Quiz 6 Flashcards
Define Backdraft Damper
Used to control air flow by only allowing it to move in one direction
-Damper blades are actuated by gravity and prevent air from flowing backwards in a way it should not go
-Similar to the check valve - difference is that it is used to control water flow instead of air
-A type of barometric damper often seen on the exhaust from an AHU that has economizer.
-Will often install backdraft damper on a series FPB so the fan can be turned off without allowing cool air to release into the plenum
Define Variable Frequency Drive (VFD)
-Device installed on an air handler to control fan capacity through changing its speed.
-Static pressure signal installed in the ductwork sends a signal to the VFD to either increase or decrease the speed of the fan.
-Work to save energy on fan use by allowing the volume of air moved to match the system demand.
Define ERV (Energy Recovery Ventilator)
-AKA Energy Recovery Wheel
-Designed to recover lost energy and create savings by reducing the load on cooling and heating equipment
-Air-to-Air heat exchanger installed to pre-condition the outside air coming into a unit
-Exchanger is a large rotating wheel installed between the outside air entering the building and the exhaust air leaving the building
- The wheel absorbs moisture form the humid OA and transfers some of it to the leaving exhaust air, reducing the latent heat level of the air
-At the same time, it equalizes the temperature of the two air streams by exchanging some of the heat in the hot outside air over to the cooler exhaust air to be taken back outside.
-Reduces sensible heat of the entering OA: together this is reduction in total heat or enthalpy
-Best used in a system with 100% OA to a space most of the time.
-In economizer mode, we want the wheel to remain stationary.
-Unfortunately, over 90% of ERV’s are not functioning properly. Incorrect ducting, incorrect set-up, bad design, or poor maintenance.
Define XCI
-Solution to convert a SZ unit to a VV unit
-Each zone gets a damper and a stat
-The stat sends signals to the XCI board, which calls on heating or cooling from the RTU, and opens the appropriate zone dampers.
-Typically uses a bypass damper to vary the volume in the system
What is the definition of a champion?
- A specific individual at our client’s who is willing to stick their neck out for this project with Ideal Impact
-Successful a winning when they stick their neck out and are able to convince others to stick their necks out for the project as well
Define DMZ (Damperless Multi Zone)
-No zone dampers or face and bypass dampers
-Can only be an OA damper
-If any zones call for cooling, air handler provides cool air to ALL zones
-Any zones not calling for cooling may engage its heating coil if it is forced below its heating set point
-System is VERY inefficient because it virtually guarantees simultaneous heating and cooling
Describe the Pareto Principle and how it applies to our work at Ideal Impact
- Principle of cause and effect stating 80% of effects are driven by 20% of the causes.
-Vilfredo Pareto found that 80% of Italy was owned by 20% of its population and that 20% of the peapods in his garden were producing 80% of the peas.
-General business rule of thumb - “80/20 Rule”
-Reminds us to not miss the basics, the big rocks, the major energy hogs, the simple campus-wide energy strategies; to “own the paint” (making sure we are taking control of the unoccupied times) and stay in the “Middle of the river”
Define Portable Dehumidification Unit
-Free-standing electrical device dedicated to moisture removal in a space
-Uses refrigeration cycle to draw moisture saturated air into the unit where it travels over cold cooling coils and transfers its heat
-Moisture from the air beads up on the coils and drains into a water reservoir at the base of the unit. Air then passes over an electric heat coil or hot gas bypass to reheat the air back to its original temp. Dry air now reenters the space
Define Texas Multi Zone Unit
-Different from traditional MZ units
-Has a Face and Bypass damper that provides either chilled air or RA
-Heating coils located within each individual zone
-Preferable to traditional MZ units because it is easier to reduce or eliminate simultaneous heating and cooling
List some reasons why installing motion detectors would be a bad choice for some of our partners, such as schools?
- Light could turn off in the middle of something important (test)
- May stay on longer than desired because the time delay is set for a long period of time. This wastes consumption.
-People will not turn out the light when they leave when it is on a motion detector, whereas they are more likely to turn off a manual switch when they leave a room - Light will turn on when it senses the person entering the room but that person may not have turned on a manual switch because they were simply coming in to grab something. Now the light is left on for an extended period of time
What does ESCo Stand for?
Energy Services Company
In the i3 office today it’s 75° dry bulb temperature and 66° wet bulb temperature. What is the relative humidity?
