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Baxi ASHP Pre-plumbed Cylinder — 170L / 210L / 250L / 300L Stainless Steel Unvented Cylinders for Air Source Heat Pumps
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Baxi ASHP Pre-plumbed Cylinder — 170L / 210L / 250L / 300L Stainless Steel Unvented Cylinders for Air Source Heat Pumps

Baxi ASHP Pre-plumbed Cylinder — 170L / 210L / 250L / 300L Stainless Steel Unvented Cylinders for Air Source Heat Pumps

The Baxi ASHP Pre-plumbed Cylinder is a fully integrated unvented hot water and heating control unit, engineered to work with Baxi's range of air source heat pumps. Available in 170, 210, 250 and 300 litre capacities, the cylinder arrives pre-wired, pre-plumbed and pre-fitted with all the components needed to manage heating and domestic hot water — including the diverter valve, expansion vessel, pressure controls and integrated controller. Built from duplex stainless steel by Megaflo and Heatrae Sadia, with 60 mm of high-efficiency PU foam insulation and built-in Bluetooth for fast commissioning via the Baxi Start app.

76 L/min
Max flow at 3 bar
170–300 L
Four capacity options
ErP B
170L & 210L models
10 years
Inner stainless steel tank*
What you get in the box
Each unit ships as a complete cold control pack ready for installation: tundish, 3.5 bar pressure reducing valve, 6 bar pressure relief valve, 3-port motorised diverter valve, 24L external expansion vessel, 13m signal cable, immersion element spanner, compression nuts and olives. The integrated controller, immersion heater and all internal pipework are factory-fitted and tested — no field assembly of the heating manifold is required.
Designed for low-labour heat pump installations
Duplex stainless steel build
Inner vessel manufactured by Megaflo and Heatrae Sadia from corrosion-resistant duplex stainless steel and 100% pressure tested to 16 bar. The outer casing uses pre-coated steel with polypropylene mouldings for long service life.
Pre-plumbed and pre-wired
All controls, the diverter valve, immersion heater, expansion vessel and safety valves are factory-fitted. Pipe connections take 22mm compression fittings or 3/4" BSP threaded fittings — cutting site labour and commissioning time.
Bluetooth + Baxi Start App
Built-in Bluetooth lets the installer commission, configure and service the cylinder from a phone using the Baxi Start app. Bluetooth can be deactivated once setup is complete to keep the unit secure.
Integrated 2-zone controller
The on-board controller drives the heat pump, DHW priority, immersion backup and automatic Legionella cycle. Heating output supports up to two zones when paired with the optional Baxi 7879380 second zone kit.
High-efficiency PU insulation
60mm of CFC/HCFC-free fire-retardant PU foam with zero ozone depletion potential keeps standing losses low — from 1.38 kWh/24h on the 170L up to 2.02 kWh/24h on the 300L.
Designed for Baxi ASHPs
Optimised to work with the Baxi HP40, HP50, HP55 and HP60 monobloc heat pumps. A 3kW immersion provides backup heating and runs the Legionella cycle when needed.
Air source heat pump compatibility

The pre-plumbed cylinder is the recommended hot water and control package for the Baxi air source heat pump range — compatible with the HP40 standard-temperature monobloc, the Baxi Assure HP50, the HP55 high-temperature monobloc and the HP60 high-temperature monobloc. The integrated controller takes the heat pump's flow temperature signal, modulates the diverter valve between heating and DHW, and falls back to the 3 kW immersion for backup or the Legionella cycle. Pair with the Baxi uSense 2 smart room thermostat via OpenTherm for weather compensation and remote control through the MyBaxi app.

