{"product_id":"castair-1-2npt-f-1-2-npt-f-outlet-vent-outlet-3-8-npt-25-max-cfm-electric-dual-3-way-pilot-valve-ndc-1","title":"Castair 1\/2\"NPT-F 1\/2\" NPT-F Outlet Vent Outlet 3\/8\" NPT 25 Max. CFM Electric Dual 3 Way Pilot Valve NDC-1","description":"\u003ch2\u003eCastair NDC-1 Three-Way Pilot Valve — 1\/2\" NPT Electric Dual, 25 CFM\u003c\/h2\u003e\n\n\u003cp\u003eThe Castair NDC-1 is a three-way pilot valve designed for electric dual-control air compressor systems. It handles the load\/unload cycle on compressors drawing up to 25 CFM, using 1\/2\" female NPT connections on both inlet and outlet, with a 3\/8\" NPT vent port. If your shop runs a mid-size reciprocating compressor with a pressure switch and you need the unloader valve to work in sync with motor start\/stop, the NDC-1 is the component that makes that happen. It is solenoid-operated, meaning it responds to the electrical signal from the pressure switch rather than requiring a separate mechanical pilot line.\u003c\/p\u003e\n\n\u003cp\u003eBefore you buy a replacement or upgrade valve, confirm two things: your compressor draws 25 CFM or less at the valve, and your control system is electric dual (pressure switch with motor starter) rather than a gas engine drive. If your compressor exceeds 25 CFM or uses a gas engine, you need a different valve — the lineup section below covers your options.\u003c\/p\u003e\n\n\u003ch3\u003eWhat the NDC-1 Does in Your Control System\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLoad\/Unload Control:\u003c\/strong\u003e The NDC-1 opens and closes the compressor unloader port based on the pressure switch signal. When tank pressure hits the cut-out setting, the valve unloads the compressor head so the motor can restart without fighting full line pressure.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eThree-Way Function:\u003c\/strong\u003e Unlike a simple two-way valve that only opens or closes a single path, a three-way valve routes flow between inlet, outlet, and vent. On unload, it vents trapped pressure through the 3\/8\" NPT vent port rather than leaving it locked in the line.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eElectric Dual Operation:\u003c\/strong\u003e Solenoid-operated, triggered directly by the pressure switch electrical signal. No separate pneumatic pilot line is needed. The solenoid coil energizes when the switch signals, shifting the valve spool to unload position.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCheck Valve Integration:\u003c\/strong\u003e The three-way design incorporates check valve function to prevent backflow through the pilot circuit during the loaded condition.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e25 CFM Rating:\u003c\/strong\u003e Sized for mid-range compressors. This rating applies to the valve's flow capacity, not the compressor's displacement — confirm your compressor's actual flow demand at the control circuit before ordering.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003ePort Configuration and Plumbing\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInlet:\u003c\/strong\u003e 1\/2\" female NPT — connects to the compressor discharge or control line from the tank\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOutlet:\u003c\/strong\u003e 1\/2\" female NPT — connects downstream to the unloader mechanism or control device\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eVent Outlet:\u003c\/strong\u003e 3\/8\" NPT — exhausts trapped pressure on unload cycle; connect to a muffler (Castair M38, 3\/8\" muffler) to reduce exhaust noise in the shop\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePilot Ports:\u003c\/strong\u003e 1\/8\" female NPT — used for the solenoid control signal connection\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePSI Range Options:\u003c\/strong\u003e Order NDC-1100 for 100–120 PSI systems, or NDC-1140 for 140–170 PSI systems. Specify the correct pressure range for your application — the internal spring and seat configuration differs between the two versions.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eElectric Dual vs. Gas Engine — Why It Matters for Valve Selection\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eElectric Dual System:\u003c\/strong\u003e The pressure switch both starts\/stops the motor and signals the unloader valve. The NDC-1's solenoid receives this electrical signal directly. This is the correct valve for electric motor-driven compressors with dual-pressure-switch control.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGas Engine Systems:\u003c\/strong\u003e Gas engine drives do not use a solenoid — the engine runs continuously and the valve must mechanically unload the compressor head. The NG-1 (same port sizes, same CFM, but mechanically operated) is the correct valve for those applications.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMixing Types is a Failure Point:\u003c\/strong\u003e Installing a gas-engine valve on an electric dual system — or vice versa — will cause the unloader to malfunction, leading to hard-start motor failures or compressor head damage. Confirm your drive type before ordering.