Free HVAC Tune-Up Checklist with Graded Readings

Whatever the rating plate on that furnace says, and nothing else. The plate states a range — commonly something like 30–60°F, 45–75°F or 50–80°F — and the measured rise has to fall inside it. There is no industry-wide range to quote, which is why this form asks you to type the plate figures in rather than printing numbers of its own. Aim near the middle of the range for best performance. Below the minimum, the blower is moving too much air: the supply feels cool to the customer and the heat exchanger can condense and corrode. At or above the maximum, the furnace limit-cycles and the exchanger overheats, which is the failure mode that ends in a crack. Measure the return at the furnace and the supply several feet downstream, so the probe has no line of sight to the heat exchanger and is not reading radiant heat.

Almost certainly yes, and this is the argument worth settling with the label rather than with opinion. Most OEM-grade HVAC run capacitors are marked ±6%, which puts a 45 µF part's acceptable band at 42.3 to 47.7 µF — a reading 5% down at 42.75 µF is inside tolerance and is a pass, not a sale. But ±6% is not universal: ±5% and ±10% parts are both sold, and the tolerance is printed on the can. That is why this builder takes the tolerance as an editable field defaulted to 6 rather than hard-coding it. What a low-but-in-tolerance reading does justify is watching the motor's amp draw, because a weakening capacitor shows up there first.

Above 400 ppm air free in the flue on a central furnace. That is the threshold in the ANSI/BPI-1200 CO thresholds table and it matches the National Fuel Gas Code figure and the ANSI Z21.47 appliance listing limit. Over it, the appliance should not be left in service — shut it down, tag it, and correct the cause. The number people get wrong is the basis: 400 ppm air free is not the same as 400 ppm as measured, and it is not the same as the BPI Building Analyst 26 / 100 / 400 ppm action levels, which are undiluted flue gas from a different document. Air-free CO = measured CO × 20.9 ÷ (20.9 − flue O₂%), so a reading of 87 ppm at 5% O₂ is really 114 ppm air free. Most analyzers show air-free CO directly; this form converts for you if you enter the O₂. Separately, well below the threshold, anything over about 100 ppm air free is worth chasing — that is the level most manufacturers and trainers actually work to.

It depends on the air entering the coil, not on how many years the person answering has been in the trade. The 18 to 22°F rule of thumb only holds around 45 to 55% relative humidity. As the return gets more humid the coil spends more of its capacity condensing moisture and less of it dropping temperature, so the dry-bulb split narrows even though total capacity is normal — a correctly operating system on an 80°F dry-bulb, 71°F wet-bulb return reads about 15°F. Take the target from the manufacturer's chart or from a target-ΔT table using the measured return dry-bulb and wet-bulb, enter it here, and the reading is graded against that. Leave it blank and the split is recorded without a verdict, which is the honest outcome rather than a made-up pass.

The figure on the appliance rating plate. Natural gas furnaces commonly sit near 3.5 inches water column and LP near 10 to 11, but those are common settings, not specifications — two-stage valves have a different figure per stage, and the plate is the authority. Gas control manufacturers publish an adjustment latitude of about ±0.3 in. w.c. from the factory-set rate, so this form treats a reading further off the plate than that as needing a reset. It matters in both directions: over-firing is a leading cause of cracked heat exchangers, and under-firing starves the appliance and drives CO up.

A maintenance checklist records what was done. This records what was measured, and grades it. The two are complementary — this builder still carries the preventive-maintenance task list for the air side, the outdoor unit, gas heat, heat pump defrost and closeout — but the readings are the point. When a customer asks what they paid for, "temperature rise 88°F against a plate range of 45 to 75, limit cycling, blower speed corrected" is an answer. "Heating — checked" is not.

Four things this form makes explicit. Force a defrost rather than trusting the board, and watch it initiate, shift the reversing valve cleanly, terminate on the sensor or timer as configured, and actually drain the melt. Check the reversing valve and solenoid in both modes — a valve that shifts fine in July can hang in a February defrost. Verify auxiliary and emergency heat staging and lockouts against the thermostat configuration, because a mis-set outdoor lockout leaves resistance heat running alongside a perfectly good heat pump all winter with nothing on the equipment to tell the customer. And confirm the outdoor unit is elevated clear of the snow and ice line with an open base pan drain, or it re-freezes its own defrost melt.

Because a switch that has never been tested is a switch that does not work, and this is the one that turns a plugged condensate drain into a ceiling claim. IMC 307.2.3 requires a water-level detection device conforming to UL 508 that shuts off the equipment served — installed in the primary drain line, the overflow line, or in the equipment drain pan above the primary connection and below the pan's overflow rim. Lift the float and confirm the equipment actually stops. Confirming the device is present is not the same check.

No. It is the technician's record of a maintenance visit. Code and standard citations appear to explain why something is checked and where a threshold comes from — they do not certify the installation, and approval rests with the authority having jurisdiction. Manufacturer instructions govern wherever they are more specific than anything printed here.