Castair I25324HC4Z-S: 25HP 3-Phase Industrial Reciprocating Air Compressor — 240 Gallon Horizontal with Mounted Starter
The Castair I25324HC4Z-S is a 25-horsepower, 3-phase, 240-gallon horizontal industrial reciprocating air compressor priced at 2,775. This is the maximum-storage configuration in Castair's 25HP lineup — the same C4 cast iron pump as the 120-gallon model, but with double the tank capacity to handle high-demand shops and production environments where air supply consistency is critical.
At 25HP and 710 RPM, the C4 pump delivers 90 CFM at 175 PSI. That output supports 6-8 simultaneous technician workstations running standard pneumatic tools, or a large body shop with an active spray booth and general shop air demand running concurrently. The 240-gallon tank stores enough compressed air to buffer significant demand spikes — keeping system pressure stable even when multiple high-CFM tools activate simultaneously.
The Z designation means a factory-mounted magnetic motor starter is included. At 25HP on 3-phase, this is not optional for a code-compliant installation — having it factory-mounted by Castair means the motor and starter are properly matched and wired before the unit leaves the factory.
C4 Pump — Engineering Details
Construction
- Pump designation: C4 — Two-stage, V4 cylinder configuration
- Rated HP range: 15-25HP
- Pump RPM at 25HP: 710
- Construction: 100% cast iron — cylinders, heads, valve plates, crankcase
- Flywheel: 13-3B
- Oil capacity: 1 gallon
- Bearings: Tapered roller bearings at both crankshaft ends for superior support and reduced friction
- Connecting rods: Precision steel with automotive-type rod insert bearings at crankshaft and wrist pin
- Valves: Disc and spring — field-replaceable, no specialized tooling needed
- Pistons: 4-ring for high efficiency and minimal oil carry-over
- Unloader: Centrifugal — every startup is loadless, protecting the motor
Tank and Frame
- Tank capacity: 240 gallons, horizontal
- Dimensions: 90 x 39 x 70 inches
- Tank construction: Powder-coated ASME-rated steel with channel saddle frame
- Safety valve: ASME-rated, factory installed
- Belt guard: Totally enclosed metal
- Discharge lines: Copper tubing or stainless braided flex line
Motor and Electrical
- Horsepower: 25HP
- Phase: 3-phase
- Motor speed: 1725 RPM industrial
- Service factor: 15% minimum
- Motor starter: Factory-mounted magnetic motor starter (Z designation)
- Max working pressure: 175 PSI
Performance Specifications
- Motor output: 25 HP
- Electrical: 3-phase with factory-mounted magnetic starter
- Tank capacity: 240 gallons, horizontal
- Pump: C4 (Two-stage, V4)
- Pump RPM: 710
- Free air delivery (0 PSI): 109 CFM
- Delivery at 175 PSI: 90 CFM
- Max pressure: 175 PSI
- Dimensions (LxWxH): 90 x 39 x 70 inches
- Weight: 1,725 lbs
- Price: 2,775
What's in the Box
- Castair I25324HC4Z-S compressor — fully assembled on 240-gallon horizontal tank
- Factory-mounted magnetic motor starter (Z designation)
- ASME safety valve (factory installed)
- Pressure switch with unloader
- Totally enclosed metal belt guard
- Copper discharge and unloader tubing (or stainless braided flex line)
- Owner's documentation
Aftercooler available as factory option (BGAC3M — for 20HP and up). Electrical connection to 3-phase service by licensed electrician. Freight delivery requires loading dock or forklift at destination.
Full Lineup Comparison — 20HP through 30HP on C4 Platform
- I20324HC4Z-S: 20HP, 3-phase, 240gal Horizontal, C4 pump, 519 RPM, 72 CFM @ 175 PSI, 1,700 lbs — 2,542
- I25324HC4Z-S (this unit): 25HP, 3-phase, 240gal Horizontal, C4 pump, 710 RPM, 90 CFM @ 175 PSI, 1,725 lbs — 2,775
- I30324HC4Z-S: 30HP, 3-phase, 240gal Horizontal, C4 pump, 794 RPM, 105 CFM @ 175 PSI, 1,750 lbs
At the 240-gallon level, the price differences between the 20, 25, and 30HP configurations are relatively modest — the major cost is the tank and pump assembly. If you are within 00 of the next HP tier, consider what your peak demand looks like in 3-5 years as your shop grows. Stepping up one tier now costs less than replacing the motor or the whole unit later.
When Does a Shop Need This vs. Stepping Up or Down?
