Commercial HVAC preventive maintenance checklist: a free PDF inspection and PM sheet for rooftop units, built on ASHRAE/ACCA Standard 180

Published September 5, 2026 · Updated November 9, 2026 · Checked against ANSI/ASHRAE/ACCA Standard 180, OSHA 1910.28 and the EPA 2026 leak-repair rule in September 2026

• Free. The download links come by email.
• Deepsel is our product. It's free estimate, invoice and scheduling software for contractors (scheduling, quotes, invoicing, card payments, with service plans on the $29 Pro plan), and the section before the FAQ says where this checklist fits in it.
• The checklist does not replace the manufacturer's service instructions, the site's written sequence of operation, or safety training. The roof safety block is the OSHA floor, not a substitute for your company's fall-protection program.

A commercial HVAC preventive maintenance checklist (PM checklist) is the task list a technician works through on each scheduled visit to the rooftop units on a commercial building, with every reading written against a target: filters, belts, coils, condensate, electrical, refrigerant, economizer, gas heat, controls and cabinet. This one is an inspection and PM template for packaged rooftop units, built on ANSI/ASHRAE/ACCA Standard 180, and it fits a six-unit roof on one page.

Scope: packaged rooftop units, split systems, exhaust fans and make-up air on small commercial buildings. Chillers, boilers, cooling towers and built-up air handlers are not on it. Boilers have their own sheet, the boiler maintenance checklist.

Get it three ways: make your own copy in Google Docs (lands in your Drive), download the Word version (.docx), or download the PDF. Pick a format, enter your email and I'll send the links. Five pages on US Letter: the roof sheet, then a four-page per-unit detail sheet you print once per unit at the spring and fall startups, listed page by page below. The residential version is the HVAC maintenance checklist, and every free checklist in the set is listed on the checklists page.

I built this because the checklist that ranks first for this search is two pages of checkboxes,²⁵ and the others are written for facilities managers (change the filter, call a contractor). None of them has a place to write a subcooling reading or a minimum outdoor-air position.

What is in the preventive maintenance and inspection PDF, page by page

The PDF is five US Letter pages, 199 KB, exported straight from the Google Doc, so the three formats carry the same text. It is a print file, not a fillable form: print it and write on it, or open the Google Docs copy or the .docx when you would rather type. Page 1 is the visit record, one sheet per roof per visit. Pages 2 to 5 are Appendix A, the per-unit detail sheet, printed once per unit at the spring and fall startups.

Sections A to J are 47 task rows in three columns: Task, Reading / target, Result. Result is three boxes, OK, Cleaned, Quote. Reading / target is where the number goes, and 27 of the rows have a blank for one. Five of those carry a printed range next to the blank: split 16 to 22 °F, voltage imbalance under 2 percent, TXV superheat 5 to 15 and subcooling 8 to 14 with condensing 15 to 20 °F over ambient, flame sensor 0.5 to 10 microamps, gas manifold 3.2 to 3.8 inches of water column on natural gas and 10.5 to 11.5 on propane. Four more rules of thumb (belt deflection of 1/64 inch per inch of span, trap depth double the static, a capacitor outside its label tolerance, CO under 100 ppm air-free) are written into the task text. The remaining 20 rows are look-and-decide items, blade seals closing without daylight and the like, and get the Result boxes only. The print note on page 2 says which sections to run: spring startup A to G and I to K, fall startup A to D and F to K. So the economizer, F, gets both startups and the gas heat section, H, waits for fall.

PM checklist, preventive maintenance checklist, inspection checklist: same file. The roof sheet is the inspection half, readings and findings on every unit in an hour or two. The detail sheet is the PM half, the tasks, with the frequency printed in each section heading. And the template, meaning the thing you put your logo on and change the rows of, is the Google Docs copy or the .docx; the PDF is what comes out of the printer.

Before writing this one I read the PDFs that rank for the same search. Most are two pages of checkboxes.

None of the five has a place to write compressor amps against RLA or a subcooling number. The EPA form is an indoor-air-quality walkthrough from an EPA building guide, written for an owner touring a mechanical room, and it has no nameplate block or frequency column. The one form I found with both is a four-page Scribd upload with a Freq. column and an equipment data block, and downloading it takes a Scribd subscription.³⁰ That is why this one carries a unit header and prints the frequency in every section heading.

What is ASHRAE/ACCA Standard 180, and why build a checklist on it?