-First, plot both of these points on the psychrometric chart.
-Find 75° dry bulb vertical line and the 66° wet bulb temperature slanted line. The intersection will fall somewhere along the curved relative humidity line.
-Allowing for inaccuracy of plotting, relative humidity would be about 63% (+/- 0.5°)
What’s the total heat content of the air in the office if it is 75° dry bulb and 66° wet bulb temperature?
-From your previously plotted point, draw a straight line out to the enthalpy scale (which is a slant).
-Total heat content would be 30.75 BTU/lb. of dry air (+/- 0.5°)
So if we got to the kitchen and get a bottles of cold water and bring it back to our 75° dry bulb and 66° wet bulb temperature office, who cold would the water bottle have to be for water to begin condensing on it?
-Use the previous plot points to determine dew point – the point at which water will condense because the air is completely saturated.
-Draw a line out on the dew point line.
- 61.4° (+/- 0.2°)
The space is too cold for me at 75° dry bulb and 66° wet bulb temperature. I think I will turn on the heat and raise the temperature to 77° dry bulb temperature. When I measure the relative humidity now, what can I expect to read?
-Relative humidity found earlier was 63%. If we move that plotted point over on the dry bulb line 2 degrees to 77°, the new relative humidity has decreased to about 58% (+/- 1%).
What is sensible heat and how is it reduced?
-Heat you can feel
-The thermostat reading or the number the weather man gives during reports
-Can be reduced by use of the refrigeration cycle in the HVAC system.
-Heat absorbed from the space and rejected outside thus reducing the amount of sensible heat in the space
What is latent heat and how is it reduced?
-Heat absorbed or released during a change of state of matter
-Occurs without a change in temp or pressure of the substances.
-AKA heat of vaporization/condensation
-When water absorbs enough heat energy, weak bonds are broken and the water is vaporized. When the vapor condenses, latent heat is released, usually becoming sensible heat.
-Water vapor in the air represents a latent load with respect to HVAC equipment. The only way to reduce it is to condense and remove the water vapor through a dehumidification process. At i3, we use long ramp times and high setbacks to “wring” the latent heat (moisture) out of the space.
Define Power Factor
-Measure of the difference in energy that must be delivered by the utility but is not reflected in the measurement of kW and kWh by a standard electric meter
-Electricity is generated, transmitted and distributed using AC, where the current oscillates between positive and negative values. At the same time, voltage measurement also oscillates between positive and negative values of the nominal voltage. When the oscillations of current and voltage are in sync with one another, the power factor is 1.00 and the measurements of kW and kWh reflect all the demand and consumption.
-Certain types of loads, especially AC electric motors, inherently cause the current to large behind the voltage. In these situations, power is consumed by the motor that is not reflected in the kW and kWh measurements. This also causes losses between the generating station and the motor, increasing the size required for every element of the transmission and distribution system to deliver that power. These power factor penalties usually work by raising the billed demand proportion to some deviation from a power factor of 1.00. Another approach is for the billing meter to measure kVA and kVAh, both of which inherently account for the effect of lagging power factor.
Define TDR (Time Delay Relay)
-Electromechanical relay that limits capacity based on a time function – example is using it on large heat kits. A portion of the capacity is brought on immediately on a call for heating and additional stages are enabled when the time delay has been met.
Define KVA
-Kilo-Volt Amps – a unit of energy measure similar to the kW or kilo-Watt. It takes into account the power factor penalty on equipment. It can be converted to kW if you know the power factor for that meter. We see this in Houston CenterPoint Bills
What is the purpose of load rolling?
- A strategy used to compensate for high setbacks we implement on client campuses. It is not used to lower peak demand. In fact, high setbacks would be a way of increasing demand on a campus. The reason for this is that spaces will now be coming down from much higher unoccupied temperatures, and, if not managed properly, could all turn on at the same time and create a large demand peak.
Name 5 strategies we use to lower demand peaks at our clients
-Reduce Lighting KW on during the time of the peak
-Eliminates simultaneous heating and cooling with dead band and consistent setpoints and many other strategies
-End continuous run fans in favor of fan cycling during run times only
-Reduce base load KW
-Reduce humidity through setbacks and long ramp times and many other strategies
-Programming changes that result in demand savings
-Repairing poorly operating economizers
-Installing time delay relays on electric heat
-HVAC equipment issues we fix during the EOI