Specification 170L 210L 250L 300L
Product code 7853985 7853986 7853987 7853988
Nominal capacity 170 L 210 L 250 L 300 L
Storage volume @ 3 bar 167 L 209 L 246 L 287 L
Hot water at >40 °C 239 L 293 L 333 L 417 L
Coil heat-up time 18.7 min 21.8 min 23 min 27.5 min
Coil surface area 2 m² 2 m² 3 m² 3 m²
Coil rating 31.3 kW 32.5 kW 37 kW 37.9 kW
Standing heat loss 1.38 kWh/24h 1.64 kWh/24h 1.86 kWh/24h 2.02 kWh/24h
Energy efficiency class B B C C
Height 1280 mm 1516 mm 1767 mm 2082 mm
Weight (empty) 61 kg 68 kg 74 kg 83 kg
Weight (full) 228 kg 277 kg 320 kg 370 kg
Common specifications (all capacities)
Width / diameter 699 mm / 579 mm
Insulation thickness 60 mm CFC/HCFC-free PU foam
Immersion element rating 3 kW @ 240 V
Max flow rate 76 L/min @ 3 bar
Pressure reducing valve / relief / T&P 3.5 bar / 6 bar / 10 bar & 90 °C
External expansion vessel 24 L
Connections 28 mm flow & return · 22 mm cold inlet · 22 mm DHW outlet
Inner vessel Duplex stainless steel — 100% tested to 1.6 MPa (16 bar)
Warranty* 2-year parts and labour, 10-year inner stainless steel tank
*Warranty subject to terms — see baxi.co.uk/terms. ErP class per EU regulations 814/2013 and 812/2013. Coil heat-up times measured at 15 L/min; cylinder tested per Annex A, BS EN 12897:2016.
Installation requirements
Installation, commissioning and annual servicing must be carried out by a competent person — typically G3 unvented hot water qualified and Gas Safe / MCS registered as appropriate. The unit must be installed in accordance with Building Regulations Part G, BS EN 12897:2016 and the Baxi Installation & Service Manual. Do not bypass any safety valve or thermal cut-out. A 22mm cold water supply (15mm acceptable subject to flow) and a discharge route from tundish to a safe, visible point are required.
Frequently asked questions
What is the difference between the Baxi pre-plumbed cylinder and the standard ASHP cylinder?
The pre-plumbed cylinder arrives fully assembled with the diverter valve, immersion heater, expansion vessel, integrated controller, pressure controls and all internal pipework factory-fitted. The standard Baxi ASHP cylinder is the cylinder vessel only and requires the installer to assemble the heating manifold and controls separately. Choose pre-plumbed for the fastest, lowest-labour installation; choose the standard cylinder if you need flexibility to design a bespoke control scheme.
Which Baxi heat pumps is this cylinder compatible with?
The pre-plumbed cylinder is engineered for the full Baxi air source heat pump range — the HP40 monobloc, the Baxi Assure HP50, the HP55 high-temperature monobloc and the HP60 high-temperature monobloc. The integrated controller is configured during commissioning via the Baxi Start app to match the connected heat pump model.
Can the cylinder support two heating zones?
Yes — the integrated controller is designed to manage up to two heating zones plus DHW priority. A second zone requires the optional Baxi second zone kit (part 7879380), available as a separate accessory, which adds the additional zone valve, sensors and wiring needed for independent control.
How is Legionella protection handled?
The integrated controller runs an automatic Legionella cycle that uses the 3kW immersion heater to raise the cylinder contents to a temperature high enough to neutralise legionella bacteria, even if the heat pump is in low-temperature operation. Frequency and target temperature are set during commissioning in line with BS 8580.
What size cylinder do I need?
As a guide: the 170L suits a 1–2 bedroom property with a single bathroom; the 210L matches a typical 3-bed home with one bathroom; the 250L is a strong fit for a 3–4 bed property with two bathrooms; and the 300L is appropriate for a 4-bed home with two or more bathrooms. Final selection should be confirmed by a property heat-loss calculation and a hot water demand assessment (number of occupants, simultaneous draws, bath versus shower use).
Does the Boiler Upgrade Scheme apply?
The Boiler Upgrade Scheme grant is paid against the heat pump installation (Baxi HP40 / HP60), not the cylinder itself. The cylinder is, however, a normal part of an MCS-certified ASHP system, so its cost forms part of the installed package that qualifies for the grant. Always check current eligibility, grant value and scheme rules with your MCS-certified installer.
Select Capacity
From $1,616.03

