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ecoFIT sustain 25, 30 and 35kW

Specification combination boiler range

  • Designed for specification in new build and social housing
  • Quiet Mark awarded
  • High efficiency ErP 'A' rated product
  • High quality lightweight aluminium heat exchanger with excellent power to weight ratio
  • Modulating high torque pump uses low energy


Combination boiler range

The ecoFIT sustain range of combination boilers offers an excellent size-to-output ratio, giving 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 properties.

Key features and benefits

  • Cupboard fit - Compact size (702mm x 390mm x 295mm) offers flexibility of siting including the option to cupboard-fit
  • Choice of rear or top flue - For flexible siting options in a wide variety of properties
  • High SAP performance - Helps reduce new build cost by up to 4% on TER. 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 1:4 - Ensuring low energy consumption and maximum efficiency
  • Clear bright LCD display - Easy to read boiler wherever it is sited
  • Best in class flue length (up to 10m) - Allows maximum flexibility for location of the boiler
  • Controls compatability - 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 tenant heating bills



Technical dataUnit of measureecoFIT sustain 825ecoFIT sustain 830ecoFIT sustain 835
Boiler type combicombicombi
Signature model output 25kW30kW35kW
Article number 001002039200100203930010020394
Gas Council number 47-044-7147-044-7247-044-73
Boiler dimensions (HxWxD)mm700 x 390 x 295700 x 390 x 295700 x 390 x 295
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
Maximum flow temperature˚C808080
Flow temperature range˚C10 - 8010 - 8010 - 80
Flow temperature factory setting˚C757575
Approximate condensate volume at 50/30˚Clitres/hr1.841.841.84
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
Lowest water pressure for maximum flow ratebar111
Domestic hot water flow rate (at DT = Δ35K) *l/min10.412.214.1
Hot water output temperature range˚C35 - 6035 - 6035 - 60
Expansion vessel sizelitres888
Gas inlet connection (pipe size)mm151515
Heating flow and return connections (pipe size)mm222222
Hot and cold water connections (pipe size)mm151515
Heat exchanger material AluminiumAluminiumAluminium
Boiler lift weightkg323333
NOx class 555
NOx (En 15502-2-1)mg/kWh38.938.337.2
ErP efficiency%939393
ErP decibel rating (sound power)dBa494445
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

*flow restrictor fitted to achieve a Δ42K rise

Related Products

Related Products

Domestic boiler cylinders

  • Slim line, pre plumbed and standard cylinders in the range
  • 2 year guarantee on parts and labour plus 25 year guarantee for the cylinder shell, giving you total peace of mind.
  • Can be retrofitted onto older systems meaning you can upgrade your cylinder without the hassle of the entire system.

VRT 15

  • Simple 230V analogue room thermostat
  • Compatible with timeSWITCH 160
  • Easy to use

VRT 50 Digital Thermostat

  • Easy to use
  • Enhanced load compensation
  • Service, maintenance & fault indicator

VRT 350 & 350f

  • New attractive, easy to use design with blue backlit display
  • Adjusts heating and hot water to British summer/winter time
  • Two temperature setting levels: desired and set-back temperatures

timeSWITCH 150 Boiler Controls

  • Single channel analogue timer
  • Mounts directly into boiler fascia
  • 24-hour timer for central heating

vSMART™ intelligent room control with app

  • Smart phone app for both Android and Apple iOS application
  • Self learning
  • Weather compensation