Castair HRM75 Duplex Mounted Hour Meters — Pair (HRM75x2M)
The HRM75x2M is a factory-mounted pair of HRM75 hour meters for Castair duplex compressor systems — two compressors, two meters, both factory-installed and wired from the Castair plant. A duplex installation runs two separate compressor units on an alternating relay (the ALT230 or ALT460 alternator), with each unit taking turns meeting demand. Because both units accumulate hours independently, you need a separate meter on each — the HRM75x2M provides exactly that, with both meters matched and installed at the factory.
For shops running a duplex Castair system, the HRM75x2M is how you track each unit's hours independently. When Unit A shows 800 hours and Unit B shows 620, you change the oil on Unit A first and schedule Unit B's change accordingly. Without individual meters on each unit, you are guessing which unit has accumulated more wear.
HRM75x2M Features
- Two-Meter Duplex Set: One meter per compressor unit — tracks each unit's operating hours independently
- Factory Wired: Pre-installed and wired at the Castair factory — arrives ready to count from first run
- Matched Set: Both meters are the same model (HRM75) — same display format, same counter range, easy to compare readings at a glance
- Non-Resettable: Hours accumulate permanently on each meter independently
- Compatible With Alternator Systems: Works alongside the ALT230 or ALT460 automatic alternator relay to provide per-unit hour tracking on duplex installations
Duplex Compressor Systems — Why Two Meters?
In a duplex system, the alternator relay rotates which compressor runs first. Over time, even with alternation, minor differences in load and runtime accumulate. One unit may have run 150 more hours than the other due to scheduling, demand patterns, or time of installation. Without individual hour meters, you don't know which unit needs service first. The HRM75x2M gives you that data on each unit at a glance.
Hour Meter Options for Castair Duplex Installations
- HRM75x2M — THIS PRODUCT: Duplex pair, factory-mounted, for 24-277V (single-phase 230V typical) compressor units
- HRM460x2M: Duplex pair, factory-mounted, for 460V three-phase duplex installations
- ALT230: Automatic two-compressor alternator relay, 230 volt (required for duplex operation)
- ALT460: Automatic two-compressor alternator relay, 460 volt
What's in the Box
- 2 x Hour meters (HRM75), factory-mounted and wired as a matched pair on duplex compressor system
Technical Specifications
- Part Number: HRM75x2M
- Quantity: 2 meters (one per compressor unit)
- Voltage: 24-277V (matches HRM75 specification)
- Mount: Factory-mounted, pre-wired at Castair factory
- Application: Castair duplex compressor systems
Why Buy From Air Compressor Factory Direct?
We have specialized in Castair compressors and duplex installations since 2016. If you are building out a duplex system — or retrofitting an existing one — we can advise on whether to add the HRM75x2M at factory order time or install individual HRM75 meters yourself afterward. Free shipping, free tech support at 866-217-0063.
Call 866-217-0063 for quick answers and help!