ANSI/ASHRAE/ACCA Standard 180 is the published minimum for inspecting and maintaining HVAC in commercial buildings. The Department of Energy's Better Buildings program describes it as establishing "minimum HVAC inspection and maintenance requirements that preserve a system's ability to achieve acceptable thermal comfort, energy efficiency, and indoor air quality in new and existing commercial buildings."² The 2018 edition is current.³ It does not cover single-family houses or multifamily buildings of three stories or fewer, which is why the residential checklist is built on ACCA Standard 4 instead.¹

The useful part of the standard is Section 5: 25 tables, one per equipment type, each listing inspection and maintenance tasks with a frequency. The table numbers below are from the 2012 edition, the only free public copy; the 2018 revision reorganized the Section 5 tables, so its numbering differs. Rooftop units are Table 5-22, with 27 tasks from "check for particulate accumulation on filters" (quarterly) through belts, drives and coils (semiannually) to contactors, refrigerant temperatures, dampers and the combustion section (annually). Air-side economizers get their own Table 5-12, fans Table 5-14, furnaces and combustion unit heaters Table 5-16, and controls Table 5-9, which includes the line most shops skip: "check time-of-day schedule to confirm consistency with facility operation," semiannually.¹

Two other clauses matter to a contractor more than the tables. Section 4.3 says that "execution of the task shall be documented and archived for future reference." And Section 4.2.2.d, on what to investigate when a unit keeps failing inspection, lists "insufficient time budgeted for tasks" right after poor field practices.¹ A checklist tied to a published standard makes the scope of a quarterly visit defensible when a property manager asks what they paid for. The commercial maintenance contract template names Standard 180 as the minimum in its Section 3.2, and this checklist is the sheet that delivers that clause.

How often should commercial HVAC be maintained?

Quarterly visits with filter changes at every visit is the working cadence for rooftop units, with the spring and fall startups as the two deep inspections. Standard 180's minimum frequencies are lower for most tasks, so a quarterly program exceeds the standard on belts, drains, electrical and controls. A tech who does mostly rooftop work put it this way when a residential contractor asked what to bid on three heat-pump RTUs: "4 visits per year should be standard also. 2 visits being in depth inspections of the units (heating/cooling startups for the season) and the other 2 simply a basic operational check. Change the filters every visit."⁵ That is the cadence this checklist assumes.

Sites push the cadence up, and the reason is usually on the ground next to the building. A tech with 12 rooftop units at one account washed the condensers twice a year until a new manager asked why: "I pointed to two Cottonwood next to their parking lot. 'Those.' When I went for winter inspection, the trees were gone."²² The roof sheet has a "roof conditions" line so those reasons end up in the customer's file, where they justify the fourth visit.

Does the maintenance pay? The federal O&M Best Practices Guide puts preventive maintenance at "12% to 18% cost savings over reactive maintenance program," and adds that facilities running purely on breakdowns "could save much more than 18%."¹⁹

The roof sheet: one row per unit

Page 1 is the sheet the tech carries: a site header, the safety block, one row per unit with the readings the office needs without opening the detail sheets, and a sign-off. Seven rows fit, six rooftop units and a line for the exhaust fan or make-up air unit. On a bigger roof, print two.

The rule printed above the table: fill every cell, even when the answer is OK. A blank cell reads as "not checked" to the customer, to the landlord who wants the report under the lease, and to the next technician.

The per-unit detail sheet, section by section

Appendix A is printed once per unit and holds the readings: a Task column, a Reading / target column with a blank for the number and, where the trade has a rule of thumb, the range printed next to it, and a Result column of OK, Cleaned and Quote boxes. The targets are trade rules of thumb from published sources; the manufacturer's charging chart, nameplate and manual override them for the unit in front of you, and the sheet says so at the top.

A. Filters and airflow (every visit)

Split is the reading the roof tech actually leans on. In a thread asking what a real rooftop maintenance includes, the longest answer was a list ("Filters, belts, amp draws on all motors/compressors. Clean both coils, check incoming voltage, check caps, temp split, check contactors for pitting if possible"), and a second tech explained why gauges stay in the bag on a healthy unit: "If your airflow is good and your coils/filters are clean, temp split is enough for me... I don't see the need to access the system unless something seems fucky."⁴ Split and amps on every unit, every visit; the refrigerant section when they disagree with the target. When the gauges do come out, the refrigerant PT chart on the HVAC cheat sheet covers R-22, R-410A, R-32 and R-454B, with separate bubble and dew columns for R-454B.

