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.
You will learn 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.
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.
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