{"product_id":"navien-lcb700-21kw-rsx-external-regular-oil-boiler-lcb700-21rsx","title":"Navien LCB700 21kW RSX External Regular Oil Boiler - LCB700-21RSX","description":"\u003ch2\u003eNavien LCB700 21kW RSX External Regular Oil Boiler - LCB700-21RSX\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eNavien LCB700-21RSX 21kW External Regular Oil Boiler\u003c\/strong\u003e is a high-efficiency condensing oil-fired heat-only boiler designed for external installation, making it an excellent option where valuable indoor space needs to be preserved.\u003c\/p\u003e\n\n\u003cp\u003ePart of Navien's advanced \u003cstrong\u003eLCB700 Blue Flame\u003c\/strong\u003e range, the LCB700-21RSX combines efficient blue flame combustion technology, a durable stainless-steel heat exchanger, HVO compatibility and long-flue capability in a robust external boiler design.\u003c\/p\u003e\n\n\u003cp\u003eThe boiler provides two-stage heating performance of \u003cstrong\u003e16kW \/ 21kW at 80\/60°C\u003c\/strong\u003e, with maximum output increasing to approximately \u003cstrong\u003e23.0kW at 50\/30°C\u003c\/strong\u003e. This makes the 21RSX particularly suitable for smaller to medium-sized properties where a regular oil boiler and stored domestic hot water system are required.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003eNavien LCB700 Blue Flame oil boiler\u003c\/li\u003e\n  \u003cli\u003eModel: \u003cstrong\u003eLCB700-21RSX\u003c\/strong\u003e\n\u003c\/li\u003e\n  \u003cli\u003eExternal Regular \/ Heat Only boiler\u003c\/li\u003e\n  \u003cli\u003eMaximum nominal heating output: \u003cstrong\u003e21kW\u003c\/strong\u003e\n\u003c\/li\u003e\n  \u003cli\u003eTwo-stage 16kW \/ 21kW output at 80\/60°C\u003c\/li\u003e\n  \u003cli\u003eUp to 23.0kW output at 50\/30°C\u003c\/li\u003e\n  \u003cli\u003eAdvanced Blue Flame combustion technology\u003c\/li\u003e\n  \u003cli\u003eErP A-rated as standard\u003c\/li\u003e\n  \u003cli\u003e93% ErP efficiency\u003c\/li\u003e\n  \u003cli\u003eCan achieve an A+ system rating with qualifying Smart Plus controls\u003c\/li\u003e\n  \u003cli\u003eHVO compatible\u003c\/li\u003e\n  \u003cli\u003eStainless-steel heat exchanger\u003c\/li\u003e\n  \u003cli\u003eLow NOx emissions\u003c\/li\u003e\n  \u003cli\u003eDesigned specifically for external installation\u003c\/li\u003e\n  \u003cli\u003eBuilt-in frost protection\u003c\/li\u003e\n  \u003cli\u003eText-driven integral display\u003c\/li\u003e\n  \u003cli\u003eDisplays operating and fuel consumption information\u003c\/li\u003e\n  \u003cli\u003e3-zone ready with Navien Smart Plus controls\u003c\/li\u003e\n  \u003cli\u003eFlexible pipework arrangements\u003c\/li\u003e\n  \u003cli\u003eCombined PRV \/ condensate drainage arrangement\u003c\/li\u003e\n  \u003cli\u003e60\/100mm coaxial plastic flue system\u003c\/li\u003e\n  \u003cli\u003eMaximum horizontal flue length up to 20 metres\u003c\/li\u003e\n  \u003cli\u003eMaximum vertical flue length up to 21 metres\u003c\/li\u003e\n  \u003cli\u003e10-year parts and labour warranty as standard, subject to Navien terms\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specification\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBrand:\u003c\/strong\u003e Navien\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRange:\u003c\/strong\u003e LCB700\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eModel:\u003c\/strong\u003e LCB700-21RSX\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eProduct Type:\u003c\/strong\u003e External Regular Oil Boiler\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBoiler Type:\u003c\/strong\u003e Condensing Regular \/ Heat Only Boiler\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInstallation Location:\u003c\/strong\u003e External\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFuel Type:\u003c\/strong\u003e Heating Oil \/ Kerosene\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHVO Compatible:\u003c\/strong\u003e Yes\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHeat Input Stage 1 \/ Stage 2:\u003c\/strong\u003e 17kW \/ 22kW\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHeat Output at 80\/60°C:\u003c\/strong\u003e 16kW \/ 21kW\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaximum Heat Output at 50\/30°C:\u003c\/strong\u003e 23.0kW\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eErP Energy Rating:\u003c\/strong\u003e A\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eErP Efficiency:\u003c\/strong\u003e 