flexoTHERM 5, 8, 11, 15 and 19kW

Ground source heat pump

  • Available in 5, 8, 11, 15 & 19kW
  • Can connect to three different sources - ground, water or air
  • High seasonal SCoP value
  • Integral components - built in ground and heating circulation pumps and three-way diverter valve


flexoTHERM with Green iQ

A modern, refreshing take on the heat pump system, our new flexoTHERM with Green iQ can use three possible heat sources. flexoTHERM can be a ground source heat pump when connected to a group loop, it can be an air source heat pump when connected to our aroCOLLECT, or it can be a water source heat pump when connected with our fluoCOLLECT.

The flexoTHERM heat pump models are available in two categories, 230V in 5, 8 & 11kW, as well as 400V in 5, 8, 11, 15 and 19kW outputs and offer state of the art EVI compressor technology giving extremely high efficiency and heating performance.

The flexoTHERM has also been awarded the "Quiet Mark", issued by the Noise Abatement Society, thanks to its exceptionally low operating noise levels. It sounds no louder than a standard domestic fridge.

Features and benefits:

  • The flexoTHERM intelligent heat pump is available in two voltages with the following outputs - 230v in 5, 8 & 11kW and 400v in 5, 8, 11, 15 and 19kW models
  • Highest ErP rating A+++ - when installed with a VRC 700
  • High quality and sustainable product - Well engineered product of outstanding quality which is both sustainable and ready for the future
  • Easy installation: Integral components - built in ground and heating circulation pumps and three-way diverter valve
  • Extended range of accessories - Water heat exchanger, passive cooling and brine filling station
  • Flexible source options - Can connect to one of three different sources: ground, water or air
  • High SCoP - 15kW flexoTHERM is 35°C - 5.22 and 35°C - 4.96 for the 19kW model
  • Excellent customer service - Delivering market leading design, installation and commissioning support
  • Exceptionally quiet - With noise levels comparable to a modern fridge 42dBA

Your customers will feel the benefits too

  • Comfort up, consumption down - The flexoTHERM with Green iQ carries the highest energy efficiency label in its class: ErP rating A++. The Green iQ operation mode also helps reduce your customer's electricity bills.
  • Smart on the inside - Innovative technology is built right into the flexoTHERM exclusive with Green iQ.
  • Flexibility - The flexoTHERM prodives you with flexibility in the ways it can be installed, it works with all heat sources; ground, air or water.
  • Future-proof investment - The flexoTHERM is designed with future proof technology with keeps in mind the needs of tomorrow.
  • Intelligent use of resources - The uses of resources in an intelligent way enables the environment to deliver around 75% of the required energy for free. As the portion of renewable energy present in the electricity mix increases, your system gets more eco-friendly every year.



