Propane Outperforms R407C in Test of Rooftop AC Units

A Saudi Arabia-based OEM, Petra Engineering Industries Co., has recently completed the design, manufacturing and performance testing of large-capacity commercial packaged rooftop air-conditioning systems, with R290 outperforming R407C.

Samir Hamed, Research & Development Manager at Petra, presented the company's findings during the ATMO/DTI Technical Conference, an online event hosted by shecco (publisher of this website) and the Danish Technological Institute, on June 24.

According to Hamed’s presentation, Petra tested several prototype units in order to compare energy performance, cooling capacity, refrigerant charge amounts, and costs.

After several performance optimizations, the company found that its 88kW (25TR) prototype using R290 resulted in 2-4% higher cooling capacities vs. R407C (as a drop-in) at four ambient temperatures (25°C, 35°C, 46.1°C, 50°C/77°F, 95°F, 115°F, 122°F).

The energy efficiency ratio improvement ranged from 4-9.5% at the same four ambient temperatures . “We can achieve the same or better efficiency with the natural refrigerant at even higher ambient temperatures, up to 50° ," said Hamed.

The cooling capacity improvement in a 185kW (52.6TR) prototype using R290 ranged from 3-6% at the aforementioned temperatures vs. R407C (drop-in). The energy efficiency ratio improvement ranged from 7-11%. 

Charge, cost and safety

The company also saw that only 4.5kg (9.9lbs) of R290 refrigerant charge was needed for its 88kW prototype vs. 8.5kg (18.7lbs) for R407C. In its 185kW prototype, 4kg (8.8lbs) of R290 refrigerant charge was needed vs. 7.5kg (16.5lbs) of R407C. 

The study found the R290  component costs about 10% higher compared to using R407C. With “mass production in the future,” Petra expects to eliminate that premium, Hamed said.

The company also detailed the safety considerations for the R290 unit. These included:

• An automatic refrigerant pump-down function in case of refrigerant leakage in the air stream, moving refrigerant to the condenser side located outside of the unit.
•  Reducing the number of electrical junction boxes.
•  A compressor and unit electrical enclosure and special compressor oil.
•  R290 leak sensors inside and outside the air stream and near refrigerant pipes.
•  Labels following the IEC 60335-2-40 safety standard.

The project was done in collaboration with the United Nations Industrial Development Organization (UNIDO) as a part of its efforts to improve the energy efficiency and reduce the use of synthetic refrigerants in the refrigeration and air conditioning sector globally.