Air conditioning
Eleven weeks a year, and one of them will be the reason you called
Twin Cities summers are short, humid and genuinely hard on a house. The complaint is almost never the whole house. It is the upstairs, and the cause is almost never tonnage.
Six things we check before anybody mentions a bigger unit
In that order. Most upstairs complaints are solved somewhere in the first three, and the fix is often free.
Return air
Is there enough of it, and is it in the right place? A two-storey house with one central return downstairs cannot move upstairs air, whatever the outdoor unit is rated at. This is the single most common finding.
Filter resistance
A MERV 13 filter in a slot designed for MERV 8 can cost you a quarter of your airflow. People fit them for good reasons and then wonder why the upstairs got worse.
Duct static pressure
Measured on both sides of the air handler. High static means the blower is fighting the ductwork, which costs capacity, adds noise and shortens the compressor life.
Refrigerant charge
Weighed and checked against superheat and subcooling, not topped up by feel. An undercharged system and a restricted system look identical from the thermostat.
Damper and register positions
Half the balance problems in this city are a damper somebody closed in 2011 and forgot. Free to fix and worth checking before anybody quotes equipment.
Attic and envelope
If the attic hatch leaks and the knee walls are uninsulated, the upstairs is being heated from above faster than any reasonable system can remove it.
The cooling numbers, plainly
- Cooling design temperature
- 89°F
- What the system is sized against here. Considerably lower than most of the country, which is why oversizing is so common and so damaging locally.
- Sensible efficiency band
- 14.3 to 16 SEER2
- A short cooling season means the payback on the very top of the range is slow, unless the same unit is also a heat pump.
- Refrigerant
- R-454B
- What new residential equipment ships with. R-410A systems are fine and still serviceable, but the two are not interchangeable.
- Target humidity
- 45 to 50%
- A correctly sized unit runs longer and removes more moisture. An oversized one cools fast and leaves the house clammy.
Cooling questions
Upstairs is always hotter. Do I need a bigger air conditioner?
Almost certainly not. In a two-storey Twin Cities house the upstairs gap is nearly always an airflow and envelope problem rather than a capacity problem: too little return air upstairs, a filter too restrictive for the blower, closed dampers, or an uninsulated knee wall baking the whole floor from the side. Oversizing the equipment makes it worse, because a bigger unit runs shorter cycles and removes less humidity.
What is SEER2 and how is it different from SEER?
SEER2 is the current seasonal cooling efficiency rating. It replaced SEER in 2023 and is measured against a higher external static pressure, which is closer to how equipment behaves in a real duct system. A SEER2 number is roughly 4.5 to 5 percent lower than the old SEER number for the same machine, so do not compare an old brochure to a new one directly.
What SEER2 makes sense in Minnesota?
Our cooling season is short, so the payback on very high efficiency is slower here than in Texas. For most homes 14.3 to 16 SEER2 is the sensible band. Where higher efficiency does earn its money is when the same outdoor unit is a heat pump doing winter work as well, because then you are buying efficiency for nine months instead of three.
What is happening with R-410A and R-454B?
New residential equipment has moved to R-454B, a refrigerant with a much lower global warming potential, as part of the HFC phase-down. Your existing R-410A system is not illegal and does not need replacing, and R-410A remains available for servicing, although the price has been climbing. It matters mainly when you replace only half a system: mismatched refrigerants are not interchangeable.
How often should the outdoor unit be cleaned?
Once a year, in spring. Cottonwood in June is the main enemy in this city and a coil packed with it loses capacity fast. Rinsing the outside of the coil with a hose from the inside out, with the power off at the disconnect, is genuinely a homeowner job and we are happy to show you.
There is a longer version of the upstairs problem inthis piece on airflow.
Let us measure it before we quote it
A cooling diagnostic includes static pressure, return sizing, charge verification and a room by room temperature sweep. You get the readings whether or not you buy anything from us.