Drayton LP522 Thermostat Wiring Diagram
Drayton LP522 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 LP522 allows different weekday and weekend programs, with independent heating and hot water timing 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 LP522 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 LP522 Thermostat Wiring Diagram, we suggest checking the Frequently Asked Questions (FAQs) section.
Printable Drayton LP522 Wiring Diagrams
Wiring Instructions
Before you start
The Drayton LP522 is a dual-channel 5/2-day programmer. It switches 230 V AC to two heating channels, hot water (HW) and central heating (CH). Every terminal on the wall-plate is at mains voltage, so the installation must be carried out by a qualified electrician or heating engineer. In the UK, the work must also follow the current IET wiring regulations (BS 7671). The unit is for fixed wiring only. Never connect it with a plug and flexible cord.
- Tools: insulated screwdrivers, an approved voltage indicator or multimeter, a wire stripper, a drill with wall plugs, and a spirit level.
- Materials: the LP522 and its wall-plate. For a new wall-plate you also need No. 6 x 1 inch (25 mm) woodscrews, or M3.5 x 14 bolts if you mount it on a flush single conduit box type UA1 (BS4662). Do not use a surface mounting box.
- Cable: no conductor size is specified for this unit. Use fixed-wiring cable sized for a circuit protected by a 3 A fuse, as your local regulations require.
- Supply: the mains input must be protected by a 3 A fuse, usually a fused spur or the mains isolator that feeds the heating controls.
- Location: about 1.4 m above the floor, with reasonable lighting and no condensation or temperature extremes. The wall must fully cover the back of the unit. Leave 70 mm clear to the right, 25 mm above, and enough room underneath to reach the securing screws.
Decide which system you have before you wire anything:
- Fully pumped: heating and hot water are controlled separately by motorized valves, such as a mid-position valve or two spring-return valves. Use the P setting.
- Gravity hot water with pumped heating: use the G setting.
The single wiring tab in the diagram covers every case. What changes between systems is where terminals 1 to 4 go in the junction box and the position of the System type link P / G.
Step-by-step wiring
- Switch off the mains isolator and remove the 3 A fuse. Use your voltage indicator to confirm that no conductor at the old programmer or junction box is live. Prove the indicator on a known live source before and after the test.
- Replacing an existing programmer: loosen the securing screws, unplug the old unit and compare its terminal layout with the LP522. Many industry-standard wall-plates already use the same N, L, 1, 2, 3, 4 layout and need no rewiring. Others use different numbers or extra links between terminals, and you must rewire those to match the LP522 terminals. Remove any old links that the LP522 does not need.
- Fitting a new wall-plate: fix it level with the terminals at the top. For surface wiring, snap out the cable entry strip on the bottom edge.
- Connect the incoming supply: the neutral to N and the fused live to L. The live also feeds the common of both internal switches, so no extra link is needed. This is the main difference from the LP timeswitches, which have voltage-free contacts.
- Connect the hot water channel. HW ON (terminal 3) carries the call for hot water to the cylinder thermostat or the hot water valve circuit. HW OFF (terminal 1) is used only where your valve arrangement needs a live signal when hot water is off.
- Connect the heating channel. CH ON (terminal 4) goes to the room thermostat feed. CH OFF (terminal 2) is used only where the system calls for it, for example with some mid-position valve layouts.
- Terminate earths on the earth (loop) terminal. The LP522 is double-insulated and does not need an earth, but the terminal lets you keep earth continuity to the rest of the circuit.
- Complete the other connections in the junction box: valves, room thermostat, cylinder thermostat, pump and boiler. If the boiler needs pump overrun, follow the boiler manufacturer's wiring instructions; the programmer does not provide this.
- Set the System type link P / G on the back of the unit to match your system.
- Tidy the conductors so that none is strained or pinched. Plug the programmer onto the wall-plate and tighten the securing screws.
Testing and start-up
- Refit the 3 A fuse and switch on the mains. The display should light, and the clock should already show the correct time because it is preset at the factory.
- Use the CH SELECT button under the flap to set CH to ON. Its red indicator should light. At the junction box you should measure about 230 V AC between the CH ON terminal and neutral, and 0 V on the CH OFF terminal. Set CH to OFF and the readings should swap.
- Repeat the test for hot water on the HW ON and HW OFF terminals.
- With both channels on, check that the right valves open, the boiler fires and the pump runs once the thermostats call. Then turn the room and cylinder thermostats down and check that each zone stops.
- Set the programs for the user. On the factory program, ON2 and OFF2 are set to the same time, so the second period does nothing until you change it. Return both channels to TIMED when you finish.
Safety notes
- Always switch off the mains before you remove or fit the programmer. Never fit the unit to a live wall-plate.
- Each output is rated 2(1) A at 230 V AC. Do not drive pumps or other heavy loads directly if they would exceed this rating; switch them through the boiler or a relay as the system design requires.
- The supply must stay within 230 V AC +10%/−10% at 50 Hz. The unit should only be maintained by a qualified electrician or heating engineer.
- The OFF terminals are live while their channel is off. Treat every terminal as live until you have isolated the supply and tested it dead.