B. Belts, sheaves, motors and bearings (check every visit; replace belts annually)

Belts are where most rooftop checklists print a myth. Amperage does not set belt tension. HVAC School's Bryan Orr, summarizing a long argument among experienced techs, quotes Browning's rule instead: "Ideal tension is the lowest tension at which the belt will not slip under peak load conditions," and gives the field method, "a deflection of 1/64 of an inch for every 1 inch of distance between the two pulley centers."⁹ The same article carries two warnings that belong on a PM sheet: the adjustable sheave changes fan speed, "NOT TENSIONING," and "all alignments must be done using the belt groove, not the outside of the sheave as they all vary in thickness."⁹ The sheet asks for span, deflection and force, and re-checks motor amps after the adjustment, which is the one thing amps are good for here.

C. Coils and condensate (every visit; clean condenser coils at spring startup and as the site needs)

D. Electrical and drives (every visit; capacitors and contactors measured at least annually)

E. Refrigerant circuit (spring startup, and whenever the split or amps look wrong)

On refrigerant regulation, the sheet carries a note because the rule changed this year and most of the summaries online get it wrong for rooftop units. From January 1, 2026, EPA's leak-repair requirements under the AIM Act apply to appliances holding 15 pounds or more of an HFC refrigerant, with a 10 percent annual leak-rate threshold for comfort cooling and repair within 30 days.¹⁷ The same fact sheet exempts appliances "used in the residential and light commercial air conditioning and heat pumps subsector," defined as equipment "for cooling air in individual rooms, single-family homes, and small commercial buildings."¹⁷ The 2024 final rule spells out who is in that subsector: ducted central air conditioners, mini-splits and "packaged rooftop units," with no tonnage cutoff, and EPA turned down a request to pull rooftop units over 5 pounds back in.³³ Older R-22 equipment stays under Section 608, which starts at 50 pounds. So a 10-ton R-410A packaged unit on a strip mall is outside the rule, whatever its charge; where the rule bites in comfort cooling is chillers of 15 pounds or more. Log every pound added regardless; leak rate is calculated from your log.

How do you check an economizer on a rooftop unit?

Stroke the dampers fully open and closed from the controller's test mode or a BAS override, confirm the outdoor and return dampers move opposite each other and close without daylight, verify the minimum outdoor-air position by measurement with the unit running and not economizing, check the sensors against a calibrated thermometer, and confirm the changeover setpoint matches the site sheet. That is section F of the detail sheet, and it is the section most likely to find something.

The failure numbers are bad enough that PNNL's federal O&M guidance says outright that "a run-to-failure maintenance approach is not appropriate for air-side economizers, and regular preventive maintenance must be performed."⁶ E Source's guide for utility customers puts it in one line: "about half of all newly installed economizers don't work properly, and their problems increase as they age," and cites a survey of California contractors who found economizers disabled because their dampers would not move "30% to 40% of the time."⁷ The expensive direction is stuck open. The same guide's simulation of a Phoenix office found a damper frozen wide open "could add as much as 80% to that building's summer peak load."⁷ When a new tech posted a low-split call that gauges could not explain, the commercial answer was blunt: "It's probably the economizer. Your damper is full open. You're pulling in too much makeup air, and the unit can't keep up."²⁴

Minimum position is the part every generic checklist reduces to a checkbox. MicroMetl, which builds the economizer sections on a lot of the units you will open, explained in January 2026 why the blade angle is useless as a setting: airflow does not rise in proportion to blade rotation, and "often, airflow at 50% open and 100% open is nearly identical." Their conclusion: "The only reliable method is measurement."⁸ So the sheet has a line for the design minimum in cfm or percent and a line for what you found. If the site has no design value on file, that is a finding: the customer is either paying to cool outdoor air all summer or under-ventilating. PNNL's own checklist puts "confirm outdoor-air dampers are at the minimum outdoor-air position when HVAC is operating but not economizing" on the quarterly list.⁶

G. Cabinet, curb and roof (every visit)

The screws line is there for a reason a commercial tech gave in one sentence: "Have fun pulling 30 screws out of a carrier rtu to do a basic maintenance, putting them all back, then doing it 11 more times for the rest of the units on the roof."²³ Missing screws on arrival tell you whether the last contractor opened the unit at all.

