Intermediate · Unit 8 · Written and being checked
Actuator anatomy
In short
Inside a valve head: a 2-port head's motor, gears, spring and end switch, watched live in its Manual's cut-away; how white and grey move a 3-port head; a head's winding and end switch read dead with the meter; and a failed head changed, its five cores landed by colour. This unit is written and being checked; it opens to learners when it is ready.
In this unit
Inside a 2-port head
A plain 2-port zone valve on a wiring centre, its Manual's live cut-away open: the motor, the gears, the spring and the end switch, watched as the room stat opens and shuts it; the end switch proved live with the meter.
How it opensOn the canvas: a fused spur, a wiring centre, a room thermostat (stat), a 2-port ZONE VALVE and a lamp. Everything is wired, and the spur is off. There is no programmer, so the stat is fed straight from block 1.
Inside a 3-port head
The Y-Plan's 3-port valve and its live cut-away: white alone takes it to MID, white and grey to A, grey alone holds it at A (in this simulator), and the spring takes it back to B.
Reading a head with the meter
S-Plan Wired, isolated and proved dead: each valve motor's winding read with the meter on ohms, the end switch open at rest, the same winding read from the wiring centre, and two windings in series.
Changing a head
The heating valve's motor has failed. Isolated and proved dead, its winding reads OL; the cores noted, the valve out and one based on the Honeywell V4043H in, pre-wired; its five cores landed by colour, the earth proved, the heating proved.
Makers’ names and model numbers are trade marks of their owners, used only to say which product a unit is based on. DrawWarm is not affiliated with, or endorsed by, any maker named on this site.
In the simulator, you practise how to
- Name the parts of a 2-port zone valve's head - the motor, the gears, the spring, the end switch - and say what each does
- Say why the end switch lets the boiler fire only once the valve is fully open
- Say how white and grey move a 3-port valve's head to A, to MID or back to B
- Read a valve motor's winding and its end switch dead with the meter, and say what OL and near 0 ohms mean
- Say why parts joined in parallel read together, and lift a core to read one part alone
- Change a failed valve head: isolate and prove dead, note the cores, land the new head's cores by colour, test the earth and prove the heating
Checks and credit
- A timed check at the end of the unit, its questions drawn at random. The score goes on your record.
Certificates of completion and credentials are DrawWarm’s own. They record practice and tests in the simulator. They are not a formal (regulated) qualification, and they do not show that anyone is competent to work on a heating system.
Where it connects
The parts it uses
Intermediate
- Bus controls
Unit 7, before this one
- Commissioning
Unit 9, next
Back to the Programme.
Practise it in the simulator.
Runs in the browser on a laptop or desktop. Cancel any time.