- HVAC spans multiple classifications. Ductwork is sheet metal. Piping is pipefitter. Controls may be a third classification. One worker doing all three in a week needs three rows on the WH-347.
- Sheet metal ≠ HVAC mechanic. Some wage determinations list these separately at different rates. Check yours before you start the job.
- Apprentice ratios apply per classification. Your sheet metal apprentice ratio is separate from your pipefitter apprentice ratio — both must be within limits.
- State forms are separate. The federal WH-347 doesn't satisfy California, New York, Illinois, or New Jersey. Each requires its own filing.
Why HVAC is the hardest trade to classify correctly
Most trades map cleanly to one prevailing wage classification. A carpenter does carpentry. A painter paints. An HVAC contractor does sheet metal work, piping, controls, and equipment installation — and each of those can be a different classification on the wage determination with a different prevailing wage rate.
This is not an edge case. On a typical school HVAC project, your crew might:
- Fabricate and hang ductwork — classified as Sheet Metal Worker
- Run refrigerant and hydronic piping — classified as Pipefitter/Steamfitter
- Set and connect rooftop units — could be Sheet Metal Worker, Pipefitter, or HVAC Mechanic depending on the wage determination
- Wire thermostats and controls — may fall under a Controls Technician or even Electrician classification in some jurisdictions
- Perform testing, adjusting, and balancing (TAB) — sometimes a separate classification entirely
When your worker spends Monday through Wednesday on ductwork and Thursday through Friday on refrigerant piping, that's two rows on the WH-347 — sheet metal worker for 24 hours at one rate, pipefitter for 16 hours at another. One row averaging the hours is a misclassification violation, even if the total pay looks right.
HVAC classifications on the WH-347
The classification on your certified payroll must match the work performed, not your company's trade license or the worker's job title. Here are the most common classifications HVAC subs encounter and the mistake that flags each one.
| Classification | Covers | Common mistake |
|---|---|---|
| Sheet Metal Worker | Ductwork fabrication and installation, air distribution systems, kitchen exhaust hoods, architectural sheet metal | Including piping hours under this classification when the wage determination has a separate pipefitter rate |
| Pipefitter / Steamfitter | Refrigerant piping, hydronic piping, chilled/hot water, gas piping, steam piping, welded connections | Classifying piping work as sheet metal (usually a lower rate) — underpayment violation |
| HVAC Mechanic / Installer | Equipment setting, startup, commissioning — where the wage determination lists this separately from sheet metal | Not checking whether the wage determination distinguishes HVAC mechanic from sheet metal worker — some do, some don't |
| Controls Technician | Building automation, DDC controls, thermostat wiring, pneumatic-to-digital conversion | Lumping controls work under sheet metal or pipefitter when the determination has a separate controls or electrician classification |
| TAB Technician | Testing, adjusting, and balancing of air and water systems after installation | Assuming TAB falls under the same classification as installation — some jurisdictions list it separately |
| Apprentice (by trade & period) | Same scope as the corresponding journeyman classification, at the apprentice percentage | Using the wrong journeyman base rate for the apprentice percentage — a sheet metal apprentice uses the sheet metal JW rate, not the pipefitter rate |
Your best HVAC tech hangs duct on Monday and Tuesday (sheet metal), runs refrigerant lines on Wednesday and Thursday (pipefitter), and wires a programmable thermostat on Friday (controls). That's three rows on the WH-347 for one worker in one week — each at a different prevailing wage rate, with different fringe. One row labeled "HVAC" doesn't exist as a classification on most wage determinations.
The sheet metal vs. HVAC mechanic distinction
This is the classification trap that catches HVAC subs who are used to doing everything under one license. On many wage determinations, sheet metal worker and HVAC mechanic (or HVAC installer) are listed separately.
When they're separate:
- Sheet metal worker covers duct fabrication, installation, and air distribution
- HVAC mechanic covers equipment installation, startup, refrigerant handling, and system commissioning
The rates are often different. In some jurisdictions, the sheet metal rate is higher (reflecting the fabrication skill). In others, the HVAC mechanic rate is higher (reflecting licensing requirements). If your wage determination lists both, you must use the correct one for the work performed. If it only lists sheet metal worker with a scope that includes HVAC installation, then one classification covers everything.
Read your wage determination before you staff the job. Search for "sheet metal," "HVAC," "pipefitter," and "controls." If you see separate classifications for any of these, your certified payroll must split hours accordingly. If you only see "sheet metal worker" with a broad scope description, confirm with the awarding agency that it covers the full HVAC scope.
Apprentice ratios for HVAC work
HVAC subs face a unique apprentice ratio challenge: the ratio applies per classification, not per crew. If your wage determination has separate sheet metal and pipefitter classifications, the sheet metal apprentice-to-journeyman ratio and the pipefitter apprentice-to-journeyman ratio are tracked independently.
Common HVAC-related apprentice ratios:
- Sheet metal: typically 1:1 to 1:3 (one apprentice per one to three journeymen)
- Pipefitter: typically 1:1 to 1:2
- Controls: varies — may follow the electrician ratio if classified under electrical
If you have four workers on site — two doing ductwork and two doing piping — you can't count the ductwork journeyman toward the piping apprentice ratio. Each classification's ratio stands on its own. Exceeding the ratio in any classification means the extra apprentices get reclassified at journeyman rates for that classification, retroactively.
Apprentices must be in a registered program. On HVAC jobs, this can mean separate registrations for sheet metal and pipefitting if the worker does both types of work. An apprentice registered in a sheet metal program cannot be classified as a pipefitter apprentice — even if they're doing piping work under supervision.