Troubleshooting
| Symptom | Probable Cause | What to Check |
|---|---|---|
| The display is blank and nothing works | The 3 A fuse has blown or been left out, the isolator is off, or N or L is loose at the wall-plate | Check the fuse and isolator. With the unit removed and the supply live, take care and measure about 230 V AC between L and N on the wall-plate. If you read nothing there, trace the fault back to the fused spur. |
| The heating only works when the hot water is on too | The System type link is set to G on a fully pumped system | Isolate the supply, remove the unit and move the link to P. Then test the CH and HW channels separately. |
| Turning the heating on brings on the hot water instead, or the other way round | The HW ON and CH ON wires (terminals 3 and 4) are swapped, often after a conversion from a different wall-plate | Switch each channel to ON in turn and measure 230 V at the junction box terminal that should be live. Swap the conductors at terminals 3 and 4 if needed. |
| The hot water runs all the time, even when it is set to OFF | A wire meant for HW ON is on HW OFF (terminal 1), or an old link from the previous programmer is still fitted | With HW set to OFF, terminal 3 should read 0 V and terminal 1 about 230 V. Remove any leftover links between terminals. |
| The mid-position valve will not move to heating only | CH OFF (terminal 2) or HW OFF (terminal 1) is not wired to the correct valve or cylinder thermostat circuit | Compare the junction box wiring with the mid-position valve layout. Check that the correct OFF terminal carries 230 V when its channel is off. |
| The red light is on, but the boiler and pump never start | The room or cylinder thermostat is not calling, there is a broken link in the junction box, or the boiler live feed is missing | Measure 230 V at the thermostat common and at its call terminal. Check the valve auxiliary switch output that feeds the boiler and pump. |
| The fuse blows as soon as the power comes on | A short between L and N or earth, a pinched conductor behind the wall-plate, or a faulty valve motor | Isolate the supply. Measure the insulation resistance between conductors, then disconnect loads one at a time to find the fault. |
| The programmer runs, but the timing seems wrong after installation | The factory program is still active, and its ON2/OFF2 period does nothing | Set the CH and HW programs for weekdays and the weekend. Check that both channels are in TIMED and not ONCE or OFF. |
| The pump stops at once while the boiler overheats or locks out | The boiler needs pump overrun, but the pump is fed from a switched live | Rewire the pump to the boiler's overrun terminals, following the boiler manufacturer's wiring instructions. |
| The unit will not seat on the wall-plate, or works only now and then | Conductors stand proud of the terminals, the screws are loose, or the wall-plate is distorted on an uneven surface | Isolate the supply. Re-terminate and tighten all terminals, fold the cables flat, and check that the wall-plate sits on a flat, fully supporting surface. |
Frequently Asked Questions (FAQs)
Can I replace my old programmer with an LP522 without rewiring?
Often you can, if the old programmer uses the same N, L, 1, 2, 3, 4 layout, which many industry-standard wall-plates share. In that case you simply unplug the old unit and plug in the LP522. Other brands number their terminals differently or use links between terminals. Before fitting the LP522, rewire those wall-plates so that live, neutral, HW ON, CH ON and the OFF terminals sit in the right places. Also check that there is 70 mm clear to the right of the wall-plate and 25 mm above it.
Should I set the link to P or G?
Set it to P if your system is fully pumped, with heating and hot water controlled separately by motorized valves. Set it to G if your hot water heats by gravity and only the heating is pumped. On G, the heating cannot run on its own without the hot water, but the hot water can still run alone. A wrong setting will not damage anything, but on a pumped system G stops the heating from working independently.
Does the LP522 need an earth connection?
No. The LP522 is double-insulated, so the programmer itself needs no earth. The wall-plate still has an earth terminal, which works as a loop. Connect all the incoming and outgoing earth conductors to it so that earth continuity reaches the junction box, valves, pump and boiler. Never leave the earths of other equipment disconnected just because the programmer does not need one.
Are the LP522 outputs voltage-free?
No. The LP522 outputs are live at 230 V AC. The internal switch commons are fed from the L terminal, so each ON or OFF terminal carries mains voltage when it is active. This is different from the LP111 and LP711 timeswitches, whose contacts are voltage-free and need a link from L to terminal 1. Do not connect the LP522 outputs to low-voltage or volt-free inputs on a boiler.
What load can each output switch?
Each switch is rated 2(1) A at 230 V AC: 2 A for resistive loads and 1 A for inductive loads such as motors. In a normal system the outputs feed thermostats and valve motors, which draw much less than this. Do not use the outputs to run a pump directly, or any other load larger than the rating. The whole unit should be supplied through a 3 A fuse.
Can I use the LP522 with a combination boiler?
Yes, but usually you only need the heating channel, because a combi heats hot water on demand. You can wire the CH ON output to the room thermostat or the boiler's switched live input, provided the boiler accepts a 230 V switched live, and leave the hot water channel unused. If you need only one channel with voltage-free contacts, a Lifestyle timeswitch such as the LP111 or LP711 may suit you better.
What is the difference between the LP522, LP241 and LP722?
They share the same wiring and wall-plate and differ only in programming. The LP241 repeats the same 24-hour program every day. The LP522 lets you set one program for weekdays and another for the weekend. The LP722 lets you set each day of the week separately. All three time heating and hot water independently, with up to three periods a day. That means you can swap one for another without rewiring, although you may still need to check the P / G link.
Will I lose my settings during a power cut?
No. Without mains power the display goes blank, but the LP522 keeps both the time and the program. When the power returns, it carries on running the stored program. The clock also changes between summer and winter time automatically, so you do not need to reset it after a power cut or at each change of season.
Can I mount the LP522 on a surface back box?
No. Do not use a surface mounting box. Fix the wall-plate directly to a flat wall with wall plugs and No. 6 x 1 inch (25 mm) woodscrews, or onto a flush single conduit box type UA1 using M3.5 x 14 bolts. Fit it with the terminals at the top. The surface behind must fully cover the back of the unit, and you need access underneath to reach the securing screws.
Where does the room thermostat connect?
The room thermostat takes its call signal from CH ON (terminal 4). It does not connect directly to the programmer. The CH ON output usually runs to the junction box, which then feeds the room thermostat's common terminal. The thermostat's call-for-heat output goes on to the heating valve or to the boiler and pump circuit. The cylinder thermostat is fed from HW ON (terminal 3) in the same way.
