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- Altitude
What 4,660 feet does to heating and cooling.
Furnaces, air conditioners and heat pumps are rated at sea level. Greeley is most of a mile higher. Here is what that changes — and what we do about it.
From a mile up to sea level.
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5,280 ftone mile
Denver
The Mile High City, about an hour south. Air pressure here is roughly 83% of sea level.
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~4,660 ftGreeley
Greeley — where we work
Air is roughly 15% thinner than at sea level. Every cubic foot the burner and blower move carries less oxygen and less mass. Evans, Windsor, Eaton and the rest of our area sit within a few hundred feet of this.
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~2,000 ftthreshold
Where high-altitude rules begin
Above about 2,000 feet, the national fuel gas code and equipment manufacturers call for gas appliances to be adjusted for elevation. Each manufacturer publishes its own high-altitude instructions.
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0 ftsea level
Where ratings are measured
Capacity and efficiency ratings on the box and the nameplate assume sea-level air.
Not to scale. Elevations are rounded; pressure figures are approximate standard-atmosphere values.
No magic numbers
We don't quote a single percentage for "altitude loss". The right setup depends on the specific appliance and its manufacturer's instructions — so that is what we follow, unit by unit.
Five things thinner air touches.
- Gas burners
- Less oxygen per cubic foot means the gas-to-air mix has to be set for this elevation — through orifices, gas pressure or a factory high-altitude kit, depending on the manufacturer. Set wrong, burners run rich, soot up and make more carbon monoxide.
- Heating output
- A correctly adjusted furnace delivers less heat than its sea-level rating. When we size a replacement, we size for the output you will actually get here.
- Air conditioning
- Thinner air carries less heat per cubic foot, so airflow across the coils matters more. We set fan speed and refrigerant charge to measured conditions, not factory defaults.
- Venting & CO
- Clean combustion and a sound vent are what keep carbon monoxide out of the house or building. Every gas service includes a combustion check and a look at the vent.
- Dry air
- High-plains air is dry, and heated winter air is drier still. Humidifiers help homes; for businesses, dry air mostly shows up as static and complaints — worth knowing before blaming the thermostat.
For your house.
If your furnace was installed by someone who treated Greeley like sea level, it may be running rich or short-cycling. A tune-up with a combustion check will tell. When it is time to replace, we size for this altitude and show you the numbers.
For your building.
Rooftop units and unit heaters are set up the same way — to the manufacturer's high-altitude instructions. In shops and ag buildings with big gas heaters, a combustion check is as much about safety as efficiency.
Not sure your equipment was set up for Greeley?
A tune-up with a combustion check will tell you — home or business.