Assess First. Recommend Second.
A compact combi configuration from Vaillant’s specification range.
A compact combi configuration from Vaillant’s specification range.
CH means central heating; DHW means domestic hot water. Heating ratings use flow/return water temperatures, not a whole-house sizing formula. Natural-gas figures are shown; no LPG rating is inferred. A cylinder-reheat rating is not instantaneous hot-water delivery.
| Model / label | CH min–max at 80/60°C | CH max at 50/30°C | DHW maximum | DHW flow at 35°C rise |
|---|---|---|---|---|
| ecoFIT sustain Combi 825 · 25 kW | 5.1–18.3 kW | 19.1 kW | Unverified — not inferred | 10.4 l/min |
| ecoFIT sustain Combi 830 · 30 kW | 6.1–18.3 kW | 19.1 kW | Unverified — not inferred | 12.2 l/min |
| ecoFIT sustain Combi 835 · 35 kW | 7.2–18.3 kW | 19.1 kW | Unverified — not inferred | 14.1 l/min |
The current specification brochure omits a separate maximum DHW heat-output row. The model labels and 35°C-rise flow rates are verified; the missing rating is not inferred.
Specification brochures differ on casing height, so exact dimensions must be confirmed against the selected installation manual.
The aluminium heat exchanger, top/rear flue options and cupboard-oriented casing support specification projects where consistent siting matters.
The March 2025 specification brochure lists the same CH maximum for all three combi labels. DHW labels and verified flow are shown without inventing a missing DHW heat-output figure.
The current specification sources do not establish one universal guarantee period for this range. The project contract and manufacturer registration terms must confirm the duration before quotation. Registration within the manufacturer deadline, correct commissioning, system-water preparation and annual servicing are required. Installer status, eligible protection kit/filter and current manufacturer terms must be confirmed in your written quotation; maximum cover is not automatic. SwiftHeat accreditation is not asserted here.
Keep commissioning, registration and annual-service records. Any extension or paid upgrade is confirmed before purchase and remains subject to current manufacturer terms.
Manufacturer guarantee information for this rangeVaillant offers eBUS controls and connected-control options. The exact boiler generation, control, gateway, wiring and system accessories must be checked together during assessment; no universal thermostat compatibility is promised.
Exact casing dimensions and service clearances are confirmed against the selected appliance manual during survey.
SwiftHeat assesses fuel, heat loss, hot-water demand, system condition, flue and condensate routing, controls and access before confirming suitability. Assess First. Recommend Second.
The table separates the manufacturer model label from heating output at 80/60°C, the condensing heating maximum at 50/30°C and any verified DHW or cylinder-reheat rating. Missing figures remain unverified; labels are not substituted for technical ratings.
The current specification sources do not establish one universal guarantee period for this range. The project contract and manufacturer registration terms must confirm the duration before quotation. Registration within the manufacturer deadline, correct commissioning, system-water preparation and annual servicing are required. Installer status, eligible protection kit/filter and current manufacturer terms must be confirmed in your written quotation; maximum cover is not automatic. SwiftHeat accreditation is not asserted here.
The March 2025 specification brochure lists the same CH maximum for all three combi labels. DHW labels and verified flow are shown without inventing a missing DHW heat-output figure. Suitability depends on the property’s calculated heating and hot-water requirements and must be confirmed following assessment.
Checked 2 October 2026. Product generation, availability and terms are reconfirmed when preparing your quotation.
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 advicePrice 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.
Understand suitable boiler types · Start the Boiler Finder · Our installation assessment · Areas we cover
