CENWAT System Controls and Zoning 2

Question 1

In a Y-plan fully pumped heating system, which type of motorised valve is used?

Accepted Answer

One 3-port mid-position valve

Answer

Two 2-port zone valves

Answer

One 3-port diverter valve

Answer

Three 2-port zone valves

Question 2

What is the key operational difference between a 3-port mid-position valve and a 3-port diverter valve?

Accepted Answer

A mid-position valve can supply both circuits simultaneously; a diverter valve cannot

Answer

A diverter valve can supply both circuits simultaneously; a mid-position valve cannot

Answer

A diverter valve handles higher flow rates than a mid-position valve

Answer

A mid-position valve is only suitable for unvented hot water systems

Question 3

In an S-plan heating system, how many motorised valves are typically installed?

Accepted Answer

Two 2-port zone valves

Answer

One 3-port mid-position valve

Answer

One 3-port diverter valve

Answer

Four 2-port zone valves

Question 4

What is the function of the end-of-travel (auxiliary) microswitch in a motorised zone valve?

Accepted Answer

To prove the valve is fully open and complete the circuit to fire the boiler

Answer

To shut the boiler down if the valve jams open

Answer

To indicate that the valve requires replacement

Answer

To regulate the speed at which the valve opens

Question 5

What happens when a 2-port zone valve closes because its thermostat is satisfied?

Accepted Answer

Power is removed from the motor; a spring return closes the valve and the auxiliary switch opens, removing the call for heat

Answer

The zone valve motor is energised to hold it shut

Answer

The circulating pump stops immediately

Answer

The boiler switches to a higher output mode

Question 6

What is the main advantage of an S-plan system over a Y-plan system?

Accepted Answer

S-plan provides fully independent time and temperature control for each zone

Answer

S-plan uses less pipework and is cheaper to install

Answer

S-plan requires only one motorised valve

Answer

S-plan valves are smaller and easier to fit in tight spaces

Question 7

A Honeywell V4073A valve is used in which system plan, and what type of valve is it?

Accepted Answer

Y-plan; 3-port mid-position valve

Answer

S-plan; 2-port zone valve

Answer

W-plan; 3-port diverter valve

Answer

C-plan; single-port motorised isolator