93%\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePotential System Rating:\u003c\/strong\u003e Up to A+ with qualifying Smart Plus configuration\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNOx Emissions:\u003c\/strong\u003e 57.2mg\/kWh\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHeat Exchanger:\u003c\/strong\u003e Stainless Steel\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCombustion Technology:\u003c\/strong\u003e Blue Flame\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFlue Type:\u003c\/strong\u003e Coaxial Plastic\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFlue Size:\u003c\/strong\u003e 60\/100mm\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaximum Horizontal Flue Length:\u003c\/strong\u003e 20m\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaximum Vertical Flue Length:\u003c\/strong\u003e 21m\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e87° \/ 90° Elbow Equivalent:\u003c\/strong\u003e 1.3m\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e45° Elbow Equivalent:\u003c\/strong\u003e 1.0m\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eExternal Width:\u003c\/strong\u003e 515mm\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eExternal Depth:\u003c\/strong\u003e 673mm\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eExternal Height:\u003c\/strong\u003e 882mm\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBoiler Weight:\u003c\/strong\u003e 64kg\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eControl:\u003c\/strong\u003e Integral text-driven display\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSmart Control Compatibility:\u003c\/strong\u003e Navien Smart Plus\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eZone Capability:\u003c\/strong\u003e Up to 3 zones with compatible Smart Plus controls\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFrost Protection:\u003c\/strong\u003e Built-in frost thermostat\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWarranty:\u003c\/strong\u003e 10-year parts and labour warranty subject to Navien terms\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eDesigned for External Installation\u003c\/h3\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eLCB700-21RSX\u003c\/strong\u003e is specifically designed for external installation, allowing the boiler to be located outside the property rather than occupying valuable kitchen, utility room or cupboard space.\u003c\/p\u003e\n\n\u003cp\u003eThe external enclosure protects the boiler components while Navien's built-in frost protection system helps protect the appliance during cold conditions, provided the boiler remains electrically powered and installed in accordance with Navien's instructions.\u003c\/p\u003e\n\n\u003ch3\u003eBuilt-In Frost Protection\u003c\/h3\u003e\n\n\u003cp\u003eNavien boilers incorporate an automatic frost protection function. If the water temperature within the boiler falls to a sufficiently low level, the boiler and pump can operate automatically to protect the appliance from freezing.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eExternal system pipework must still be correctly insulated and protected against freezing.\u003c\/strong\u003e Additional frost protection may be required depending on the installation location and system design.\u003c\/p\u003e\n\n\u003ch3\u003eBlue Flame Oil Technology\u003c\/h3\u003e\n\n\u003cp\u003eThe LCB700 range uses Navien's \u003cstrong\u003eBlue Flame combustion technology\u003c\/strong\u003e to provide highly efficient oil combustion with reduced emissions.\u003c\/p\u003e\n\n\u003cp\u003eThe LCB700-21RSX achieves an \u003cstrong\u003eErP A rating and 93% efficiency\u003c\/strong\u003e as standard while producing NOx emissions of approximately \u003cstrong\u003e57.2mg\/kWh\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003ch3\u003eTwo-Stage 21kW Heating Performance\u003c\/h3\u003e\n\n\u003cp\u003eThe 21RSX provides two-stage heating output of approximately \u003cstrong\u003e16kW and 21kW at 80\/60°C\u003c\/strong\u003e. At lower-temperature condensing conditions of 50\/30°C, maximum useful output is approximately \u003cstrong\u003e23.0kW\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003cp\u003eThis two-stage operation allows the boiler to respond more effectively to changing heating demand than a simple fixed-output appliance.