CENWAT Commissioning and Fault Finding

Question 1

During the commissioning of a sealed central heating system, what should the cold fill pressure typically be set to?

Accepted Answer

1.0-1.5 bar

Answer

0.5 bar

Answer

2.5 bar

Answer

3.5 bar

Question 2

What does a high CO/CO2 ratio reading during combustion analysis typically indicate?

Accepted Answer

Incomplete combustion, possibly due to insufficient air supply or burner fault

Answer

Overgassing of the appliance

Answer

The flue is too long

Answer

The condensate trap is blocked

Question 3

When commissioning a condensing boiler, what is the expected flue gas temperature when the boiler is operating in condensing mode?

Accepted Answer

Below 57 degrees C

Answer

Over 150 degrees C

Answer

Between 100-130 degrees C

Answer

Exactly 80 degrees C

Question 4

What is the most likely cause of a sealed central heating system that keeps losing pressure over time with no visible leaks?

Accepted Answer

The expansion vessel has lost its air charge or the diaphragm has failed

Answer

The boiler thermostat is set too high

Answer

The room thermostat battery is flat

Answer

The pump speed is too high

Question 5

What instrument is used to measure the gas burner pressure (working pressure) at a boiler?

Accepted Answer

A manometer or digital pressure gauge connected to the burner pressure test point

Answer

A multimeter

Answer

A gas detector

Answer

A thermometer

Question 6

During balancing of a central heating system, which radiator should be balanced first?

Accepted Answer

The radiator nearest to the boiler

Answer

The largest radiator

Answer

The radiator furthest from the boiler

Answer

The radiator in the coldest room