115 unit 14-1 review

A dual pressure control consists of a low-pressure control and a high-pressure control connected in parallel with each other.

• True

• False

A helix coil is used in some applications to sense temperature in a moving air stream.

• True

• False

A low pressure control has a “high event” and a “differential” setting. The technician wants the system to turn on at 28 psig and shut down at 2 psig. What would be the proper settings?

• High event: 28 psig; differential: 2 psig

• High event: 2 psig; differential: 2 psig

• High event: 28 psig; differential: 26 psig

• High event: 2 psig; differential: 28 psig

High-pressure control contacts are normally ________ and then they ________ in response to a rise in pressure.

• closed; open

• open; close

• closed; reset

• cut in; cut out

If the suction pressure of a system is 60 psig and the oil pump outlet is 85 psig, what is the net oil pressure?

• 60 psig

• 25 psig

• 85 psig

• 145 psig

In a pressure control, why is it important that the transmission line not touch the compressor?

• The temperature of the compressor can give false pressure readings.

• The vibrations of the compressor can rub a hole in the tube.

• Deposits can build up in the line, causing a blockage.

• Excessive pressure can cause an explosion.

Line-voltage thermostats have heavier contacts and use which type of sensing element?

• Bimetal

• Bellows

• Remote bulb

• All of these are used.

Many natural gas-fired heating units operate at a manifold pressure of 3.5 in. WC.

• True

• False

Most modern pressure transducers are designed to sense changes in ________.

• flexibility

• amperage

• temperature

• capacitance

Oil pressure safety controls measure the difference in pressure to establish that____.

• the compressor is running

• the oil pump is running

• negative oil pressure is present

• positive oil pressure is present