What a Furnace Tune-Up Actually Includes in Monmouth County

Ask what a furnace tune-up includes and you will get a list of verbs. Inspect, clean, check, tighten, lubricate. Every one of those is real work and none of them tells you whether your furnace is actually alright, because a verb is not a result. A tune-up worth what you paid ends with numbers, and this is what those numbers are and what yours should say.

What does a standard furnace tune-up checklist cover?

Start with the industry baseline. ENERGY STAR's maintenance checklist says a typical check-up should cover thermostat settings, tightening every electrical connection and measuring voltage and current on the motors, lubricating moving parts, inspecting the condensate drain, checking the controls, and watching the start-up cycle to confirm the system starts, runs and shuts off properly. On the heating side specifically it calls for checking all the gas or oil connections, gas pressure, burner combustion and the heat exchanger, and it says plainly why: improperly operating gas or oil connections are a fire hazard, and a dirty burner or a cracked heat exchanger causes improper burner operation.

That is a good floor and almost every company will tell you they do all of it. The trouble is that you cannot check any of it after the fact. Our guide on how often a furnace needs service lays out what a real check-up covers and why it happens yearly. What follows is the other half: the readings that turn that list into something you can hold the work to.

What is static pressure, and why should I ask for it?

Total external static pressure is the resistance your blower fights to push air through the ducts. It is measured with a manometer, in inches of water column, and it is the single most useful number on the report because it describes the duct system rather than the box.

Here is the scale. A normal range is roughly 0.2 to 0.7 in. w.c. Your own equipment also has a maximum static pressure it was designed around, and that number belongs to your specific model, so ask what it is rather than assuming. Now the real readings we have measured on real houses:

• On a Manalapan replacement job, a TrueFlow test before the swap read 0.933 in. w.c., well above that normal range.
• On a Freehold job, other companies were pushing the homeowner to buy a new unit. Static pressure mapping came back over 1 in. w.c. on a unit rated for 0.5, more than double what the equipment was built to work against, and the supply side was essentially a plenum box with flex runs coming off it, old and leaky. What he actually needed was a duct rebuild, not the new unit everyone else was selling him.
• On a Roseland house, the second floor unit measured 1.3 in. w.c. and the basement unit 1.1. The upstairs unit was whistling and obviously struggling.

None of those three houses had an equipment problem. On the Manalapan job the existing cooling equipment was correctly sized for the home's load, and on the Freehold job a Manual J load calculation showed the unit was actually a bit oversized, not undersized. In all three the ductwork was the limit. That is why the number matters: it is the difference between buying a new furnace and fixing what is around the one you have. ENERGY STAR puts a figure on the cost of ignoring it, noting that airflow problems can reduce a system's efficiency by up to 15 percent.

And because the diagnosis was right, the fix moved the number. On the Manalapan job static pressure came down from 0.933 to 0.49 in. w.c., and the system vitals score came back 100 percent, A plus, with all five loss categories scoring zero. On the Freehold job it went from over 1 in. w.c. to 0.55, matching the equipment's rating. On the Roseland house the second floor unit dropped from 1.3 to about 0.75. That is what the number is for. None of it can be shown to you with a sticker.

Where the pressure actually goes

A good technician does not just hand you a total. They tell you which part of the system is eating it, because that is what turns a number into a repair you can price. On that Manalapan job the 0.933 broke down like this:

Read that top to bottom and the story writes itself. The return plenum alone came to 0.343, which is inside the range a whole system is supposed to run at, and it was only one of four components. Those four together are where the 0.933 came from. The return ductwork on that job turned out to be undersized, with some sections completely disconnected once the old system was opened up. A total tells you something is wrong. A breakdown tells you where, and whether the answer is duct sealing, a bigger return, or a different filter.

Where do I find my furnace's temperature rise and gas pressure specs?

These two you can partly check yourself, tonight, without tools. Open the furnace closet and read the rating plate, the metal label on the cabinet. It lists a temperature rise range, usually as two numbers in degrees Fahrenheit, and a manifold gas pressure the furnace is supposed to run at. Both are manufacturer specifications for that exact model.

