Thank you HVAC-Talk for having this forum.
I'm trying to educate myself as I near the time to having a new furnace & A/C installed. The current furnace is 100k BTU (I think - its a Rheem Criterion 4 burner) and the A/C is 3 tons.
Based on everything I've read here, the furnace is probably oversized by a good bit (i.e. the guys in Canada and Minnesota possibly oversized with 60k BTU).
Here is what I come up with on sizing:
1) Observation of current furnace:
At 32°F outside (per HVAC-Calc the low temp for our area is 10°F) and inside set to 69°F, it runs for 5-6 minutes, waits 13-15 minutes, then does it over again.
2) HVAC-Calc estimates:
Infiltration set to 'average': 25.5k cool and 44.2k heat
Infiltration set to 'excellent': 23.1k cool and 34.6k heat
(house is standard vinyl-sided split-foyer built in 1992 with a vapor barrier, but a few leaky spots.)
Can the real-world observation be extrapolated to indicate proper sizing or validate the HVAC-Calc result?
How does a consumer know if the load calc done by a contractor is correct? Even with my (pretty good I think) data in HVAC-Calc, just the change of opinion on infiltration makes a big difference in result. I'm not trying to be a PIA customer, just improve my odds of getting the right thing.