Drayton LP241 Thermostat Wiring Diagram
Drayton LP241 programmer wiring
Wall plate with the 230 V mains and the hot water (HW) and central heating (CH) outputs.
Terminals and components · 7
- Live
- Neutral
- HW OFF
- CH OFF
- HW ON
- CH ON
- P/G link
Connection
Run the neutral from the same 230 V AC, 50 Hz circuit that feeds terminal L. The equipment the programmer controls takes its neutral from the junction box, not from this terminal.
Function
Inside the programmer, L feeds the clock and the commons of both changeover switches. That's why terminals 1 to 4 deliver 230 V when their switch is closed; no link is needed.
Caution
- Installation must only be carried out by a qualified electrician or heating engineer.
- Switch off the mains before starting and before removing the unit; never fit it to a live wall plate.
- The mains input must have a 3 A fuse.
- Fixed wiring only, in line with current wiring regulations.
Earth
The unit is double insulated and needs no earth; the wall plate has an earth loop terminal to keep the cable's earth continuous.
Connection
Use it only if the system needs a signal while hot water is off, for example the "hot water off" input of a three-port mid-position valve. Otherwise leave it free.
Caution
- The output delivers the 230 V live from L: don't use it to switch low-voltage circuits.
- Rating of each switch: 2(1) A at 230 V AC.
Connection
Usually left free. Use it only if some equipment must be powered while heating is off.
Caution
- The output delivers the 230 V live from L: don't use it to switch low-voltage circuits.
- Rating of each switch: 2(1) A at 230 V AC.
Connection
Run this terminal to the system junction box, towards the cylinder thermostat and hot water valve, which in turn call the boiler and pump.
Tip
Consult the boiler handbook for pump overrun wiring details.
Caution
- The output delivers the 230 V live from L: don't use it to switch low-voltage circuits.
- Rating of each switch: 2(1) A at 230 V AC.
Connection
Run this terminal to the system junction box, towards the room thermostat and heating valve, which in turn call the boiler and pump.
Tip
Consult the boiler handbook for pump overrun wiring details.
Caution
- The output delivers the 230 V live from L: don't use it to switch low-voltage circuits.
- Rating of each switch: 2(1) A at 230 V AC.
Settings
Setting System Operation P Fully pumped and controlled Heating and hot water are set separately. G Gravity-fed hot water Heating can't run without hot water; hot water can run alone. Tip
The LP241 makes use of its independent heating and hot water timings in the P setting.
Check
Set the link to the system type before fitting the programmer to the wall plate.
About This Diagram
This diagram is redrawn from pages 2–3 of the Drayton LP241 Thermostat Installation Instructions, and we offer it completely free and in English. We have also categorized it in the Thermostats (HVAC & Water Heating) section on Diagramverse, and it has been rated by 1 user with an average rating of 5.0. If you have any specific questions about the Drayton LP241 Thermostat Wiring Diagram, we suggest checking the Frequently Asked Questions (FAQs) section.
Printable Drayton LP241 Wiring Diagrams
Wiring Instructions
Before you start
The Drayton LP241 is a dual-channel programmer: one channel for hot water (HW) and one for central heating (CH). It switches 230 V AC onto its output terminals, so this is mains work. Installation and maintenance must be done by a qualified electrician or heating engineer. In many areas this work must be notified or certified, so check your local rules first.
You will need:
- Insulated screwdrivers and a voltage tester or multimeter rated for mains voltage.
- Fixed-wiring cable sized for the circuit, as your local wiring regulations require. The unit is for fixed wiring only, never a plug-in lead.
- A supply protected by a 3 A fuse, usually a fused spur or mains isolator.
- For a new wall-plate: wall plugs and No. 6 x 1 in (25 mm) woodscrews, or M3.5 x 14 bolts for a flush single conduit box. Do not use a surface mounting box.
Switch off and lock off the mains, then use your tester to prove the wall-plate is dead. Never fit the programmer to a live wall-plate.
Next, identify your system. A fully pumped system with independently controlled heating and hot water, using two-port zone valves or a three-port mid-position valve, needs the P setting. Gravity-fed hot water with pumped heating needs G. With G, heating cannot run without hot water, although hot water can run on its own.
Step-by-step wiring
- If you are replacing an old programmer, loosen its securing screws and unplug it. Compare its terminal layout with N, L, 1, 2, 3, 4. Many industry-standard plates already match, but some older or competitor models number their terminals differently or use links. Rewire the plate where needed.
