When your boiler is not working there are a number of boiler components which might require replacing to get your boiler working again. Before calling in the professionals, it might be a simple case of figuring out how to repressurise your boiler.
| Common boiler repairs | Cost |
|---|---|
| Replace heat exchanger | £400 |
| Replace diverter valve | £187 |
| Replace automatic air vent | £98 |
| Replace pressure relief valve (PRV) | £101 |
| Replace printed circuit board (PCB) | £268 |
| Replace boiler circulator pump | £225 |
| Average boiler repair cost | £213 |
Cost to replace a heat exchanger
Average cost to replace a heat exchanger (main, domestic and condensing) is £400
Gas and oil boilers burn fuel to create a flame which heats the outside metal surface of a main heat exchanger. The heat from the flame transfers through the metal to the inside of the main heat exchanger to heat the water which circulates around pipes and radiators, through the heating coil of a hot water cylinder or if you have a combination boiler the same heating water can be sent inside your boiler, via a diverter valve, to a secondary smaller domestic heat exchanger to heat the clean domestic hot water for your taps. Condensing boilers have another heat exchanger which recycles energy from flu gases to improve the overall energy efficiency of the boiler.
Cost to replace a boiler diverter valve
Average cost to replace a boiler diverter valve is £187
Diverter valves are part of a combination boiler and they control whether hot water is used to heat radiators or the domestic hot water that comes out of taps (by diverting hot water to a secondary domestic heat exchanger). When the central heating system is calling for heat the diverter valve will direct the heating water into the heating flow pipe, towards the central heating radiators and then back via the heating return pipe back to the boiler. When a hot water tap or shower is turned on a flow sensor will tell the boiler that hot water is required. The boiler will change the diverter valve position closing flow to the heating pipes and opening flow to the domestic hot water heat exchanger. The hot water in the boiler enters the domestic heat exchanger and heats the metal plate to plate structure. Clean cold domestic mains water enters the domestic heat exchanger passing through alternate plates ie not mixing with the heating water. The clean water is instantly heated and pushed along under mains pressure out of the boiler towards the open hot water tap or shower.
Cost to replace an automatic air vent
Average cost to replace an automatic air vent is £98
When air enters or gases generate inside a heating system various problems can occur. Air locks can reduce heating water flow rates causing the temperature inside the boiler to increase and boilers turning off. Other problems can be corrosion and noises. Manually removing these unwanted gases is difficult and costly in labour and so automatic air vents are used. Automatic air vents can be fitted along heating system pipework, integrated into circulator pumps, system filters or fitted as a planned component inside the boiler. Automatic air vents generally operate using a float with when in air/gas drops to open a valve and releases the gas which is pushed out by the water pressure. Once the float in surrounded by water it lifts up and closes the valve.
Cost to replace a pressure relief valve
Average cost to replace a pressure relief valve (PRV) is £101
PRV stands for pressure relief valve and they are a safety release valve present to prevent pressure building up to a dangerous level. If pressure built up in a boiler to a dangerous level the PRV would open and release the pressure via a pipe which goes through an external wall to outside the building (turned back onto the wall so as not to burn anyone). Once the pressure has dropped the valve automatically closes.
Most PRVs use a spring to push closed a valve holding back water pressure until pressure builds enough to over power the spring at a pre calibrated pressure. Water will then pass by the valve, the system pressure will drop and the PRV spring will then reassert itself to close the valve.
Cost to replace a printed circuit board
Average cost to replace a printed circuit board (PCB) is £268
PCBs are the electronic control centre of your boiler which communicate with all the sensors monitoring temperature and pressures before sending instructions to motors ensuring the boiler runs safely and efficiently.
- Common PCB problems
- Intermittent display panel operation
- Smell of burning
- No power light
- Boiler functions sporadically
The biggest cause of PCB failures is water or even water vapour coming into contact with the sensitive electrical wiring or components on a PCB. Cracks or faulty connections can exist but a leak or operation spill if more likely.
Cost to replace a boiler circulator pump
Average cost to replace a boiler circulator pump is £225
Your boiler circulatory pump (probably made by Grundfos) pushes the hot water through your boiler and around your central heating system. Combi and system boilers usually contain pumps while some other boilers may have circulation pumps outside the boiler on the large primary pipework.
Possible causes of pump failures
- If the pump becomes air locked it could overheat and then the plastic impeller inside may warp and get jammed.
- If corrosion debris is present then the impeller can become clogged and over time lose efficiency.
- Corrosion could cause a leak at the connection to pipes and then lead to an electrical fault.