Original: $4,617.22

-65%
Baxi ASHP Pre-plumbed Cylinder — 170L / 210L / 250L / 300L Stainless Steel Unvented Cylinders for Air Source Heat Pumps—

$4,617.22

$1,616.03

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Baxi ASHP Pre-plumbed Cylinder — 170L / 210L / 250L / 300L Stainless Steel Unvented Cylinders for Air Source Heat Pumps - Image 2

Baxi ASHP Pre-plumbed Cylinder — 170L / 210L / 250L / 300L Stainless Steel Unvented Cylinders for Air Source Heat Pumps

The Baxi ASHP Pre-plumbed Cylinder is a fully integrated unvented hot water and heating control unit, engineered to work with Baxi's range of air source heat pumps. Available in 170, 210, 250 and 300 litre capacities, the cylinder arrives pre-wired, pre-plumbed and pre-fitted with all the components needed to manage heating and domestic hot water — including the diverter valve, expansion vessel, pressure controls and integrated controller. Built from duplex stainless steel by Megaflo and Heatrae Sadia, with 60 mm of high-efficiency PU foam insulation and built-in Bluetooth for fast commissioning via the Baxi Start app.

76 L/min
Max flow at 3 bar
170–300 L
Four capacity options
ErP B
170L & 210L models
10 years
Inner stainless steel tank*
What you get in the box
Each unit ships as a complete cold control pack ready for installation: tundish, 3.5 bar pressure reducing valve, 6 bar pressure relief valve, 3-port motorised diverter valve, 24L external expansion vessel, 13m signal cable, immersion element spanner, compression nuts and olives. The integrated controller, immersion heater and all internal pipework are factory-fitted and tested — no field assembly of the heating manifold is required.
Designed for low-labour heat pump installations
Duplex stainless steel build
Inner vessel manufactured by Megaflo and Heatrae Sadia from corrosion-resistant duplex stainless steel and 100% pressure tested to 16 bar. The outer casing uses pre-coated steel with polypropylene mouldings for long service life.
Pre-plumbed and pre-wired
All controls, the diverter valve, immersion heater, expansion vessel and safety valves are factory-fitted. Pipe connections take 22mm compression fittings or 3/4" BSP threaded fittings — cutting site labour and commissioning time.
Bluetooth + Baxi Start App
Built-in Bluetooth lets the installer commission, configure and service the cylinder from a phone using the Baxi Start app. Bluetooth can be deactivated once setup is complete to keep the unit secure.
Integrated 2-zone controller
The on-board controller drives the heat pump, DHW priority, immersion backup and automatic Legionella cycle. Heating output supports up to two zones when paired with the optional Baxi 7879380 second zone kit.
High-efficiency PU insulation
60mm of CFC/HCFC-free fire-retardant PU foam with zero ozone depletion potential keeps standing losses low — from 1.38 kWh/24h on the 170L up to 2.02 kWh/24h on the 300L.
Designed for Baxi ASHPs
Optimised to work with the Baxi HP40, HP50, HP55 and HP60 monobloc heat pumps. A 3kW immersion provides backup heating and runs the Legionella cycle when needed.
Air source heat pump compatibility

The pre-plumbed cylinder is the recommended hot water and control package for the Baxi air source heat pump range — compatible with the HP40 standard-temperature monobloc, the Baxi Assure HP50, the HP55 high-temperature monobloc and the HP60 high-temperature monobloc. The integrated controller takes the heat pump's flow temperature signal, modulates the diverter valve between heating and DHW, and falls back to the 3 kW immersion for backup or the Legionella cycle. Pair with the Baxi uSense 2 smart room thermostat via OpenTherm for weather compensation and remote control through the MyBaxi app.

