Name: Ideal Pro Horizontal Indirect Unvented Cylinders | 585mm Height Duplex Stainless with G3 Kit
Brand: AIZO Quality Heating
SKU: ideal-pro-horizontal-indirect-unvented-cylinders
Availability: InStock

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Ideal Pro Horizontal Indirect Unvented Cylinders | 585mm Height Duplex Stainless with G3 Kit

The Ideal Pro Horizontal Indirect Unvented Cylinder brings full mains-pressure hot water to properties where a conventional upright cylinder simply will not fit. Lying on its side on factory-supplied cradle supports, every model in the range stands just 585 mm tall — the height of a standard kitchen appliance — making it the right choice for low-pitch loft conversions, under-stair cupboards, basement plant rooms, and any space where headroom is the limiting factor. The cylinder is heated by a boiler via a high-efficiency corrugated stainless steel coil, with a 3 kW immersion heater included for backup and off-peak electric heating. Four sizes cover the range: 180 L, 210 L, 250 L and 300 L. All share the same 585 mm height and 550 mm diameter; only the floor length varies with capacity. Manufactured from duplex stainless steel, supplied with a complete G3-compliant valve and control package, and backed by a 25-year vessel warranty and 2-year parts & labour warranty. Compatible with gas, oil and LPG boilers in both sealed and open-vented primary systems. ERP hot water efficiency rating: C.

585mm

Fixed height all sizes

4 Sizes

180–300L

27min

Min. heat-up time

Duplex SS

Made in UK

25-yr

Vessel warranty

Full G3

Kit included

ℹ When to choose horizontal over vertical: Choose horizontal only when the available ceiling height prevents a vertical cylinder of the same capacity. The 585 mm standing height is the key advantage. The trade-off is floor length: the 300 L model occupies 1,990 mm along the floor. If your cupboard or plant room has adequate height, a vertical cylinder of the same capacity will have a smaller footprint.

⚠ G3 Competent Person installation required: This cylinder is a controlled service under Building Regulation G3. It must be installed by a qualified G3 Competent Person (e.g. ACS Unvented or C&G 6161). The installer must complete the Benchmark log, notify the local authority, and register the product with Ideal Heating to activate the warranty.

What’s Included — Complete G3 Package in Every Box

Combination Inlet Group

Incorporates PRV (set to 3 bar), strainer, check valve, balanced cold take-off, expansion relief valve and expansion vessel connection points.

Potable Expansion Vessel & Wall Bracket

Sized to the cylinder, pre-charged to 3 bar. Absorbs thermal expansion so the T&P valve is not triggered on every heat cycle.

Pressure & Temperature Relief Valve

Set at 89 – 96°C / 6 bar. Last-resort protection against over-temperature and over-pressure.

Dual Control + Overheat Thermostat

Control thermostat maintains target temperature. Separate overheat thermostat triggers the energy cut-out circuit if limits are exceeded.

Energy Cut-Out Motorised Valve (22 mm)

On the primary circuit. Closes on overheat to stop boiler heat input — the correct G3-compliant method of shutting down an indirect heat source.

Tundish

Air-gap break in the discharge pipework. Provides a visible indicator of valve operation and prevents backflow. Required by Building Regulation G3.

3 kW Immersion Heater

1¾″ BSP, 16A / 250V. Integral control thermostat and thermal cut-out. For backup or off-peak / solar PV diversion heating.

Factory-Fitted Cradle Supports

Hold the cylinder at the correct orientation ensuring the T&P valve is vertical when installed. Align with embossed markings on the shell.

Technical Documentation

Installation & servicing manual, Benchmark commissioning and service log checklist.

Size Guide — All Models Stand 585 mm Tall

Measure your available floor length before selecting a size. The 250 L and 300 L models include two immersion heaters and a 22 mm secondary return tapping.

