Error E87

Safety precautions:

1. If you smell gas, stop, ventilate the area, turn off the gas supply at the meter if safe to do so and call the gas emergency number immediately. Do not touch electrical switches or operate the boiler.

2. Before doing any inspection that involves opening the boiler casing, switch off the electrical supply at the isolator or fuse and allow the boiler to cool. Only qualified persons should work inside the casing.

3. Do not repeatedly reset the boiler if the fault keeps reappearing; repeated resets can hide the underlying issue.

Initial checks a homeowner can do:

1. Take note of the full displayed code and any other codes or lights visible on the boiler. Record when the fault started and any events (power cuts, storms, works, thermostat changes).

2. Check the boiler has power: is the display on, are other electrical appliances working? Check the house fuse/spur for the boiler.

3. Check the mains gas supply is on by confirming other gas appliances work. If you have a prepay meter, check credit.

4. Check the CH pressure gauge. Ensure system pressure is in the normal range (typically about 1.0–1.5 bar for a cold system). If pressure is very low, top up via the filling loop following the boiler manual and then try a reset.

5. Check external controls: room thermostat batteries, programmer settings, any smart controls or wireless relays. Disable or bypass external controls temporarily (set programmer to call for heat) to rule them out.

6. Try a normal reset: press and hold the boiler reset button (or set selector to R) for 5–10 seconds. Wait for the boiler to attempt restart and watch for reappearance of the E87 code.

Specific diagnostic steps and simple fixes:

1. Power cycle: switch the boiler off at the electrical isolator, leave off for 60 seconds, then restore power and see if the code returns. This can clear temporary comms errors caused by spikes.

2. Check wiring and connectors you can safely access without removing the boiler cover: thermostat connections at the external terminal block, any visible low-voltage plugs. Look for loose connectors or damaged cable sheaths. Tighten only accessible terminal screws if secure work is possible and safe.

3. If you are competent and comfortable working safely: isolate electrical supply, remove the outer casing following the manual, visually inspect the PCB area for signs of water ingress, corrosion, burn marks or obvious loose ribbon connectors. Do not touch the PCB components. If you find a visibly loose plug, reseat it firmly and refit the casing, restore power and test. If you are unsure, stop and call an engineer.

4. If the code appears after a power cut or lightning, intermittent communications can be caused by a failing PCB or power supply components. Note whether the fault is permanent or intermittent and any patterns.

When to call a professional and information to give them:

1. Call a Gas Safe registered engineer if the E87 persists after the basic checks and resets, if you find signs of damage or damp inside the casing, or if you are not comfortable opening the boiler. Communication faults frequently require specialist test equipment and may need PCB, CSU or module replacement or wiring repair.

2. When you call, provide: exact error code (E87), any other displayed codes, what you have already tried (resets, power cycle, pressure check), whether the fault is constant or intermittent, whether the boiler shows any other symptoms (no heating/hot water, noise, leaks) and whether there was a recent power outage or storm.

3. If the boiler locks out repeatedly, or you detect any gas smell, isolate gas and power and contact emergency services or your gas supplier plus a Gas Safe engineer.

Remember: simple resets and external control checks are reasonable DIY steps. Internal electrical, PCB and gas-related work must be completed by a qualified Gas Safe engineer to ensure safety and compliance.