No Heating in London? Check These 5 Things Before Calling an Engineer
Most London heating failures have a simple fix you can try in under 10 minutes. Work through this list first -- if none resolve it, call us and we will have a Gas Safe engineer with you same day.
Try These First
5-Step Heating Check -- Do This Before Calling
Work through these in order. Each one takes under 2 minutes. Two of them are the cause of more than half of all no-heating calls we receive in London.
Thermostat
Is it set to a temperature ABOVE the current room temperature? Is it in heating mode -- not off or hot-water-only?
Programmer / timer
Is heating scheduled on right now? Check date, time and day of week -- a single wrong setting can silence the whole system.
Boiler pressure gauge
Should read 1 to 1.5 bar. Below 0.8 bar? Repressurise via the filling loop.
How to repressurise -- step by stepReset button
Hold the boiler reset button for 10 seconds. Wait 2 full minutes for re-ignition before assuming failure.
Circuit breaker
Open the consumer unit and check whether the boiler fuse has tripped. Flick it back on if so -- if it trips again immediately, call an engineer.
Gas smell? Do not attempt any checks. Leave the property immediately and call the National Gas Emergency line on 0800 111 999.
What You Found
What to Do Based on What You Found
| What you find | What to do |
|---|---|
| Boiler shows error code | See our error code decoder -- /blog/boiler-not-working-london |
| Boiler fires but all radiators cold | Pump failure or sludge blockage -- see causes section below |
| Boiler won't ignite at all | Ignition fault -- Gas Safe engineer required |
| Boiler shows low pressure reading | Repressurise the filling loop (see step 3 above) |
| Thermostat shows correct temp but boiler won't run | Thermostat fault or wiring issue -- check RF connection, replace batteries |
| One heating zone off, others working | Zone valve failure -- see causes section below |
| Heating on constantly, won't switch off | Motorised valve stuck open -- engineer required |
Root Causes
5 Reasons London Heating Fails
Listed from most to least common. The first cause accounts for roughly 60% of no-heating calls in London during winter.
Boiler fault (most common)
A boiler lockout -- where the boiler shuts itself down and won't restart without a reset -- is the single most common cause of no heating in London. Lockouts are triggered by low pressure, ignition failure, overheating, or PCB faults. Check the display for an error code (letter + numbers) before calling: it tells the engineer exactly which part to bring.
Gas Safe engineer required
Pump failure
The pump circulates hot water from the boiler around the radiator circuit. When it seizes or burns out, the boiler fires normally but no heat reaches the radiators. Symptom: a faint humming from inside the boiler casing, all radiators completely cold despite the boiler running. Pumps inside combi and system boilers require a Gas Safe engineer; a standalone pump in an airing cupboard can be replaced by a plumber.
Gas Safe engineer required
Zone valve failure
Homes with separate heating zones (upstairs/downstairs, or heating/hot water) use motorised zone valves to direct flow. When a valve fails closed, that zone gets no heat while other zones or hot water may work normally. Diagnosing a zone valve requires isolating which circuit has stopped and testing the valve motor -- a straightforward job for an experienced engineer.
Gas Safe engineer required
Thermostat or programmer failure
Even when settings look correct, the thermostat or programmer may have failed internally and stopped sending a run signal to the boiler. Wireless thermostats can lose their RF pairing after power cuts. Replace batteries first. If a wired thermostat, the room stat may have an internal fault. A new smart thermostat (Hive, Nest, Drayton) eliminates this class of failure and costs 80-200 fitted.
Motorised valve stuck open or closed
A motorised valve controls whether heating, hot water, or both are allowed to run. If stuck closed, the circuit it controls produces no heat. If stuck open, that circuit runs continuously even when it should be off -- so you may notice excessive heat or fuel bills rather than cold radiators. Replacing the valve head is often sufficient without draining the system.
Gas Safe engineer required
London Context
Why Winter Heating Failures Hit London Hard
Engineer demand spikes November to February
London's heating engineers are at peak demand during winter. Average wait time for a non-emergency booking in cold months is 3 to 7 days. Booking a boiler service in September or October -- before the cold snap -- significantly reduces wait times and is often 10 to 20% cheaper.
Below 5 degrees C: heating becomes a health emergency
When external temperatures fall below 5 degrees C, a heating failure becomes dangerous for elderly residents, young children, and anyone with cardiovascular or respiratory conditions. In these circumstances, call an emergency heating engineer rather than waiting for a standard appointment.
Older London housing stock
Many London properties were built before World War II. Older pipework, original radiators and ageing pump systems mean London heating failures are statistically more common -- and often more complex -- than in newer builds elsewhere in the UK.
Tenants and Landlords
Your Rights if the Heating Fails in a Rented Property
Landlord legal obligation
Failure to provide adequate heating is classified as a Category 1 hazard under the Housing Health and Safety Rating System (HHSRS). Landlords are legally required to maintain heating in working order.
Notify in writing immediately
Send an email to your landlord the moment heating fails. This creates a timestamped record. Include the date, time, current temperature and any effect on vulnerable occupants.
24-hour repair obligation in cold weather
In cold weather (below 10 degrees C), the landlord must arrange a repair within 24 hours. Failure to do so entitles tenants to arrange their own repair and deduct the cost from rent in many circumstances.
Council and emergency housing assistance
If the landlord fails to act and the property becomes uninhabitable, contact your local London council's housing team. Emergency housing assistance may be available.
Repair Costs
No Heating Repair Cost Guide -- London 2026
| Fix | Cost (inc. VAT) | Emergency surcharge |
|---|---|---|
| Thermostat replacement | £80-200 | +40-80 |
| Zone valve replacement | £150-300 | +40-80 |
| Pump replacement | £200-400 | +40-80 |
| PCB replacement | £300-700 | +60-100 |
| Full boiler service + reset | £80-150 | +40-80 |
| Same-day London engineer (call-out) | £60-100 call-out | Included in above |
All prices include VAT. Fixed quote given before any work starts. See full price list
Heating Questions
Frequently Asked Questions
Heating Still Off After Checking These?
Gas Safe heating engineers, same-day across London. Call now and we will diagnose the fault and fix it in one visit -- most London heating repairs are completed the same day.
No call-out fee on jobs over 2 hours · Gas Safe registered · 24/7 London