Who needs a monster in the basement when you have an old furnace?
Tonight’s forecast calls for al low of 19, the day after tomorrow 1 degree (-17 C). This will be an adventure by itself. Hopefully nothing will freeze. Back to the furnace – it turns out the the blower fan was running continuously and that the prior owner turned the fan (and the furnace) off and on from the breaker in the main panel. In his defense he is 96 years old and understandably not getting around to fixing things.
Not knowing anything about old oil furnaces I crawled into the basement. There is only 4 or so of headroom there so brushing the cobwebs aside I was able to get access tot he furnace and find it’s nameplate. It is a Lennox model OS7-140C and with a slight bit of searching I was able to find a service manual online.
With manual in hand I discovered that the air blower is controlled by a “Fan and Limit control” switch that is mounted in the output air stream. Removing the unit and inspection showed that it was past its prime and ready for replacement. Shopping around I found a replacement from www.lennoxpros.com and soon after we had fan control. No need to shut off the furnace from the breaker box.
The fan and limit control measures the heated outlet air from the furnace burner. It controls 2 things. Perhaps the most important is the limit function. If it gets too hot it will shut the furnace down. This could happen if the blower fan stops working or there is an excess of fuel in the burner or anything else that causes an over temperature to happen. A great safety feature.
The other function is to turn on the air blower to move heated air through the ducts and into the house. There is a delay so that heated air goes into the house rather than cold air. And to shut off the air blower when the air temperature in the furnace drops below 90 degrees. This also is to prevent cold air from coming out of the ducts. The shutoff temperature is adjustable but 90 degrees is the most recommended setting.
With the furnace working more or less we discovered that the thermostat was also past its prime and we wanted to be able to program in heating cycles so we replaced the thermostat with a programmable model. More later on the program.
The oil filter holder had a tag that showed that the filter had been last replaced a decade ago, Yikes! Amazon to the rescue and we soon had a new filter installed. The old did not look to bad so I think that no one bother to record when the filter was last replaced. The oil burner is of the type that takes oil from the tank, squirts some oil out the burner nozzle and returns the rest to the tank. In effect the oil in the tank is constantly being passed through the filter and returned to the tank. This is very much like a fuel polishing system and has a tendency to keep the oil in the tank cleaner provided the filter is changed frequently or at least inspected and changed as needed.
The air filter was another story. There is a layer of fiberglass mat that serves as the air filter. This was rather filthy. But sitting next to the furnace was a role of mat so that filter got changed. Also, a “standard” 1″ air filter was placed on the inlet duct. Kinda hanging there but still filtering air.
The inlet duct is sourced from 2 places in the house and the 1″ filter only in in the flow of one of them. We were able to place another 1″ filter over the unfiltered inlet duct so now all air into the furnace is filtered.
I should add the grease cups on the blower fan and motor were filled. I think that regular maintenance had been done at least up until the prior owner was unable to do it anymore. Even so he was doing great for a 96 year old. By the way he moved to a new place and is still going strong.
Heating oil is up around $5 per gallon and we are burning 1.5 to 2 gallons per day depending the the outside temperature. It appears that we have a 420 gallon tank that had only around 70 gallons in it when we bought the house. We put about 300 gallons (ouch!) in the tank and hope to make that cover the winter.
We have programmed the thermostat to match our needs and that has kept our oil usage down. We like to sleep in a cooler house so the thermostat is set for 65 degrees at night. For the most part the oil furnace does not come on at night very often. Some night not at all.
In the morning the thermostat is set for 70 degrees. Heat control is not very precise and even though the thermostat shuts off the furnace there is an overshoot and it can reach 74 in the living room as the house comes up to temperature. 2 hours later when we are up and about the temperature is set to 72 and the living room stays around 72 or 73.
In the evening we drop the thermostat back down to 70 and then at bedtime back to the nighttime 65.
WE can get away with this because we have an electric baseboard heater in the living room that picks up some of the heating load at night and we keep an oil filled electric heater in our room set on low at night. Our room runs 68 all night long. Our room is a small addition on the side of the house that has large 3 exterior walls and much of those walls have minimal if any insulation.
