Intermediate · Unit 5 · Written and being checked
Underfloor and mixed systems
In short
Underfloor heating and a mixed system: the UFH manifold set and its wiring box - its supply, its floor stat fed from the box, the actuators opening before the pump runs and the boiler is called, the heat source contact volt-free until it is linked from L; the floor added to a radiator system, its call on block 10 beside the radiator valve's orange; the interlock, and a mistake that fires the boiler with every loop shut; the actuators and the mixing unit; and the practical: radiators and UFH wired from memory. It earns the credential Mixed Systems (simulator). This unit is written and being checked; it opens to learners when it is ready.
In this unit
Underfloor heating on its own
An underfloor heating (UFH) manifold set and its wiring box. The box is fed from a spur and feeds its own floor thermostat. Its actuators open before its pump runs. Its heat source contact is volt-free, until a link from the box's L gives it a live to switch. A lamp stands in for the boiler.
How it opensOn the canvas are a fused spur, an UNDERFLOOR HEATING (UFH) manifold set, its floor thermostat (stat) and a lamp. In this lesson you wire the set and see how it calls the boiler.
Underfloor downstairs, radiators upstairs
Underfloor heating (UFH) added to a working system. The radiators upstairs are already wired as an S-Plan zone. You wire the new floor downstairs: the box from blocks 1, 2 and 3, its floor thermostat, the Ls link, and its Lr to block 10 beside the radiator valve's orange. Then you prove the floor alone, both zones together, and the radiators alone.
The UFH interlock
Why the boiler must wait for the floor: with every loop shut, its heat has nowhere to go. You prove the right order. Then you wire a mistake on purpose, the floor thermostat's call straight to block 10, see what it does in the simulator, and put it right.
Actuators and the mixing unit
Inside the manifold set: the actuators on the return rail, opened by 230 V from the box and shut again when it goes. The readings that tell a faulty actuator from a missing call. The mixing unit's blending valve and its pump, which keep the floor cooler than the boiler's water.
The practical: radiators and UFH from memory
The mixed system's parts on the wall, with no wires. You wire the radiators' zone and the floor from memory: the supply through the boiler's 230 V IN and OUT, the pump on PUMP OUT, the timeswitch, the room thermostat and its valve, the underfloor heating (UFH) box, its thermostat and its link, and both calls to block 10. Each step names the job, never the block. Every state is proved. No hints. Recorded.
The practical · recorded, no hints
In the simulator, you practise how to
- Wire a UFH wiring box: its supply, its zone's stat fed from the box, the stat's call back on SL
- Use the heat source contact: volt-free, linked from L for a boiler that wants a switched live, left unlinked for a boiler that feeds it
- Add an underfloor zone to a radiator system: the box on the permanent live, its call for heat on block 10 with the radiator valve's orange
- Explain the interlock: the boiler waits for the floor's loops to open, and a call wired around the box fires it before any loop is open
- Read the actuators' supply and the zone's call with the meter, and tell a faulty actuator from a missing call
- Say what the mixing unit's blending valve and pump do
- Wire a radiator and underfloor system from memory and prove every state
- 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.
- A practical with no hints, every step recorded.
- The unit earns the credential Mixed 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
- C-Plan and W-Plan
Unit 4, before this one
- Protection and extras
Unit 6, next
Back to the Programme.
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