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Troubleshooting and Repairing your Boiler

Updated Apr 4, 2018
By Gary Sprague

A boiler problem will usually occur in the middle of winter, on the coldest night of the year. At least, it always seems that way. So what do you do if your boiler stops working properly? Some problems you can troubleshoot yourself, while others will require the attention of a heating contractor.

First Steps

If your boiler stops running, here are five troubleshooting steps you should take before doing anything else:

  1. Check that the emergency shut off switch hasn’t been turned off by mistake. The switch looks like a regular light switch but with a red cover plate. You should have two switches – one mounted on the side of your boiler, and one near the top of your basement stairs or near the door of your boiler room.
  2. Check for a bad fuse or tripped breaker in your main electrical panel.
  3. Check to be sure that you haven’t run out of propane or oil.
  4. Make sure the thermostat is on and set to “Heat”. Check that the temperature setting is not too high or low. Also check the thermostat batteries and change them if needed.
  5. Press the red reset button, usually located on the burner at the front of the boiler. If your boiler shuts down for some reason, a simple reset may be all it needs to get running again.

These are simple steps, but they can save you an embarrassing and potentially expensive service call. Here are a few other common boiler problems:

No Heat from Radiators

A bad circulator pump or zone valve can cause this problem. Air in the pipes is another common reason for cold radiators. If there are bleeder plugs on your radiation you can loosen them to let the air out. If not, the entire zone where you have no heat will need to have the air bled out. This can sometimes be done by the homeowner, but flushing air from heat pipes can be tricky and will often require a call to your heating contractor.

Pilot Light Won’t Stay On

This is usually caused by a damaged thermocouple that will need to be replaced. It can also be caused by a draft blowing the pilot out, or a dirty flame sensor. A flame sensor is fragile but can be easily cleaned using steel wool or fine sandpaper to clean the rod.

A Noisy Boiler

Noises such as banging, knocking or gurgling can be a sign of air in your heat pipes. Air is a common cause of boiler problems. The sounds can also be caused by "kettling", which is a buildup of mineral deposits in the heat exchanger. Bleeding your pipes will usually help with the noises. If not, your heating contractor can use a chemical additive to get rid of the deposits.

Boiler Leak

A boiler leak can come from the pipes leading to and from the boiler, from one of the fittings threaded into the boiler, or from a crack in the boiler. Most boiler leaks require shutting down and often draining the system and will need to be repaired by a heating professional.

Having your boiler serviced annually can help prevent many problems. Soot can build up and components can wear over time, but an annual cleaning and adjustment can keep your unit functioning properly for many years. Always keep the manufacturer's manual handy and if you don't have one, request one from the manufacturer.

Annual Boiler Maintenance

Having your boiler prepared for the upcoming winter is something that can save you significant money while maintaining a better level of heat. In fact, without proper maintenance, you could be spending as much as 10% more on your energy bill than needed. The goal is to have all of the components of the boiler system inspected, ensuring they are in proper working condition and that anything corroded or damaged is replaced.

Although it is possible for you to do the work on your own if you have the right expertise, considering the potential risk involved, you should give serious thought to having a professional complete the maintenance check for you. The following are the standard steps involved to ensure your boiler is at peak performing level:

  • Fireside: This will need to be checked first. With this feature, if there is a high level of dirt buildup, then you will be losing precious energy. For this to be cleaned, the boiler must first be cleaned. Then, the boiler tubes and the furnace are checked to look for any soot or non-combustible deposits, which will need to be cleaned with a brush or vacuum cleaner.
  • Refractory: Typically, a boiler will have some minor repair to be done on this piece. Therefore, erosion or cracking would be checked and then the professional would use the proper repair substance according to the manufacturer recommendation.
  • Waterside: This will need to be inspected next. In fact, it will usually be done immediately upon the boiler cooling down to around 120 degrees. The boiler will be drained with the goal being to have clear tubes without sludge, mud, sediment, or scale. If the water treatment system fails, then the boiler would need to be chemically cleaned by a licensed professional specializing in this area.
  • Burner: Once the burner is open, all the components to include moving parts, oil nozzle, damper, diffuser, and shutter will be checked.
  • Controls: Since these controls are used to monitor the level of water, they need to be in excellent working order. In this case, both the electrical and mechanical operations would be checked. The work on the controls is done after they are reinstalled and mounted but prior to starting the boiler.
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