A shop-built vacuum pump for vacuum bagging and vacuum kilns
The Infinity Turbine VPC-02 is a 4-cylinder, crank-driven vacuum pump on a rolling four-post cart. It runs from a 1 HP 3-phase motor and VFD, has six hose valves on the front panel, and is sized to pull a vacuum on 3,000 BF of lumber in about 4 hours, or a full 10-cord firewood bag overnight. It is light enough on power to run from solar and batteries.
2.2 CFM baseline · ~28 inHg ultimate · 0.9 kW · six hose valves · E-stop & VFD rear panel
Built from proven parts, laid out for real use
VPC-02 grew out of the VPC-01 prototype, which reused the FastFilter-24 drive train. The second version keeps the slow, quiet crank drive and adds three more cylinders, variable speed and a proper cart.
Four-cylinder pump
Four 3.5 in bore × 2 in stroke air cylinders on a common crank, each sweeping 19.2 in³ per stroke. The slow crank speed (~58 rpm) keeps wear and noise low.
Worm-gear drive
A 1 HP motor through a 30:1 worm gearbox drives the crank. Plenty of torque to keep pulling at deep vacuum.
3-phase motor + VFD
The VFD gives soft start and speed control from 60 Hz up to about 90 Hz for faster pump-down. A VFD with single-phase input runs it from ordinary shop power or a solar inverter.
Six-valve front panel
Six hose valves let one cart serve several bags at once, or isolate a leaking bag without stopping the pump.
Four-post cart
Removable vented side panels for cooling and service access, and a 1 in HDPE top that works as a bench.
Rear control panel
The emergency stop and VFD keypad are on the rear panel, away from the hoses.
How long to pull a vacuum on a real load?
The air to remove is the gas in the gaps between pieces, plus about 10% for slack in the bag. A stickered 3,000 BF lumber stack has about 209 ft³ of free air. A 10-cord bag of split firewood has about 473 ft³, more than twice as much.
- 20 inHg is enough to clamp a vacuum bag.
- 26 inHg is a typical vacuum kiln target; water boils near 50 °C (122 °F) at this pressure.
- Air inside the wood cells bleeds out more slowly and overlaps with the drying cycle. Pine has more of it than hardwood.
Model: t = (V / S) · ln[(Patm − Pu) / (P − Pu)], with no bag leakage. Ultimate pressure Pu ≈ 1 psia (~28 inHg).
| Load (baseline 2.2 CFM) | Free air | Pore air | To 20 inHg | To 26 inHg | To 26 inHg incl. pore air |
|---|---|---|---|---|---|
| 10 cords firewood | 473 ft³ | 382 ft³ | 4.5 h | 9.7 h | 17.5 h |
| 3,000 BF hardwood | 209 ft³ | 112 ft³ | 2.0 h | 4.3 h | 6.6 h |
| 3,000 BF pine | 209 ft³ | 150 ft³ | 2.0 h | 4.3 h | 7.3 h |
Four ways to run the same cart
Adding check valves to the rod side of each cylinder makes it pull on both strokes, roughly doubling the flow. Turning the VFD up to 90 Hz adds another 50%. Together they cut pump-down time to about a third.
| Configuration | Crank rpm | Flow |
|---|---|---|
| Single-acting, 60 Hz | 58 | 2.2 CFM |
| Double-acting, 60 Hz | 58 | 4.4 CFM |
| Single-acting, 90 Hz | 87 | 3.3 CFM |
| Double-acting, 90 Hz | 87 | 6.6 CFM |
Before running at 90 Hz, check that the motor has enough torque at that speed. A bag leaking 0.2–0.5 CFM uses 10–25% of the baseline pump's flow, so a tight bag matters as much as pump size.
Pennies to dollars per pump-down
Electrical input is taken as 0.9 kW: the 1 HP motor at full load through the VFD, about 83% combined efficiency. Load drops at deep vacuum, so real costs should be lower.