H. Gas heat section (fall startup)

I. Controls and thermostat (every visit)

J. Exhaust fans and make-up air units (every visit, where listed in the contract)

Exhaust gets skipped because it is never the reason for the call. It is also what explains the kitchen that is 90 degrees with the rooftop unit running flat out. A tech who does rooftop-and-exhaust PMs at restaurants listed economizers, exhaust fans and the BMS trend as the three things that separate a commercial PM from a residential one: "If it has an economizer you should check the dampers/linkages and test operation. You might have an exhaust fan that also needs checked. If it's connected to a BMS you should look at trends and make sure it's communicating properly."⁴

Roof safety before the first panel comes off

The safety block at the top of the roof sheet is short on purpose, so it gets read. Its longest line is the OSHA rule for low-slope roofs, 29 CFR 1910.28(b)(13), because it is the rule most often misremembered as "you're fine if you stay away from the edge." The regulation has three zones. Within 6 feet of the edge, a guardrail, safety net, travel restraint or personal fall arrest is required. From 6 to 15 feet, the same systems are required, but "the employer may use a designated area when performing work that is both infrequent and temporary." At 15 feet or more, no fall protection is required for infrequent, temporary work, provided the employer enforces "a work rule prohibiting employees from going within 15 feet (4.6 m) of the roof edge without using fall protection."¹⁸ Quarterly PM on a unit set 4 feet from the parapet is not infrequent, and the parapet is not always tall enough to count as a guardrail. That decision belongs to your safety program, which is why the edge rule has its own line in the safety block, citation printed, so the call gets made before a panel comes off.

The rest of the block is the roof-specific stuff: ladder at 4:1 and tied off, skylights and soft spots located, the disconnect opened and tested dead before a compartment is opened, the gas shutoff located and a CO meter on the tech before the burner section runs, and the site contact told which units are going off and for how long. A dining room at noon should hear that RTU-3 is going off before it notices.

What the tech writes down, and why the readings matter

Most rows on the detail sheet ask for a number, and where the trade has a range it is printed next to the blank. The blank is the product. A checkmark says the tech looked; a number says what they saw, and a column of numbers across four visits says where the unit is going. Compressor amps creeping up against RLA, or a split that was 20 in April and 15 in July with clean coils, is a compressor or a leak announcing itself a quarter early, at contract rates instead of emergency rates.

The same numbers protect the shop. Standard 180 requires that task execution be "documented and archived for future reference,"¹ and a landlord's lease usually requires the reports. When a compressor fails in year six, the sheet showing amps, subcooling and a clean coil at every visit is the difference between "you maintained it, the compressor failed" and "you never opened the panel."

The honest objection is time. The first reply in the thread I quoted earlier was "Filters, belts, clean the coils, bump the contactors and go to lunch," and the reply below it was the reason: "Some accounts have so few hours you barely have time to jump it out."⁴ A checklist does not create hours. What it does is make the mismatch visible, which is the advice one tech gave in the same thread: "I always ask what was sold and how much time was allocated per unit. If the two don't match up I ask what they want change either time or scope."⁴ That is exactly the investigation Standard 180 prescribes when a unit keeps failing inspection, "insufficient time budgeted for tasks,"¹ and it is why the roof sheet records arrival and departure time. The contract template's pricing note says the same thing from the other side: cost out one quarterly visit honestly and multiply by four before you sign.

The other free checklists in this set cover the residential side of the same job: the HVAC inspection checklist for a first look at a system you have never seen, the tune-up checklist for the split-system visit, the heat pump checklist, and the equipment maintenance log for the per-unit history. The preventive maintenance schedule template is the annual calendar that says which sites get which visit in which month.

After the quarterly PM: where the roof sheet's data goes

The roof sheet is one equipment record per RTU in Deepsel, our free estimate, invoice and scheduling software for contractors: unit tag, make, model, serial, tons, refrigerant and filter sizes, captured from the nameplate on the phone. Each quarter's readings go on a checklist the tech fills in on the visit from the phone, flagged when one is outside the range you set, and stay with the photos on that visit's job. The next tech can pull up last quarter's compressor amps and split there before opening the panel, though Deepsel doesn't chart the last four visits on the unit yet. Fourteen sites on quarterly contracts is 56 visits a year on the dispatch board, and each one is invoiced to the property manager from the phone. All of that is on the Free plan: scheduling and dispatch, quotes, invoicing, card payments, and customer and equipment records, with 30 estimates and 30 invoices a month for your whole team.

If the sites are on PM contracts, the service plans module on Pro ($29 a month, unlimited users, estimates and invoices) keeps visits owed against visits delivered per covered unit and reminds the site contact by email when a quarterly visit comes due, so the visit skipped in May because the hatch was locked shows up as owed instead of forgotten. The module is built for membership-style programs: residential and light-commercial agreements billed to a card on file or invoiced. A restaurant with five rooftop units on a quarterly plan fits that shape. A distribution center with forty units and a facilities team wants a maintenance management system instead, and the maintenance agreement software page says where that line is.