Electrical dataVWF 87/4
VWF 117/4
VWF 157/4VWF 197/4
Nominal voltage/rated voltage
Heating circuit/CompressorV/Hz1~/N/PE 230/50 2~/N/PE 230/503~/N/PE 400/50
Auxiliary Heating V/Hz1~/N/PE 230/50 2~/N/PE 230/503~/N/PE 400/50
Power factor  cos φ = 0.75 -0.9cos φ = 0.75 -0.9cos φ = 0.75 -0.9cos φ = 0.75 -0.9cos φ = 0.75 -0.9
Required network impedance Xmax with inrush current limiterΩ≤ 0.472≤ 0.472≤ 0.472≤ 0.472≤ 0.472
fuse type, caracteristic C, delay, three-pole switching (interrupt of the three power lines in one switching operation)ADesigning in accordance with the selected connection diagrams 32
Optional building earth leakage circuit breaker RCCB type A (type A current sensitive residual-current circuit breakers) or
RCCB type B (type B universial current sensitive residual-current circuit breakers)
Inrush currents - with initial current breakerA ≤19≤60≤26≤30
Rated current (compressor + Auxiliary heater)A 19.124.926.131.2
min. electrical power consumption of compressorkW 2.102.603.304.70
max. electrical power consumption of compressorkW 3.104.1015.6017.80
Protection class IP 10B
Hyrdraulic connection
Heating flow/return G 1 1/2"
Heat source flow/return G 1 1/2"
Central heating water expansion vessel G 3/4"
Heat source circuit/brine circuit
Volume of the brine circuit in the heat pump l
Materials of the brine circuit in the heat pump Cu, CuZn-Alloy, Stainless Steel, EPDM, Brass, Fe
min. pressure Brine liquidMPa (bar)≥ 0,07 (≥0,7)
max. pressure Brine liquidMPa (bar)≤ 0,3 (≤3)
Heating circuit/building circuit
Water volume of the heating circuit in the heat pumpl
Materials of the heating circuit Cu, CuZn-Alloy, Stainless Steel, EPDM, Brass, Fe
min. pressureMPa (bar)≥ 0,07 (≥0,7)
max. pressure MPa (bar)≤ 0,3 (≤3)
min. flow temperature heating °C25
max. flow temperature heating with compressor°C65
min. flow temperature cooling °C5
max. electrical power heating circuit pump W63140
Type of pump  High efficiency
Refrigerant circuit
Refrigerant type R 410 A
Volume of refrigerant circuit in the heat pumpkg 2.402.503.053.95
Global warming potential in accordance with (EU) No.517/2014 2088
CO2 equivalentt 5011522063688248
Global warming potential 100 (GWP100) in accordance with (EU) No. 842/2006 19751774
type expansion valve Electronic
Permissable pressure (relative) ≤ 4,6 (≤46,0)
Compressor type EVi Scroll
Oil type Ester (EMKARATE RL32-3 MAF)
Oil filing quantity 0.741.251.241.89
Heat source circuit/brine circuit
min. resource input temperature (Brine warm) when heating °C-10
max. resource input temperature (Brine warm) when heating °C25
min. resource input temperature (Brine warm) when cooling °C0
Nominal flow rate T 3K at BOW35l/h13002110287035904780
min. flow rate during continuous operation at the application limits l/h11901990257033804300
max. flow rate during continuous operation at the application limitsl/h13002110287035904780
max. rest pressure heat T 3K at BOW35mba0.630.0.4100.5500.9800.820
Electrical power for brine pump at BO/W35 T 3K at 250 mbar pressure drop in the external source circuitW49788083121
Kind of brine  Ethylene glycol 30% vol.
Heating circuit
Nominal flow rate ΔT 5Kl/h9301450193024503320
Rest pressure head ΔT 5Kbar0.6500.4400.300.7300.450
Nominal flow rate ΔT 8Kl/h600930129016002180
max. remaining feed head with ΔT 8Kbar0.6800.6500.5400.8600.800
min. flow rate at continuous working on the limitation of use l/h7101120151016002180
max flow rate at continuous working on the limitation of usel/h10251730227024503320
Electrical power heating circuit pump for BO/W35 T 5K at 250 mbar pressure drop in the external heating circuit W2437496074
Performance data
BOW35 ΔT5K -> EN 14511
Heating powerkW5.408.4011.5014.5019.70
Power consumption kW1.402.102.803.404.70
COP 4.504.404.604.904.70
BOW45 ΔT5K -> EN 14511
Heating power kW5.308.5011.4014.1019.60
Power consumptionkW1.702.603.503.803.70
COP 3.503.503.503.803.70
BOW55 T8 -> EN 14511
Heating powerkW5.408.7011.7014.7020.00
Power consumptionkW2.
COP 2.903.003.103.20
ErP - Data heating mode
Label 35 A++
Label 55 A++
Sound power level indoors (LWl)dB(A)43.845.648.549.948.4
MCS SCoP performance
flexoTHERM Ground Source Heat Pump35°C40°C45°C50°C55°C
flexoTHERM 5kW 230v 4.904.173.853.513.57
flexoTHERM 8kW 230v 4.674.123.783.503.68
flexoTHERM 11kW 230v 4.994.233.873.603.73
flexoTHERM 15kW 415v 5.394.614.233.893.74
flexoTHERM 19kW 415v 5.074.364.053.763.68
flexoTHERM with fluoCOLLECT water source     
flexoTHERM 5kW 230v 4.944.414.023.873.87
flexoTHERM 8kW 230v
flexoTHERM 11kW 230v 5.224.634.194.034.02
flexoTHERM 15kW 415v 5.915.24.644.424.34
flexoTHERM 19kW 415v 5.634.974.464.274.23
flexoTHERM with aroCOLLECT air source     
flexoTHERM 15kW 415v 4.513.913.463.373.42
flexoTHERM 19kW 415v 4.083.573.213.163.27

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Alternative products

Alternative products

geoTHERM 22, 30, 38, 46kW

Ground source heat pump

  • "Quiet Mark" approved thanks to geoTHERM multi-stage sound insulation
  • Energy yield display
  • MCS accredited, RHI eligible

VRC 700

Wired weather compensating programmable room thermostat

  • Works with our complete range of Vaillant boilers
  • Flexible time programs
  • Works with S & Y plan systems
  • Clear, high contrast backlit display

aroTHERM hybrid 5, 8, 11 and 15kW

Air-to-water hybrid heat pump

  • Unique triVAI® intelligent control system
  • Total system solution – Available in an easy to order pack
  • Excellent green credentials
  • Compatible with all boiler systems running on gas, oil or LPG
  • Easy to install and commission

aroTHERM 5, 8, 11 and 15kW

Air-to-water heat pump

  • Blue fin coated evaporator as standard
  • MCS accredited
  • ErP rated A++
  • 'Quiet Mark' approved