Furnace Repair in Green Mountain, Lakewood CO

Green Mountain is the only neighborhood we cover on the metro floor that sits above 6,000 feet, and at 6,020 feet a gas furnace here gives up 16.1% of its rated input. A 100,000 BTU/h nameplate puts in about 83,900 BTU/h here; an 80,000 BTU/h unit, roughly 67,100. The rest of Lakewood sits 502 feet lower at 5,518 feet and derates 14.1%, so one city contains two different sizing answers and this hillside holds the harder one.

Why does one Lakewood address need a bigger furnace than another?

Because the derate follows the ground, not the city limit. Green Mountain stands 4,020 feet above the 2,000 feet at which gas equipment is rated, against Lakewood's 3,518, and at 4% per 1,000 feet that is 16.1% versus 14.1%. Two points sounds academic until it is applied: on a 100,000 BTU/h furnace it is 2,000 BTU/h of input, and on the cold end of the season that is the difference between a system that recovers overnight and one that slowly loses ground. A contractor working from a lower Lakewood job sheet, or from a nameplate copied off the outgoing unit, imports a number that was never right for 6,020 feet.

Why does a hillside split-level heat unevenly here?

Multi-level floor plans put the thermostat on one level and most of the return air on another, and warm air stacks toward the top of the house on its own. The furnace satisfies the thermostat, shuts down and leaves the lowest level several degrees behind. At sea level a slightly oversized furnace papers over that. At 16.1% down there is no surplus to paper with, so the imbalance shows. The real fix is rarely a bigger furnace: it is return air on the level that is short of it, damper balancing across the trunk, and in some houses a two-stage furnace whose long low-fire runs give the air time to mix rather than blasting and quitting.

Why does my furnace lock out when the wind comes off the foothills?

Green Mountain sits directly in the path of downslope wind coming off the Front Range, and sidewall vent terminations are sensitive to it. A condensing furnace will not open its gas valve until the inducer pulls a vacuum strong enough to close a proving switch, and the setpoint on that switch is a small fraction of an inch of water column. A gust pressing on the exhaust termination is enough to collapse the signal, so the board locks out. The wind drops, and by the time anyone looks at it the unit restarts and tests fine. Termination height, clearance from the corner of the house and the condition of the screen are what get inspected on those calls, not the switch itself.

What does short cycling actually cost at 6,020 feet?

Short cycling on this hill usually starts as an attempt to outrun the 16.1%. Someone sizes up two nameplate steps, the furnace then satisfies the thermostat in a handful of minutes, and every cycle is a full heat-and-cool sweep on the exchanger plus one more ignition on the igniter. Parts wear by cycle count as much as by run hours, so an oversized Green Mountain furnace consumes igniters and stresses the exchanger while delivering less comfort than a correctly sized one. The right correction for a 16.1% derate is one size up on derated output with the duct system checked to carry the extra air.

What should I check before calling about no heat in Green Mountain?

Thermostat set to heat with fresh batteries, furnace breaker on, blower door closed hard against its switch, clean filter. Then watch one attempt. Igniter glows and nothing lights: gas supply, gas valve or pressure switch. Burner lights and drops out in about seven seconds: flame sensing. Burner runs but no air moves: blower or capacitor. Nothing at all on a windy night, with the unit running fine an hour later: look at the outside terminations for ice, snow or a wind-loaded screen before assuming a board failure.

Is an older Green Mountain furnace worth repairing?

Often. Igniters, flame sensors, capacitors, pressure switches, inducers, gas valves and boards are all economic repairs on a structurally sound furnace, and the only hard stop is a breached heat exchanger. If the unit does need replacing, size it on the 0.839 altitude factor for 6,020 feet rather than matching the outgoing nameplate, which on this hillside was frequently selected against Lakewood's lower figure. Ask for the static pressure reading at the same time, because a hillside house with long duct runs to a lower level often needs duct work more than it needs equipment.

Who permits the work, and where else nearby do you go?

Green Mountain is part of Lakewood in Jefferson County; replacement is permitted work and component repairs generally are not. We run this neighborhood together with Golden at 5,676 feet and Morrison at 5,764 feet, both several hundred feet below the hill, which is exactly why the truck carries more than one orifice set for the same nominal furnace.

Where else we work

The same trucks run furnace repair in Lakewood, furnace repair in Golden, furnace repair in Morrison on the same rotation.

For the other half of the system, AC repair in Green Mountain.

Wider view: furnace repair, or everything in Green Mountain.