Overview
F7 on an Ideal Logic Max or Logic Plus regular/system boiler means the boiler has detected low mains supply voltage. The boiler monitors incoming electrical voltage and will lock out if the voltage falls below a safe operating threshold to protect internal electronics and ensure safe combustion control. Common causes are a genuine low supply from the electricity network, a sag caused by heavy loads in the property, a blown or partially blown supply fuse or breaker, or a loose/damaged incoming cable or connection at the consumer unit, fused spur or at the boiler termination. Occasionally an internal boiler power supply or printed circuit fault can give the same symptom. Severity: this is an electrical supply issue; the boiler will normally shut down or refuse to operate while the fault exists, so you will lose heating and possibly hot water. It is a safety-related fault rather than an immediate gas hazard, but because electrics and gas are both involved it should be treated seriously. Initial checks can be done by the homeowner, but diagnosing and repairing wiring, consumer unit faults, or internal boiler electrical faults should be carried out by a qualified electrician and/or a Gas Safe registered heating engineer. If the mains supply from the network is low, contact your electricity supplier to report low voltage or a supply problem.
Troubleshooting Steps
Safety first: do not remove the boiler cover or work on internal electrical parts unless you are a qualified engineer. If you are not electrically competent, stop at the basic checks and call a qualified electrician or your energy supplier. Always isolate the boiler at its fused spur or consumer unit before touching any wiring. Never work on live terminals inside the boiler.
Initial checks homeowners can do:
1. Note whether F7 is persistent or intermittent and whether it appeared after any recent electrical work. Try a boiler reset using the boiler controls or RESTART button once only; if F7 returns, do not repeatedly reset. 2. Check whether other appliances or lights in the house are dimming, flickering or behaving oddly; if so this points to a wider mains supply issue. 3. Check the consumer unit (fuse box) for tripped MCBs or RCDs and any blown fuses. Reset a tripped breaker once; if it trips again immediately, stop and call an electrician. 4. Check the fused spur or isolator switch serving the boiler is on and that its fuse is intact. Replace a blown fuse only with the correct type and rating.
Specific diagnostic steps (only if you are competent and safe to do so):
1. With the boiler switched off at the fused spur, remove the fused spur cover to inspect for loose terminals or burn marks. If you see damage, do not proceed and call an electrician. 2. If you are electrically qualified, measure the incoming supply voltage at the boiler mains terminals or at the boiler fused spur using a calibrated multimeter: UK nominal is 230V AC; voltages below around 185V are likely to cause the F7 fault. Do not measure live terminals unless you are trained and confident; keep hands clear of exposed live parts. 3. If mains voltage measured at the boiler is within normal range, the problem may be intermittent or internal to the boiler (poor internal connection, PSU or PCB fault). In that case isolate power and do not open the boiler further; contact a Gas Safe engineer or Ideal service support.
Simple remedial actions homeowners can try:
1. Switch off non-essential heavy electrical loads in the house (electric ovens, chargers, pumped appliances) and see if the boiler will reset and run. 2. If a tripped consumer unit device was the cause, reset it and monitor. 3. If the fault started after an appliance was connected or after electrical work, isolate that appliance or contact the person who worked on the system.
When to call professionals:
- Contact your electricity supplier immediately if you see widespread low voltage, flickering lights, or confirmed low voltage at the incoming meter. They can investigate the external supply and log a low-voltage complaint. - Call a qualified electrician if you find blown fuses, tripping breakers, damaged wiring, loose connections at the fused spur or consumer unit, or if you are not confident to carry out voltage checks. - If the supply voltage at the boiler is normal but F7 persists, contact a Gas Safe registered heating engineer or Ideal service: there may be an internal boiler electrical fault (PSU, PCB or wiring) that requires specialist diagnosis and repair. If the boiler is under warranty, contact the manufacturer or your installer first.
Do not attempt internal PCB or gas-side repairs yourself. Document the fault code, when it occurs and any other observations (other electrical faults, time of day, weather) to provide clear information to the electricity supplier, electrician or heating engineer.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Ideal Logic Max & Logic Plus Regular Boiler.