Step one costs nothing. Run the shop on Deepsel Free, no card to start, and keep the contract book beside it in the free maintenance agreement tracking spreadsheet: one row per agreement, the equipment covered, the visits owed and delivered with dates, the renewal date and payment method. How to track HVAC maintenance agreements explains the columns. For residential members the contract is the HVAC maintenance agreement template; for the roofs on this page it is the commercial contract template, whose Section 3.4 bills a return trip when the hatch is locked on a confirmed date. That clause only helps if the confirmed date and the no-access were logged against the visit. A sheet holds a small book fine. You outgrow the pair when the shop sends more than 30 estimates or 30 invoices a month, or the sheet's hand-work (reminders, renewals, visits owed) starts eating the office's week. Then move up to Pro: the sheet's customers import in one upload, and each plan is set up once in the service plans module.

Frequently asked questions

How often should commercial HVAC units be serviced?

Quarterly is the working cadence for rooftop units, with filters changed at every visit and the two big inspections at the spring and fall startups. ANSI/ASHRAE/ACCA Standard 180 sets the floor lower for most tasks: filters quarterly, belts, drives and controls semiannually, most other rooftop-unit items once a year. Restaurants, retail with long hours and roofs near cottonwoods or grease exhaust need the quarterly visit; a small office with two units can run on the two startups plus filter changes.

What does a commercial HVAC maintenance checklist include?

Per unit: filters and airflow, belts and sheaves, motor and compressor amps, condenser and evaporator coils, condensate trap and pan, contactors and capacitors, refrigerant pressures with superheat and subcooling, the economizer (damper stroke, seals, minimum position, sensors), the gas heat section in fall, thermostat or BAS setpoints, cabinet and curb, and the exhaust fans and make-up air listed in the contract. Per site: a roof safety block and a sign-off. Each reading gets a written value, not a checkmark.

What is ASHRAE Standard 180?

ANSI/ASHRAE/ACCA Standard 180, Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems, is the published minimum for maintaining HVAC in commercial buildings. It lists inspection and maintenance tasks with a frequency for each, by equipment type, in 25 tables (rooftop units are Table 5-22 and air-side economizers 5-12 in the 2012 numbering; the current 2018 edition reorganized the tables). It does not apply to single-family homes or multifamily buildings of three stories or fewer.

Does the 2026 EPA leak-repair rule apply to rooftop units?

No. From January 1, 2026 the rule (40 CFR 84.106) covers appliances holding 15 pounds or more of HFC refrigerant, with a 10 percent annual leak-rate threshold for comfort cooling and repair within 30 days, but it exempts the residential and light commercial air conditioning and heat pump subsector, and EPA counts packaged rooftop units, split systems and mini-splits in that subsector with no tonnage cutoff. So a rooftop unit is outside the rule whatever its charge. In comfort cooling the rule reaches chillers of 15 pounds or more, and R-22 equipment of 50 pounds or more stays under the Section 608 rule. Log refrigerant added on every visit anyway; the customer's insurer and the next contractor will ask.

What MERV filter should a rooftop unit use?

MERV 8 is the minimum ASHRAE 62.1 requires upstream of any cooling coil or other wetted surface, and it is what most packaged units ship with. MERV 13 is common where the owner or tenant asks for it after the pandemic-era guidance, but it raises static pressure, so check total external static against the nameplate after the change and drop back if the blower cannot make the airflow. Record size, quantity and MERV on the sheet so the next visit arrives with the right box.

Is there an Excel or fillable version?

Google Docs, Word and PDF, no Excel, and the PDF is a print file rather than a fillable form. A checklist is a sheet the tech fills on the roof, so it lives in a document: the copy link puts an editable version in your Drive and the .docx opens in Word. The spreadsheet-shaped part of the job is the schedule, which unit is due in which month, and that already exists as the free preventive maintenance schedule template: one row per unit, a quarterly frequency, the done dates typed into the month columns, in Google Sheets, Excel and PDF. The contract-level ledger, visits owed and delivered per agreement with the renewal date, is the maintenance agreement tracking spreadsheet.

How many pages is the PDF, and what do I print for a visit?

