Boiler cleaning and maintenance

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  • OVERALL DIFFICULTY INDEX: 5/10
  • IF YOU HAVE NO TOOLS, YOU PAY $120 TO GET THEM FOR THIS JOB
  • IF YOU HAVE NO EXPERIENCE YOU SPEND 6 HOURS TO CARRY OUT THIS JOB
  • ELECTRICAL ELECTROCUTION HAZARDS
BEFORE YOU START
It is obvious that such works are to be carried out on a cold boiler.
Make sure to isolate the electrical circuit feeding the boiler. You should not proceed by simply shutting it off with the switch or thermostat but rather isolate its breaker.
DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.

Boiler maintenance intervals 

It is recommended to service boilers equipped with oil-fired burner based on the below intervals:

Yearly boiler maintenance
  • Check for fuel leaks
  • Check for fumes leak
  • Check and adjust burner electrodes
  • Start boiler and check and adjust flame
  • Make sure the hot water circulation pump is not stuck

Maintenance to be carried out on boilers every 2 years
  • Clean boiler from soot and deposits
  • Replace gaskets if and when needed

Maintenance to be carried out on boilers every 3 years
  • Replace burner nozzle and electrodes

Removing the boiler panels, covers and access traps

Start by removing the boiler panels which are normally held in place by simple push-springs.
You should be able to pull them off easily with no tools.
Pay attention to the copper thermocouple and wires that connect to the switch, thermostat and safety thermostat on the front panel.
Remove the nut (s) or bolt (s) that hold the access trap on top of the burner and take out the iron cover:

Removing the burner from the boiler

In this case, the removal of the burner requires only loosening a couple of nuts, tilting the burner and taking it out.
Do steps 2 and 3 with care not to damage the gasket between the burner and its holder.
Visit our specific page for burner servicing and repair.

DIY cleaning of the boiler chamber 

  • The access trap located above the burner allows you to clean the so called "second-pass exchanger" because this is where the fumes still hot do heat up the water while the first pass is obviously the one happening in the flame chamber. If your burner is well adjusted, a hard plastic brush will do the job perfectly or else you have to use a metallic brush.
  • The advantage of plastic brushes is that they are found so easily in all supermarkets for having many house uses while metallic cylindrical brushes of various diameters can only be found at a hardware shop.
  • Complete your action by using a vacuum cleaner. It is not advised to use your daily vacuum machine, rather a specific one used only for DIY tasks. Note that the vacuum hose supplied with the machine would not go inside the flue gas chamber and between the fins; in this case a thinner extender was used.
  • Have the vacuum hose cross the boiler fumes chamber to behind the boiler and clean well the residues that were left in the pipe connecting the boiler to the main chimney. 
  • Take your time and make sure you don't leave carbon deposits behind. This is when you don't hear them moving into the vacuum hose anymore.
  • Now use the vacuum machine to clear the main chamber (flame chamber) before dismantling the burner support to avoid having particles falling to the floor.
  • Depending on the gas-oil quality you are using, you may find loose deposits of black, red or yellow color. Red and yellow denote the presence of sulfur (left).
  • The main chamber walls will be covered by a black coating which needs to be cleaned in order to enhance the boiler efficiency (right).
Time now to remove the main chamber cover which is at the same time the burner's support.
Loosen the bolts or nuts that hold it and take it off.
You might face corroded bolts that refuse to slacken and eventually break.
I am showing further below how to  replace broken bolts.
Note well how the inner insulation of the boiler cover is burnt all around. It needs replacement.
The flame chamber is covered with black carbon deposits that need to be removed. This also denotes a bad flame setting during at least the last year of operation. 
At this stage, the use of a good dust protection mask is mandatory.
A 1" spatula is used first followed by the brushing of the iron with a metallic brush.
DO NOT START by the brush as this makes it more difficult.
Use the spatula first and you will notice that not less than 80% of the deposits could simply peel off the chamber walls.
You need then to work into the flue gas passages on top of the chamber and towards the second-pass exchanger.
The spatula will still go in there and remove 90% of the deposits but this is to be followed by brushing the passages using various cylindrical brushes of various sizes.
The fumes passage upwards is shown in this picture and the fins are starting to be cleared and clean. Note how the plastic brush passes through and in between all fins sometimes better than a metallic brush. 
Buy your boiler brushes from our partners' stores:
When done, your chamber should be as clean as the one pictured here (at least).

This is the maximum achievable by hand brushing.

If you like, you can fit a disc brush on your drill and have the chamber look like new but this is only possible if the boiler is in a place where you can generate as much dust.

Cutting and preparing replacement boiler gaskets

In case you need to replace some flat gaskets, you may do so by yourself, by cutting new gaskets into gasket making material.
See also how to fix a broken bolt if this happens to you

See also our other tips and tutorials for boiler and burner maintenance:

And buy your oil or gas boiler and burner parts from our partners' stores:

See also our other tutorials for central heating and home heating: