CCN1 Gas Appliance Installation and Commissioning 2

Question 1

What is the acceptable CO/CO2 ratio in flue gas for a correctly adjusted natural gas boiler?

Accepted Answer

Below 0.004

Answer

Above 0.010

Answer

Between 0.008 and 0.010

Answer

Between 0.004 and 0.008

Question 2

What is the correct working gas pressure for natural gas at a domestic appliance inlet, measured while the appliance is operating at full load?

Accepted Answer

20 mbar

Answer

17 mbar

Answer

21 mbar

Answer

25 mbar

Question 3

When commissioning an open-flued gas appliance, which test confirms that the flue is performing correctly and removing combustion products safely?

Accepted Answer

A spillage test using a smoke match or smoke pellet

Answer

A pressure test using a manometer

Answer

A flow rate test using an anemometer

Answer

A temperature measurement using an infrared thermometer

Question 4

What should an engineer do if a gas appliance cannot achieve the correct working pressure during commissioning?

Accepted Answer

Do not commission the appliance and investigate the cause of the low pressure

Answer

Commission the appliance and note the pressure deficit in the paperwork

Answer

Adjust the appliance gas valve to compensate for the low pressure

Answer

Inform the customer and leave the appliance in service at reduced input

Question 5

What is the primary reference document for setting the correct burner pressure on a gas appliance during commissioning?

Accepted Answer

The appliance manufacturer's installation instructions

Answer

Gas Safety (Installation and Use) Regulations 1998

Answer

BS 6400 Part 1 — Domestic gas meter installation

Answer

IGE/UP/1 — Strength and tightness testing

Question 6

What must an engineer do immediately if a CO alarm activates during the commissioning of a gas appliance?

Accepted Answer

Shut off the appliance immediately and investigate the cause

Answer

Reset the alarm and continue commissioning at reduced input

Answer

Ventilate the room and continue commissioning with windows open

Answer

Check the CO alarm's battery and continue if the alarm stops

Question 7

What percentage of CO2 would you typically expect in the flue gases of a correctly adjusted natural gas boiler?

Accepted Answer

7–9%

Answer

Less than 3%

Answer

4–6%

Answer

12–14%