- If you are fitting a new wall-plate, mount it about 1.4 m above the floor with the terminals at the top. Choose a flat surface that fully covers the back of the unit, away from condensation and extreme temperatures. Leave 70 mm clear to the right, 25 mm above, and room below to reach the securing screws.
- For surface wiring, snap out the cable entry strip on the bottom edge of the wall-plate.
- Set the System type link on the back of the programmer to P or G.
- Connect the supply: neutral to N and fused live to L. L also feeds the commons of both switches internally, so you don't need an extra link.
- Connect CH ON (terminal 4) to the room thermostat circuit, usually through the wiring centre.
- Connect HW ON (terminal 3) to the cylinder thermostat circuit.
- Use HW OFF (terminal 1) and CH OFF (terminal 2) only where your system drawing calls for them, as some mid-position valve layouts do. Otherwise leave them empty.
- Join the earth conductors. The programmer is double-insulated and needs no earth, but its earth continuity terminal lets you carry the earth through to the rest of the system.
- For a pump overrun boiler, follow the boiler manufacturer's wiring for the permanent live and overrun connections.
- Check that every screw is tight and no bare copper shows. Then plug the programmer onto the wall-plate and tighten the securing screws.
Testing and start-up
Confirm the 3 A fuse is fitted, then switch the mains back on. The backlit display should come on. The clock is set at the factory and changes for summer time automatically.
- Set the CH channel to ON with its SELECT button. At the wiring centre, you should measure about 230 V AC between the CH ON conductor and neutral, and 0 V on CH OFF. Set CH to OFF and the two readings should swap.
- Repeat the test for the HW channel on terminals 3 and 1.
- Turn the room thermostat up and check that the valve, pump and boiler respond. Do the same with the cylinder thermostat and HW ON.
- With P selected, use each Advance/Boost button to confirm that the two channels work independently.
- Set the timings or keep the factory program, then return both channels to TIMED.
Safety notes
- L is live whenever the supply is on, and each output carries 230 V when it is active. Treat every terminal as live.
- Each switch is rated 2(1) A at 230 V AC: 2 A for resistive loads and 1 A for inductive loads. Pumps and valve motors are inductive. As general good practice, drive anything larger through a suitably rated relay or contactor.
- Keep the 3 A fuse. A larger fuse will not protect the programmer's switches or wiring.
- Always switch off the mains before you remove the programmer from its wall-plate.
- On 28 mm valves the white wire becomes live when the valve closes. Connect it to a spare terminal and never leave it loose.
Troubleshooting
| Symptom | Probable Cause | What to Check |
|---|---|---|
| The display stays blank and nothing works | No supply at N and L: blown 3 A fuse, isolator off, or the programmer not fully seated on the wall-plate | Isolate, then check the 3 A fuse. With power restored, measure between L and N at the wiring centre. You should read about 230 V AC. Reseat the unit and tighten the securing screws. |
| The CH light is on but the heating never starts | The heating call wire is on CH OFF (2) instead of CH ON (4), or the room thermostat circuit is open | With CH set to ON, measure CH ON to neutral at the wiring centre. You should read about 230 V AC. If the voltage appears only when CH is OFF, move the wire to terminal 4. Then turn the room thermostat up. |
| The heating runs when the programmer says it is off | The heating circuit is connected to CH OFF (2), which is live while heating is off | Move the room thermostat feed to terminal 4. Leave terminal 2 empty unless your system drawing uses it. |
| The hot water button controls the heating, and the heating button controls the hot water | HW ON (3) and CH ON (4) are swapped | Trace each conductor to the wiring centre. Terminal 3 must go to the cylinder thermostat and terminal 4 to the room thermostat. |
| The heating will not run unless the hot water is also on | The System type link is set to G on a fully pumped system | Isolate, remove the programmer and move the link to P. G is only for gravity-fed hot water. |
| A new programmer on an old wall-plate does the wrong things or nothing at all | The old plate came from a brand that numbers its terminals differently or relies on links | Compare the old programmer's terminal functions with N, L, 1, 2, 3, 4. Rewire the plate so that live, neutral and each on/off function land on the matching terminal, and remove any links the old unit needed. |
| The 3 A fuse blows when heating or hot water switches on | An output is shorted to neutral or earth, or the load is too large for the 2(1) A switch rating | Isolate and disconnect terminals 1 to 4. Test each output conductor for shorts to N and E. Check the combined load on each output. Larger loads need a relay. |
| The pump or boiler runs with both channels off | A back-feed: the white wire on a 28 mm valve is connected to a live terminal, or there is a wiring centre error | With both channels OFF, measure for voltage on the boiler and pump live feeds. Move the 28 mm valve's white wire to a spare terminal. |
| The boiler pump stops instantly and the boiler overheats or locks out | The pump overrun boiler's pump is wired through the programmer's switched outputs instead of the boiler's permanent live | Rewire the pump and the permanent live as the boiler manufacturer requires. |
Frequently Asked Questions (FAQs)
Is the Drayton LP241 a thermostat?
