Martin Cooke, Technical Manager at EOGB Energy Products Ltd, provides guidance on correctly replacing oil burners, fault finding and servicing…
When problems arise with an oil boiler it is often down to age. However, as long as the boiler is sound and the water jacket and/or heat exchanger and electrical controls are still in good condition, problems may be caused by one or more of the components on the burner.
Of course everything has a working life and components such as ignition transformers and oil solenoids which operate at high temperatures can eventually fail or fail intermittently causing nuisance lockouts. These parts are still available to replace as many burners fitted over the past twenty years or so are industry standard and have ignition transformers, oil pumps with solenoid and photocell.
The engineer working on the appliance often needs to weigh up the pros and cons of fixing versus replacing the burner unit. For example, if the burner requires a new fan motor, fan and oil pump then you could easily be approaching the cost of a replacement burner, especially if you factor in the labour costs involved. Burner manufacturers will be able to advise on a suitable burner replacement for the boiler model, and then the engineer can make the decision on what is the best plan of action.
Burner replacement tips
Often burner replacement is relatively simple and a retrofit burner can be a quick solution to get the boiler back up and running, plus you are able to offer the customer a warranty from the burner manufacturers. However there are a few essential questions that must be answered before replacing a burner, such as:
If an engineer is new to fault find on an oil burner, a simple methodology is to follow the burner sequence of operation. The burner sequence of many common burners is:
Then check if the burner is locked out or sat waiting for a signal to run. The control box neon indicator will display when a lockout has occurred but if there is no light on the control box then check the electrical supply to the burner. Most oil burners have a simple 220 volt AC supply down to the control box or terminal strip on the burner so if no voltage is present then check the thermostat, overheat stat, frost stat, or time clock before undertaking any work on the burner as the fault may be external.
Before starting work always fit a pressure gauge to the oil pump as this will tell you if you have the pressure adjusted correctly. You don’t want to work on the burner for an hour only to discover you have no oil pressure to start with! This is also a good indication that the drive coupling between the pump and the motor is connected and not stripped out.
Identifying the fault
When you press the reset does the fan run and then the burner locks out before igniting? Remove the burner and check if the blast tube is wet with fuel. If so, then it is probably ignition transformer failure or electrode problems. If the tube is dry it could be solenoid coil on oil pump or photocell detecting ‘stray light’.
Try disconnecting photocell and firing the burner again. If the burner lights then locks out after ten seconds, replace the photo cell. If the burner doesn’t ignite after disconnecting the photocell, check the solenoid coil. This could be checked with a multi-meter on ohms resistance and if you get open circuit then replace solenoid. If the burner runs for a few seconds and lockouts it is most likely a photocell failure. If the burner runs for a few minutes and lock out then it could be an oil pump solenoid failure.
These are a few of the common oil burner failures that are relatively easy to rectify. If an engineer is new to oil, most manufacturers offer oil burner training courses to go over the commissioning, serving and fault finding procedures.
Servicing quick guide
Domestic oil boilers should be serviced every twelve months. Check manufacturer’s instructions and relevant local authority legislation regarding oil storage and ensure the following is checked or changed where necessary:
By following the correct guidelines above, installers can ensure that they make a quick and accurate diagnosis to effectively repair the heating system and minimise shutdown time.