Bas Flashcards
Two pipe controllers receive and output how much psi
Receive 20 psi and output 0 - 20 psi
Two pipe controllers usually have what as part of their assembly
Temperature/humidity sensor
What are the 3 connections of a three pipe controller and their pressures
Supply of 20 psi, branch of 0 - 20 psi, and a sensor of 3 - 20 psi
Where are two pipe and three pipe controllers usually located.
Two pipe controllers usually on the wall
Three pipe usually in a secure cabinet
When selecting a pneumatic sensor what should you consider
The sensitivity and type of sensor for the appropriate medium
What are the 2 sections of pneumatically controlled devices?
The actuator and the final control devices
Electric to pneumatic solenoids have what ports
Pressure signal in and out and an exhaust
What are the 3 types of BAS system designs
1.Centralized supervisory
2. Centralized direct digital
3. Distributed direct digital
What’s variable frequency drive
Adjusts motor speeds through analog signal from the CPU
How else would you refer to the operator interface?
Head end/front end
What is used to adjust the throttling range of a two pipe controller?
Sensitivity slider
Pressure relief valve
Relieves pressure up to 120 psi
Blow down valve
Removes condensation from the receiver
Wet bulb temperature measures what type of heat and is related to what type of heat
Measures sensible heat as a result of latent heat changes
The higher the vapour pressure, the _ the rate of evaporation and the _ the rate of sublimation
Slower evap, slower sublimation
2 ways of expressing relative humidity
- Percentage of moisture in the air vs how much it can hold
- Percentage of water vapour vs water vapour pressure
How’s humidity ratio expressed
Amount of moisture in any volume of air
What’s the prefered RH at 68°F vs 80°F
60% at 68°F and 20% at 80°F
How many grains are in 1lb of water
7000
Specific volume vs specific density
SV: cuft/lb SD: lb/cuft
What’s NTP and it’s conditions
(Temp, pressure, density, volume, specific heat)
68°F, 14.7psi, density: 0.075lb/ft3, volume: 13.33ft3/lb, specific heat: 0.24Btu/lb•°R
Mass flow rate
Determines how much heat is flowing
lb/min
MERV ratings
Basic resi = 1-4
Good resi/basic com = 5-9
Best resi/good com = 10-14
Hospital = 15-17
Clean rooms = 18-20
Pitot tubes measure what pressures
Static and total pressure
Anemometers 2 types
- Velometer
- Thermal and vane
Barometers reads how much air flow
0 - 2000cfm
How to start calculating airflow
• determine cfm (balometer) or
• measure velocity pressure (pitot tube) or
• measure velocity (anemometers)
Velometer measures
Velocity
How do you do duct traverse
For ⏹️: divide duct by 12-64, <6” apart rounded up
For ⭕: take readings in ➕ avoiding the center.
What are the capacity ranges for portable air conditioners
6000 - 18 000 Btuh
