High-pressure systems & components: EPA 608 Practice Questions

Under Section 608, a high-pressure appliance uses a refrigerant whose saturation pressure at 104°F is between which values?

High-pressure: 170 to 355 psia at 104°F (for example R-410A). Medium: 45 to 170 psia (R-134a). Low: below 45 psia (R-123). Very high: above 355 psia or critical temperature below 104°F.

R-134a is classified as what kind of refrigerant under the Section 608 pressure definitions?

R-134a is listed as a medium-pressure refrigerant, so a centrifugal chiller using it is a Type II appliance.

Which refrigerant is listed as an example of a very high-pressure refrigerant?

R-13, R-23 and R-508B are very high-pressure refrigerants, used mainly in ultra-low-temperature equipment. Work on them needs Type II.

What is the job of a receiver in a high-pressure system?

The receiver stores extra liquid refrigerant on the high side. It is also a good place to recover liquid or to pump refrigerant into during service.

What does a suction-line accumulator do?

The accumulator traps liquid in the suction line and lets it boil off, protecting the compressor, especially on heat pumps.

A technician wants to read pressure at a service valve with a back seat. In what position should the valve stem be?

Back-seated closes the gauge port; front-seated blocks the line. Turning the stem a little off the back seat opens the gauge port while the system keeps running.

What does a heat pump's reversing valve do?

The reversing valve changes the direction of refrigerant flow, so each coil acts as condenser or evaporator depending on the mode.

Bubbles in the liquid-line sight glass of a TXV system that has been running steadily usually indicate what?

Steady bubbles show vapor in the liquid line, caused by low charge or a pressure drop such as a restricted drier. Confirm with subcooling before adding refrigerant.

Why does removing the Schrader valve cores with a core-removal tool help during evacuation?

Valve cores are a major restriction. Removing them under the tool's seal speeds evacuation, and they are reinstalled before the tool is removed.

Which equipment does Type II certification cover?

Type II covers medium-, high- and very high-pressure appliances, except small appliances, MVACs and MVAC-like appliances (which also accept Section 609 certification).

An off-road tractor cab AC with an open-drive compressor holds 4 lb of R-134a. Which certification may a technician use to service it?

This is an MVAC-like appliance (off-road vehicle, open-drive compressor, 20 lb or less). Technicians need Type II or Section 609 certification.

Where is the liquid-line filter-drier installed in a split system?

The liquid-line drier protects the metering device from moisture and debris before the refrigerant enters it.

Ice forms on the indoor coil of an air conditioner. Besides low charge, what is a common cause?

Low airflow lowers the evaporator temperature below freezing. Check filters and blower before assuming a leak.

What does a high-pressure cutout switch protect against?

The high-pressure cutout stops the compressor when discharge pressure rises too high, for example from a failed condenser fan or a blocked coil.