Specification 170L 210L 250L 300L
Product code 7853985 7853986 7853987 7853988
Nominal capacity 170 L 210 L 250 L 300 L
Storage volume @ 3 bar 167 L 209 L 246 L 287 L
Hot water at >40 °C 239 L 293 L 333 L 417 L
Coil heat-up time 18.7 min 21.8 min 23 min 27.5 min
Coil surface area 2 m² 2 m² 3 m² 3 m²
Coil rating 31.3 kW 32.5 kW 37 kW 37.9 kW
Standing heat loss 1.38 kWh/24h 1.64 kWh/24h 1.86 kWh/24h 2.02 kWh/24h
Energy efficiency class B B C C
Height 1280 mm 1516 mm 1767 mm 2082 mm
Weight (empty) 61 kg 68 kg 74 kg 83 kg
Weight (full) 228 kg 277 kg 320 kg 370 kg
Common specifications (all capacities)
Width / diameter 699 mm / 579 mm
Insulation thickness 60 mm CFC/HCFC-free PU foam
Immersion element rating 3 kW @ 240 V
Max flow rate 76 L/min @ 3 bar
Pressure reducing valve / relief / T&P 3.5 bar / 6 bar / 10 bar & 90 °C
External expansion vessel 24 L
Connections 28 mm flow & return · 22 mm cold inlet · 22 mm DHW outlet
Inner vessel Duplex stainless steel — 100% tested to 1.6 MPa (16 bar)
Warranty* 2-year parts and labour, 10-year inner stainless steel tank
*Warranty subject to terms — see baxi.co.uk/terms. ErP class per EU regulations 814/2013 and 812/2013. Coil heat-up times measured at 15 L/min; cylinder tested per Annex A, BS EN 12897:2016.
Installation requirements
Installation, commissioning and annual servicing must be carried out by a competent person — typically G3 unvented hot water qualified and Gas Safe / MCS registered as appropriate. The unit must be installed in accordance with Building Regulations Part G, BS EN 12897:2016 and the Baxi Installation & Service Manual. Do not bypass any safety valve or thermal cut-out. A 22mm cold water supply (15mm acceptable subject to flow) and a discharge route from tundish to a safe, visible point are required.
Frequently asked questions
What is the difference between the Baxi pre-plumbed cylinder and the standard ASHP cylinder?
The pre-plumbed cylinder arrives fully assembled with the diverter valve, immersion heater, expansion vessel, integrated controller, pressure controls and all internal pipework factory-fitted. The standard Baxi ASHP cylinder is the cylinder vessel only and requires the installer to assemble the heating manifold and controls separately. Choose pre-plumbed for the fastest, lowest-labour installation; choose the standard cylinder if you need flexibility to design a bespoke control scheme.
Which Baxi heat pumps is this cylinder compatible with?
The pre-plumbed cylinder is engineered for the full Baxi air source heat pump range — the HP40 monobloc, the Baxi Assure HP50, the HP55 high-temperature monobloc and the HP60 high-temperature monobloc. The integrated controller is configured during commissioning via the Baxi Start app to match the connected heat pump model.
Can the cylinder support two heating zones?
Yes — the integrated controller is designed to manage up to two heating zones plus DHW priority. A second zone requires the optional Baxi second zone kit (part 7879380), available as a separate accessory, which adds the additional zone valve, sensors and wiring needed for independent control.
How is Legionella protection handled?
The integrated controller runs an automatic Legionella cycle that uses the 3kW immersion heater to raise the cylinder contents to a temperature high enough to neutralise legionella bacteria, even if the heat pump is in low-temperature operation. Frequency and target temperature are set during commissioning in line with BS 8580.
What size cylinder do I need?
As a guide: the 170L suits a 1–2 bedroom property with a single bathroom; the 210L matches a typical 3-bed home with one bathroom; the 250L is a strong fit for a 3–4 bed property with two bathrooms; and the 300L is appropriate for a 4-bed home with two or more bathrooms. Final selection should be confirmed by a property heat-loss calculation and a hot water demand assessment (number of occupants, simultaneous draws, bath versus shower use).
Does the Boiler Upgrade Scheme apply?
The Boiler Upgrade Scheme grant is paid against the heat pump installation (Baxi HP40 / HP60), not the cylinder itself. The cylinder is, however, a normal part of an MCS-certified ASHP system, so its cost forms part of the installed package that qualifies for the grant. Always check current eligibility, grant value and scheme rules with your MCS-certified installer.

