The house was built in 1975–I doubt the furnace was replaced in 1989.
The Model #100D indicates to me this is an older furnace. If it is original
1975 sounds better to me than 1989. That’s why I suggested calling
BDP (Bryant-Day/Night-Payne) for clarification… and that is also why
the company publicizes that phone number.
This unit has 100,000 BTU’s and was manufactured in 1973.
I also have an optional phone number…905-672-0606
This is one ancient furnace. If this oldie were on my inspection, this is what I’d be noting in my report…
The heating system was paced through it’s normal sequence of operating modes, with no obvious defects noted at time of inspection. However, due to systems age, it is clearly beyond it’s life expectancy, and replacement should be considered. Until then, I recommend annual maintenance and a heat exchanger evaluation from a licensed HVAC contractor.
Trying to use model numbers to determine manufacture dates will get one close, as will using the ANSI date. However, model numbers typically indicate the date that the model was introduced to the buying public, not when that specific unit was actually manufactured.
In 1945, Dresser Industries acquired Payne and Day & Night. Bryant was already a part of Dresser Industries. In 1949, Payne, Day & Night, and Bryant bought themselves out of Dresser Industries and formed Affiliated Gas Equipment (AGE). Carrier purchased AGE in 1955 and then formed the BDP Company in 1974 from Bryant, Day & Night, and Payne. United Technologies bought Carrier in 1979 and Payne separated from BDP in 1996 to form Payne Heating & Cooling but is still owned by Carrier. However, each company is its own company, doing its own research and manufacturing except as might be contracted with other companies. So Carrier doesn’t really “manufacture” Bryant, Payne, and Day & Night.