No, the LP241 is a 24-hour programmer, not a thermostat. It decides when heating and hot water are allowed to run, using up to three periods a day for each channel. A room thermostat and a cylinder thermostat still decide whether heat is actually needed. If the room thermostat is satisfied, the heating stays off even during a CH period. The same applies to hot water once the cylinder thermostat reaches its set temperature.
Are the LP241 outputs volt-free?
No, the LP241 outputs are not volt-free: they switch 230 V AC. Live from terminal L feeds the commons of both the HW and CH switches inside the unit, so each output carries mains voltage in its active state. If you need volt-free contacts, Drayton's single-channel Lifestyle timeswitches such as the LP111 and LP711 provide them. On those, you must bring power to the common yourself.
Does the LP241 need an earth connection?
No, the LP241 is double-insulated and needs no earth connection. The wall-plate still has an earth continuity terminal. Use it to join the incoming and outgoing earth conductors so the earth continues to the boiler, pump, valves and thermostats. Never cut back or leave loose an earth that serves the rest of the system.
Should I set the link to P or G?
Choose P for a fully pumped system in which heating and hot water are controlled separately, normally with two-port zone valves or a three-port mid-position valve. Choose G for a gravity-fed hot water system with pumped heating. In G, the heating cannot run on its own without hot water, but hot water can run alone. If you are unsure, check whether the cylinder is heated through a motorized valve and pump (P) or by gravity circulation (G).
Can I swap my old programmer for an LP241 without rewiring?
Often yes, because the LP241 uses an industry-standard wall-plate with the N, L, 1, 2, 3, 4 layout. Many current programmers, including the Drayton SM2 and similar units, share this layout, and you can simply unplug the old one and plug in the new one. Older or competitor models may number terminals differently or use links, so compare the terminal functions before you swap. Also check that there is 70 mm of space to the right and 25 mm above.
What size fuse does the LP241 need?
The mains input to the LP241 must be protected by a 3 A fuse, normally in a fused spur or isolator. Don't use a larger fuse: each internal switch is rated only 2(1) A at 230 V AC, and a larger fuse would not protect it. If the fuse keeps blowing, look for a short circuit or an overloaded output rather than fitting a larger fuse.
Will I lose the clock and program in a power cut?
No, the LP241 keeps both the time and the program during a power cut. While the mains is off, the display goes blank, but the clock and all program times are kept. Once power returns, the programmer carries on with its schedule, so you don't need to reprogram it after an outage or after isolating it for maintenance.
Is the LP241 suitable for a combi boiler?
The LP241 is designed for systems with heating and stored hot water, where the two channels can run at different times. A combi boiler heats water on demand, so the hot water channel would normally go unused. For a combi, Drayton recommends its single-channel timeswitches such as the LP111 or LP711. Those have volt-free contacts that suit most boiler control inputs.
Is the LP241Si, LP522 or LP722 wired differently from the LP241?
No, the LP241, LP241Si, LP522 and LP722 all use the same N, L, 1, 2, 3, 4 terminals and the same P/G link. They differ only in programming. The LP241 repeats the same 24-hour program every day, the LP522 has separate weekday and weekend programs, and the LP722 can be programmed for each day. Si versions add a reminder when the boiler service is due.
Where should I mount the LP241?
Mount the LP241 about 1.4 m above the floor, in a spot with reasonable light and good access. Avoid condensation and extreme temperatures, and use a flat surface that fully covers the back of the unit. Leave 70 mm clear to the right, 25 mm above, and enough room below to reach the securing screws. Fix it to a flat wall or a flush single conduit box, never to a surface mounting box.
