I've had multiple contractors out this past week to bid on a new heating/cooling system. The equipment sizing has been very different. I don't know which contractor to trust in terms of sizing.
For reference, we live near Denver. Our house is a 2-story with about 1900 sq ft on those levels, plus an extra 1000 in the basement. Our current system is an 80% AFUE furnace producing 105k BTUs of heat and a 3.5 ton A/C. The furnace has served us well, but the A/C has never cooled the house very well since we've lived there.
The contractors with the most detailed manual J calculations say we need 45k BTUs of heat and 25k BTUs of cooling. They have bid the smallest sized systems (2.5 tons of cooling and between 60-70k BTU heating for 80% AFUE systems).
Most contractors have bid 3 tons (36000 BTUs) of cooling and 80k BTUs at 80% AFUE for heating.
I also had one had bid all the way up to a two-stage 4-5 ton heat pump paired with a 95% AFUE 90k BTU furnace. That contractor says that the two-stage heat pump allows it to pump something close to 2-3 tons of cooling, but could ramp up if necessary. They would expand our supply line to handle the extra airflow (they say the return is large enough). The furnace is comparable to our current one when accounting for efficiency. So, while it sounds large compared to the manual J, it's kept us comfortable.
Wise professional, who do I trust?
For reference, we live near Denver. Our house is a 2-story with about 1900 sq ft on those levels, plus an extra 1000 in the basement. Our current system is an 80% AFUE furnace producing 105k BTUs of heat and a 3.5 ton A/C. The furnace has served us well, but the A/C has never cooled the house very well since we've lived there.
The contractors with the most detailed manual J calculations say we need 45k BTUs of heat and 25k BTUs of cooling. They have bid the smallest sized systems (2.5 tons of cooling and between 60-70k BTU heating for 80% AFUE systems).
Most contractors have bid 3 tons (36000 BTUs) of cooling and 80k BTUs at 80% AFUE for heating.
I also had one had bid all the way up to a two-stage 4-5 ton heat pump paired with a 95% AFUE 90k BTU furnace. That contractor says that the two-stage heat pump allows it to pump something close to 2-3 tons of cooling, but could ramp up if necessary. They would expand our supply line to handle the extra airflow (they say the return is large enough). The furnace is comparable to our current one when accounting for efficiency. So, while it sounds large compared to the manual J, it's kept us comfortable.
Wise professional, who do I trust?
source https://hvac-talk.com/vbb/threads/2228644-Who-to-trust-regarding-sizing?goto=newpost
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