The best way to keep heating equipment operating at peak efficiency is with a regular program of expert cleaning, servicing and burner tune-up. This must be done at least once a year, preferably well before the heating season arrives, and it must be done properly. It is not a half-hour job. Furnace manufacturers and the instructors who train servicepersons agree that a proper cleaning and tune-up cannot be done in less than one-and-a-half hours, but often, it takes longer. A boiler may take two-and-a-half hours to clean and service thoroughly.
Here are the tasks that a serviceperson should perform at every annual cleaning and checkup:
Inspect the inside and outside of the chimney.
Clean the furnace flue pipe, barometric damper and chimney base.
Check the condition of the furnace heat exchanger.
Use brushes and a vacuum cleaner to remove soot buildup from the heat exchanger cavities inside the furnace. These are difficult to reach in many furnaces, and it takes patience and perseverance to do a good job.
Clean the furnace fan thoroughly. (This step applies only to warm air systems.) Dirt buildup on the curved blades can reduce the amount of air that is moved, which decreases furnace efficiency. On a belt-driven fan, the motor should be oiled where possible and the belt tension checked. Every two or three years, the fan should be removed from the furnace for a thorough examination and cleaning.
Clean or replace the air filter (forced-air systems only).
Open the burner and clean and lubricate the motor and blower fan if required. If the nozzle is dirty, it should be replaced, not cleaned.
Check the oil pressure in the burner and examine all fittings for leaks.
Clean the oil filter bowl and replace the cartridge if necessary.
Check the performance of the safety features, such as the high limit control and the cad cell flame sensor.
Next comes the equally important job of adjusting the furnace for maximum efficiency. This cannot be done by visual inspection alone; it requires four different measurements made through a pencil-sized hole in the flue pipe, close to the furnace. Do not worry about flue gases escap-ing through this hole. In a properly adjusted furnace, this will not happen.
After the furnace has been running for about 15 minutes to a steady flue temperature, a sample of the flue gases is tested for its smoke content and the draft pressure is checked. Then the final two measurements are taken to determine the steady-state efficiency of the furnace: the temperature and the carbon dioxide or oxygen content of the flue gases leaving the furnace.
All four measurements are essential to the proper adjustment of an oil furnace for optimum combustion performance.
You can tell whether your furnace has ever had such attention simply by looking for a pencil-sized hole in the flue pipe. If there is no hole, then the smoke level and draft pressure have never been tested, and the steady-state efficiency has never been checked. If this is the case, talk to your fuel oil supplier or serviceperson about it.
You may find it helpful to buy an annual furnace service plan. This provides an annual inspection, cleaning and tune-up, and 24-hour emergency repairs. Some plans include parts and labour; others cover labour only, which means you must pay for all parts required. Some firms offer additional insurance for complete furnace replacement, if this is ever necessary. An inspection is required before the service contract is signed. Payment is usually made annually.
There are a number of maintenance tasks that you can do yourself to keep your system working well. But even if you do these properly and regularly, you should still have your system serviced annually by an expert heating contractor.
Other than the sidewall-venting models, which have special venting requirements, all oil-fired furnaces and boilers require a Type A chimney (a double-walled, insulated, prefabricated metal chimney with a stainless steel lining), a masonry chimney lined with a clay flue tile, or a certified stainless steel liner in a masonry chimney. Sizing of the flue liner should be in accordance with the new CSA Standard CAN/CSA-B139-M91, Installation Code for Oil-Burning Equipment.
Although an oil furnace chimney rarely, if ever, needs to be cleaned, it should be checked occasionally for any sign of deterioration. You can check this simply by inserting a mirror in the cleanout opening at the bottom of the chimney on a bright day. Look for broken or flaking flue liner or interior chimney damage, as well as for water running out of the cleanout door or around the bottom of the chimney behind the furnace. Then examine the outside of the chimney. Look for the appearance of a white, powdery efflorescence on the outside of the chimney, spalling or flaking of the bricks, crumbling mortar joints, and wet patches on inside walls behind the chimney.
Certain types of higher efficiency systems, however, have special needs that may require your attention. Check your owner’s manual or discuss this with your installer or serviceperson.
