Nti 84749 O-ring D17X4 Large Combi Block Inlet Outlet

Product Description

The NTI 84749 is a replacement O-ring designed for use with the large combi block inlet and outlet connections on NTI combination boilers. This O-ring carries the D17X4 designation, which refers to its specific dimensional profile. The inner diameter measures 17 millimeters and the cross-section thickness measures 4 millimeters. These dimensions are critical for ensuring a proper fit and a leak-free seal in the combi block assembly. NTI combination boilers are hydronic heating systems that provide both space heating and domestic hot water from a single compact unit. The combi block is a central manifold component that routes water flow between the heating loop and the domestic hot water heat exchanger. Inlet and outlet ports on the combi block rely on precision-fit O-rings to maintain a pressure-tight connection. When these O-rings wear out, crack, or deform over time, water leaks can develop at the manifold connections. Replacing a failed O-ring with the correct OEM part restores the integrity of the seal and prevents ongoing water damage or system inefficiency. HVAC technicians and boiler service professionals working on NTI combination boilers should keep this O-ring on hand as a standard service part. It is commonly needed during annual maintenance, heat exchanger cleaning, or any service call that requires disassembly of the combi block. Using the correct manufacturer part number 84749 ensures compatibility and proper sealing performance. This is a genuine NTI replacement part and is the correct specification for the large combi block configuration. Accurate identification of the combi block size is important before ordering, as NTI produces both standard and large combi block variants requiring different O-ring sizes.

• Replacement O-ring for NTI large combi block inlet and outlet connections
• D17X4 profile with 17 millimeter inner diameter and 4 millimeter cross-section thickness
• Restores leak-free seal at combi block manifold ports on NTI combination boilers

Product Highlights

The NTI 84749 O-ring is a precision replacement seal for the large combi block inlet and outlet on NTI combination boilers. Correct fitment with this OEM part prevents water leaks and maintains reliable boiler operation.

Product Information

Standard Information

• Brand: NTI
• Manufacturer Part Number: 84749

Technical Specifications

• O-Ring Designation: D17X4
• Inner Diameter: 17 millimeters
• Cross-Section Thickness: 4 millimeters
• Application: Large Combi Block Inlet and Outlet
• Compatible Equipment: NTI Combination Boilers
• Part Type: OEM Replacement O-Ring