Auto Duct Line Buying Guide 2026: Line 2 vs 3 vs 4 vs 5

Auto Duct Line: The Heart of Rectangular Duct Production

If spiral duct is the bread and butter of HVAC, then rectangular duct auto lines are the industrial bakery. A single auto duct line can replace 5–8 manual workers, producing complete rectangular duct sections — from coil to finished TDF flange — in under 2 minutes per piece.

But choosing the right automation level is critical. Buy too little and you're still feeding material manually. Buy too much and you're paying for features you don't need. This guide breaks down Preda's complete auto duct line lineup.

Auto Duct Line 2 vs 3 vs 4 vs 5: Full Comparison

Linear vs U-Shape: Which Layout Fits Your Shop?

Preda offers two layout configurations for Line 5: Linear (straight) and U-Shape. The choice depends entirely on your factory floor plan.

Linear Layout

• Material flows straight from decoiler to finished duct stacker
• Requires 18–25m of linear floor space
• Easier for material handling and forklift access
• Best for long, narrow factory layouts

U-Shape Layout

• Material loops back, so loading and unloading happen at the same end
• Requires only 10–14m of floor space (more compact)
• One operator can oversee both ends
• Best for square or compact factory layouts

How to Choose the Right Auto Duct Line

1. Calculate your daily duct output: If you produce <500m²/day, Line 2 or 3 suffices. 500–1000m² → Line 3 or 4. >1000m² → Line 5.
2. Count your workers: Labor costs in your country? Line 5 saves 2–3 workers per shift — calculate the ROI.
3. Measure your floor space: Under 15m available? Go U-Shape Line 5. Over 20m? Linear works fine.
4. Consider duct size range: All lines handle 0.4–1.2mm galvanized. If you need stainless or aluminum, specify at ordering.
5. Plan for 5-year growth: If you expect volume to double, buy Line 5 now — it's cheaper than upgrading later.

Matching Line Capacity to Your Monthly Tonnage

An auto duct line is the single largest capital item in most duct factories, and the most common buying mistake is sizing it for today's order book instead of next year's. Here is the practical capacity of each configuration.

How to read your own numbers. Take the largest month in the past year, convert it to square metres of finished rectangular duct, divide by working days and then by 0.8 to allow for changeovers, rework and coil changes. Choose the line whose published output sits about 20–30 % above that figure. Buying exactly to today's peak means you will be capacity-constrained within a year, and the cost of an upgrade later is a whole machine, not a module.

The labour argument is usually stronger than the throughput argument. A Line 3 needs two operators where manual fabrication needs six for the same output. At a loaded rate of $25/hour, that is roughly $100,000 a year of labour saved against a $38,500 machine — payback around four to five months on labour alone, before you count the material savings from coil-fed processing.

Floor Space, Coil Handling and Utilities

Layout is where auto duct line projects most often go wrong. The machine dimensions are published; the space you actually need is considerably larger.

Straight or U-shape? The U-shape line folds the process back on itself, cutting the required length by roughly a third at the cost of additional width. It is the right answer when your building is long and narrow — a common situation in industrial parks. The straight line is simpler to feed and to maintain, and gives better visibility along the whole process, so prefer it whenever the building allows.

Don't forget coil logistics. A 1,250 mm coil of 1.0 mm galvanised weighs about 2.5 tonnes. You need a coil car or overhead crane rated above that, a clear path from the delivery door to the decoiler, and floor loading capacity to match. More installations are delayed by floor and access problems than by the machine itself.

Payback Model: Build It Before You Buy

Work through these five inputs before you sign anything. They take about twenty minutes and they will tell you which line you actually need.

1. Peak month output in m² of rectangular duct — use last year's peak, not the average.
2. Labour cost per m² today — total shop wages for rectangular work divided by monthly output.
3. Material yield — coil-fed processing typically recovers 3–6 % of material that sheet-fed fabrication loses to offcuts. Multiply that by your annual steel spend.
4. Leakage-related rework — shops moving from manual to automated forming commonly cut field rework substantially, because flange and lock geometry becomes consistent.
5. Financing — at typical equipment finance rates, add roughly 8–12 % per year to the capital cost if you are not paying cash.

Worked example. A shop running 2,000 m² a month with six fabricators at a loaded $25/hour produces about 12 m² per labour-hour. A Line 3 at $38,500 running the same output with two operators raises that to roughly 38 m² per labour-hour. The annual labour saving is about $190,000; add 4 % material recovery on $300,000 of annual steel for $12,000. Payback lands at roughly two and a half months. Even halving those savings for conservative assumptions, the machine pays for itself in under six months.