Fringe benefits for HVAC contractors
HVAC fringe packages are complicated by the multi-classification problem. Each classification on the wage determination has its own fringe rate and its own fringe components. A typical package might include:
- Health and welfare — per-hour contribution, often at different amounts per classification
- Pension — defined benefit or defined contribution
- Training fund — sheet metal JATC is separate from UA (pipefitter) training
- Annuity / supplemental — additional retirement contribution
- Industry fund — SMACNA or UA industry promotion, depending on classification
When a worker splits time between sheet metal and pipefitter work in the same week, the fringe calculation is different for each set of hours. The sheet metal hours carry the sheet metal fringe package. The pipefitting hours carry the pipefitter fringe package. The Statement of Compliance must account for both.
If you pay fringe in cash, each classification's cash-in-lieu amount must meet that classification's fringe obligation separately. You can't average fringe across classifications — the math has to work for each row on the WH-347 independently.
State forms for HVAC contractors
The WH-347 covers the federal requirement. State-funded projects — schools, government buildings, water treatment plants — almost always require their own state form on top of the federal one.
California: California eCPR records generally must be submitted to the DIR at least monthly, or more frequently if the contract requires it. The penalty of up to $200/day/worker under Labor Code §1775 applies to prevailing-wage underpayment, not simply a late submission. A separate §1776 penalty applies when requested records are not produced within 10 days.
New York: Electronic filing required since January 2026. The late-filing penalty is $100 per day once a filing is more than 14 days late; it is not multiplied by worker count. Classification and rate errors can separately create back-pay liability.
Illinois: Monthly filing to the IDOL, with personal liability for the business owner. Illinois classifies HVAC work under both sheet metal and pipefitter — check the Illinois prevailing wage schedule for your county.
New Jersey: Filing through the NJ Wage Hub. Ten-day deadline. Penalties up to $5,000 and 3-year debarment.
The most expensive mistakes for HVAC subs
These errors show up in HVAC contractor audits most often, ranked by cost:
- One row for a multi-classification week. A worker who does ductwork and piping in the same week needs separate rows. Lumping everything under "sheet metal worker" or "HVAC" underpays or misclassifies the piping hours.
- Using "HVAC" as a classification. Most wage determinations don't have an "HVAC" classification. The work maps to sheet metal worker, pipefitter, HVAC mechanic, or controls tech. Writing "HVAC" on the WH-347 is ambiguous and will get flagged.
- Ignoring the controls classification. Thermostat wiring and DDC controls work may fall under a different classification than the installation — often at a different rate. If your wage determination has a controls or electrician classification, use it.
- Exceeding apprentice ratios across classifications. Having the right total number of apprentices isn't enough — the ratio must hold within each classification separately.
- Mixing fringe across classifications. Sheet metal fringe and pipefitter fringe are different packages. Each row's fringe must meet its own classification's requirement independently.
A 10-person HVAC crew in California, underpaid after being misclassified between sheet metal and pipefitter for 10 days, could face up to $200/day × 10 workers × 10 days = $20,000 under Labor Code §1775, plus back wages. The Labor Commissioner determines the amount under the statute. Federal projects use a different remedies framework. Run your scenario through the fine calculator.
Certified payroll checklist for HVAC subs
Before you submit each week, verify these — they catch the errors that hit HVAC contractors hardest:
- Every worker classified by work performed — sheet metal, pipefitter, HVAC mechanic, controls, or TAB — matched to the wage determination.
- Multi-classification weeks have separate rows for each type of work, with hours allocated correctly.
- No "HVAC" as a catch-all classification. Use the specific classification from the wage determination.
- Apprentice ratios tracked per classification — sheet metal and pipefitter ratios are independent.
- Apprentice registration matches the classification. A sheet metal apprentice can't be classified as a pipefitter apprentice.
- Fringe components match each classification's requirements on the Statement of Compliance — no averaging across classifications.
- Base + fringe meets or exceeds the prevailing wage for each classification independently.
- State form filed separately if the project has state or local funding.
Frequently asked questions
Do HVAC contractors have to file certified payroll?
Yes. Every subcontractor on a government-funded public works project must file a federal WH-347 every week the job runs. Most states also require a separate state filing. See the step-by-step WH-347 guide.
How do I classify HVAC workers on the WH-347?
By the work performed each day, not by trade license or job title. Ductwork is typically sheet metal worker. Piping is pipefitter. Controls may be a separate classification. Check your project's wage determination for the specific classifications and rates — then split hours accordingly on the form.
Is "sheet metal worker" the same as "HVAC mechanic" on prevailing wage?
Not always. Some wage determinations list them as separate classifications at different rates. If yours does, you must use the correct one for the specific work performed. If only one is listed with a scope broad enough to cover HVAC installation, one classification covers it — but confirm with the awarding agency.
What happens if I use the wrong classification?
Misclassification can mean back wages at the correct rate for every affected hour. California may assess up to $200 per affected worker per day under §1775 when the error results in prevailing-wage underpayment; that is distinct from the §1776 records-production penalty. Federal remedies can include withholding, termination, and three-year debarment.
Stop sorting classifications by hand
PrevailComply handles the multi-classification splits, per-trade apprentice ratios, fringe calculations, and state forms that make certified payroll the worst part of public works for HVAC contractors. Sign up for PrevailComply, or grab the free WH-347 checklist below.
Related guides
How to fill out WH-347 in 2026 · Free WH-347 generator · Electrical contractor certified payroll · Plumbing contractor certified payroll · First-timer's prevailing wage guide · Fine calculator
This guide is general information for HVAC subcontractors, not legal or compliance advice. Classifications, apprentice ratios, wage rates, and remedies vary by jurisdiction and project. Confirm current official guidance and the wage determination attached to your contract. Have qualified counsel review regulatory claims before relying on them for a specific matter.