{"product_id":"castair-adjustable-belt-tensioner-base-for-25-30hp-motors-284d","title":"Castair Adjustable Belt Tensioner Base for 25 \u0026 30HP Motors 284D","description":"\u003ch2\u003eCastair Adjustable Belt Tensioner Base — 284D, 25 HP and 30 HP, 284 Frame Motors\u003c\/h2\u003e\n\u003cp\u003eThe Castair 284D is the adjustable belt tensioner base for Castair belt-drive air compressors using 25 HP or 30 HP motors on the NEMA 284 frame. This is the base-only component — the adjustable slide plate and motor mounting bracket. At $203.28, it is the correct replacement when the tensioner base on your large-capacity Castair compressor is damaged or non-functional and the tensioner mechanism itself is still serviceable.\u003c\/p\u003e\n\u003cp\u003eAt 25 to 30 HP, a belt-drive compressor is putting serious torque through the drive. The belt forces acting on the motor mount are substantial — if the tensioner base cannot hold the motor firmly at the correct tension position, the entire drive system suffers. Slipping belts at this power level generate heat rapidly, wear sheave grooves, and can cause motor overcurrent from the torque load of trying to drive a slipping belt.\u003c\/p\u003e\n\u003ch3\u003ePart Details\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e 284D\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e Adjustable belt tensioner base (slide\/bracket only — tensioner mechanism not included)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible Motor Sizes:\u003c\/strong\u003e 25 HP and 30 HP\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMotor Frame:\u003c\/strong\u003e NEMA 284 (284T or equivalent)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $203.28\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eWhere the 284D Fits in the Castair Tensioner Range\u003c\/h3\u003e\n\u003cp\u003eCastair offers tensioner bases matched to motor HP and frame across their belt-drive line:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e215D ($138.91):\u003c\/strong\u003e For 7.5-10 HP, 215 frame motors\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e254D ($186.34):\u003c\/strong\u003e For 15 HP, 254 frame motors\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e256D ($186.34):\u003c\/strong\u003e For 20 HP motors\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e284D ($203.28, this part):\u003c\/strong\u003e For 25 HP and 30 HP, 284 frame motors\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe 284D covers both 25 HP and 30 HP because both use the NEMA 284T motor frame. Confirm your motor HP is 25 or 30 HP before ordering. Do not use a smaller tensioner base on a larger motor — the structural load from the belt tension and motor weight exceeds what a smaller base is rated to handle.\u003c\/p\u003e\n\u003ch3\u003eCompanion Motor for This Tensioner Base\u003c\/h3\u003e\n\u003cp\u003eThe standard 25 HP Castair motor for this tensioner base is the 25-284-3 (25 HP, 208\/230\/460V, 3-phase, 284T frame, 1725 RPM, $2,360.74). If you are replacing the tensioner base as part of a motor replacement, you may also need the 25-284-3 motor.\u003c\/p\u003e\n\u003ch3\u003eAdjustable Base Function at 25-30 HP\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSliding adjustment:\u003c\/strong\u003e Motor moves along the base to set belt tension. At 25-30 HP, correct tension is critical — too loose causes slippage, too tight overloads pump and motor bearings\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStructural requirement:\u003c\/strong\u003e The 284D is built to handle the reaction forces from a 25-30 HP belt drive. The base must resist the belt tension force without flexing or shifting\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLock-down mechanism:\u003c\/strong\u003e Heavy-duty fasteners hold the motor in position under load. Verify all fasteners are properly torqued after any tension adjustment\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eWhen Does a Shop Need This Part?\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDamaged base on a large-capacity Castair compressor:\u003c\/strong\u003e Physical damage, corrosion, or structural failure of the tensioner base on a 25 or 30 HP unit requires replacement — the 284D is the correct OEM part\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStripped adjustment hardware:\u003c\/strong\u003e If the slide adjustment hardware is stripped and the motor cannot be secured at the correct tension position, replace the base\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMajor service on a 25-30 HP Castair compressor:\u003c\/strong\u003e When the compressor is already down for motor or pump service, evaluating and replacing an aging tensioner base is straightforward preventive maintenance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBuilding or rebuilding a large Castair belt-drive compressor:\u003c\/strong\u003e The 284D paired with the 25-284-3 motor and appropriate pump and sheaves gives you the correct drive assembly for 25 HP operation\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e 284D\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMotor HP Range:\u003c\/strong\u003e 25 HP, 30 HP\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMotor Frame:\u003c\/strong\u003e NEMA 284 (284T)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e Adjustable tensioner base only\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eList Price:\u003c\/strong\u003e $203.28\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eNote: Manufacturer product page data was not available at time of writing. Specifications are derived from the product name and part number. Contact us to confirm fit for your specific Castair compressor model before ordering.\u003c\/em\u003e\u003c\/p\u003e\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eWe have specialized in industrial air compressor equipment since 2016. The Castair tensioner base family — 215D through 284D — is part of our regular inventory. When you call us with your compressor model number, we can confirm the 284D is the correct base for your 25 or 30 HP installation, and advise on companion parts if you are doing a broader service.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on qualifying orders\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree tech support:\u003c\/strong\u003e Call 866-217-0063 to confirm the right part for your compressor\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e on all Castair parts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHonest guidance:\u003c\/strong\u003e We stock the full range of Castair tensioner bases and will confirm the correct one for your motor HP and frame\u003c\/li\u003e\n\u003c\/ul\u003e\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":53342504485077,"sku":"284D","price":374.88,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/3.jpg?v=1772652479","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-adjustable-belt-tensioner-base-for-25-30hp-motors-284d","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}