\u003c\/p\u003e\n\n\u003ch3\u003eHVO Compatible\u003c\/h3\u003e\n\n\u003cp\u003eNavien identifies the LCB700 range as \u003cstrong\u003eHVO compatible\u003c\/strong\u003e, helping provide flexibility for properties that may move towards lower-carbon liquid heating fuels.\u003c\/p\u003e\n\n\u003cp\u003eAny change of fuel type or burner setup must be undertaken in accordance with Navien's latest technical requirements by a suitably qualified oil heating engineer.\u003c\/p\u003e\n\n\u003ch3\u003eStainless-Steel Heat Exchanger\u003c\/h3\u003e\n\n\u003cp\u003eA durable \u003cstrong\u003estainless-steel heat exchanger\u003c\/strong\u003e is used within the LCB700 range, providing resistance to the acidic condensate produced by a high-efficiency condensing oil boiler while helping maintain long-term efficiency.\u003c\/p\u003e\n\n\u003ch3\u003eFlexible Flue Options\u003c\/h3\u003e\n\n\u003cp\u003eThe LCB700 uses a \u003cstrong\u003e60\/100mm coaxial plastic flue system\u003c\/strong\u003e and provides unusually flexible flue routing options.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eMaximum horizontal equivalent length: up to 20m\u003c\/li\u003e\n  \u003cli\u003eMaximum vertical equivalent length: up to 21m\u003c\/li\u003e\n  \u003cli\u003e87° \/ 90° elbow equivalent: approximately 1.3m\u003c\/li\u003e\n  \u003cli\u003e45° elbow equivalent: approximately 1.0m\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eActual permitted flue length depends on the complete flue arrangement and must be calculated in accordance with Navien installation instructions.\u003c\/p\u003e\n\n\u003ch3\u003eSmart Plus Heating Controls\u003c\/h3\u003e\n\n\u003cp\u003eThe Navien LCB700 is compatible with the \u003cstrong\u003eNavien Smart Plus control system\u003c\/strong\u003e. A correctly configured system can provide up to three heating zones, offering greater control over different areas of the property.\u003c\/p\u003e\n\n\u003cp\u003eNavien states that a qualifying Smart Plus configuration can improve the overall heating system rating from ErP A to \u003cstrong\u003eErP A+\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003ch3\u003eRegular \/ Heat Only Boiler\u003c\/h3\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eLCB700-21RSX is a Regular \/ Heat Only boiler\u003c\/strong\u003e and does not produce instantaneous domestic hot water like a combination boiler.\u003c\/p\u003e\n\n\u003cp\u003eIt is designed to form part of a traditional heating system incorporating the appropriate external components and, where domestic hot water is required, a separate hot water cylinder.\u003c\/p\u003e\n\n\u003ch3\u003e10-Year Warranty\u003c\/h3\u003e\n\n\u003cp\u003eNavien currently supplies the LCB700 range with a \u003cstrong\u003e10-year parts and labour warranty as standard\u003c\/strong\u003e, subject to qualifying installation, commissioning, product registration, servicing and Navien's current warranty terms.\u003c\/p\u003e\n\n\u003ch3\u003eImportant Product Information\u003c\/h3\u003e\n\n\u003cp\u003eThis listing is for the \u003cstrong\u003eNavien LCB700-21RSX 21kW External Regular Oil Boiler\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDo not confuse the LCB700-21RSX with the internal LCB700-21RS, the external LCB700-21LSX System Boiler or the external LCB700-21LCX Combi Boiler.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFlue components, hot water cylinder, system controls, oil line components, filters, valves, chemicals, pipework and other installation accessories are not included unless specifically stated elsewhere in the listing.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003ch3\u003eProfessional Installation Required\u003c\/h3\u003e\n\n\u003cp\u003eThis oil boiler must be installed and commissioned by a suitably qualified oil heating engineer. In the UK, installation by an \u003cstrong\u003eOFTEC registered technician\u003c\/strong\u003e is recommended.\u003c\/p\u003e\n\n\u003cp\u003eThe installer must confirm heat-loss requirements, boiler sizing, oil supply, fuel specification, heating system design, flue arrangement, frost protection, condensate disposal and all required controls and accessories before commissioning.\u003c\/p\u003e","brand":"Navien","offers":[{"title":"Default Title","offer_id":50557827547392,"sku":"NAVIEN-LCB700-21RSX","price":1801.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1050\/2814\/files\/Ext.webp?v=1792526697","url":"https:\/\/spares-direct.com\/products\/navien-lcb700-21kw-rsx-external-regular-oil-boiler-lcb700-21rsx","provider":"Spares Direct","version":"1.0","type":"link"}