Five pages, US Letter. Page 1 is the roof sheet, print one per roof per visit. Pages 2 to 5 are the per-unit detail sheet, print one set per unit at the spring and fall startups, so a six-unit roof at a startup is 25 pages, and a summer or winter check is page 1 alone unless a unit's split or amps send you to the detail sheet.

Sources

1. ANSI/ASHRAE/ACCA Standard 180-2018, "Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems," ASHRAE and ACCA, 2018. This is the current edition (ashrae.org, read September 24, 2026). The task frequencies, table numbers (5-9, 5-12, 5-14, 5-16, 5-22) and section numbers (2.2.1, scope excludes "single-family houses or multi-family structures of three or fewer stories above grade"; 4.2.2.d, "insufficient time budgeted for tasks"; 4.3, "execution of the task shall be documented and archived for future reference") quoted on this page come from the 2012 edition, the only free public copy, hosted by Philco Air Control, philcoaircontrol.com, read September 5, 2026. The 2018 revision reorganized the Section 5 tables, so its numbering differs.
2. U.S. Department of Energy, Better Buildings Solution Center, "ANSI/ASHRAE/ACCA Standard 180: Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems" - "establishes minimum HVAC inspection and maintenance requirements that preserve a system's ability to achieve acceptable thermal comfort, energy efficiency, and indoor air quality in new and existing commercial buildings." betterbuildingssolutioncenter.energy.gov, published August 15, 2022, read September 5, 2026.
3. ASHRAE, "Standards 180 and 211" - lists Standard 180-2018 as the current edition. ashrae.org, read September 5, 2026.
4. r/HVAC, "What do you do exactly on RTU maintenance" - "Filters, belts, clean the coils, bump the contactors and go to lunch"; "If your airflow is good and your coils/filters are clean, temp split is enough for me"; "Filters, belts, amp draws on all motors/compressors. Clean both coils, check incoming voltage, check caps, temp split, check contactors for pitting if possible"; "Some accounts have so few hours you barely have time to jump it out"; "I always ask what was sold and how much time was allocated per unit"; "If it has an economizer you should check the dampers/linkages and test operation." reddit.com, June 10, 2025, read September 5, 2026.
5. r/HVAC, "Reasonable rate for RTU maintenance at small commercial building?" - "4 visits per year should be standard also. 2 visits being in depth inspections of the units (heating/cooling startups for the season) and the other 2 simply a basic operational check. Change the filters every visit." reddit.com, July 9, 2020, read September 5, 2026.
6. Pacific Northwest National Laboratory, O&M Best Practices, "Best Practices for Air-Side Economizers Operation and Maintenance" - "a run-to-failure maintenance approach is not appropriate for air-side economizers, and regular preventive maintenance must be performed"; Table 1 sample checklist including "Confirm outdoor-air dampers are at the minimum outdoor-air position when HVAC is operating but not economizing" and "Confirm dampers achieve 100 percent closure with no air leakage." pnnl.gov, read September 5, 2026.
7. E Source, Business Energy Advisor (SMUD edition), "Economizers" - "about half of all newly installed economizers don't work properly, and their problems increase as they age"; "a survey of California contractors found that economizers were disabled because their dampers wouldn't move 30% to 40% of the time"; a damper stuck wide open "could add as much as 80% to that building's summer peak load." smud.bizenergyadvisor.com, read September 5, 2026.
8. MicroMetl, "Economizers: How to Set Minimum Position Correctly" - "Even closed dampers on older economizers may leak 5 to 10% of outside air"; "Often, airflow at 50% open and 100% open is nearly identical"; "The only reliable method is measurement." blog.micrometl.com, January 15, 2026, read September 5, 2026.
9. HVAC School, Bryan Orr, "Some Belt Tensioning Thoughts" - Browning: "Ideal tension is the lowest tension at which the belt will not slip under peak load conditions"; "a deflection of 1/64 of an inch for every 1 inch of distance between the two pulley centers"; "THIS ADJUSTMENT IS FOR FAN SPEED ONLY, NOT TENSIONING"; "all alignments must be done using the belt groove, not the outside of the sheave." hvacrschool.com, June 1, 2022, read September 5, 2026.