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow a Three-Way Pilot Valve Works\u003c\/h3\u003e\n\u003cp\u003eA three-way pilot valve has three ports: inlet, outlet, and exhaust (vent). In the loaded position, the valve connects inlet to outlet, allowing the control signal to pass through and hold the compressor in the operating (loaded) condition. When the pressure switch reaches cut-out and signals the valve, the spool shifts: inlet is blocked, and outlet is connected to the vent port. This exhausts the trapped pressure from the unloader line, allowing the unloader mechanism to open and unload the compressor head. When the switch signals to reload, the spool shifts back, re-pressurizing the control line and closing the unloader.\u003c\/p\u003e\n\n\u003cp\u003eThe vent function is critical. Without proper venting on unload, residual pressure holds the unloader partially open or causes erratic cycling. The NDC-1's 3\/8\" NPT vent port handles the exhaust volume for compressors up to 25 CFM. Blocking or restricting this port — including connecting it to a line with back-pressure — will cause control failures.\u003c\/p\u003e\n\n\u003ch3\u003ePilot Valve Selection Guide — Complete Castair Lineup\u003c\/h3\u003e\n\u003cp\u003eCastair makes 1-way, 2-way, and 3-way pilot valves across a range of port sizes and flow ratings. Here is the complete lineup with part numbers to help you identify the correct replacement or upgrade:\u003c\/p\u003e\n\n\u003ctable\u003e\n  \u003cthead\u003e\n    \u003ctr\u003e\n      \u003cth\u003ePart #\u003c\/th\u003e\n      \u003cth\u003eType\u003c\/th\u003e\n      \u003cth\u003eInlet\u003c\/th\u003e\n      \u003cth\u003eOutlet\u003c\/th\u003e\n      \u003cth\u003eVent\u003c\/th\u003e\n      \u003cth\u003eMax CFM\u003c\/th\u003e\n      \u003cth\u003eApplication\u003c\/th\u003e\n    \u003c\/tr\u003e\n  \u003c\/thead\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003ctd\u003eD2M\u003c\/td\u003e\n\u003ctd\u003e1-way\u003c\/td\u003e\n\u003ctd\u003e1\/4\" F NPT\u003c\/td\u003e\n\u003ctd\u003eN\/A\u003c\/td\u003e\n\u003ctd\u003eDirect w\/felt\u003c\/td\u003e\n\u003ctd\u003e20\u003c\/td\u003e\n\u003ctd\u003eGas or Electric\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eBG2-M\u003c\/td\u003e\n\u003ctd\u003e2-way\u003c\/td\u003e\n\u003ctd\u003e1\/4\" F NPT\u003c\/td\u003e\n\u003ctd\u003eN\/A\u003c\/td\u003e\n\u003ctd\u003eDirect w\/felt\u003c\/td\u003e\n\u003ctd\u003e20\u003c\/td\u003e\n\u003ctd\u003eGas engine\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eBE2-M\u003c\/td\u003e\n\u003ctd\u003e2-way\u003c\/td\u003e\n\u003ctd\u003e1\/4\" F NPT\u003c\/td\u003e\n\u003ctd\u003eN\/A\u003c\/td\u003e\n\u003ctd\u003eDirect w\/felt\u003c\/td\u003e\n\u003ctd\u003e20\u003c\/td\u003e\n\u003ctd\u003eElectric dual\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eBLG\u003c\/td\u003e\n\u003ctd\u003e2-way\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e1\/4\" F NPT pilot\u003c\/td\u003e\n\u003ctd\u003e60\u003c\/td\u003e\n\u003ctd\u003eGas engine\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eBLE\u003c\/td\u003e\n\u003ctd\u003e2-way\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e1\/4\" F NPT pilot\u003c\/td\u003e\n\u003ctd\u003e60\u003c\/td\u003e\n\u003ctd\u003eElectric dual\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eNDC-1\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e3-way\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e1\/2\" F NPT\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e1\/2\" F NPT\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e3\/8\" NPT\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e25\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eElectric dual\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eNG-1\u003c\/td\u003e\n\u003ctd\u003e3-way\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e3\/8\" NPT\u003c\/td\u003e\n\u003ctd\u003e25\u003c\/td\u003e\n\u003ctd\u003eGas engine\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eNG-18\u003c\/td\u003e\n\u003ctd\u003e3-way\u003c\/td\u003e\n\u003ctd\u003e3\/4\" compression\u003c\/td\u003e\n\u003ctd\u003e1\/2\" F NPT\u003c\/td\u003e\n\u003ctd\u003e3\/8\" NPT\u003c\/td\u003e\n\u003ctd\u003e25\u003c\/td\u003e\n\u003ctd\u003eGas engine\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eNLDC-1\u003c\/td\u003e\n\u003ctd\u003e3-way\u003c\/td\u003e\n\u003ctd\u003e3\/4\" F NPT\u003c\/td\u003e\n\u003ctd\u003e3\/4\" F NPT\u003c\/td\u003e\n\u003ctd\u003e1\/2\" NPT\u003c\/td\u003e\n\u003ctd\u003e50\u003c\/td\u003e\n\u003ctd\u003eElectric dual\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eNLG-7\u003c\/td\u003e\n\u003ctd\u003e3-way\u003c\/td\u003e\n\u003ctd\u003e3\/4\" male comp.