{"product_id":"castair-24-to-277-volt-hour-meter-with-varistor-hrm75","title":"Castair 24 to 277 Volt Hour Meter with Varistor HRM75","description":"\u003ch2\u003eCastair Hour Meter — 24 to 277 Volt with Varistor (HRM75)\u003c\/h2\u003e\n\u003cp\u003eThe HRM75 is the standard electric-motor hour meter in Castair's lineup, designed to track operating hours on air compressors running anywhere from 24 to 277 volts. This is the meter Castair lists on their accessories page for general compressor installations, priced at 58.44. It connects directly to the motor circuit and accumulates hours only when the motor is actually running — so it gives you an accurate count of actual pump operating hours, not wall-clock time. That number is what drives your oil change schedule, pump maintenance intervals, and valve service timing.\u003c\/p\u003e\n\u003cp\u003eThe varistor included with the HRM75 provides overvoltage transient protection — when the motor circuit switches, it generates voltage spikes that can damage unprotected electronics. The varistor absorbs those spikes and protects the meter's internal counter mechanism from premature failure.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Put an Hour Meter on a Compressor?\u003c\/h2\u003e\n\u003cp\u003eCastair specifies oil changes at 400 hours (semi-synthetic) or 800 hours (full synthetic). Valve service, belt inspection, and bearing checks also run on hour-based intervals. Without an hour meter, you are guessing — and most shops either change oil too frequently (wasted money) or not frequently enough (worn valves, oil degradation). The HRM75 removes the guesswork. One meter. One number. Change oil when it hits 800. Service valves when it hits the manufacturer's interval. Period.\u003c\/p\u003e\n\u003cp\u003eIt also gives you immediate diagnostic feedback. If your HRM75 shows 4,200 hours and the compressor has never had a valve job, that tells you something. If you are selling a used compressor, hour meter reading is the single most credible data point for a buyer.\u003c\/p\u003e\n\n\u003ch3\u003eHRM75 Features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWide Voltage Range:\u003c\/strong\u003e 24 to 277 volts AC\/DC — covers virtually all single-phase compressor installations (120V, 230V, 240V) without needing a separate voltage-matched meter\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVaristor Included:\u003c\/strong\u003e Transient voltage suppressor protects the meter from motor-switching voltage spikes — a common cause of premature hour meter failure\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCounts Running Hours Only:\u003c\/strong\u003e Meter advances only when powered — counts actual compressor operating hours, not elapsed calendar time\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNon-Resettable Counter:\u003c\/strong\u003e Hours accumulate permanently — useful for maintenance tracking and resale documentation\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCastair Factory Listed:\u003c\/strong\u003e This is the meter Castair specifies for standard electric compressor installations in their accessories catalog\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompact Size:\u003c\/strong\u003e Designed for panel mounting on compressor control boxes and enclosures\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eHRM75 vs. HRM460 — Which Meter Do You Need?\u003c\/h2\u003e\n\u003cp\u003eCastair offers two electric compressor hour meters. The distinction is voltage:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHRM75 (24-277V) — THIS PRODUCT:\u003c\/strong\u003e For virtually all single-phase compressors — 120V, 208V, 230V, 240V. Also works on 24V control circuits. Use this for standard shop compressors running on single-phase power.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHRM460 (460V):\u003c\/strong\u003e For three-phase compressors running on 460-volt power. A standard 277-volt-max meter will be destroyed by 460V — you must use the HRM460 on 460V three-phase installations.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHRM50 (Gas Engine):\u003c\/strong\u003e For gasoline-engine-powered compressors. Connects to the ignition circuit rather than an AC motor circuit.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFactory Mounting Options\u003c\/h2\u003e\n\u003cp\u003eCastair offers factory-mounted versions of this meter for new compressor installations:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHRM75M (230 volt)\u003c\/strong\u003e — Factory-mounted version, ordered as an option on new Castair compressors. Same meter, pre-wired and panel-mounted at the factory.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHRM75x2M\u003c\/strong\u003e — Factory-mounted duplex version for dual-compressor alternating systems (two meters for two compressors).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1 x Hour meter (HRM75)\u003c\/li\u003e\n\u003cli\u003e1 x Varistor (overvoltage protection)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e HRM75\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVoltage Range:\u003c\/strong\u003e 24 to 277 VAC\/VDC\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Single-phase electric motor compressors (120V, 208V, 230V, 240V)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVaristor:\u003c\/strong\u003e Included\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCounter Type:\u003c\/strong\u003e Non-resettable hour accumulator\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMount:\u003c\/strong\u003e Panel mount\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCastair Part Number:\u003c\/strong\u003e HRM75\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eWe have specialized in Castair compressors and accessories since 2016. The HRM75 is a direct Castair factory part — same meter Castair installs on their own compressors. Installing an hour meter is one of the highest-value maintenance investments you can make on a compressor: it costs less than one oil change and eliminates guesswork for every maintenance interval going forward. Free shipping, free tech support at 866-217-0063, full warranty.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342553735381,"sku":"HRM75","price":107.92,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/HOUR-METER_3b4972b2-3b77-41bf-bfa5-e2d7d3d79a29.jpg?v=1772652702","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-24-to-277-volt-hour-meter-with-varistor-hrm75","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}