The JAB DUC 2 Indirect Hi-Flo is a high-recovery unvented stainless-steel hot water storage cylinder built for households and light commercial premises with heavy simultaneous hot water demand. Heated indirectly from a boiler coil and backed up by twin 3kW immersion heaters, it combines a duplex stainless-steel shell with a factory-fitted safety group and a remote-mounted expansion vessel, and is manufactured in Britain.
2 x 3kW
Back-Up Immersion
29 min
75% Reheat (Boiler)
7 bar / 90°C
T&P Relief Setting
The remote expansion vessel ships with its own wall-mounting bracket, and the full unvented installation kit is included, so the only additions on site are pipework, insulation lagging where required, and the structural connections listed below.
Installer requirement: this is an unvented hot water cylinder and must be installed, commissioned, and notified to Building Control by a G3-qualified (Benchmark) installer in line with Building Regulations Part G3. Unqualified installation is unsafe and may invalidate warranty cover.
All electrical connections, including the twin immersion heaters, must be wired by a qualified electrician in accordance with BS 7671; actual cable sizing should be calculated on site rather than assumed from generic figures.
Why Choose the JAB Indirect Hi-Flo
Duplex Stainless-Steel Shell
The duplex stainless-steel construction resists pitting and stress corrosion far better than standard 304-grade tanks, so the vessel holds up in hard-water areas without the enamel-lining failures common in steel cylinders.
High-Output Coil Design
A generously sized internal coil is engineered for fast recovery even after heavy simultaneous draw-off, which is why JAB rates this range for restaurants, salons, and multi-bathroom houses rather than single-occupancy homes.
Remote Expansion Vessel
Rather than clamping the expansion vessel to the cylinder body, JAB supplies it as a separate wall-mounted unit with its own bracket, freeing up airing-cupboard space and simplifying servicing access.
Dual Back-Up Immersion
Twin 3kW immersion elements give a fully independent electric back-up route to hot water, so the household isn't left without hot water if the boiler or heat source is ever down for repair.
Factory-Set Safety Group
The temperature and pressure relief valve is factory-calibrated and tested before dispatch, removing a common on-site commissioning error and shortening installation time.
Full Unvented Kit Included
Because the complete unvented kit ships in the box, the installer isn't left sourcing tundish, valves, or pipework fittings separately, which keeps first-fix time down and avoids incompatible third-party parts.
Technical Specification
| Capacity & Construction |
| Nominal Capacity |
300L |
| Cylinder Type |
Indirect, unvented, duplex stainless-steel |
| Grade |
316L stainless-steel body |
| Manufacture |
Made in Britain |
| Energy Rating (ErP) |
C |
| Dimensions |
| Overall Height |
1800mm |
| Overall Diameter |
580mm |
| A – Immersion Height |
195mm |
| B – Thermostat Pocket Height |
225mm |
| C – Boiler Flow Height |
555mm |
| D – Secondary Return Height |
1255mm |
| E – Hot Water Draw-Off Height |
1435mm |
| Performance |
| Coil Output |
32kW |
| Reheat Time (from cold) |
40 min |
| Reheat Time (75% draw-off, with boiler) |
29 min |
| 24-Hour Standing Heat Loss |
2.71 kWh / 24hrs |
| Connections & Safety |
| Hot Water Draw-Off |
28mm |
| Secondary Return |
28mm |
| Boiler Flow |
28mm |
| Boiler Return |
28mm |
| Cold Feed |
28mm |
| Inlet Valve Group |
1″ hot and cold, 28mm inlet control valve |
| Temperature & Pressure Relief Valve |
1/2″, factory-set 7 bar / 90°C |
| Immersion Heater(s) |
2 x 3kW single phase |
| Expansion Vessel |
Remote-mounted, wall bracket supplied |
| Unvented Kit |
Full kit supplied |
Frequently Asked Questions
Does this cylinder need to be installed by a qualified installer?
Yes. As an unvented hot water cylinder it must be installed and commissioned by a Benchmark or G3-qualified installer in line with Building Regulations Part G3, and the installation must be notified to Building Control.
What heat source does the Indirect Hi-Flo use?
It's designed to be heated indirectly via a boiler coil connected to a gas, oil, or heat pump boiler, with the twin 3kW immersion heaters providing independent electric back-up.
Can this cylinder be used with a heat pump?
Yes, the indirect coil can be run from a heat pump circuit, though coil surface area and flow temperature should be checked against the heat pump's output to confirm expected reheat performance, since the published reheat times assume a boiler heat source.
What's the difference between the Hi-Flo range and the standard JAB Duc 2 Indirect range?
The Hi-Flo range uses a larger-capacity coil for faster recovery under heavy demand and is aimed at light commercial or high-occupancy applications, whereas the standard Indirect range is sized for typical domestic use.
Does the cylinder come with a warranty?
JAB cylinders are supplied with a manufacturer's warranty; please confirm the current warranty term and registration process directly with JAB Products or your supplier at the time of purchase, as terms are subject to change.
What space is needed around the cylinder for servicing?
Because the expansion vessel is wall-mounted separately from the cylinder body, allow clear wall space nearby for the bracket in addition to the airing-cupboard footprint of the cylinder itself.
