Heating repair on the Costa Blanca

Most frequent faults at the start of the season

First firing of heating each autumn is when most faults appear. The boiler has been off for six months, circulation pumps have seized from inactivity, seals have dried, sensors drifted and sludge has settled in radiators. When you try to fire up the system, one of these components fails. Totally normal and predictable. That’s why we always recommend booking a preventive review in September or October before the first cold, avoiding the classic November rush when all technicians are oversubscribed.

Symptoms we hear most: boiler ignites but heating doesn’t warm up, circuit pressure drops constantly and needs topping up every few days, hot water flow is fine but heating warmth isn’t felt, boiler short-cycles repeatedly without reaching temperature, odd water-circulation noise, visible leaks at valves or unions, error code on a modern boiler display.

Step-by-step diagnosis

Professional diagnosis follows a logical sequence to find the cause efficiently. We start by checking circuit pressure cold and hot: if it drops constantly, there’s a leak somewhere. Then we check pump operation by feeling the supply pipe, if it’s not warm and vibrating, the pump isn’t pushing flow. Then combustion analysis on a gas boiler, measuring CO, CO2 and excess air to verify combustion is right. We check ignition electrodes and safety thermocouple. Finally we read error codes stored in the modern boiler’s electronics, they say exactly which subsystem had trouble.

Once cause is identified, fixed-price repair quote. Common parts (electrodes, temperature sensors, three-way valves, pump capacitors, pressure switches) ride in the van and the repair completes in the same visit. For specific parts like full control board or heat exchanger, we order from the official service and return in 2-7 days with the material.

Typical boiler repairs

By far the most common fault is pressure dropping. Usual cause is a failed expansion vessel: an internal diaphragm splits and stops absorbing water expansion, so pressure drops every time the circuit cools. Expansion vessel replacement is a 1-2 hour job and definitively fixes the issue. Another cause of pressure loss is a safety valve opening on overpressure: replace it and check sizing.

Circulation pump not pushing flow is the second common fault. Easy to spot because radiators don’t heat even though the boiler runs fine. Pump replacement is a 2-3 hour operation. Modern high-efficiency pumps draw far less electricity than old ones, so the swap also drops the electricity bill.

Plate heat exchanger blocked by scale or sludge is the third serious fault. When radiators barely heat even though the boiler is fine and the pump is pushing, the internal exchanger is losing efficiency. Fix is a chemical flush of the exchanger or, if very degraded, full replacement.

Electronic problems on boilers over 8 years old are increasingly common. The control board accumulates wear from thermal cycles and eventually fails. Board replacement costs a significant share of a new boiler, so on old boilers you have to weigh repair vs full replacement.

Underfloor repairs

Hydronic underfloor can have similar faults to radiator heating (pressure, pump, expansion vessel) plus its own. Manifold electrothermal heads that fail and block one or several circuits are the most common. Swap is quick once the affected circuit is identified. Embedded tubing leaks are rare but serious: they need thermal location with camera and, if confirmed, controlled floor opening only at the exact point. The pipe is repaired with electroweld sleeves that leave the joint as strong as the original pipe.