Product Information

Shipping & Returns

Description

The Baxi ASHP Pre-plumbed Cylinder is a fully integrated unvented hot water and heating control unit, engineered to work with Baxi's range of air source heat pumps. Available in 170, 210, 250 and 300 litre capacities, the cylinder arrives pre-wired, pre-plumbed and pre-fitted with all the components needed to manage heating and domestic hot water — including the diverter valve, expansion vessel, pressure controls and integrated controller. Built from duplex stainless steel by Megaflo and Heatrae Sadia, with 60 mm of high-efficiency PU foam insulation and built-in Bluetooth for fast commissioning via the Baxi Start app.

76 L/min
Max flow at 3 bar
170–300 L
Four capacity options
ErP B
170L & 210L models
10 years
Inner stainless steel tank*
What you get in the box
Each unit ships as a complete cold control pack ready for installation: tundish, 3.5 bar pressure reducing valve, 6 bar pressure relief valve, 3-port motorised diverter valve, 24L external expansion vessel, 13m signal cable, immersion element spanner, compression nuts and olives. The integrated controller, immersion heater and all internal pipework are factory-fitted and tested — no field assembly of the heating manifold is required.
Designed for low-labour heat pump installations
Duplex stainless steel build
Inner vessel manufactured by Megaflo and Heatrae Sadia from corrosion-resistant duplex stainless steel and 100% pressure tested to 16 bar. The outer casing uses pre-coated steel with polypropylene mouldings for long service life.
Pre-plumbed and pre-wired
All controls, the diverter valve, immersion heater, expansion vessel and safety valves are factory-fitted. Pipe connections take 22mm compression fittings or 3/4" BSP threaded fittings — cutting site labour and commissioning time.
Bluetooth + Baxi Start App
Built-in Bluetooth lets the installer commission, configure and service the cylinder from a phone using the Baxi Start app. Bluetooth can be deactivated once setup is complete to keep the unit secure.
Integrated 2-zone controller
The on-board controller drives the heat pump, DHW priority, immersion backup and automatic Legionella cycle. Heating output supports up to two zones when paired with the optional Baxi 7879380 second zone kit.
High-efficiency PU insulation
60mm of CFC/HCFC-free fire-retardant PU foam with zero ozone depletion potential keeps standing losses low — from 1.38 kWh/24h on the 170L up to 2.02 kWh/24h on the 300L.
Designed for Baxi ASHPs
Optimised to work with the Baxi HP40, HP50, HP55 and HP60 monobloc heat pumps. A 3kW immersion provides backup heating and runs the Legionella cycle when needed.
Air source heat pump compatibility

The pre-plumbed cylinder is the recommended hot water and control package for the Baxi air source heat pump range — compatible with the HP40 standard-temperature monobloc, the Baxi Assure HP50, the HP55 high-temperature monobloc and the HP60 high-temperature monobloc. The integrated controller takes the heat pump's flow temperature signal, modulates the diverter valve between heating and DHW, and falls back to the 3 kW immersion for backup or the Legionella cycle. Pair with the Baxi uSense 2 smart room thermostat via OpenTherm for weather compensation and remote control through the MyBaxi app.

