Our oil fired boiler service is an annual check-up of your boiler, which is thorough and gives the technician a chance to look for other issues that may arise with your boiler at a future date. Don’t let this happen! Let our oil technician deal with the problem before it happens, so you don’t get caught out at an inconvenient time. Below you will find information on what factors to consider with oil boilers, the service procedure and the brands of boilers we have experience of working with.
- a room thermostat, ideally located in a living room, not the hallway
- thermostatic radiator valves (TRVs) on all but one of the radiators
- an electronic 7 day timer with separately programmable hot water and room heating
- a cylinder thermostat on the hot water tank
- the boiler and thermostats wired in an interlock to prevent short-cycling when there is no demand for either hot water or room heating
Oil boilers are available with both balanced flues (where the air for combustion is drawn in through a pipe concentric with the extract flue) and with open flues, where the air for combustion is drawn from the room in which the boiler is sited. Although Building Regulations permit both types of boiler to be located in domestic garages, we recommend that only balanced flue boilers are used in those areas. Most modern boilers use a pressure jet burner; although some vaporising burner machines are still available on the market, they may only be fitted into a limited number of locations.
As the sulphur content of oil has fallen, some domestic oil suppliers have added additional lubricants to kerosene to enable fuel to be pumped to the boiler more easily. This is not usually necessary for most systems, as modern pumps have been engineered to operate effectively with low-sulphur fuels, but if you are unsure if you would benefit from using such fuels, speak to your equipment supplier.
Many people are concerned by the threat of Global Climate Change, and are keen to reduce their personal emissions of carbon dioxide (CO2), the main gas contributing to this effect. Official figures from the UK’s Department for the Environment, Farming and Rural Affairs (Defra) indicate a carbon content for domestic heating oil (kerosene) of 0.24kg CO2 per kWh, compared to figures of 0.214kg CO2 per kWh for LPG and 0.19kg CO2 per kWh for gas. However these figures are for gross calorific values, and a typical “A” rated condensing oil boiler achieving 95% efficiency would be responsible for around 5% more CO2 in use. Equivalent gas condensing boilers are a little less efficient, reducing the carbon penalty for oil systems to less than 10% compared to LPG and around 20% for mains gas.
OFTEC, the Oil-Fired Technical Association, as the manufacturers will only validate guarantee when properly installed and commissioned by an OFTEC registered engineer.
You may also have to check whether or not your house insurance is current and up to date, if you do not use an OFTEC registered engineer.

Long term damage can also occur if the boiler is not serviced regularly. During the combustion process, when the air mixes with oil and is burnt, deposits such as sulphur build up on the internal surfaces of the heat exchanger and the baffles, which redirect the flow of flue gases inside a boiler to make it less efficient. If left for a number of years these deposits harden and with some designs of heat exchanger render it impossible to remove the baffles without destroying them. A replacement baffle will come at a significant cost on to the routine service charge.
There are many reasons why the efficiency of an oil fired boiler could be reduced. Here are a few:
- Excessive smoke and partially burnt fuel deposits soot on the heat exchanger which restricts the amount of heat which the heat exchanger can transfer into the water. A heat exchanger carries water around the boiler, absorbs the heat from the hot flue gasses and transfers it into the water. The cleaner the heat exchanger the more efficient the boiler will be
- Oil Nozzles will wear. They regulate how much oil is used and if it is not regularly replaced it could cause “sooting up” of the heat exchanger, and so reduce heat transfer
- Photocells can glaze over with soot. Photocells are an important safety feature which detects whether the flame is lit. If a photocell is dirty it may not be able to monitor the flame correctly and could cause the boiler to shut down randomly causing inconvenience. Boilers switching on and off frequently will be less efficient than when running for longer periods
- Electrodes can wear and carbon up. Electrodes make a spark to light the fuel, if they are worn or covered with carbon it will cause poor ignition so the boiler may not light. Again, causing inefficiency and increasing fuel cost. Efficiency is decreased as soot builds up within a heat exchanger. For example, 3.0mm layer of soot can reduce the amount of heat absorbed by more than 8%

- Clean primary air combustion fan and housing
- Remove and clean blast tube and check condition
- Clean electrodes and inspect ceramic holders
- Remove existing pressure jet nozzle and replace with a new one
- Check electrode dimensions
- Replace blast tube
- Remove and clean flame failure device (photocell). Reinstate and check for operation and safety cut off
- Replace or clean oil filters
- Remove, clean and check all baffles including any turbulators
- Clean all boiler flue ways up to and including the first flue bend
- Clean and check combustion chamber
- Replace all Baffles after inspection
- Refit burner, fire up and test
- Carry out full combustion test and record results
- Check fire valves for correct operation
- Check room ventilation
- Check all electrical controls i.e. programmer, time clock and stats
- Inspect oil tank
- Check oil line integrity
- Complete CD11 (OFTEC Service completion record)
Oil Fired Boiler Brands
These are the brands of oil-fired boilers we have experience of installing and servicing:











