various

Question 1

Give FOUR reasons why spillage from a gas appliance may occur

Answer 1

• High gas pressures.
• Cracked heat exchanger
• Blocked flue.
• Lack of ventilation

Question 2

A fault has developed on a gas-fired, electronic continuous-flow water heater. When the
water tap is turned on, the appliance starts and the gas ignites, but the appliance shuts down after a few seconds. An error code is displayed which indicates failed ignition.
Give FOUR likely reasons this may have occurred.

Answer 2

• PCB Fault.
• Low gas pressure
• Faulty/dirty flame sensor probe
• Partially blocked burner or heat exchanger.

Question 3

A line of soot has appeared on the front of a radiant/convector gas heater installed in an
existing fire place.
Give FOUR likely reasons this may have occurred.

Answer 3

• The flue is blocked causing incomplete combustion.
• The aeration for the burner could be blocked with lint.
• The mixing tube could be blocked.
• The burner ports could have enlarged or corroded.
• The gas pressure may be incorrect.

Question 4

State FIVE factors that need to be specified when selecting a regulator for a gas installation.

Answer 4

• Type of gas being used.
• Inlet or upstream pressure.
• Outlet or downstream pressure.
• Maximum flow anticipated.

Question 5

List SIX items of information that must be permanently marked on every gas appliance.

Answer 5

• Manufacturer.
• Model Number.
• Type of gas.
• Working pressure.
• Input rating.
• The gas safety compliance label.

Question 6

A fault has developed on a gas oven. After the oven has been running for 20 minutes, it shuts the
gas off and must be manually restarted.
Give THREE likely causes for this to occur.

Answer 6

• The thermocouple is too far from the flame.
• The oven by-pass is set incorrectly.
• The thermostat is faulty.

Question 7

A natural draught flue for a gas appliance is being designed.
State FOUR ways in which condensation in the flue can be minimised.

Answer 7

• Insulate flue.
• Select shortest route to atmosphere.
• avoid offsets
• avoid lateral runs

Question 8

Give TWO factors that affect heat loss of a gas flue.

Answer 8

• Length of flue.

* Elbows or bends.

Question 9

Give FOUR factors other than heat loss that determine the diameter of a gas flue.

Answer 9

• The spigot size
• Lateral run.
• Number of elbows and bends.
• Total length of the flue.

Question 10

State THREE factors that determine the size of a rotary gas meter for an industrial boiler

Answer 10

• Gas inlet pressure.
• Maximum gas flow rate.
• Pipe size.

Question 11

Give TWO advantages of using a rotary gas meter instead of a diaphragm gas meter.

Answer 11

• operate at high pressures.

* steady/smooth output.

Question 12

A natural gas appliance is to be converted to operate on LPG.
List SIX items that must be checked and that may need changing in the conversion.

Answer 12

• Data plate.
• Aeration.
• Operating pressure.
• Regulator.
• By-passes.
• Injectors.

Question 13

An installation is being converted from LPG to natural gas.

Give TWO aspects of the installation pipework that must be checked and that may need changing.

Answer 13

• Size/diameter.

* Labelling.

Question 14

State the specific compliance document that should be used for the installation of commercial catering equipment in a catering vehicle.

Answer 14

AS/NZS 5601: Part 1