AC Repair in Roxborough Park, Colorado

The cheapest component in a Roxborough Park cooling system is the one most likely to be taking capacity away from it. A filter is a deliberate restriction placed in the path of the air the system depends on, and at 5,751 feet there is less margin to give away than the filter manufacturer's packaging assumes. MoJo Home Services covers this community of 9,099 in Douglas County. Licensed, insured, EPA-certified: 720-807-4050.

How does a filter reduce cooling capacity in Roxborough Park?

By eating the static pressure budget the blower was designed around. Most residential air handlers are rated to develop about 0.5 inches of water column of total external static pressure, and that budget has to cover the supply ducts, the return ducts, the coil and the filter together. A one-inch pleated filter with a high MERV rating can consume a large fraction of it on its own once it starts to load. Every inch of water column lost is airflow lost, and Roxborough Park needs roughly 475 CFM per ton rather than the 400 CFM per ton reference tables assume, because the air here is about 15.8% less dense than at sea level.

What filter pressure drop is actually acceptable?

The reading that matters is taken across the filter itself with a manometer, one probe upstream and one downstream, while the blower runs. That number is compared to the filter's clean pressure drop and to what remains of the total budget after the ducts and coil have taken their share. A practical rule is to change the filter once its measured drop reaches roughly double the clean value. MERV is a capture rating, not an airflow rating; a four or five inch media cabinet at the same MERV presents far more surface area and a much lower pressure drop than a one-inch filter doing the same filtration job.

Why does particulate loading matter more in some weeks than others?

Because loading is not steady. Dust and airborne particulate along the western edge of Douglas County rise and fall with wind and regional smoke, and a filter can go from acceptable to restrictive inside a couple of weeks rather than over a full season. Airflow then falls gradually, so nobody notices a specific day when the system stopped keeping up. The complaint usually arrives as the house slowly getting warmer through the afternoon, which is exactly what a slow airflow decline produces.

What happens when airflow keeps falling?

Coil temperature follows it down. With less air crossing the evaporator, less heat arrives to boil the refrigerant, so the coil runs colder, the suction pressure drops and eventually the surface goes below freezing. Ice forms, which blocks more air, which drops the temperature further. Left running, the system can return liquid refrigerant to a compressor built to pump vapour. That chain starts at a restriction, and a filter is the most common restriction there is.

What does 15.0% mean at Roxborough Park's elevation?

It is the gas-appliance derate, and Roxborough Park lands on an unusually round one: 5,751 feet works out to almost exactly 15.0% under the NFPA 54 convention of 4% per 1,000 feet above 2,000. Cooling uses the separate density correction of about 15.8%, which is where the 475 CFM per ton comes from. On a three-ton system that is roughly 1,425 CFM of delivered air, and a loaded one-inch filter is entirely capable of putting a system several hundred CFM below it.

What gets measured on a Roxborough Park service call?

Total external static pressure across the air handler, the pressure drop across the filter on its own, delivered airflow, the temperature drop across the indoor coil, and the blower tap or speed setting against what the equipment requires. Then the refrigerant side: superheat, subcooling and condenser approach. Taking the airflow readings first is what stops a restriction being misdiagnosed as a low charge, because a starved coil produces low suction pressure that looks convincingly like missing refrigerant on a gauge.

Where is the filter on a Roxborough Park system, and is there more than one?

It is either in a slot at the air handler or behind a return grille in a wall or ceiling, and occasionally both, which is the problem. Two filters in series double the pressure drop for no additional filtration benefit, and it happens quietly whenever a grille filter gets added to a system that already has one at the cabinet. The other common fault is a filter that does not seal to its track, letting unfiltered air bypass the media and load the evaporator coil directly. A coil fouled from the inside cannot be cleaned from a service panel.

Nearby Douglas and Jefferson County service

We run Sedalia to the south, Ken Caryl north along the hogback, and Highlands Ranch to the east.

Other Roxborough Park-area pages

We work AC repair in Sedalia, AC repair in Ken Caryl, AC repair in Highlands Ranch out of the same dispatch.

If it is the other system acting up instead, start at furnace repair in Roxborough Park.

More on the service itself: AC repair.