# HVAC interview questions

**URL:** <https://forumautomation.com/t/hvac-interview-questions/4363>\
**Category:** Interview Q & A\
**Created:** [August 10, 2018, 5:55pm UTC](https://forumautomation.com/t/hvac-interview-questions/4363 "2018-08-10T17:55:38Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sivaranjith](https://forumautomation.com/letter_avatar_proxy/v4/letter/s/ba9def/32.png) [@sivaranjith](https://forumautomation.com/u/sivaranjith)\
**Post date:** [August 10, 2018, 5:55pm UTC](https://forumautomation.com/t/hvac-interview-questions/4363/1 "2018-08-10T17:55:38Z")

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## 1.What is HVAC system?

Heating, Ventilation and Air Conditioning ([**HVAC**](https://forumautomation.com/t/hvac-system-basics/4357)) system work to maintain a controlled environment in a building.

## 2. What is VAV & CAV?

VAV: Variable Air Volume & CAV: Constant Air Volume.

## 3. What are the things we have in Indoor unit & Outdoor Unit

Indoor Unit: Evaporator Coils and Blower Fan

## 4. Which units consume power?

Compressor, Axial fan & Blower fan.

## 5. What is the local comfort cooling system/split air conditioning?

The local comforting cooling system has its evaporator is housed in a room unit and the condenser is housed in a separate outdoor unit. Both units are connected with the refrigerant flow and return pipes.

## 6. Difference between Axial and Centrifugal Fans

Axial Fan: Has the Parallel Movement of Air. Centrifugal Fan: Has the Perpendicular Movement of Air.

## 7. Name the different types of material used for duct fabrication.

GI Duct, Aluminium Sheet Metal, Fibre Glass Duct, Thick Black Mild Steel, Galvanized Steel Sheet & PUF.

## 8. What is cladding?

The cladding is a material used to coat structure interior, cladding be or cannot be waterproof, but it often controls how elements hit or fall on a surface.

## 9. What are the types of condensers?

There are three types of condensers:

- Air-cooled: condenses refrigerant vapor by rejecting heat to ambient air blown over the finned condenser coil with the aid of a fan.

- Water-cooled: condense refrigerant in the shell and on the outside of tubes through which water passes.

- Evaporative: cooling tower, with the condenser tubes washed by the water spray.

## 10. How does vapour compression cycle work?

The Vapor-Compression Refrigeration Cycle is comprised of four steps.

**Compression:** The refrigerant enters the compressor as a low-pressure gas with low temperature. Then, the refrigerant is compressed adiabatically, so that the fluid leaves the compressor at high pressure and with a high temperature.

**Condensation:** High-pressure, high-temperature gas releases thermal energy and condenses within the “condenser” portion of the system. The condenser is in contact with the hot tank of the cooling system.

**Throttling:** The liquid refrigerant is pushed through a throttling valve, which causes it to expand. As a result, the refrigerant now has low pressure and lower temperature, while still in the liquid phase.

**Evaporation:** The low pressure, low temperature refrigerant enters the evaporator. The liquid absorbs heat from the cold reservoir and evaporates. The refrigerant leaves the evaporator as a gas at low temperature and low pressure, and re-enters the compressor, at the beginning of the cycle.