Unit 61 Exam

Question 1 of 15

1

Why is it important to cycle the furnace on and off several times when replacing a sequencer?

Select one of the following:

It is important to make sure the heating elements and the blower are switching on and off in the correct cycle.
It is important to make sure the heating elements and the blower are turning on at the same time.
It is important to make sure the power is working correctly.
It is important to make sure that only the heating elements are coming on and not the blower.

Explanation

Question 2 of 15

1

What could cause a false high reading for the supply-air temperature?

Select one of the following:

If the temperature is taken with the blower on at the same time the heating elements are on.
If the temperature is taken after the unit has been running for too long.
If the temperature is taken with a probe inserted upside down.
If the probe is inserted in the supply plenum in a direct line of sight with the heating elements.

Explanation

Question 3 of 15

1

If the furnace has one or more broken heating elements or one or more fusible links open, what should the technician do?

Select one of the following:

The technician should check the furnace airflow.
The technician should check the power source to the furnace.
The technician should replace all the heating elements.
The technician should replace all the fusible links.

Explanation

Question 4 of 15

1

The two general types of sequencers used on electric furnaces are

Select one of the following:

High current sequencers and low current sequencers
Fast acting sequencers and slow acting sequencers
Mechanical and electronic
Individual time delay relays and all-in-one sequencers that control all the strips and the blower motor

Explanation

Question 5 of 15

1

The most effective method of checking the heating elements of an electric furnace during operation is

Select one of the following:

A visual inspection
Checking the Amp draw of each heat strip
Measuring the temperature of each heat strip
Checking the resistance of each heat strip

Explanation

Question 6 of 15

1

What is the purpose of the white ceramic pieces on the strip heaters?

Select one of the following:

They insulate the heater wire from the metal frame supporting it
They make it easier to identify where the heat strips are installed
They concentrate the heat of the strips
They seal the heat produced by the strips inside the furnace

Explanation

Question 7 of 15

1

An electric furnace that runs continuously, regardless of the thermostat setting probably has

Select one of the following:

An open strip heater
An open fusible link
A bad transformer
A stuck sequencer

Explanation

Question 8 of 15

1

If a voltmeter shows a reading of 240 volts across the thermal limit to a strip heater on an electric furnace

Select one of the following:

The limit is closed, breaking the circuit to the heater
The limit is open, breaking the circuit to the heater
The limit is open, completing the circuit to the heater
The limit is closed, completing the circuit to the heater

Explanation

Question 9 of 15

1

Whenever a thermal limit or fusible link needs replacing, the technician should always check

Select one of the following:

The power wire for voltage drop
The transformer control voltage
The thermostat calibration
The air filter and airflow

Explanation

Question 10 of 15

1

Overheating can cause a terminal to discolor or the wiring insulation to melt. What should you consider when repairing the wire or the terminal?

Select one of the following:

Replace the terminal end only. It is okay to cut off the end and repair the wire. If the terminal is on a relay, sequencer or fuse block, the component should also be replaced in addition to the wire.
Replace the terminal end only. It is okay to cut off the end and repair the wire. If the terminal is on a relay, sequencer or fuse block, only the wire needs to be replaced. The component does not need to be replaced.
It is recommended to replace the entire wire with another wire of the same or larger gauge. If the terminal is on a relay, sequencer, or fuse block, the component should also be replaced in addition to the wire.
It is recommended to replace the entire wire with another wire of the same or larger gauge. If the terminal is on a relay, sequencer, or fuse block, only the wire needs to be replaced. The component does not need to be replaced.

Explanation

Question 11 of 15

1

Given the following readings from an electric furnace, use the formula to calculate airflow.

CFM = (V x A x 3.412)/(∆T x 1.08)

What is the airflow in CFM and does this furnace have the recommended air flow?

Voltage at strips = 240 V
Amp draw of strips = 22.6 A
Return-air temperature = 65 ºF
Supply-air temperature = 120 ºF

Select one of the following:

The airflow is 336 CFM; No, the air flow is too low.
The air flow is 312 CFM; No, the air flow is too low.
The air flow is 312 CFM; Yes, the air flow is at the recommended level.
The air flow is 336 CFM; Yes, the air flow is at the recommended level.

Explanation

Question 12 of 15

1

A technician finds that a wire in an electric furnace is brittle and discolored from overheating. The technician should

Select one of the following:

Cut off the overheated end, strip the remaining wire end, and reinstall it
Cut off the overheated end and splice on a short length of similar wire using high quality electrical tape
Replace the entire wire
Cut off the overheated end and add a short length of similar wire using a wire nut

Explanation

Question 13 of 15

1

A technician takes the following readings while checking the operation of an electric furnace with 2 heat strips: 220 volts, 36 amps, 70ºF return air temperature, and 120ºF supply air temperature. What is the airflow through the furnace?

	Created by Neil Revollo almost 9 years ago

Unit 61- Troubleshooting Electric Heat

Unit 61 Exam

Question 1 of 15

Why is it important to cycle the furnace on and off several times when replacing a sequencer?

Select one of the following:

Explanation

Question 2 of 15

What could cause a false high reading for the supply-air temperature?

Select one of the following:

Explanation

Question 3 of 15

If the furnace has one or more broken heating elements or one or more fusible links open, what should the technician do?

Select one of the following:

Explanation

Question 4 of 15

The two general types of sequencers used on electric furnaces are

Select one of the following:

Explanation

Question 5 of 15

The most effective method of checking the heating elements of an electric furnace during operation is

Select one of the following:

Explanation

Question 6 of 15

What is the purpose of the white ceramic pieces on the strip heaters?

Select one of the following:

Explanation

Question 7 of 15

An electric furnace that runs continuously, regardless of the thermostat setting probably has

Select one of the following:

Explanation

Question 8 of 15

If a voltmeter shows a reading of 240 volts across the thermal limit to a strip heater on an electric furnace

Select one of the following:

Explanation

Question 9 of 15

Whenever a thermal limit or fusible link needs replacing, the technician should always check

Select one of the following:

Explanation

Question 10 of 15

Overheating can cause a terminal to discolor or the wiring insulation to melt. What should you consider when repairing the wire or the terminal?

Select one of the following:

Explanation

Question 11 of 15

Select one of the following:

Explanation

Question 12 of 15

A technician finds that a wire in an electric furnace is brittle and discolored from overheating. The technician should

Select one of the following:

Explanation

Question 13 of 15

A technician takes the following readings while checking the operation of an electric furnace with 2 heat strips: 220 volts, 36 amps, 70ºF return air temperature, and 120ºF supply air temperature. What is the airflow through the furnace?

Select one of the following:

Explanation

Question 14 of 15

When replacing a transformer, the technician should always check

Select one of the following:

Explanation

Question 15 of 15

What problems can be caused by overlubricating a blower motor?

Select one of the following:

Explanation