Servicing the pilot furnaces
Pilot furnaces mechanism
The old furnaces are working with the pilot system can be divided into two parts. The drive Belt, and direct belt. The both system have pilot system that should be on 24 hours.
If the call for heat is in place, the gas valve get open and the burner starts. When the furnace heated up, the fan switch get closed and the blower start working. Two things will happen here. First the blower blow the hot air to inside the house, second cool down the furnace. If the thermostat is satisfied, the gas valve get open and disconnect the gas line. With that the burner get off, the blower works until the furnace cool down and the fan switch get open and the blower get off.
We can divide the service in two parts. First a section that the home owner can do it, and the second part that need a certified person.
You Can Do part furnace service
Replacing the filter is most important part of the furnace service. The best is at least every two months change the furnace. However, need to check visually see if the filter needs more often or not. For example if you have animal at the house you should replace the filter more often.
You should check the belt of the blower. If there is crack or is loose normally the best way is to replace the belt. The information is on the belt. You can have them from Home Depot, Canada Tier, Rona and so on
Lubricating the motor
This type of motor has two shafts and two bearings both need lubricating. Need to note, not too much oil are necessary. There is spot for lubricating with a cap. First need to clean the are and few drops every year in August is the best.
With a vacuum you are able to clean the blower. It is better to take out the blower then vacuum it.
Service part need to do by certified person
When the thermocouple is hot produce us a millivolt electricity. There is a test called “Open Circuit Test” we should take out the thermocouple out of the gas valve while the pilot is still on and measure the electricity, if it produces 17-32 millivolt, then the thermocouple is working fine, if not the thermocouple need to replace.
When the thermocouple connect to the gas valve (closed circuit test), the thermocouple shall have 8-17 millivolt electricity.
The final test need to be done for the old furnaces tune up is Turn Down Test
When the thermocouple is hot, we blow out the pilot. We measure the time and listen to the gas valve. If we heard a click, which turn off the gas valve, look at the time. If the time is less than 180 second and the measured the millivolt is 2 millivolt to 6 millivolt then the gas valve it working fine. Otherwise the gas valve need to replace.
The gas valve adjustment
The gas valve gas pressure need to be measured, in and out. The inlet gas pressure is about 11” of water column (max of 14’’) and at least 6” WC. If not the gas line must be inspect and the pipe sizing must be reviewed.
The outlet gas pressure must be around 3.5”WC if not must be adjust it.
The inlet power to the transformer should be 120 volt and the outlet should be 24V (practically 27V)
If not or too much gap should replace the transformer.
Blower motor test
Put the Amp meter’s clamp around the hot line of the blower motor and measure the Amperage in two ways. First turn off the on-off switch for the furnace and turn on the switch and measure the start-up power, it should be around 20 amp then turn to 7 to 8 amp. If it is not like this the motor blower has a problem.
For more info please visit us at: www. Bbbplumbing.ca or call us at: 587.433.3335