BASIC HOT WATER HEATING SYSTEMS (030203e)

Question 1

What is the max loading of a 40VA Class 2 transformer that supplies motorized valves on a hot water heating boiler?

Answer 1

32VA

Question 2

True or false

Gas and water pipes don’t need to be bonded to ground

Answer 2

False

They do

Question 3

What is the purpose of a reverse acting control?

Answer 3

Prevents the circulating pump from running until the water reaches minimum operating temperature

Question 4

A _-____ zone valve is energized to open or close

Answer 4

3-wire

Question 5

What are the 2 mounting methods for aquastats

Answer 5

Surface
Immersion

Question 6

What does a pyrostat sense?

Answer 6

Heat of the flame

Question 7

What is the most common LWCO (low water cut out) used in hot water heating systems?

Answer 7

Float switch

Question 8

How does a cad-cell sense the existence of a flame?

Answer 8

Light

Question 9

When a cad-cell senses light from a flame, what is the resistance?

Answer 9

300 - 1000 ohms

Question 10

When the water level in a boiler gets too low, what is the purpose of the LWCO?

Answer 10

To shut off the fuel supply

Question 11

How does a direct spark ignite the main burner of a boiler?

Answer 11

With high voltage

Question 12

What is the proper sequence of troubleshooting a suspected circulating pump failure?

Answer 12

Pump voltage and winding continuity

Question 13

What does a reverse acting controller prevent?

Answer 13

Circulation of cold water

Question 14

What happens when a sensing bulb in an aquastat ruptures?

Answer 14

Contacts open, de-energizing the burner

Question 15

How are single-stage centrifugal pumps lubricated?

Answer 15

With water and oil

Question 16

Which aquastat is more sensitive to changes in temperature?

Surface mount OR immersion

Answer 16

Immersion

Question 17

LWCO are good visual indicators of ___ _____ levels

Answer 17

Low water