I am planning to replace my current AC (3.5 ton Carrier single-stage) and Furnace (5 ton Carrier 2-stage, variable speed), both are 21 years old.
Background
My current AC is not able to keep up with the cooling demand when the outside temp is 90F+ (set point is 75F, indoor temp will climb to 78-80F despite AC running constantly).
My home is 3700 sqft: finished basement (where furnace is located), main level (where thermostat is located), and second level with 3 bedrooms (ducting is in fairly well insulated attic). I live in Northern Utah (95-105F and dry summers).
My main objective is to get an AC that can better handle the hot summers. I am not overly concerned with temperature differentials between floors and do not have the budget to install a leveling system.
I have received quotes and recommendations from several contractors (with a few more coming next week). I have spoken at length with them and have spent several hours reading helpful posts on this forum (thank you!). I am feeling fairly confident in choosing a furnace, but have several questions regarding an AC.
Questions
My current solution is to go with a 4 ton single-stage AC and run the furnace in recirculating mode to help (slightly) with pulling and distributing air throughout the house when the AC is not running.
What are your thoughts?
Background
My current AC is not able to keep up with the cooling demand when the outside temp is 90F+ (set point is 75F, indoor temp will climb to 78-80F despite AC running constantly).
My home is 3700 sqft: finished basement (where furnace is located), main level (where thermostat is located), and second level with 3 bedrooms (ducting is in fairly well insulated attic). I live in Northern Utah (95-105F and dry summers).
My main objective is to get an AC that can better handle the hot summers. I am not overly concerned with temperature differentials between floors and do not have the budget to install a leveling system.
I have received quotes and recommendations from several contractors (with a few more coming next week). I have spoken at length with them and have spent several hours reading helpful posts on this forum (thank you!). I am feeling fairly confident in choosing a furnace, but have several questions regarding an AC.
Questions
- All of the contractors thus far have recommended a 2-stage AC. Based on my engineering knowledge and what I have read on this forum, I do not agree with this. I believe there are two main reasons a two-stage AC is a poor choice: 1) The lower speed of the 1st stage will struggle to push sufficient cold air to the second story and 2) the slower moving cold air will loose much of it's cooling ability as it picks up heat traveling through the ducts in the attic.
- All contractors have recommended a 4 ton AC unit based on the inability of my current 3.5 ton to keep up with demand. Is 4 ton sufficient or should I consider a 5 ton (to match the 5 ton furnace)?
My current solution is to go with a 4 ton single-stage AC and run the furnace in recirculating mode to help (slightly) with pulling and distributing air throughout the house when the AC is not running.
What are your thoughts?
source https://hvac-talk.com/vbb/threads/2240307-2-Story-Home-Single-vs-Two-Stage-AC?goto=newpost
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