1 Appliance Types, Pressure Hazards, and Safety Free Online FlashCards

What reference condition determines EPA refrigerant pressure classes?

EPA appliance classes are based on a refrigerant’s liquid-phase saturation pressure at $104^\circ\mathrm{F}$, not on a single pressure reading during service.

What saturation-pressure range defines the high-pressure class?

The high-pressure class covers refrigerants with saturation pressures from $170$ to $355\ \mathrm{psia}$ at $104^\circ\mathrm{F}$.

What criteria define the very-high-pressure class?

A refrigerant is very-high-pressure if its saturation pressure is above $355\ \mathrm{psia}$ at $104^\circ\mathrm{F}$, or if its critical temperature is below $104^\circ\mathrm{F}$.

How do psia and psig differ?

Psia is absolute pressure; psig is measured relative to atmospheric pressure. They are not interchangeable.

Why can carbon dioxide qualify as very high pressure?

Carbon dioxide $R\-744$ has a critical temperature below $104^\circ\mathrm{F}$, so it meets the very-high-pressure criterion and is used in high-pressure, often transcritical, systems.

Where are high- and very-high-pressure refrigerants commonly used?

High-pressure refrigerants are common in air conditioners, heat pumps, and commercial refrigeration. Very-high-pressure refrigerants are associated with specialized low-temperature or cryogenic refrigeration.

Which components may be part of a refrigerant circuit?

A refrigerant circuit may include a compressor, condenser, evaporator, receiver, piping, valves, fittings, and service connections.

Can an isolated circuit section remain pressurized when a system is off?

Yes. Isolated sections can remain pressurized even when the system is off; a stopped compressor does not prove a component is depressurized.

What impact hazards can a sudden refrigerant release create?

A sudden release can form a fast-moving jet, propel debris, or whip a hose. A damaged or overheated cylinder or component can rupture.

Why can liquid refrigerant cause cold burns?

Liquid refrigerant evaporates rapidly and cools, so contact can freeze skin or eyes and cause cold burns or eye injury.

How can a refrigerant release create an inhalation hazard?

A release can create a hazardous atmosphere: some refrigerants displace oxygen, while others have additional hazards. Carbon dioxide is colorless and odorless and can cause asphyxia at dangerous concentrations.

What hazards can heat and ignition create around refrigerants?

Heating a pressurized vessel can raise its pressure. Refrigerant exposed to flame or hot work may produce hazardous decomposition products; some refrigerants or lubricants also present fire risks.