I25324HC4Z-S is right when:
- You need 80-90 CFM at 175 PSI continuously — large body shop, production line, multi-bay truck service facility
- Your demand includes high-volume spikes (spray booth + general shop air simultaneously) and you need the 240-gallon buffer to maintain pressure
- You have 3-phase service and a factory-mounted starter simplifies your installation
Step down to the 120-gallon (I25312HC4Z-S) if:
- Your installation space limits you to the smaller footprint and your demand is steady enough that 120 gallons provides adequate pressure recovery
Step down to 20HP if:
- Your actual running demand is below 72 CFM at pressure — running a 25HP compressor lightly wastes electricity and can cause short-cycling issues
Step up to 30HP (I30324HC4Z-S) if:
- Your continuous demand is above 90 CFM — the 30HP delivers 105 CFM at 175 PSI from the same C4 platform at 794 RPM
Why Buy From Air Compressor Factory Direct?
Since 2016, we have specialized in industrial air compressors and shop equipment. A 25HP, 240-gallon unit at this price point is a capital equipment purchase — we treat it accordingly. Before you order, we can review your shop layout, electrical service specs, and CFM requirements to confirm this is the right configuration. After your purchase, we provide ongoing tech support at no charge.
- Free shipping to commercial addresses in the lower 48 states (freight — loading dock or forklift required)
- Free tech support at 866-217-0063
- Full Castair manufacturer warranty
- Honest configuration guidance — we will tell you if the 20HP or 30HP is the better fit
- Authorized dealer with direct Castair factory support
Call 866-217-0063 for quick answers and help!
Frequently Asked Questions
What is the duty cycle on the I25324HC4Z-S, and can it run continuously in a production environment?
The Cast Air I25324HC4Z-S is rated for continuous-duty operation — the 25 HP motor and all-cast-iron pump are built to run production shifts without thermal shutdown concerns you'd see with aluminum-cylinder compressors. The 240-gallon horizontal tank gives you enough stored volume that the pump isn't short-cycling constantly, which is where most compressors accumulate wear. For high-demand shops running air tools, spray booths, or plasma cutters back-to-back, this unit is sized to keep up without babysitting.
What type of oil does the Cast Air I25324HC4Z-S require, and how often does it need to be changed?
Cast Air recommends a non-detergent compressor oil — SAE 30 weight for ambient temps above 40°F, SAE 20 below that. Change interval is every 500 hours under normal conditions; bump that to 250 hours if you're running in a dusty environment or the intake air quality is poor. Because the pump is full cast iron throughout, it's not as sensitive to oil breakdown as an aluminum-cylinder unit, but sticking to the interval matters for ring seal and bearing life on a pump you want running 10–15 years.
Why does the I25324HC4Z-S require 3-phase power instead of single-phase — can I run it on 240V single-phase?
No — at 25 HP, single-phase power is not a practical option. Starting current on a 25 HP single-phase motor would require service entrance capacity most shops simply don't have, and the motor itself would be significantly larger and less efficient. Three-phase power gives you smoother torque delivery, lower amperage draw at startup, and longer motor life. If your shop is on single-phase only, the realistic ceiling is around 10–15 HP; anything above that, you're looking at a phase converter or getting 3-phase service brought in — which, for a machine at this output level, is the right call.
Is a 240-gallon tank actually necessary at 25 HP, or is the tank just marketing on this model?
Tank size matters for two separate reasons: pressure recovery lag and pump duty cycle. At 25 HP, the pump is producing plenty of CFM, but high-draw tools like 1-inch impact wrenches, DA sanders running in parallel, or intermittent blast cabinet use will pull pressure down fast if the tank is undersized. The 240-gallon vessel on the I25324HC4Z-S means you have a meaningful buffer — the pump runs longer charging cycles and fewer total cycles per shift. For a shop running 4–8 air drops simultaneously, that tank volume is the difference between stable line pressure and hunting for pressure mid-task.
What size shop is the Cast Air I25324HC4Z-S actually suited for, and is it overkill for a smaller operation?
This unit is built for serious commercial and light industrial environments — think a 6–10 bay auto repair shop, a medium production floor, a fabrication shop with multiple welders and grinders running air, or a body shop with multiple spray booths. At 25 HP and 240 gallons, it's not cost-effective for a 1–2 bay garage; you'd be buying more compressor than you'll ever use. If you're unsure whether this model is the right match for your CFM demand and shop layout, call us at 866-217-0063 — as an authorized Cast Air dealer, we can work through your actual air demand numbers and point you to the right unit rather than oversell you.