Temperature rise is the difference between the air going into the furnace and the air coming out. It has to land inside the range on that plate. Too low usually means too much air or not enough fire. Too high means the opposite, and a furnace running above its range is a furnace on its way to tripping a high limit switch and short cycling. Gas pressure at the manifold has to sit at the number stamped on the plate, because too high and too low cause problems that look identical from the thermostat.

So write both ranges down before the visit. Then ask what the measured rise was and what the measured manifold pressure was, and see whether the answers land inside the numbers printed on your own equipment. That one question separates a technician who measured from a technician who did not.

What does airflow in CFM per ton tell you?

Static pressure tells you the resistance. Airflow tells you what actually got through. It gets reported as CFM per ton, and on that same Manalapan job it measured about 313 SCFM per ton, which is very low for that equipment. Low airflow is what turns a correctly sized system into one that cannot keep up, and it is invisible from the thermostat.

This matters more than average in Freehold Township's 1980s and 1990s subdivisions. They are the bulk of the stock there, with about 60.7 percent of Township homes built between 1970 and 1999, and they are mostly two-story four-bedroom colonials. The classic complaint in those houses is a floor that never keeps up, and the classic mistake is treating it as a sizing problem when the load calculation and the duct system are where the answer actually is.

What does a combustion check measure?

The readings above are about performance, and this one is about safety. A combustion analyzer goes into the flue and reads what is actually coming out of the furnace: carbon monoxide in parts per million, oxygen, and efficiency. ENERGY STAR's checklist groups gas connections, gas pressure, burner combustion and the heat exchanger together, and says a dirty burner or a cracked heat exchanger causes improper burner operation. Ask for the carbon monoxide number in ppm, and keep it with the rest of your readings.

What should I do with my furnace tune-up report?

Keep it. That is most of the value and it costs nothing.

• File it where you will find it next fall, with the model and serial number on it.
• Next year, compare the static pressure reading to this year's. A number that climbs season over season means something is closing up: a coil loading with dirt, a filter that is too restrictive, a duct that has come apart.
• If a technician cannot give you a static pressure number at all, you did not get a diagnostic. You got a visual inspection, which is a legitimate thing to buy, but it is a different thing.
• If any reading lands out of range, ask which component is responsible before you accept a recommendation to replace anything. A total with no breakdown behind it is not a diagnosis.
• Ask for a system score if the technician runs software that produces one. On a different Manalapan job, a two-year-old system scored 42 percent, a very low score that matched what could be seen and felt by hand.

When the tune-up turns into a different conversation

Sometimes the readings say the problem is not maintenance at all. Static pressure well over the rating, a return that is too small to enlarge, ductwork that is more flex than trunk: none of that gets fixed by a yearly visit, and no new furnace fixes it either. That is the point where a heating system check-up stops being routine and starts being the first honest measurement anybody has taken of the house.

It is also the moment to be skeptical of a quote to replace the equipment. On both the Manalapan and the Freehold jobs above, other companies had already recommended new equipment. On the Manalapan job the existing equipment turned out to be correctly sized for the home's load. On the Freehold job the Manual J showed it was a little oversized, not undersized. Neither house needed the new box it was being sold.

FAQ

What should a furnace tune-up include?
The ENERGY STAR baseline covers thermostat settings, electrical connections and motor readings, lubrication, the condensate drain, the controls and the start-up cycle, plus gas connections, gas pressure, burner combustion and the heat exchanger. On top of that, ask for five measured numbers: total static pressure and its component breakdown, temperature rise, manifold gas pressure, airflow in CFM per ton, and combustion readings.

What is a normal static pressure reading?
Roughly 0.2 to 0.7 in. w.c. total external static pressure. Your specific equipment also carries its own maximum rating, so ask what that is too. Readings near or above 1.0 mean the duct system is choking the equipment, and we have measured 0.933, over 1.0 and 1.3 on real New Jersey houses.

How long should a furnace tune-up take?
Long enough to take readings and write them down. Rather than timing it, judge it by the output: if you were handed numbers you can compare against your rating plate and against last year, the visit did what it was supposed to do.

If your last tune-up ended with a sticker instead of a static pressure reading, get in touch and we will give you the numbers for your own house. Call (848) 288-1133 to get on the schedule.