hvac interview question

7/30/2019 Hvac Interview Question

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Total Experience: Page 1/5

Inteviewed by:

Position:

Q1 What are the standards use in A/C duct fabrication?

Ans SMACNA US ,dw 142

Q2 What are the different method used for duct sizing?

Ans Equal Friction, Velocity,Static Regain.

Q3 What are the conversion of following?

1CFM= 0.472LPS

1CMH= 0.588CFM

1inch= 25.4mm

1LPS= 15.8GPM

Q4 Classify the air conditioning Units?

Ans Window, Split, Chiller, DX, Package Unit etc.

Q5 What is the use of strainer?

Ans It is installed before the cooling coil to protect dirt & foreign material entering into the cooling coil /

evaporator.

Q6 How do you measure & control the noise level in A/C system?

Ans Noise level can be measured by dB meter.It can be controlled by providing acoustic to the unit

panels, if the sound crosses the set noise criteria we have to go for sound attenuatos.

Q7 What is the use of straircase pressurization?

Ans To provide fresh & clean air in the staircase when fire occurs in the floor. The pressurized air

keeps the smoke away from the stair wall. It is used for creating positive pressure.

Q8 What are the recommended pressure drop in Chilled water pipes?

Ans 210 PASCAL'S per meter (0.84 inches).

Q9 Where do you use Fire Damper,Spliter Damper & Non Return Damper?

Ans Fire dampers (FD) are used to stop the fire wherever duct passes thro fire wall..

Spliter dampers(SD) are used to split the main duct for propotional air balancing

Non Return Dampers(NRD) are used to stop the back flow of air in the duct. NRD's used in

exhaust and ventilation system only.

Passport No:

Name Of Candidate

Interview on:


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Q10 What is use of U-Trap and where it is used?

Ans It is used in Drain connection as water seals/smell.

Q11 What are the different types of exhaust fans used to extract the air?

Ans Axial type propeller fan, forward curved, twin fan, direct driven centrifugal fan.

Q12 What are different duct shapes normally used?

Ans Rectangular, Round, Spiral, Oval.

Q13 How do you control vibration of AHU & Chillers?

Ans Spring vibration isolators, Rubbers pads, Kinetic Chain, flexible bellows.

Q14 What is the difference between VAV & CAV?

Ans Variable Air Volume & Constant Air Volume

Q15 What is the difference betwwen NRV & Check valve?

Ans Both are same

Q16 Mention typical valve arrangement for chiller connection?

Q17 What do you consider while making plant room layout explain briefly?

Ans Space, site orientation, plant room location, A/C unit (ready made or tailor made).

Q18 What are the different type of Louvers used?

Ans Fresh air louvers, sand trap louvers, door louvers, acoustic louvers, supply air and return air

louvers.back draft louvers.

Q19 Classify the different types of chillers?

Ans Reciprocating,screw,centrifugal & scroll chillers.

Q20 What is the Primary & Secondry pump?Where it is used?

Ans Primary Pump Supplies return water to chiller & Secondary Pump supplies supply water from

chiller.


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Q21 What are the standard test pressure for chilled water piping for Industrial application?

Ans Test pressure 1.5 times of working pressure.

Q22 What is VFD? & Where it is used?

Ans Variable Frequency Drive it is used to control the speed of motor by controlling the frequency

applied to it. It is used with Chillers,AHU etc.

Q23 Name some fine controlled Valves?

Ans Needle valve,Spindle valve, regulating valve, motorized valved etc.

Q24 What are the Securities checking in chillers?

Ans Flow switch, Chiller and Pump interlocking, High Pressure cut-out, Oil Pressure switch,

High Suction superheat, Anti Freeze.

Q25 What are the temperature & RH required for human comfort?

Ans 22 2 degree celcius & 50%RH

Q26 What is Boiling Point temperature of water in Fahrenheit scale?

Ans 212 degree Fahrenheit?

Q27 At what temperature degree Ferhenite & degree Celcius are same?

Ans -40C

Q28 Which gas is used to purge the refrigerant line during the brazing?

Ans Nitrogen gas.

Q29 1 TR= 365 to 400 CFM

3.7KW

Q30 How much design velocity required in the main duct of an office building?

Ans 900-1100 FPM

Q31 What should be the max distance between sewer line & portable water line?

Ans 3 meter

Q32 How much size of clean out is provided for sewer pipe below 10" dia?

Ans 6"

Q33 What should be height of fire cabinet from floor level?

Ans 1 meter


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Q34 What are the different types of sprinkler heads used in fire protection system?

Ans Upright sprinkler,Pendent Recessed sprinkler,Pendent sprinkler,Side wall sprinkler,extended side wall

sprinker.

