Navien LCB700 Combi

At a glance

Fuel and arrangement

Oil — fuel grade and setup checked at survey · Combi

Nominal model labels

21 kW | 28 kW | 36 kW

Range position

Current UK oil directory; internal and external configurations

Warranty headline

Up to 10 years · Parts and labour · eligibility to be confirmed · subject to conditions

How this boiler works

An oil combi with a 30-litre internal storage tank, offered in indoor and outdoor casings.

Heating and hot-water specifications

Oil manual: two-stage heating outputs at 80/60°C (stage 1/stage 2); maximum condensing output at 50/30°C. Stage 1 is not a continuously modulating minimum.

The installation manual identifies kerosene Class C2 and light oil. The current product pages also describe HVO compatibility; do not assume HVO is a drop-in fuel without manufacturer-approved setup and fuel-supply checks.

Gas and LPG recommendations do not include this oil appliance. It remains a research listing requiring a fuel-specific assessment.

Retail order codes and current local stock must be confirmed; the model codes shown identify arrangement, output and casing.

The manual verifies a 30-litre combi tank. The brochure’s 14/18/20 l/min figures have ±15% tolerance and a 40°C maximum rise for a 90-litre draw-off; they are not gas-combi flow ratings at a 35°C rise.

Technical context for your assessment

A+ is a conditional package rating with the specified Navien Smart Plus controls, not the appliance alone. Lift weight and shipping weight can differ.

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.

Key benefits

The Blue Flame platform uses stainless-steel heat exchangers and two-stage heating output. Separate indoor and outdoor casings allow different siting plans; neither removes the need for service access, flue assessment and fuel-tank checks.

Key takeaway

Stored assistance changes the draw-off profile. Compare the 90-litre test with household routines rather than treating its peak delivery as unlimited instantaneous flow.

Warranty and ongoing care

Current Navien UK product pages advertise 10-year parts and labour cover. The oil service manual instead describes 2-year standard cover with extensions up to 10 years: confirm the applicable terms and installer eligibility with Navien before quotation. Register within 30 days, complete commissioning and the Benchmark checklist, and retain annual service records from a suitably qualified OFTEC registered engineer. Servicing is separately chargeable. Incorrect installation, unsuitable fuel or water, misuse and missed servicing can invalidate cover. The written quotation confirms actual cover; 10 years is not guaranteed.

Controls and installation space

Smart Plus support and three-zone control-pack compatibility are documented. Connected functions require the appropriate controls and network setup. Confirm the complete control design against the selected arrangement.

Casing dimensions vary by location: internal 860 × 600 × 600 mm (H × W × D); external 900 × 650 × 673 mm (H × W × D). Allow additional flue, pipework and service clearances.

Internal and external casing views

Internal model

Manufacturer warranty · Parts and labour · eligibility to be confirmedUp to 10 years

Subject to registration, correct commissioning and recorded annual servicing.

Your written quotation confirms the cover included. Register within 30 days; confirm applicable oil warranty terms and installer eligibility before quotation.

Warranty eligibility & conditions

Current Navien UK product pages advertise 10-year parts and labour cover. The oil service manual instead describes 2-year standard cover with extensions up to 10 years: confirm the applicable terms and installer eligibility with Navien before quotation. Register within 30 days, complete commissioning and the Benchmark checklist, and retain annual service records from a suitably qualified OFTEC registered engineer. Servicing is separately chargeable. Incorrect installation, unsuitable fuel or water, misuse and missed servicing can invalidate cover. The written quotation confirms actual cover; 10 years is not guaranteed.

Official model warranty information · Check registered warranty · Installation and servicing requirements

External model

Manufacturer warranty · Parts and labour · eligibility to be confirmedUp to 10 years

Subject to registration, correct commissioning and recorded annual servicing.

Your written quotation confirms the cover included. Register within 30 days; confirm applicable oil warranty terms and installer eligibility before quotation.

Warranty eligibility & conditions

Current Navien UK product pages advertise 10-year parts and labour cover. The oil service manual instead describes 2-year standard cover with extensions up to 10 years: confirm the applicable terms and installer eligibility with Navien before quotation. Register within 30 days, complete commissioning and the Benchmark checklist, and retain annual service records from a suitably qualified OFTEC registered engineer. Servicing is separately chargeable. Incorrect installation, unsuitable fuel or water, misuse and missed servicing can invalidate cover. The written quotation confirms actual cover; 10 years is not guaranteed.

Official model warranty information · Check registered warranty · Installation and servicing requirements

Continue your assessment

The Finder includes all six internal/external output configurations in this oil family. Select oil fuel, arrangement and casing location; unknown or conflicting requirements need assessment. Confirm storage, fuel supply and final output before specifying an appliance.

Model questions

Installation and pricing

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.

Official manufacturer sources

Product 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.

Installation pricing

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.

Your home comes first

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.