\u003c\/td\u003e\n\u003ctd\u003e3\/4\" male NPT\u003c\/td\u003e\n\u003ctd\u003e1\/2\" NPT\u003c\/td\u003e\n\u003ctd\u003e50\u003c\/td\u003e\n\u003ctd\u003eGas engine\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cp\u003e\u003cstrong\u003ePSI Suffix:\u003c\/strong\u003e Add 100 (for 100–120 PSI) or 140 (for 140–170 PSI) to the part number when ordering. Example: NDC-1100 or NDC-1140. \u003cstrong\u003eMuffler:\u003c\/strong\u003e Castair M38 fits the 3\/8\" vent port on the NDC-1, NG-1, and NG-18.\u003c\/p\u003e\n\n\u003ch3\u003eWhen Does a Shop Need the NDC-1 vs. Alternatives\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNDC-1 is right when:\u003c\/strong\u003e You have an electric motor-driven reciprocating compressor, a dual-pressure-switch control system, 1\/2\" NPT control lines, and the compressor runs 25 CFM or less through the valve. It is also the correct replacement when the original NDC-1 has failed and the original plumbing is intact.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStep up to NLDC-1 when:\u003c\/strong\u003e Your compressor exceeds 25 CFM at the valve, or you have 3\/4\" NPT control lines. The NLDC-1 handles 50 CFM with 3\/4\" fem. NPT inlet and outlet. It costs more ($324.94 vs. $110.11), but undersizing the valve on a larger compressor causes pressure drop and failed unload cycles.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUse NG-1 instead when:\u003c\/strong\u003e Your compressor is gas engine-driven. The port sizes are identical to the NDC-1 (1\/2\" NPT inlet and outlet, 3\/8\" vent), but the NG-1 is mechanically operated rather than solenoid-operated. Gas engines do not produce the electrical switching signal the NDC-1's solenoid needs.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStep down to BE2-M when:\u003c\/strong\u003e Your control system only needs a 2-way function with 1\/4\" NPT connections at 20 CFM or less. The BE2-M is a simpler, lower-cost valve for smaller electric dual systems.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDo not use on gas engine compressors:\u003c\/strong\u003e The NDC-1 is electrically operated. It will not function correctly without the solenoid trigger signal that an electric dual control system provides.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e NDC-1\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eValve Type:\u003c\/strong\u003e 3-way pilot valve\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Electric dual air compressor control systems\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOperation:\u003c\/strong\u003e Solenoid-operated\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInlet Port:\u003c\/strong\u003e 1\/2\" female NPT\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOutlet Port:\u003c\/strong\u003e 1\/2\" female NPT\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eVent Outlet Port:\u003c\/strong\u003e 3\/8\" NPT\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePilot Ports:\u003c\/strong\u003e 1\/8\" female NPT\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaximum Flow Capacity:\u003c\/strong\u003e 25 CFM\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePressure Range Options:\u003c\/strong\u003e 100–120 PSI (order as NDC-1100) or 140–170 PSI (order as NDC-1140)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Castair\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $110.11\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCompatible Muffler:\u003c\/strong\u003e Castair M38 (3\/8\" vent port)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eAir Compressor Factory Direct has specialized in compressor parts and controls since 2016. We stock Castair pilot valves including the complete NDC-1 lineup across both pressure ranges. When you call, you talk to someone who understands how pilot valves fit into the load\/unload circuit — not a general parts counter that will guess at a substitute.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree Shipping:\u003c\/strong\u003e All orders ship free. No minimum.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree Tech Support:\u003c\/strong\u003e Call 866-217-0063 before you order if you are not sure whether the NDC-1 or a different valve fits your application. We will confirm the correct part number and pressure range.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFull Manufacturer Warranty:\u003c\/strong\u003e Castair warranty applies to every valve we sell. No grey-market parts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHonest Guidance:\u003c\/strong\u003e If you need the NLDC-1 instead of the NDC-1, we will tell you. We would rather lose a $15 upsell than have you install the wrong valve and call back with a failed compressor.\u003c\/li\u003e\n\u003c\/ul\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":53342572282069,"sku":"NDC-1","price":203.06,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/AirCompressorPilotValve_72055a64-794e-443f-8809-98dd7aba5a37.jpg?v=1772652745","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-1-2npt-f-1-2-npt-f-outlet-vent-outlet-3-8-npt-25-max-cfm-electric-dual-3-way-pilot-valve-ndc-1","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}