What is an RTU HVAC System? How Does It Works ?

If you’re planning to adding or replacing heating and air conditioning equipment in a commercial space, your contractor may recommend an RTU HVAC unit.

What exactly is an RTU? 

It stands for “roof top unit.”

A rooftop unit, like the name implies, is a packaged unit installed on the roof.These packaged units contain all air conditioning components, including:

• Evaporator coil
• Fan
• Compressor
• Condenser

People are accustomed to seeing rows of air conditioner cabinets along the top of office and retail buildings. Some commercial buildings still use “split” systems that are similar to the ones seen in residential housing, while restaurants and bars often use ductless heat pumps that send conditioned air wall-mounted blowers that are connected to an outdoor condenser. But the rooftop unit, because of its space saving quality and ease of service, continues to be the most popular for business use.

They also can be slab-mounted on the ground and have heating capabilities, depending on the particular model. Unlike split systems commonly used in residential properties, packaged units don’t separate the evaporator coil and fan from the compressor and condenser.

Types Rooftop Package Units :-

Typical System Types: 

• Package “cooling/only” units 
• Package “gas/electric” units 
• Package heat pumps 

How Does a Rooftop Unit Work?
Getting the Heat Out :- Once a rooftop AC unit is installed, cool, low-pressure refrigerant arrives at the compressor as a gas and then compresses into a hot, high-pressure gas as it flows into the condenser coil. There, the metal fins on the coil absorb and disperse the heat, and the condenser fan blows the exhaust away from the building.

As warm return air travels through the ductwork into the rooftop unit, fresh air enters as well for ventilation. Positioned over the return air duct are air filters to prevent contaminants from landing on the sensitive cooling equipment.

The Refrigerant Cycle :-

• Now that you understand how a packaged unit gets the heat out, below we’ve listed the steps in the refrigerant cycle:
• The now-cooled liquid refrigerant passes through the evaporator coil.
• As the pressure drops, the liquid converts back to a gas.
• As warm air from the building passes over the evaporator coil, the refrigerant extracts heat from the air.
• The evaporator fan returns the ice-cold air back into the building.
• The warmed refrigerant (having absorbed the heat) circulates back to the compressor to release its heat through the exhaust system.
• And the cycle repeats again and again until your building’s temperature reaches the thermostat setting.

Rooftop Units That Can Heat :-
Rooftop units that also provide heating often contain a gas heat exchanger downstream from the evaporator fan. In heating mode, return air is discharged into the heater and blows over gas-fired coils. A fan then sends newly heated supply air back into the building.

Advantages and Disadvantages of RTU HVAC System :-