10. HVAC School, Bryan Orr, "The '5 Pillars' of Residential A/C Refrigerant Circuit Diagnosis" - "The air temperature split during typical conditions will be between 16 and 22 degrees' difference from the return to the supply"; TXV superheat "between a 5 to 15° superheat"; "Typical ranges for subcooling are between 8 and 14 degrees on a TXV system"; head pressure "a 15-20° saturation above outdoor ambient." hvacrschool.com, July 24, 2019, read September 5, 2026.
11. HVAC School, Bryan Orr, "Refrigerant Charging Basics for Air Conditioners and Heat Pumps" - "The piston/fixed orifice type system primarily uses the superheat method"; "the TXV/EEV primarily uses the subcooling method." hvacrschool.com, February 25, 2025, read September 5, 2026.
12. HVAC School, Bryan Orr, "Capacitor Testing and Replacement Procedure" - "If a capacitor shows physical damage, such as the top bubbling or oil leakage, it should be replaced." hvacrschool.com, March 20, 2024, read September 5, 2026.
13. HVAC School, Bryan Orr, "Gas Furnaces - What a Tech Needs to Know" - "Below 100 PPM is the recommended CO air free target, but you can leave a furnace operational above 100 PPM as long as the CO number is stable"; natural gas manifold "usually between 3.2 and 3.8" WC"; propane "10.5 to 11.5" WC"; temperature rise inside the nameplate range. hvacrschool.com, March 3, 2023, read September 5, 2026.
14. HVAC School, Bryan Orr, "Flame Sensing - The Basics" - "When the flame lights, you should read between 0.5 and 10 microamps (μA), depending on the furnace. Readings between 2 and 6 are common." hvacrschool.com, December 17, 2021, read September 5, 2026.
15. HVAC School, "Drain Trap Depth and Negative Pressure" - "The trap depth (in inches) is double the static pressure (in inches of water column)." hvacrschool.com, August 24, 2024, read September 5, 2026.
16. ANSI/ASHRAE Addendum m to Standard 62.1-2016, Section 5.8 Particulate Matter Removal - filters with "a minimum efficiency reporting value (MERV) of not less than 8" or the ISO ePM10 equivalent "shall be provided upstream of all cooling coils or other devices with wetted surfaces through which air is supplied to an occupiable space." ashrae.org, approved by ANSI February 13, 2019, read September 5, 2026.
17. U.S. EPA, "Summary of Leak Repair Requirements" (Emissions Reduction and Reclamation rule fact sheet) - "Beginning January 1, 2026, owners or operators and certified technicians must comply with leak repair requirements for certain refrigerant-containing appliances with a charge size of 15 pounds or more of refrigerant that contains an HFC"; a 10% threshold for "Comfort cooling"; "repair leaks within 30 days"; appliances "used in the residential and light commercial air conditioning and heat pumps subsector are not covered," a subsector that "includes equipment for cooling air in individual rooms, single-family homes, and small commercial buildings"; Section 608 comparison at "50 pounds or more." epa.gov, January 13, 2026, read September 5, 2026.
18. Occupational Safety and Health Administration, 29 CFR 1910.28(b)(13), "Work on low-slope roofs" - the 6-foot, 6-to-15-foot and 15-foot-or-more rules; "The employer may use a designated area when performing work that is both infrequent and temporary"; "a work rule prohibiting employees from going within 15 feet (4.6 m) of the roof edge without using fall protection." osha.gov, read September 5, 2026.
19. U.S. Department of Energy, Federal Energy Management Program, "Operations & Maintenance Best Practices: A Guide to Achieving Operational Efficiency," Release 3.0 - preventive maintenance: "Estimated 12% to 18% cost savings over reactive maintenance program"; facilities "purely reliant on reactive maintenance could save much more than 18%." energy.gov, August 2010, read September 5, 2026.
20. Accurex, "When Make-Up Air is Required for Commercial Kitchens" - quoting IMC 508.1: "Make-up air shall be supplied during the operation of commercial kitchen exhaust systems that are provided for commercial cooking appliances"; NFPA 96 8.3.1 limits kitchen negative pressure to 0.02 inches of water column. accurex.com, October 24, 2022, read September 5, 2026.
21. Instrumentation Tools, "Preventive Maintenance of Variable Frequency Drive (VFD)" - "cooling fans should be replaced every three to five years and main bus capacitors should be replaced every seven years"; dust on heat sinks and circulation fans; check connections for loose or over-tightened terminals. instrumentationtools.com, February 24, 2022, read September 5, 2026.
22. r/HVAC, comment on "Rheem must of sucked up a cat (or two)" - "Had an account that I would have to wash the condensers twice a year. (12 RTUs 7.5 ton) New manager climbed up to take a look at the roof and the equipment. He asked why I was doing this again. I pointed to two Cottonwood next to their parking lot. 'Those.' When I went for winter inspection, the trees were gone." reddit.com, August 23, 2024, read September 5, 2026.
