AC Repair in Montbello, Denver

Montbello is a far-northeast Denver neighborhood at 5,305 feet, and its most common cooling complaint is not a broken air conditioner. It is a duct system designed to move warm air through a house in winter that is now asked to move cold air through it in July. MoJo Home Services measures the air side before touching refrigerant on a Montbello call. Family-owned since 2009, licensed, insured, EPA-certified. Call 720-807-4050.

Why does a Montbello AC cool the front of the house but not the back?

Because cooling airflow requirements are higher than heating airflow requirements, and the ducts were sized for the smaller number. A furnace delivers its heat with a modest volume of very warm air. An air conditioner needs roughly 350 to 400 CFM per ton to keep the evaporator from freezing and hold the capacity on the nameplate. When cooling gets added to a heating-only trunk, the branches nearest the plenum take what they need and the far runs get whatever is left. In Montbello that shows up as a back bedroom that stays warm while the hallway thermostat reads satisfied and shuts the system off.

What is total external static pressure and why is it measured first?

It is the resistance the blower is fighting, measured in inches of water column with a manometer at two points: between the filter and the blower, and downstream of the coil in the supply plenum. Most residential air handlers are rated at 0.5 inches. Real systems in Montbello frequently read well above that, and every increment above rated drives delivered CFM below the blower table. High static explains weak cooling, a frozen evaporator, short blower life and wide temperature splits all at once, and it costs a few minutes to measure. Charging a system with high static is treating a symptom on the wrong side of the coil.

How much return air does a Montbello system need at 5,305 feet?

More than the same system would need at sea level. Air at 5,305 feet is about 14.6% less dense, so moving the same mass across the coil takes about 17% more volume. A rule of thumb calling for a given free area per ton of cooling is a sea-level rule, and free area is not the same as grille size, since the filter and the grille bars themselves take a share of it. A single central return that was adequate for a furnace is the most common restriction we find in Montbello, and it is usually the cheapest one to correct.

Does the 13.2% gas derate have anything to do with a cooling call?

Indirectly, and it explains a lot of what we find here. At 5,305 feet the derate is 13.2% under the 4% per 1,000 feet above 2,000 feet convention, so a furnace has to be specified with larger input to make its rated output. The blower comes with the furnace, tabled to that heating capacity. When an evaporator coil is later set on that cabinet, the airflow the coil needs and the airflow the blower was chosen to give were never part of the same calculation. Weak cooling with a correct charge often traces straight back to that sequence.

What can be fixed without replacing the ductwork?

A good deal. Adding or enlarging a return, moving to a lower-resistance filter of the same efficiency with more media area, correcting a crushed or kinked flex run, cleaning a coil that has loaded up on the upstream face, sealing return leaks that pull attic air, and setting the blower to the correct speed tap for cooling rather than the tap left over from a furnace install. We measure static before and after so the change is demonstrated rather than assumed. Full duct redesign is a real option in Montbello, but it is the last one, not the first.

Who permits air conditioning work in Montbello?

Montbello is within the City and County of Denver, so replacements and change-outs are permitted through Denver, while straight repairs are not permitted work. If a system is being replaced, insist the load calculation is run for 5,305 feet rather than pulled from a sea-level table, and that return capacity is addressed at the same time. New equipment on an old restriction produces a new version of the same complaint. We work the same corrections in Green Valley Ranch, Central Park and Commerce City.

Nearby towns we cover

If you are comparing notes with someone a town over, we cover AC repair in Green Valley Ranch, AC repair in Central Park, AC repair in Commerce City too.

The opposite season has its own failure list: furnace repair in Montbello.

Background on the service is at AC repair; the full local list is at everything in Montbello.