JAB DUC 2 Standard Indirect Unvented Cylinders (90L-300L)

Description

The JAB DUC 2 Indirect is a standard-format unvented hot water cylinder built for typical domestic installations, heated indirectly from a gas or oil-fired boiler and backed up by factory-fitted immersion heating. Available in seven capacities from 90L to 300L, it combines a duplex stainless-steel shell with a remote-mounted expansion vessel and a factory-set safety group.

90–300L

Capacity Range

7

Sizes Available

1–2 x 3kW

Immersion (By Size)

26–40 min

Reheat Time (10°C–60°C)

7 bar / 90°C

T&P Relief Setting

Remote

Expansion Vessel

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.

Secondary return not standard on smaller sizes: the 22mm secondary return connection is not supplied as standard on the 90L–170L models – it's only fitted as standard from 200L upwards. Confirm this against the project requirement before specifying a smaller cylinder for a system with a secondary return circuit.

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 2 Indirect

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.

Remote Expansion Vessel

The expansion vessel is supplied as a separate wall-mounted unit with its own bracket rather than clamped to the cylinder body, freeing up airing-cupboard space and easing servicing access.

Fast Reheat Across the Range

Reheat time from 10°C to 60°C stays within a tight 26–40 minute band across the whole capacity range, so larger sizes don't mean a proportionally longer wait for hot water.

Tariff-Flexible Immersion Heating

A single 3kW immersion gives back-up heating on the 90L–200L sizes, stepping up to 2 x 3kW on the 250L and 300L models to match the larger stored volume.

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

The complete unvented kit ships with every cylinder, so the installer isn't left sourcing safety-group components separately.

Sizes & Specification

Capacity	Height	Diameter	Immersion	Reheat (10°C–60°C)	Standing Heat Loss	Full Weight
90L	750mm	510mm	1 x 3kW	26 min	1.59 kWh/24h	121kg
125L	900mm	510mm	1 x 3kW	36 min	1.64 kWh/24h	156kg
150L	1075mm	510mm	1 x 3kW	37 min	1.85 kWh/24h	187kg
170L	1200mm	510mm	1 x 3kW	36 min	1.97 kWh/24h	210kg
200L	1500mm	510mm	1 x 3kW	33 min	1.85 kWh/24h	240kg
250L	1500mm	580mm	2 x 3kW	35 min	2.00 kWh/24h	301kg
300L	1750mm	580mm	2 x 3kW	40 min	2.22 kWh/24h	355kg

Connection Dimensions

Capacity	A	B	C	D	E	F
90L	171mm	201mm	401mm	497mm	–	551mm
125L	171mm	201mm	401mm	497mm	–	671mm
150L	171mm	201mm	401mm	497mm	–	876mm
170L	171mm	201mm	451mm	601mm	–	1026mm
200L	171mm	201mm	451mm	601mm	1231mm	1311mm
250L	193mm	223mm	553mm	843mm	973mm	1293mm
300L	193mm	223mm	553mm	843mm	1253mm	1543mm

Technical Specification

Construction
Cylinder Type	Indirect, unvented, duplex stainless-steel
Energy Efficiency Class	C
Operating Pressure	3 bar
Max Incoming Supply Pressure	12 bar
Connections & Safety (All Sizes)
Hot Water Draw-Off	22mm
Secondary Return	22mm (standard on 200L+ only, see note above)
Boiler Flow	22mm
Boiler Return	22mm
Cold Feed	22mm
Temperature & Pressure Relief Valve	1/2″, factory-set 7 bar / 90°C
Expansion Vessel	Remote-mounted, wall bracket supplied
Unvented Kit	Full kit supplied

Frequently Asked Questions

Does this cylinder come with a secondary return connection?

Not as standard on the 90L–170L sizes – the 22mm secondary return connection is only fitted as standard from 200L upwards. Check this before specifying if a secondary return circuit is required on a smaller cylinder.

What heat source does this cylinder use?

It's designed to be heated indirectly via a boiler coil connected to a gas or oil-fired boiler, with the immersion heater(s) providing independent electric back-up.

How many immersion heaters does each size have?

The 90L–200L models have a single 3kW immersion, while the 250L and 300L models have 2 x 3kW immersion heaters.

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.

How fast does this cylinder reheat?

Reheat time from 10°C to 60°C ranges from 26 minutes on the 90L model to 40 minutes on the 300L model, based on the manufacturer's rated coil performance.

What's the difference between the actual and nominal capacity?

The nominal litre rating is a rounded figure; the actual stored capacity is slightly lower once the coil and fittings are accounted for – for example, the “90L” model holds 89L, and the “300L” model holds 294L.

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Good (New Build)

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