Even at $0.50/kWh, pulling a full 3,000 BF hardwood charge to kiln vacuum costs under $3.
Cost per pump-down
| Load / target | kWh | $0.10/kWh | $0.15/kWh | $0.20/kWh | $0.50/kWh |
|---|---|---|---|---|---|
| 10 cords firewood – 20 inHg | 4.1 | $0.41 | $0.61 | $0.82 | $2.04 |
| 10 cords firewood – 26 inHg | 8.7 | $0.87 | $1.30 | $1.74 | $4.35 |
| 10 cords firewood – 26 inHg + pore air | 15.7 | $1.57 | $2.36 | $3.14 | $7.86 |
| 3,000 BF hardwood – 20 inHg | 1.8 | $0.18 | $0.27 | $0.36 | $0.90 |
| 3,000 BF hardwood – 26 inHg | 3.8 | $0.38 | $0.58 | $0.77 | $1.92 |
| 3,000 BF hardwood – 26 inHg + pore air | 5.9 | $0.59 | $0.89 | $1.18 | $2.95 |
| 3,000 BF pine – 20 inHg | 1.8 | $0.18 | $0.27 | $0.36 | $0.90 |
| 3,000 BF pine – 26 inHg | 3.8 | $0.38 | $0.58 | $0.77 | $1.92 |
| 3,000 BF pine – 26 inHg + pore air | 6.6 | $0.66 | $0.99 | $1.32 | $3.30 |
Holding vacuum during a drying cycle
The pump cycles on and off to make up for leakage and to carry away water vapor. Pump only; no heater.
| Pump run time | kWh/day | kWh/month | $0.10/kWh | $0.15/kWh | $0.20/kWh | $0.50/kWh |
|---|---|---|---|---|---|---|
| 6 h/day (25% duty) | 5.4 | 162 | $16 | $24 | $32 | $81 |
| 12 h/day (50% duty) | 10.8 | 324 | $32 | $49 | $65 | $162 |
| 24 h/day (100% duty) | 21.6 | 648 | $65 | $97 | $130 | $324 |
Run the vacuum pump from the sun
Design basis: the pump runs 12 hours a day (10.8 kWh/day). Three days a week each get 6 hours of full sun, the rest get none, and the battery must carry the cart for two full days without sun.
- Array: 12 × 580 W bifacial panels, 22.5% efficient = 6.96 kWp, about 31 m² of panel area. Rear-side gain of +8% assumes a light ground surface.
- Battery: 7 × 5.12 kWh 48 V LFP modules = 35.8 kWh. That covers 66 hours of load: two dark days plus the night after a sunny day, at 90% depth of discharge.
- Worst case: one 6-hour sun day must recharge enough for itself and the two dark days after it.
- Surplus: over a normal week the array makes about 40% more than the pump uses.
This works if the sun days are spread out (e.g. Mon/Wed/Fri). If the three sunny days fall back to back, the dark stretch is four days, and the battery roughly doubles.
Solar + battery sizing by pump duty
| Pump run time | kWh/day | Array (kWp) | 580 W panels | Battery (kWh nominal) | 5.12 kWh modules |
|---|---|---|---|---|---|
| 4 h/day | 3.6 | 2.32 | 4 | 15.4 | 3 |
| 6 h/day | 5.4 | 3.48 | 6 | 20.5 | 4 |
| 8 h/day | 7.2 | 4.64 | 8 | 25.6 | 5 |
| 12 h/day | 10.8 | 6.96 | 12 | 35.8 | 7 |
| 16 h/day | 14.4 | 9.28 | 16 | 51.2 | 10 |
| 24 h/day | 21.6 | 13.92 | 24 | 71.7 | 14 |
Assumptions: system derate 0.80, bifacial gain 1.08, LFP round-trip efficiency 0.92, inverter 0.95, 90% usable depth of discharge. These sizes cover the vacuum pump only. See the heat notice below.
