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ecoFIT sustain 25, 30 and 35kW

Specification combination boiler range

  • Designed for specification in the new build and social housing market
  • Compact cupboard fit with rear flue option
  • High efficiency ErP 'A' rated product with strong SAP ratings
  • Compatible with the full range of Vaillant controls and accessories
  • High quality lightweight aluminium heat exchanger with excellent power to weight ratio
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Combination boiler range

The ecoFIT sustain range of combination boilers offers an excellent size-to-output ratio, providing great comfort whilst ensuring a small footprint. Use of sustainable materials also means the boiler is 100% recyclable. The range features 25, 30 and 35kW models to suit all types of homeowner and tenant properties.

Key features and benefits

• Compact, cupboard fit solution – A smaller boiler footprint (702mm x 390mm x 295mm) means the ecoFIT Sustain offers siting flexibility, including cupboard fit

• Top and rear flue options - For flexible siting options in a wide variety of properties

• High SAP performance - Helps reduce new build cost. Highly efficient and economical to run up to an 89.3% efficiency rating (SAP 2009)

• High-quality lightweight aluminium heat exchanger - Lightweight, compact design offers long life with an excellent power-to-weight ratio makes installs/maintenance easier

• Patented 4 sided cooling - Reduces stress on all components to minimise the cost of maintenance over the life of the product

• Familiar Vaillant diagnostics - Offers quick and easy maintenance for your maintenance team

• Patented condensate trap - Easy install with a safety back-up

• Fully modulating low NOx burner and fan - For improved energy efficiency

• Recognised Grundfos high-efficiency pump - Modulating high-torque pump uses low energy to deliver a balanced output to meet the boiler demand helping to reduce energy consumption

• Built-in two-stage frost protection - To ensure optimal performance all year round

• Warm start function - Provides tenants with instant hot water

• Modulation range up to a 1:5 - Ensuring low energy consumption and maximum efficiency

• Clear bright LCD display - Easy to read boiler wherever it is sited

• Up to 10m flue lengths - Allows maximum flexibility for location of the boiler

• Controls compatibility - The wide range of Vaillant room thermostats, wired & wireless controls including the vSMART™ app-based controls with weather compensation to lower running costs for tenants

• Quiet Mark accredited - Thanks to being ultra-quiet whilst in operation

• ErP 'A' Rated product - Suitable for both refurbishment and new build with lower running cost to reduce heating bills



Technical dataUnit of measureecoFIT sustain 825ecoFIT sustain 830ecoFIT sustain 835
Boiler type CombiCombiCombi
LPG Convertible NoNoNo
Article number 001002039200100203930010020394
PCDB Number 017958017959017960
Boiler dimensions (HxWxD)mm702 x 390 x 295702 x 390 x 295702 x 390 x 295
Side Clearancemm555
Top Clearancemm150150150
Top clearance if using rear fluemm202020
Bottom Clearancemm150150150
Front Clearance *mm600600600
Can be reduced to 5mm if fitted behind a removable door/panel    
Nominal heat output range at 50/30˚C (Condensing mode)kW5.3 - 19.16.3 - 19.17.5 - 19.1
Nominal heat output range at 80/60˚C (Non condensing mode)kW5.1 - 18.36.1 - 18,37.2 - 18.3
Flow temperature range˚C10 - 8010 - 8010 - 80
Modulation (max/min)1 : X1:51:51:5
Domestic Hot Water  
Maximum heat output for water generationkW25.730.,635.7
Lowest water pressure to operate boilerbar0.30.30.3
Lowest water flow for operationl / min1.91.91.9
Domestic hot water flow rate (at DT = Δ35K)l / min10.412.214.1
Hot water output temperature range˚C35 - 60 35 - 6035 - 60
Gas inlet connection (pipe size)mm151515
Heating flow and return connections (pipe size)mm222222
Hot and cold water connections (pipe size)mm151515
Heat exchanger materialStainless/ AluminiumAluminiumAluminiumAluminium
Filling loop suppliedYes/noNoNoNo
Boiler lift weight (Dry boiler)kg323333
Spacer frame availableYes/noYesYesYes
NOx (En 15502-2-1)mg/kWh38.938.337.2
ErP efficiency%939393
ErP decibel rating (sound power)dBa494445
PCDB seasonal efficiency (SAP2009/2012)%89.389.389.3
Fluing options 
Maximum horizontal flue length 60/100m101010
Maximum vertical flue length 60/100m101010
Maximum horizontal flue length 80/125m252525
Maximum vertical flue length 80/125m252525
Rear flue optionsYes/noYesYesYes
Permissible flue classifications C13, C33, C43, C53C13, C33, C43, C53C13, C33, C43, C53


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