Assess First. Recommend Second.
A higher hot-water-output combi with an integral recirculation pump and NaviCirc compatibility.
Subject to registration, correct commissioning and recorded annual servicing.
Your written quotation confirms the cover included. Register within one month of installation.
The model-specific UK page advertises 12 years of boiler warranty. The installation manual requires registration within one month, correct installation and commissioning, a completed Benchmark checklist and servicing at least annually by a competent Gas Safe registered engineer, with records retained. System-water treatment and any required protection components must meet the selected manual. Maximum cover is not automatic; the written quotation confirms actual cover. No manufacturer accreditation or paid extension entitlement is assumed. Any proposed extension, qualifying components or installer eligibility must be verified before agreement. Component-only cover must not be presented as whole-boiler cover.
Official model warranty information · Check registered warranty · Installation and servicing requirementsA higher hot-water-output combi with an integral recirculation pump and NaviCirc compatibility.
Natural-gas specification table: heating at 80/60°C; condensing heating at 50/30°C. LPG conversion is supported but no LPG performance figure is inferred.
| Model / configuration | Heating at 80/60°C | Heating at 50/30°C | Hot-water output | Hot-water delivery |
|---|---|---|---|---|
| NCB700-2S+/42K | 3.4–34 kW | 37.1 kW | 42 kW | 17.2 l/min at 35°C rise |
| NCB700-3S/54K | 3.4–34 kW | 37.1 kW | 54 kW | 22.1 l/min at 35°C rise |
Navien documents natural-gas/LPG conversion for these configurations using the supplied kit. A Gas Safe engineer qualified for LPG must verify the correct kit, gas supply and manual, then convert, label and commission the appliance. The displayed output, flow and efficiency figures are natural-gas data, not verified LPG performance.
Model designations are verified; a separate merchant SKU or retail order code has not been verified and must be confirmed before ordering.
The product webpage shows flow at a 30°C rise; the linked installation manual separately confirms 17.2 and 22.1 l/min at a 35°C rise, used here. These are test ratings, not guaranteed household delivery.
| Configuration | Weight | Published modulation | Energy rating |
|---|---|---|---|
| NCB700-2S+/42K | 43 kg | 10:1 — manufacturer table | ErP A (94%) |
| NCB700-3S/54K | 46 kg | 15:1 — manufacturer table | ErP A (94%) |
A+ is a conditional package rating with the specified Navien Smart Plus controls, not the appliance alone. Lift weight and shipping weight can differ. Navien publishes different modulation ratios by configuration; the heating-output range and DHW output must be read separately.
Outlet descriptions are manufacturer guidance, subject to sufficient measured water flow and dynamic pressure, outlet temperatures and pipework. Bathroom count alone does not establish delivery or suitability.
The two variants share a 34 kW maximum heating rating at 80/60°C, while hot-water outputs are 42 and 54 kW. Recirculation can reduce waiting where the pipework and controls are designed for it.
A high hot-water rating cannot correct a restricted mains supply. Assess dynamic flow, pipework and recirculation design before making a multi-outlet plan.
The model-specific UK page advertises 12 years of boiler warranty. The installation manual requires registration within one month, correct installation and commissioning, a completed Benchmark checklist and servicing at least annually by a competent Gas Safe registered engineer, with records retained. System-water treatment and any required protection components must meet the selected manual. Maximum cover is not automatic; the written quotation confirms actual cover. No manufacturer accreditation or paid extension entitlement is assumed. Any proposed extension, qualifying components or installer eligibility must be verified before agreement. Component-only cover must not be presented as whole-boiler cover.
Official model warranty statement · Registered warranty lookupNavien documents an integral DHW recirculation pump, NaviCirc return-system support and Smart Plus control-pack compatibility. Check the required valve, circulation route and control configuration at survey.
Casing: 695 × 440 × 353 mm (H × W × D). Pipework, flue and installation/service clearances are additional.
The Finder can shortlist individual configurations from your fuel and design answers. LPG conversion compatibility is recorded, but LPG-specific performance and supply must be confirmed at survey. Final output is subject to heat-loss, water and installation assessment.
Combi guidanceA high hot-water rating cannot correct a restricted mains supply. Assess dynamic flow, pipework and recirculation design before making a multi-outlet plan.
The model-specific UK page advertises 12 years of boiler warranty. The installation manual requires registration within one month, correct installation and commissioning, a completed Benchmark checklist and servicing at least annually by a competent Gas Safe registered engineer, with records retained. System-water treatment and any required protection components must meet the selected manual. Maximum cover is not automatic; the written quotation confirms actual cover. No manufacturer accreditation or paid extension entitlement is assumed. Any proposed extension, qualifying components or installer eligibility must be verified before agreement. Component-only cover must not be presented as whole-boiler cover.
Navien lists natural-gas and LPG support with an included conversion kit. Conversion, gas supply and commissioning must be completed by a suitably qualified engineer. The natural-gas figures in this guide are not assumed LPG ratings.
The installed price for your selected boiler is confirmed after assessment. The quotation covers the appliance, controls, flue, system preparation and any required pipework. A conversion or relocation can have a different scope from a straightforward replacement.
New boiler installations from £1,790 inc. VAT apply to a qualifying standard, straightforward replacement: one bathroom, fewer than 10 radiators and a standard horizontal flue, subject to survey. Specification and warranty selection affect the final cost. This is a general starting offer and is not a price for every model in this catalogue.
Read the starting-package conditions0% options over 3, 6, 9 or 12 months through Humm Group Limited, subject to application, affordability, eligibility, approval and provider terms. Any applicable deposit, fees and repayment conditions are confirmed during your enquiry/application. Acceptance is not guaranteed.
Finance terms and chargesTwo free annual services and a Hive Mini are available on qualifying installations only. Every model is considered under the qualification rules; inclusion in this catalogue does not confirm eligibility. Ask us to confirm the offer in your quotation.
Ask about Care+ eligibilityPlan the maintenance your appliance requires and keep its service records. If you are considering replacement because of a fault, diagnosis can help establish whether repair is a suitable option first.
Boiler servicing · Repair adviceProduct photography and technical information: Navien UK. Checked 2 October 2026. Family casing views may be shared across outputs; current stock and the precise supplied model are confirmed before quotation.
Price confirmed following assessment for this configuration. The general New boiler installations from £1,790 inc. VAT offer does not apply to every model or property.
From or indicative prices remain provisional. SwiftHeat issues a written fixed quotation for the agreed scope after the appropriate property and installation assessment, technical checks and warranty-package verification. Remote information gathering may be suitable initially; a home survey is required where the necessary checks cannot be completed remotely.
We assess heat loss, heating and hot-water requirements, water supply, controls and installation access before recommending an appliance. Bedroom count or a catalogue model number alone cannot establish the right boiler.
Gas Safe registration 978273 · Serving Cardiff, South Wales and across the UK.
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