The JAB DUC IE Direct is a compact, internal-expansion unvented hot water cylinder built for modern domestic installations where space, efficiency, and reliability matter. Available in seven capacities from 90L to 300L, it's constructed from duplex stainless-steel with no boiler coil – heating is provided entirely by factory-fitted immersion heaters, whose count increases with capacity. Because the expansion volume is built in, there's no external expansion vessel to find wall space for. It is manufactured in Britain.
550mm
Diameter (All Sizes)
1–3 x 3kW
Immersion (By Size)
10 bar / 90°C
T&P Relief Setting
Internal
Expansion Design
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.
No boiler coil fitted: as a Direct model, the immersion heater(s) are the sole heat source – there is no indirect coil connection for a boiler or heat pump. Immersion count varies by capacity (1 x 3kW on 90L, 2 x 3kW on 120L–200L, 3 x 3kW on 250L–300L); confirm the exact configuration in the size table before ordering.
All electrical connections, including the immersion heater(s), 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 DUC IE Direct
Internal Expansion Design
Building the expansion volume inside the cylinder removes the need for a separate external expansion vessel, simplifying installation and freeing up airing-cupboard space.
Duplex Stainless-Steel Shell
The duplex stainless-steel body resists pitting and stress corrosion far better than standard 304-grade tanks, giving reliable long-term performance in hard-water areas.
Mains-Pressure Delivery
Engineered for mains-pressure hot water, giving strong flow rates to showers, taps, and appliances without a cold-water storage tank.
Compact 550mm Diameter
A consistent 550mm diameter across the whole range keeps the footprint predictable when planning airing-cupboard space, whatever the capacity chosen.
Tariff-Flexible Immersion Heating
Factory-fitted immersion heaters (count varies by size – see the table below) let the cylinder heat water on different schedules and tariffs, useful where electricity is the sole heat source.
Full Unvented Kit Included
The complete unvented kit ships with every cylinder, so the installer isn't left sourcing safety-group components separately.
Sizes & Pricing
| Capacity |
Dimensions (H x D) |
Immersion Heaters |
| 90L |
750 x 550mm |
1 x 3kW |
| 120L |
925 x 550mm |
2 x 3kW |
| 150L |
1125 x 550mm |
2 x 3kW |
| 170L |
1225 x 550mm |
2 x 3kW |
| 200L |
1425 x 550mm |
2 x 3kW |
| 250L |
1725 x 550mm |
3 x 3kW |
| 300L |
1950 x 550mm |
3 x 3kW |
Technical Specification
| Construction |
| Cylinder Type |
Direct, unvented, duplex stainless-steel, internal expansion |
| Coil & Fittings Grade |
316L stainless-steel (fittings) |
| Manufacture |
Made in Britain |
| Note |
Actual water capacity is slightly less than the nominal litre rating due to the internal air gap |
| Connections & Safety (All Sizes) |
| Fittings |
22mm compression, 316L stainless-steel |
| Temperature & Pressure Relief Valve |
Factory-set 10 bar / 90°C |
| Expansion |
Internal – no external expansion vessel required |
| Unvented Kit |
Full kit supplied |
| Warranty |
| Inner Container |
Lifetime manufacturing warranty* |
| Components |
2 years* |
Frequently Asked Questions
Does this cylinder need a boiler connection?
No. This is a direct cylinder – it has no boiler coil and is heated solely by its factory-fitted immersion heaters, making it suited to properties where electricity is the only available heat source.
Do I still need an external expansion vessel?
No. The internal expansion design builds the expansion volume into the cylinder itself, so a separate wall-mounted expansion vessel isn't required, unlike JAB's Duc 2 external-expansion ranges.
How many immersion heaters does each size have?
It varies by capacity: the 90L model has 1 x 3kW, the 120L–200L models have 2 x 3kW, and the 250L and 300L models have 3 x 3kW immersion heaters. Check the size table for the exact configuration.
Does this cylinder need to be installed by a qualified installer?
Yes. As an unvented hot water cylinder it must be installed, commissioned, and notified to Building Control by a G3-qualified (Benchmark) installer in line with Building Regulations Part G3.
What T&P relief valve setting does this range use?
The factory-fitted temperature and pressure relief valve is set at 10 bar / 90°C, which is higher than JAB's external-expansion Duc 2 range (7 bar); check this against your system design.
What warranty does JAB provide?
JAB cylinders carry a lifetime manufacturing warranty on the inner container (2 years on components); confirm current terms and registration with JAB Products or your supplier at the time of purchase.
