Mid Term NOTES

Question 1

What is an aerated burner?

Answer 1

air mixes with gas before ignition

Question 2

What is a non-aerated burner?

Answer 2

Gas supplied to combustion before mixing with air

Question 3

What controls primary air in an atmospheric burner?

Answer 3

Air shutter

Question 4

What is the Venturi principle?

Answer 4

Gas speeds up through restriction, pressure drops, air is drawn in

Question 5

Calorific value of natural gas?

Answer 5

~1000 BTU per cubic foot

Question 6

Calorific value of propane?

Answer 6

~2500 BTU per cubic foot

Question 7

Typical air-to-gas ratio for natural gas?

Answer 7

10:1

Question 8

Typical air-to-gas ratio for propane?

Answer 8

24:1

Question 9

Purpose of a pilot burner?

Answer 9

Ignite the main burner

Question 10

What is a continuous pilot?

Answer 10

Pilot stays lit all the time

Question 11

What is an intermittent pilot?

Answer 11

Pilot lights only on a call for heat

Question 12

What is an interrupted pilot?

Answer 12

Pilot shuts off after main burner lights

Question 13

What is direct spark ignition?

Answer 13

Ignition system with no pilot flame

Question 14

What principle does a thermocouple work on?

Answer 14

Seebeck effect

Question 15

Normal thermocouple output?

Answer 15

25–30 mVDC

Question 16

What happens if thermocouple mV is too low?

Answer 16

Gas valve closes and pilot goes out

Question 17

Thermocouple flame coverage should be?

Answer 17

3/8–1/2 inch of the tip

Question 18

What is a thermopile?

Answer 18

Multiple thermocouples connected together

Question 19

Thermopile output range?

Answer 19

325–750 mVDC

Question 20

Larger DMS number means what?

Answer 20

Smaller orifice size

Question 21

What does MBH mean?

Answer 21

1000 BTU per hour

Question 22

67 MBH equals how many BTU/hr?

Answer 22

67,000 BTU/hr

Question 23

When is deration required?

Answer 23

10% in 2000 to 4500
4% for every 1000ft Above 4500 ft

Question 24

Deration rate above 4500 ft?

Answer 24

4% per 1000 ft

Question 25

Why derate at high altitude?

Answer 25

Lower air density reduces oxygen for combustion

Question 26

Purpose of a gas regulator?

Answer 26

Reduce and maintain constant outlet pressure

Question 27

Regulator measuring element?

Answer 27

Diaphragm

Question 28

Regulator loading element?

Answer 28

Spring

Question 29

Internal relief valve function?

Answer 29

Vents excess outlet pressure

Question 30

Sea level altitude range?

Answer 30

0–2000 ft

Question 31

Thermocouple open-circuit mV range?

Answer 31

17–32 mVDC

Question 32

Thermocouple closed-circuit mV range?

Answer 32

8–17 mVDC

Question 33

Thermocouple dropout mV range?

Answer 33

0.75–6 mVDC

Question 34

Thermocouple turn-down mV (from notes)?

Answer 34

~2 mVDC

Question 35

Thermopile output mV range?

Answer 35

325–750 mVDC

Question 36

What is the main purpose of a gas regulator?

Answer 36

Reduce and maintain a constant outlet pressure

Question 37

Name the four regulator types.

Answer 37

Service, system, appliance, servo

Question 38

What is a service regulator used for?

Answer 38

Regulates gas from utility to the building

Question 39

Who is allowed to work on a service regulator?

Answer 39

Utility company only

Question 40

What is a system regulator used for?

Answer 40

Reduces gas pressure inside a building

Question 41

What is an appliance regulator?

Answer 41

Final pressure regulation at/within the appliance

Question 42

What is a servo regulator?

Answer 42

Regulator built into a combination gas valve

Question 43

What are the three main regulator elements?

Answer 43

Restricting, measuring, loading

Question 44

What is the restricting element?

Answer 44

Orifice and valve plug

Question 45

What is the measuring element?

Answer 45

Diaphragm (senses outlet pressure)

Question 46

What is the loading element?

Answer 46

Spring (sets outlet pressure)

Question 47

What is the purpose of the regulator vent?

Answer 47

Provides atmospheric reference for the diaphragm chamber

Question 48

Can a regulator vent be blocked?

Answer 48

No—never block the vent

Question 49

What is the purpose of an internal relief valve?

Answer 49

Relieves excess outlet pressure by venting

Question 50

Propane two-stage pressures: after 1st stage and after 2nd stage?

Answer 50

~10 PSI after 1st stage; 11–14 in. w.c. after 2nd stage