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43 Cards in this Set
- Front
- Back
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What does an averaging sensor look like if the thermostat is looking for 10k ohms? |
Back (Definition)
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What is load shedding? |
Load shedding is when we lower the set points and lighting requirements of the building. Turn the room heat down iff the motion sensor isn’t picking up motion and the lights are off. If not, leave temperature are 22 |
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What is a form c contact? |
One normally closed and one normally open contact |
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What are some common control voltages? |
4-20mA 0-10Vdc signal |
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What is some other names for digital signaling? |
Discrete, on-off, digital, binary |
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How does a boiler controller regulate hot water temp? |
Temperature reset is set by the outdoor air sensor |
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Chillers can go over the maximum peak demand when a service tech turns up the chiller up to full load. What should you do? |
Tell the customer and possibly call Enmax. The customer might get penalized if they go over the agreed upon maximum service load. |
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What are some common power supplies? |
24V ac or 24Vdc |
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What is the skin effect? |
When the velocity of the air on the edge of the duct is faster |
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Not on test: rule of thumb for averaging sensor |
1 foot for every 5 square feet |
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Temperature sensors? |
25-30 millivolts thermocouple can be used for other things besides flames Seebeck effect -2 dissimilar metals will create a voltage ——————— Type k are thermocouples Not thermistors ———————- Averaging sensor use gas ——————— RTD Resistance temperature device |
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RTD |
Negative temperature co Thermistor and RTD Temp (up) = resistance (down) |
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RTD better than Thermistor? |
Negative temperature co Thermistor and RTD Temp (up) = resistance (down) NOTE: IN THE ILM RTDs have a positive temperature coefficient. Teacher was just trying to show how RTDs have a more linear curve. |
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How do you calibrate the thermistor sensor? |
Add an offset a half degree in the controller Dont adjust too much because if you get close to freezing bad things can happen |
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What are RTDs usually made from? |
Platinum |
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If you have a 0-10Vdc And you have a 50 %rh on a humidity sensor? |
5Vdc |
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High event - differential = low event |
True, just remember the equation |
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What are humidity sensors made from? |
Humidity Sensor • Senses the amount of moisture in the air • Sends either a digital or analog signal back to the controller. • Uses a hygroscopic element • Polymer may also be used. |
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If you have pressure drop across a boiler can you measure the flow rate? |
Yes. The manufacture will tell you the flow rate. |
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How far away does the flow meter have to be away from any bend in the duct? |
6-8 ft? (Mentioned in class) |
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What is a unitary controller? |
Preprogrammed from the factor. It is basically a ignition control module |
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What is RAM? Volatile or non-volatile? |
Remote access memory
It is volatile memory |
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What is RAM? Volatile or non-volatile? |
Random access memory
It is volatile memory |
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What is EEPROM? |
Electronically Erasable Read only Memory Its non-volatile |
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What is the difference between the control point and the set point? |
“Control” is what the room temperature is right now. “Set point” is that you want the room temperature to be. “Off set” is the difference between the two |
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What does “front end”? |
Front end is the “front end user” Aka the operator, the coder is a backend user |
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Who is a dumb terminal? |
No one But it has no processing capabilities. Usually just shows I/O readings |
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What is the difference between NTC and PTC? |
Negative temperature coefficient (ohms(down)= temp (up)) Positive temperature coefficient (ohms (up) = temp (up))
RTDs have a PTC |
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What is the difference between corrective, preventative, and Predictive maintenance? |
Corrective is fixing the problem Preventative is changing wear items based on investigation. Predictive is monitoring wear and changing the system on a schedule based on feedback. |
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What is the difference between
Lead lag Lead standby |
Lead lag = both pumps need to be on for full capacity but will alternate which one turns on first. Lead standby= both pumps are capable of supplying full capacity and are alternated. |
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Who controls Bacnet? |
Ashrae All refrigeration and HVAC equipment but has expanded to security, lighting, and VFD |
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What is the front end? |
The front end is the main controller. It has supervisory control. Schedules, alarms, and input/output monitoring |
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What is a “Gateway” in reference to a BacNet system? |
A Gateway can convert a Bacnet capable RTU to the protocol needed by a monitoring system. |
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Modbus made by Schneider |
Used for Ford Factory |
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LonWorks used primarily used in Europe |
Its big and its in calgary |
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How do you calculate the EUI? |
• All of this information is used to calculate the energy utilization index (EUI). • The EUI is determined by dividing the energy consumption in British thermal units (Btus) by the square footage of the building. |
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What is optimum start stop? |
You can use automation to turn off loads when you need them. |
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Describe optimal start? |
A supervisory control strategy in which the HVAC load is turned ON as late as possible to obtain the proper building space temperature at the beginning of building occupancy. |
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What is the most common control signal? |
0-10Vdc |
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What does RTD stand for? |
Resistance temperature detector |
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Who administers BacNet? |
Ashrae |
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Who administers BacNet? |
Ashrae |
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Which communication language is most common in industrial? |
Modbus |