23. r/HVAC, comment on "A very unfortunate event" - "Have fun pulling 30 screws out of a carrier rtu to do a basic maintenance, putting them all back, then doing it 11 more times for the rest of the units on the roof." reddit.com, September 6, 2024, read September 5, 2026.
24. r/HVAC, comment on "Help a new tech diagnose low delta T" - "Commercial. It's probably the economizer. Your damper is full open. You're pulling in too much makeup air, and the unit can't keep up." reddit.com, August 11, 2024, read September 5, 2026.
25. ServiceTitan, "Commercial HVAC Maintenance Checklist: Free PDF Download" - "To get your free template, simply fill out the form above (on mobile devices) or to the right (on desktop), and we'll email it to you right away." servicetitan.com, dated March 13, 2026, read September 5, 2026. The file behind the form is a two-page fillable PDF: a 20-task table with Task, Completed and Notes columns, a three-way summary and customer and technician signature lines; no reading blanks or target values. assets.ctfassets.net, read September 24, 2026.
26. ServiceChannel, "HVAC Maintenance Checklist" - three-page PDF: a cover, then a Warmer Months page of 11 tasks and a Colder Months page of 11 tasks, with Task and Notes columns and a header for company, worksite, inspected by, date and time. servicechannel.com; PDF at servicechannel.com, dated February 6, 2024, read September 24, 2026.
27. Camcode, "HVAC Preventive Maintenance Checklist" - two-page PDF, 33 checkboxes, a Spring/Summer page of 18 tasks and a Fall/Winter page of 16; the one stated interval is filters every 30 to 90 days; no header fields, readings or signature. camcode.com, September 2021, read September 24, 2026.
28. FMX, "Spring & Summer Commercial HVAC Maintenance Checklist" - two-page PDF with Excel and Word downloads and no form; 16 tasks, header fields for inspection date and technician only; the Excel file is a single column of the same 16 tasks. gofmx.com, read September 24, 2026.
29. U.S. EPA, "HVAC Checklist - Long Form" - 15 pages (14 of form plus a blank continuation page) with Component, OK, Needs Attention, Not Applicable and Comments columns covering outside-air intake, dampers, filters, coils, drain pans, fans, ducts, thermostats, boilers, cooling towers and chillers; temperature entries are blank fields marked °F. epa.gov, read September 24, 2026.
30. Scribd, "Preventive Maint AC Form" - four-page upload with an equipment data block (equipment number, type, model, serial, capacity), PM frequency and last PM date, and evaporator and condenser tables with Check, Freq. (M, S/A), Condition and Action Taken columns; page 1 visible in the viewer, download behind a Scribd subscription. scribd.com, read September 24, 2026.
31. Genteq (Regal), capacitor catalog GTC-02/10 - "Capacitance Tolerance: ±6%"; the label diagram lists "Tolerance" as a printed field. pdf.product.network. Titan Pro spec sheet, "Capacitance Tolerance … ±5%," totalhomesupply.com. Both read September 24, 2026.
32. International Fuel Gas Code, Appendix D, Table D.6 (2015 text as adopted by Seattle) - "Central Furnace (all categories) 400 ppm air free"; "Measure the CO in the vent after 5 minutes of main burner operation. The CO should not exceed threshold in Table D.6." seattle.gov. U.S. Consumer Product Safety Commission, "Furnace CO Emissions Under Normal and Compromised Vent Conditions" - "ANSI Z21.47 standard (1998) requires that an air-free flue gas sample of CO not exceed a maximum of 400 ppm." cpsc.gov. Both read September 24, 2026.
33. U.S. EPA, "Phasedown of Hydrofluorocarbons: Management of Certain Hydrofluorocarbons and Substitutes Under Subsection (h) of the American Innovation and Manufacturing Act of 2020," final rule, 89 FR 82718, October 11, 2024 - the residential and light commercial air conditioning and heat pump subsector "includes … central air conditioners (i.e., ducted); non-ducted systems (both mini and multi splits); packaged rooftop units; water-source and ground-source heat pumps"; "An air conditioning appliance at a light commercial building would most likely be a rooftop AC unit … hence are exempt from the leak repair requirements"; EPA "disagrees with one commenter's recommendation to apply the leak repair requirements to light commercial rooftop systems with a charge size greater than five pounds." govinfo.gov. The exemption is 40 CFR 84.106(a)(3)(ii), ecfr.gov. Both read September 24, 2026.