Since the low temperature of the chimney itself is the major cause of condensation inside it, the problem can be overcome by installing an insulated metal liner such as a Type L, double-walled, stainless steel liner, or a single-walled stainless steel liner surrounded by insulation, as per ULC requirements. Check with your provincial/territorial fuel safety division to find out which method it approves.
Remember, the use of a sealed, double-walled stainless steel flue pipe from the furnace to the chimney is a good way to keep flue gases at a high enough temperature to help prevent condensation in the chimney.
There is a simple way to keep your eye on the condition of your furnace or boiler and monitor how efficiently it is using fuel. As we have seen, the heat that is not distributed through your house goes up the chimney, so measuring the temperature of the flue gases leaving the furnace will give a fairly accurate indication of its performance.
For a conventional oil-fired furnace, manufactured during the past 30 years, the maximum allowable temperature for the flue gases leaving the furnace was 400°C (750°F). It is normally between 175°C (350°F) and 280°C (540°F) – the lower the better, of course. To measure this, you will need a special probe-type metal thermometer (Figure 10) that looks like a kitchen meat thermometer but reads much higher temperatures – to at least 400°C (750°F). You can get one from a heating supply company, or ask your hardware store to order one for you from their thermometer supplier.
Figure 10 Flue pipe thermometer
If the flue pipe does not have a hole, make one in the side of the furnace flue pipe about 40 cm (15 in.) from the furnace exit (but not right after a large bend) with a large nail or an electric drill. Insert the flue pipe thermometer probe, the end of which should be somewhere near the centre of the pipe. You can leave the thermometer in the hole permanently if you want – that way, you will not lose it. If you do this, remember to remove the thermometer and clean the probe end of any sooty deposit that may have built up before reinserting it to take a new reading. Turn the thermostat up to the maximum heat and let the furnace run for at least 15 minutes before taking a reading on the thermometer. Don’t forget to turn your thermostat back down after you have finished. Check the temperature before and after the furnace is serviced to see if it has changed. Note any steady increase through the heating season; a rise of 25°C (77°F) represents a drop of about 3 percent in furnace efficiency and a corresponding increase in fuel consumption. In a forced-air heating system, this may mean only that the air filter is dirty and needs to be cleaned or replaced. If replacing the air filter does not reduce the flue temperature down to near where it was before, call your service company.
Cleaning or Changing the Air Filter
|IMPORTANT! Turn off the power to the furnace before opening the furnace access panel to check the filter or fan.|
Few homeowners give the air filter in a furnace the attention it needs. It should be cleaned or replaced once a month. You can get permanent filters made of aluminum or plastic mesh that can be washed in a laundry tub, but these are not as fine as glass fibre filters and do not trap as much dirt.
If you have added an electrostatic air filter to your furnace, you do not need a standard filter as well. Remember that these electrostatic filters also need to be cleaned regularly; check your owner’s manual for instructions.
Except for a superficial vacuuming, there is no maintenance that a homeowner can perform on a direct-drive furnace fan with an internal motor. On belt-driven fans, however, some motors have small oiling cups over the bearings on each end of the motor. These should be given a few drops of oil once or twice during the heating season and in the summer if you use your fan for ventilation or air conditioning. (Check your owner’s manual to find out the type and quantity of oil to use.)
Check the tension of the fan belt by pressing it firmly in the centre with your thumb. You should be able to depress it by about 20 mm (3/4 in.) and no more than 25 mm (1 in.). The tension of the fan belt can be adjusted by loosening the bolts on the motor mount and moving it forward or backward. Make sure the fan and motor pulleys remain perfectly aligned. This job is best done by your furnace serviceperson.
Remove obstructions from ducts, warm air registers and cold air returns, so that air can move freely around the system. Use a special water-based duct mastic to seal any cracks in the duct joints, as described on page 21. At the same time, consider insulating as many of your warm air ducts as you can easily access.
Here are a few things you can do with a hot water heating system:
Insulate hot water pipes.
Once or twice a year, bleed air bubbles out of radiators so that they can fill with water.
Vacuum the radiators.
Check to see that the level of water in the expansion tank is below flood level.
Oil the circulating pump (according to the manufacturer’s instructions).
Allow air to flow freely around radiators: make sure they are not covered by curtains or by ventilated wood panelling, and try to ensure that they are not directly behind furniture so that the heat generated can get into the rest of the room.
Source: Natural Resources Canada (NRCan) - Office of Energy Efficiency