Specification 170L 210L 250L 300L
Product code 7853985 7853986 7853987 7853988
Nominal capacity 170 L 210 L 250 L 300 L
Storage volume @ 3 bar 167 L 209 L 246 L 287 L
Hot water at >40 °C 239 L 293 L 333 L 417 L
Coil heat-up time 18.7 min 21.8 min 23 min 27.5 min
Coil surface area 2 m² 2 m² 3 m² 3 m²
Coil rating 31.3 kW 32.5 kW 37 kW 37.9 kW
Standing heat loss 1.38 kWh/24h 1.64 kWh/24h 1.86 kWh/24h 2.02 kWh/24h
Energy efficiency class B B C C
Height 1280 mm 1516 mm 1767 mm 2082 mm
Weight (empty) 61 kg 68 kg 74 kg 83 kg
Weight (full) 228 kg 277 kg 320 kg 370 kg
Common specifications (all capacities)
Width / diameter 699 mm / 579 mm
Insulation thickness 60 mm CFC/HCFC-free PU foam
Immersion element rating 3 kW @ 240 V
Max flow rate 76 L/min @ 3 bar
Pressure reducing valve / relief / T&P 3.5 bar / 6 bar / 10 bar & 90 °C
External expansion vessel 24 L
Connections 28 mm flow & return · 22 mm cold inlet · 22 mm DHW outlet
Inner vessel Duplex stainless steel — 100% tested to 1.6 MPa (16 bar)
Warranty* 2-year parts and labour, 10-year inner stainless steel tank
*Warranty subject to terms — see baxi.co.uk/terms. ErP class per EU regulations 814/2013 and 812/2013. Coil heat-up times measured at 15 L/min; cylinder tested per Annex A, BS EN 12897:2016.
Installation requirements
Installation, commissioning and annual servicing must be carried out by a competent person — typically G3 unvented hot water qualified and Gas Safe / MCS registered as appropriate. The unit must be installed in accordance with Building Regulations Part G, BS EN 12897:2016 and the Baxi Installation & Service Manual. Do not bypass any safety valve or thermal cut-out. A 22mm cold water supply (15mm acceptable subject to flow) and a discharge route from tundish to a safe, visible point are required.
Frequently asked questions
What is the difference between the Baxi pre-plumbed cylinder and the standard ASHP cylinder?
The pre-plumbed cylinder arrives fully assembled with the diverter valve, immersion heater, expansion vessel, integrated controller, pressure controls and all internal pipework factory-fitted. The standard Baxi ASHP cylinder is the cylinder vessel only and requires the installer to assemble the heating manifold and controls separately. Choose pre-plumbed for the fastest, lowest-labour installation; choose the standard cylinder if you need flexibility to design a bespoke control scheme.
Which Baxi heat pumps is this cylinder compatible with?
The pre-plumbed cylinder is engineered for the full Baxi air source heat pump range — the HP40 monobloc, the Baxi Assure HP50, the HP55 high-temperature monobloc and the HP60 high-temperature monobloc. The integrated controller is configured during commissioning via the Baxi Start app to match the connected heat pump model.
Can the cylinder support two heating zones?
Yes — the integrated controller is designed to manage up to two heating zones plus DHW priority. A second zone requires the optional Baxi second zone kit (part 7879380), available as a separate accessory, which adds the additional zone valve, sensors and wiring needed for independent control.
How is Legionella protection handled?
The integrated controller runs an automatic Legionella cycle that uses the 3kW immersion heater to raise the cylinder contents to a temperature high enough to neutralise legionella bacteria, even if the heat pump is in low-temperature operation. Frequency and target temperature are set during commissioning in line with BS 8580.
What size cylinder do I need?
As a guide: the 170L suits a 1–2 bedroom property with a single bathroom; the 210L matches a typical 3-bed home with one bathroom; the 250L is a strong fit for a 3–4 bed property with two bathrooms; and the 300L is appropriate for a 4-bed home with two or more bathrooms. Final selection should be confirmed by a property heat-loss calculation and a hot water demand assessment (number of occupants, simultaneous draws, bath versus shower use).
Does the Boiler Upgrade Scheme apply?
The Boiler Upgrade Scheme grant is paid against the heat pump installation (Baxi HP40 / HP60), not the cylinder itself. The cylinder is, however, a normal part of an MCS-certified ASHP system, so its cost forms part of the installed package that qualifies for the grant. Always check current eligibility, grant value and scheme rules with your MCS-certified installer.