ecoTEC exclusive Green iQ 835, 843

ecoTEC exclusive combination boilers

  • Wide modulation range of up to 1:10
  • Extra-condense heat exchanger
  • High power, 43kW output model available
  • Green iQ mode
  • 7 year warranty available with options up to 10 years when registered on Vaillant Advance


The new ecoTEC exclusive Green iQ is our first ever boiler product with the power of Green iQ technology.

Combining our complete range of smart technologies and features, you can be sure you’re fitting the very best when you fit new ecoTEC exclusive. As well as providing great performance, the new ecoTEC exclusive intelligently manages consumption and output to keep all its components running at peak performance, for longer, providing a low-maintenance solution that you can rely on.

The ecoTEC exclusive range consists of two large output combination boilers with Extra-Condense technology, and a single system boiler, which includes an integrated diverter valve for the first time in UK Vaillant history.

Features and benefits:

  • Wide modulation range of up to 1:10 - adapts perfectly to all systems in every situation, ensuring lowest fuel bills for your customers
  • All-gas system - always reaches optimal combustion with lowest emissions. As a self-adaptive system, it automatically adjusts to all types of gas
  • Extra-Condense heat exchanger - taking overall combi boiler efficiency to the next level, and almost eliminating plume in DHW mode
  • Green iQ Mode - outstanding eco-credentials from Vaillant’s latest boiler range, which optimises running cycles, results in even lower gas consumption and the boiler is highly recyclable (85%) at the end of its life
  • High power, 43kW output model available - delivers Vaillant’s highest ever flow rate of 17.8 l/min
  • Compatible with Vaillant’s vSMART™ heating control
  • Standard 2 year warranty, can be upgraded to a free 7 year warranty when registered through Vaillant Advance
  • Option to purchase extended warranty up to 10 years when registered through Vaillant Advance



ecoTEC exclusiveecoTEC exclusive 835ecoTEC exclusive 843
Article number 00100170640010017065
Nominal heat output range P at 50/30°C (kW)"3.9 - 26.4
(LPG 8.6 - 26.4)"
"4.8 - 36
(LPG: 8.5 - 36.0)"
Nominal heat output range P at 80/60°C (kW)"3.4 - 24.6
(LPG: 7.6 - 24.6)"
"4.3 - 33.4
LPG: 7.6 - 33.4)"
Maximum heat output for water generation (kW)35.343.4
Nominal heat input for Central heating (kW)"3.6 - 24.8
(LPG: 8.0 - 24.8)"
"4.5 - 33.7
(LPG: 8.0 - 33.7)"
Heating setting range (kW)
4 - 25

5 - 34
Max. Flow temperature (°C)8585
Max. Flow temperature setting range (factory setting 75°C) (°C)30 - 8530 - 85
Expansion vessel capacity (l)1010
Nominal Gas consumption (m3/hr)"3.5
(LPG: 2.54)"
(LPG: 3.12)"
DHW mode
Lowest water volume for operation (I/min)1.51.5
DHW performance (at DT=∆35K) (I/min)14.517.8
Hot water output temperature range (°C)35 - 6535 - 65
Boiler-side gas connection (mm)1520
Flow/return heating connections, boiler side (mm)G3/4"G3/4"
Hot and cold water connection, boiler side (inches)G3/4"G3/4"
Approved flue gas connectionsC13, C33, C54C13, C33, C54
Nox (mg/kWh)34.936.8
ErP efficiency94%94%
ErP Rating (Heating/Hot Water)A/AA/A
Boiler dimensions (H x W x D)720 x 440 x 406 720 x 440 x 474
Mounting weight approx.42.550

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