- Humidity – Amount of moisture in the air.
- Calorie – The quantity of heat required to raise the temp of one gram of water one degree celcius.
- Absolute Pressure – psia – Pressure in pounds per square inch above a complete vacuum.
- Gage Pressure – psig – Pressure in pounds per square inch above normal atmospheric air pressure. 14.696 psi
What refrigerant is used in a centrifugal system?
Dielene, R11, R113, Methylene chloride
What is a hermetic compressor?
Motor and compressor in a gas tight housing.
What is a hermetic system?
A closed centrifugal system to include the compressor, condenser and cooler. The refrigerant cools the m
What is a safety head?
A space designed in the head to increase clearance and capacity control.It lifts or expands when a liquid slug of refrigerant enters the cylinder of the compressor and has a discharge valve on a separate plate.
How would you control a compressor capacity?
With the bypass capacity control.
Name three different types of compressors.
Centrifugal, Rotary and Piston type.
What is gallon degrees per minute per ton?
Heat required to raise the flow of one gallon of water per minute one degree Fahrenheit or 8.33 BTUs.
Name 5 types of condensers.
Shell and tube, shell and coil, double pipe, atmospheric, evaporative and air cooled.
How would you control water levels in cooling tower?
Water regulating valve or float valve.
What is the main concern in cooling tower water treatment?
Name the types of evaporators.
Dry or flooded.
What are the two types of refrigeration?
Direct and indirect.
Name the different types of expansion valves.
Hand expansion, cap tube, automatic, thermostatic, high side float and low side float.
- Latent heat – Heat added to or removed from a substance to cause a change of state but not a change in temperature.
- Conduction – Heat transfer by contact.
- Convection – Heat currents between hot and cold.
- Vacuum – Pressure below atmospheric pressure.
- Standard ton of refrigeration – Amount of heat needed to melt one ton of ice in 24 hours or 200/btu per minute or 1200/btu per hour.
- Wet bulb – Temp to include moisture in air.
- BTU – Measurement of the quantity of heat. Amount of heat needed to raise one pound of water one degree. 778 foot/lbs.
- PSIG – Gauge pressure above atmospheric pressure.
What should your temperature rise from the inlet to the outlet of the evaporator be?
About 16 to 18 degrees.
What would be the evaporator pressure of R11 at standard Ton?
What would be the evaporator pressure of ch3cl at standard ton?
What would frost on the evaporator cause?
It would like an insulator and prevent heat transfer.
Give some reasons for low evaporator pressures.
Low refrigerant charge, light load, clogged strainer, bad expansion valve.
What is a liquid seal and where would you find it?
It is a pipe to be extended down in the receiver from the king valve to be submerged in liquid at all times.
Can a safety device and fire valve be on the same pipe?
How is a safety device piped?
From the receiver to the atmosphere / From the compressor to the receiver.
What is the latent of ?
- R11 – 84 BTUs per LB at 5 degrees
- R22 – 93.21
- R717 — 565
- R764(SO2 / Sulfur dioxide) – 169.38
Name some types of compressor valves.
Feather, reed, ring, poppet, diaphragm
What two types of dryers are there and what is there purpose?
Absorbers absorb moisture in the refrigerant and Adsorbers mix and dilute the moisture in the refrigerant.
A cut view of a rooftop package unit.
So that’s where the condensate is going. Must be a leak down there!
First vehicle arrived for our new fleet.
We were having a new refrigerant monitor system installed in the plant and the service tech asked where the breakers were located for the two areas he was was installing the equipment. Locating the one for the main monitor was easy, everything was marked. The remote monitor wasn’t that clear cut. After locating a panel I saw a breaker marked flow meter. We used to have a city water pressure monitor installed where the new remote monitor was being mounted, so I switched it off. Bad idea. it shutdown the boilers! While I was trying to get the boilers back online, the service tech come by and said he didn’t need the breaker off, he installed while the circuit was live. A plant shutdown, switching a 20 amp breaker off, wasn’t required. I hate when these incidents are self induced. Oh, the breaker was for the steam flow indicators.
Make sure your MCC breakers are clearly marked before experimenting to find the right one.