Basic Gas-Fired, Forced-Air Heating Systems Flashcards Preview

Second Period Electrician > Basic Gas-Fired, Forced-Air Heating Systems > Flashcards

Flashcards in Basic Gas-Fired, Forced-Air Heating Systems Deck (19)
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1
Q

The safety gas valve provides for:

A

100% shutdown

2
Q

The electrical energy for operating the power unit in a combination gas valve comes from the _____

A

thermocouple

3
Q

The solenoid valve is ___ acting and requires _____ to operate

A

fast, electrical energy

4
Q

What is the recommended setting for the blower motor to turn on?

A

49 - 60 degrees celsius

5
Q

What is the recommended setting for the blower motor to turn off?

A

32 - 38 degrees celsius

6
Q

How does a thermocouple opearte as a flame proving device?

A

It provides the energy to hold the power armature coil in. If the pilot goes out the thermocouple no longer provides any energy, so the power unit plunger releases aand closes the gas valve

7
Q

How does the open circuit test differ from the closed circuit test?

A

open circuit is performed without power

8
Q

In a deomestic furnace (under 400,000 BTU/h), the thermocouple shoudl respond to a flame failure within ____ minutes

A

3

9
Q

How can we verify that the thermocouple responds to flame failure within the specified time?

A

by doing a response time test

10
Q

What device may be connected in the 24 V circuit or in the 120 V circuit of a domestic furnace?

A

high limit switch

11
Q

What is the recommended setting range for the high limit setting?

A

80 - 120 degrees celsius

12
Q

Why is it not recommended to use a 120V thermostat in a 24 V system?

A

because it won’t be as accurate and the temperature differential will be greater

13
Q

Are wiring diagrams the most useful for troubleshooting control circuit problems?

A

no

schematic

14
Q

In a 24 V control system, which components may be found in the 120 V circuit?

A

fan, fan control, high limit, transformer

15
Q

A fan OFF setting is reached and shuts off. 30 seconds later it restarts even though the burner is off. What is this condition called?

A

fan cycling

16
Q

What is the normal open circuit voltage of a thermocouple?

A

30-32 mV

17
Q

How is the summer switch connected in respect to the fan?

A

series

18
Q

Should solenoid valves be located upstream or downstream of the pilotstat?

A

downstream

19
Q

What is an HRV?

A

heat recovery ventilator