Q35 What is standered for fire protection system?

Ans NFPA

Q36 What is the test pressure for fire fighting pipe network?

Ans 1.5 times of working pressure.

Q37 What is the temperature rating for fire fighting sprinkler head?

Ans 170F

Q38 What is the fire department connection known as?

Ans Siamese

Q39 Name the different types of fire extinguisher?

Ans Portable type CO2,Portable type Dry Powder & water.

Q40 What are the different types of Pump used in fire protection system?

Ans Main Pump,Jockey Pump & In case of power failure Diesel driven pump.

Q41 What are the different types of Valve used in fire protection system?

Ans Alarm valve,Zonal valve etc.

Q42 Who gives final approval to fire fighting network after installation?

Ans Civil Defence.

Q43 What is the test pressure for domestic water supply pipe?

Ans 1.5 times of working pressure.

Q44 Name the different types of Traps used for Water Closet?

Ans P-Trap & S-Trap.

Q45 What are the different pipe material used in plumbing installation?

Ans CI,Acid resistant CI,Bituminous fiber pipe,virtified clay pipe,Lead pipe,Galvanized steel pipe,

Galvanized wrought iron pipe,brass pipe,copper pipe,Plastic & synthetic pipe.

Q46 What are the impotant factor to consider while installing waste pipe?

Ans Selection of right kind of material,

Conservative use of fittings.

Right location of cleanoutsRight pitch or slop of pipe line.

Manner of joining the pipe.


5/9

Total Experience: Page 1/4

Inteviewed by:

Position:

Q1 What are the standards use in A/C duct fabrication?

Ans

Q2 What are the different method used for duct sizing?

Ans

Q3 What are the conversion of following?

1CFM= LPS

1CMH= CFM

1inch= mm

1LPS= GPM

Q4 Classify the air conditioning Units?

Ans

Q5 What is the use of strainer?

Ans

Q6 How do you measure & control the noise level in A/C system?

Ans

Q7 What is the use of straircase pressurization?

Ans

Q8 What are the recommended pressure drop in Chilled water pipes?

Ans

Q9 Where do you use Fire Damper,Spliter Damper & Non Return Damper?

Ans

Passport No:

Name Of Candidate

Interview on:


6/9

Page 2/4

Q10 What is use of U-Trap and where it is used?

Ans

Q11 What are the different types of exhaust fans used to extract the air?

Ans

Q12 What are different duct shapes normally used?

Ans

Q13 How do you control vibration of AHU & Chillers?

Ans

Q14 What is the difference between VAV & CAV?

Ans

Q15 What is the difference betwwen NRV & Check valve?

Ans

Q16 Mention typical valve arrangement for chiller connection?

Q17 What do you consider while making plant room layout explain briefly?

Ans

Q18 What are the different type of Louvers used?

Ans

Q19 Classify the different types of chillers?

Ans

Q20 What is the Primary & Secondry pump?Where it is used?

Ans


7/9

Page 3/4

Q21 What are the standard working & test pressure for chilled water piping for Industrial application?

Ans

Q22 What is VFD? & Where it is used?

Ans

Q23 Name some fine controlled Valves?

Ans

Q24 What are the Securities checking in chillers?

Ans

Q25 What are the temperature & RH required for human comfort?

Ans

Q26 What is Boiling Point temperature of water in Fahrenheit scale?

Ans

Q27 At what temperature degree Ferhenite & degree Celcius are same?

Ans

Q28 Which gas is used to purge the refrigerant line during the brazing?

Ans

Q29 1 TR= CFM

KW

Q30 How much design velocity required in the main duct of an office building?

Ans

Q31 What should be the max distance between sewer line & portable water line?

Ans

Q32 How much size of clean out is provided for sewer pipe below 10" dia?

Ans

Q33 What should be height of fire cabinet from floor level?

Ans


8/9

Page 4/4

Q34 What are the different types of sprinkler heads used in fire protection system?

Q35 What is standered for fire protection system?

Q36 What is the test pressure for fire fighting pipe network?

Q37 What is the temperature rating for fire fighting sprinkler head?

Q38 What is the fire department connection known as?

Q39 Name the different types of fire extinguisher?

Q40 What are the different types of Pump used in fire protection system?

Q41 What are the different types of Valve used in fire protection system?

Q42 Who gives final approval to fire fighting network after installation?

Q43 What is the test pressure for domestic water supply pipe?

Q44 Name the different types of Traps used for Water Closet?

Q45 What are the different pipe material used in plumbing installation?

Q46 What are the impotant factor to consider while installing waste pipe?


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