A vacuum kiln also needs heat
A vacuum pump on its own does not dry wood. Lowering the pressure lowers the boiling point of water, but the wood still has to be supplied with the energy to turn its moisture into vapor. Every vacuum kiln needs a heat source inside the vacuum chamber, such as electric resistance heaters or heated platens between the layers of lumber, to drive moisture out of the wood.
- Heater and platen energy is not included in any figure on this page: pump-down times, kWh, electricity costs, or solar PV and battery sizes.
- The solar and battery sizes above cover the vacuum pump only. Adding a resistance heater or platens will raise the energy demand a great deal, and the array and battery would have to be resized.
- Heater sizing depends on wood species, thickness, starting and target moisture content, chamber insulation and the drying schedule. Size it separately before you build.
- Pump-down times assume a leak-free bag or chamber and are calculated from the VPC-02 geometry. Replace the assumed values with measured pump flow, power draw and leak rate before final sizing.
Electrical heaters, VFD wiring and solar interconnection must follow the NEC and local codes. Some of this work requires a licensed electrician.
At a glance
| Pump | 4 × 3.5 in bore × 2 in stroke air cylinders on a common crank; 19.2 in³ swept per cylinder per stroke |
|---|---|
| Drive | 1 HP 3-phase motor, 30:1 worm gearbox, crank at ~58 rpm (60 Hz), up to ~87 rpm (90 Hz) |
| Speed control | VFD with soft start; single-phase-input VFD option for shop or solar inverter power |
| Flow | 2.2 CFM single-acting at 60 Hz · 4.4 CFM double-acting · up to 6.6 CFM double-acting at 90 Hz |
| Ultimate vacuum | About 28 inHg (~1 psia), limited by cylinder clearance volume |
| Electrical input | About 0.9 kW at full load (design value) |
| Cart | Four-post frame, removable vented side panels, 1 in HDPE top |
| Front panel | 6 hose valves for running several bags |
| Rear panel | Emergency stop and VFD |
| Uses | Vacuum bagging (veneer, laminates, firewood bags) and vacuum kiln pump-down and holding |
Plans, kit or a finished cart
VPC-02 Plans
- Printable plan set (PDF)
- Cart, drive train and cylinder drawings
- VFD and E-stop wiring
- Parts list and build checklist
VPC-02 Kit
- Cylinders, crank and gearbox
- Motor and VFD package
- Valve manifold and hoses
Vacuum kiln consulting
- Bag and chamber sizing
- Heater / platen and solar sizing
- Firewood and lumber setups
Common questions
Will the pump dry my wood by itself?
No. The pump removes air and carries away water vapor, but the wood needs heat to release its moisture. Every vacuum kiln needs electric resistance heaters or heated platens. That heat is not included in the figures on this page.
How deep a vacuum will it pull?
About 28 inHg, limited by the dead space left in each cylinder at the end of the stroke. That is enough for 20 inHg bag clamping and a 26 inHg vacuum kiln target.
Why is hardwood the same speed as pine?
The gauge responds to the free air between the boards, and a stickered 3,000 BF stack has about the same free air whatever the species. Pine has more air inside the wood cells, so it takes longer to fully degas.
Can I run it from solar?
Yes. At 0.9 kW the pump is a small load. About 7 kWp of bifacial panels and a 36 kWh LFP battery runs it 12 hours a day with two days of autonomy, under the sun pattern described above. A heater would need its own, much larger, power budget.
Do I need 3-phase power?
No. A VFD with single-phase input runs the 3-phase motor from 240 V shop power or a 48 V hybrid inverter.
How do I make it faster?
Add rod-side check valves so each cylinder pulls on both strokes (about 2× faster), run the VFD toward 90 Hz (about 1.5× faster), and make sure the bag doesn't leak.
Build the vacuum pump your kiln needs
A slow, tough, solar-ready vacuum pump you can build and repair yourself.
Questions? Email greg@infinityturbine.com