Intermediate · Unit 4 · Written and being checked
C-Plan and W-Plan
In short
The two older plans: gravity hot water with pumped heating and the programmer's GRAVITY / PUMPED switch, the C-Plan wired with its six-core valve on the cylinder's circuit (the heating call through the white while the valve is shut), the W-Plan with its two-position diverter valve, hot water priority and a backfeed read for what it is, an old C-Plan read with the meter as found, and the usual upgrade once the pipework is fully pumped: the C-Plan converted to an S-Plan. It earns the credential Older Systems (simulator). This unit is written and being checked; it opens to learners when it is ready.
In this unit
Gravity hot water, pumped heating
An older system: the cylinder is heated by gravity circulation, and only the radiators are pumped. You wire and prove the supply and the programmer. Then you set the programmer's GRAVITY / PUMPED switch to GRAVITY to see its rule, and back to PUMPED: this system's valve gives the hot water its own control.
How it opensOn the canvas are a fused spur, a boiler, a pump, a programmer and two thermostats (stats). There is also a 2-port valve with its own lead, and a wiring centre. Some wires are in already.
The C-Plan wired
The C-Plan, with one six-core 2-port valve on the gravity hot water circuit. The grey goes on the permanent live, the white on the room stat's call through a link, and the orange to the boiler; the cylinder stat is fed on its 1. Hot water alone fires the boiler with the pump still and the white dead. The heating fires it through the white, with the valve shut.
W-Plan: the diverter valve
A fully pumped system with hot water PRIORITY. One two-position diverter valve rests on the cylinder's port, and its brown drives it to the heating port. The cylinder stat is fed on its 1: its C is the boiler's live, and its 2 feeds the brown. The pump runs from the boiler's pump live (PL). You see priority, a backfeed, then the valve driving to the radiators.
Reading an old C-Plan
A C-Plan as you might find it: one six-core valve on the cylinder's circuit, and the pump on the room stat's call.
Converting a C-Plan to an S-Plan
The usual upgrade, once the plumber has made the pipework fully pumped. You take the six-core's white off and make it safe, take the link out, and feed the pump from the boiler's pump live (PL) through block 9. Then you add a 2-port valve for the heating, and prove each zone alone and both together.
In the simulator, you practise how to
- Read a gravity hot water system, and set a programmer's GRAVITY / PUMPED switch for the system it controls
- Wire a C-Plan as the makers draw it: the cylinder stat's call to the valve's brown, the grey on the permanent live, the white on the heating call, the orange to the boiler, the pump on the heating call
- Wire a W-Plan: the cylinder stat fed on its call contact, its common to the boiler, its satisfied contact to the diverter's brown, the pump on PL; prove hot water priority and read a backfeed for what it is
- Read an older system as found with the meter, naming each wire's job before anything is changed
- Convert a C-Plan to an S-Plan once it is fully pumped: the white made safe, the link out, the pump on PL, a 2-port on the heating, every state proved
- Isolate and prove dead before any wire is touched, and test the earth of what was changed before switching back on
Checks and credit
- A timed check at the end of the unit, its questions drawn at random. The score goes on your record.
- The unit earns the credential Older Systems (simulator).
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
- More zones
Unit 3, before this one
- Underfloor and mixed systems
Unit 5, next
Back to the Programme.
Practise it in the simulator.
Runs in the browser on a laptop or desktop. Cancel any time.