Temp of the wetted bulb of a sling psychrometer
Define Dew Point Temperature
- Atmospheric temp (varying according to pressure and humidity) below which water droplets begin to condense and dew can form
-Average for DFW is 73°F.
When is Dry bulb, wet bulb, and dew point the same value?
When relative humidity is 100%
Define Dehumidification
- Most common form of dehumidification is the mechanical process
-Return air is cooled to condensate moisture out of the air and then reheated to an acceptable temperature to be sent back to the space. This is inefficient and uses more energy than necessary.
-Best plan is through the process of passive solar dehumidification – this is our process using setbacks and long ramp times to wring the humidity out of the air using the AC system in our current markets
Define Humidification
- Process of adding humidity (water) to the air by using a humidifier to introduce water vapor to the air when a sensor indicates the humidity is too low
-We never want to use these because there should never be a reason a space needs more humidity
-Define Open Protocol
-Communication protocol is the “language” used by devices to communicate data
-Early EMS typically used proprietary protocols, meaning only devices from that manufacturer are able to use it
-Open protocol means any manufacturer can create a device using that standard, which allows for integration of many brands of devices
-Some devices, such as Tridium JACE, have special software to work with proprietary protocols and integrate them into Open Protocol systems
Define BACnet/LON
- BACnet and LON are examples of common open protocol networks seen in EMS systems
-Unitary controllers communicate with the supervisory controllers over this network.
Define Tridium Overlay
-Company who specializes in creating open networks for communication in building automation among other things
-Make open protocol software called Niagara that allows for diverse devices and systems to speak to one another across this common network
-Tridium Overlay means installing a JACE and the Niagara software network over the existing controls at a client site so they will all speak together
What are the advantages of Tridium Overlay
-With JACE, multiple EMS systems can interlink and communicate with each other. If the client has more than one type of system, a JACE will allow them all to communicate over one supervisory controller
-JACE allows client to not be tied to one proprietary system. This enables them better future pricing on repairs as anyone can operate on their system instead of the one proprietary manufacturer
-JACE allows multiple systems to share common points within the system such as the OA set point
Name 6 EMS Systems and Who Makes Them-
1) Niagara - Tridium
2)Envision - Alerton
3) Tracer Submit - Trane
4) RC Studio - JCI
5) WebCTRL - Automated Logic
6) ORCAweb - Delta Controls
7) I/NET - Schneider Electric
Explain static pressure control of a VV Unit and answer the following: Where should the sensor be located and what is the most typical set point?
- VV Unit is controlled using static pressure
-Sensor is BEST located 2/3 or 3/4 of the way down the longest straight run of ductwork from the unit - The VFD (variable frequency drive) or inlet banes will operate the fan based on static pressure rises in the duct
-Greater pressure = fan slowing down and less pressure = fan speed up
-Typical set point is 1.2 - 2.0 inches water column - Most common is 1.5 inches water column