Dimensions

Capacity	Part number	Actual volume	Height	Diameter	Floor length
180 L	IDEPROIN180H	172 L	585 mm	550 mm	1,306 mm
210 L	IDEPROIN210H	206 L	585 mm	550 mm	1,494 mm
250 L	IDEPROIN250H	244 L	585 mm	550 mm	1,744 mm
300 L	IDEPROIN300H	288 L	585 mm	550 mm	1,990 mm

Performance & Weight

Capacity	Heat loss	Heat-up ⨼	Immersions	Sec. return	Empty	Full
180 L	78 W	27 min	1	No	29 kg	201 kg
210 L	82 W	27 min	1	Yes	31 kg	237 kg
250 L	86 W	36 min	2	Yes	35 kg	279 kg
300 L	91 W	32 min	2	Yes	46 kg	334 kg

⨼ Heat-up: 15°C → 60°C via primary coil, adequate boiler output assumed. Source: Ideal/Gledhill product brochure.

ℹ 180 L and 210 L models have one immersion heater: The 250 L and 300 L models are supplied with two immersion heaters (top and bottom) giving independent boost and economy zone control. The 180 L and 210 L models are supplied with one immersion heater. If you need dual-immersion capability in a smaller size, consider the vertical Pro range instead.

Key Features

585 mm Standing Height — Fits Under Low-Pitch Roofs and Under Stairs

All four models share a fixed 585 mm standing height, equal to the height of a standard kitchen appliance. The cylinder lies on its side on factory-fitted cradle supports, so the installation space only needs to be tall enough to accommodate the 550 mm diameter plus the cradle clearance. This makes it the correct solution where a full-height airing cupboard is not available: loft conversions with low eaves, under-stair cupboards, basement plant rooms with restricted headroom, and purpose-built horizontal enclosures. Only the floor length (width) changes with capacity, from 1,306 mm (180 L) to 1,990 mm (300 L).

585mm height1,306–1,990mm floor lengthCradle supports included

High-Efficiency Corrugated Stainless Steel Coil — Heat-Up in as Little as 27 Minutes

The primary heating coil uses a corrugated stainless steel design rather than a plain smooth tube. Corrugation dramatically increases the coil surface area in contact with the stored water and creates turbulence in the primary flow, both of which accelerate heat transfer from the boiler water to the cylinder. The result: the 180 L and 210 L models heat from 15°C to 60°C in just 27 minutes via the primary coil. The 250 L heats in 36 min; the 300 L in 32 min (the larger coil on the 300 L compensates for the greater volume). Faster recovery means less time waiting for hot water after a heavy draw-off.

Corrugated SS coil27–36 min heat-upFaster than plain coil

Duplex Stainless Steel — Made in the UK, 25-Year Vessel Warranty

The pressure vessel is manufactured from duplex stainless steel in the United Kingdom. Duplex grade provides higher corrosion resistance than standard 304 stainless, handles a wider range of UK water chemistries, and carries a 25-year manufacturer’s warranty on the vessel shell. A separate 2-year parts and labour warranty covers all supplied components. Annual servicing and product registration with Ideal Heating are required to maintain the full warranty.

Duplex stainlessMade in UK25-yr vessel2-yr parts & labour

Full G3-Compliant Package — Every Required Component Included

Every model ships with a complete, ready-to-install safety package: combination inlet group (PRV at 3 bar, strainer, check valve, balanced cold take-off, expansion relief valve), potable expansion vessel with wall bracket, T&P relief valve (89 – 96°C / 6 bar), dual control and overheat thermostats, energy cut-out motorised zone valve, tundish, 3 kW immersion heater (two on 250 L and 300 L), and factory-fitted cradle supports. No separate G3 kit purchase is required.

PRV at 3 barT&P at 6 barMotorised cut-outNo extras needed

Energy Cut-Out Motorised Valve — Safe Shutdown of the Primary (Boiler) Circuit

The Ideal Pro Horizontal includes a dedicated 22 mm two-port motorised zone valve on the primary circuit as standard. When the overheat thermostat detects a temperature above safe limits, this valve closes and prevents the boiler from continuing to heat the cylinder. This is the correct engineering solution for an indirect unvented cylinder: the secondary-side thermostats alone cannot stop heat input from the boiler-side primary circuit.

22mm motorised valvePrimary circuit shut-offOverheat protection

3 kW Immersion Heater — Backup, Off-Peak and Solar PV Diversion

The included 3 kW immersion heater (1¾″ BSP, 16A / 250V) has an integral control thermostat and thermal cut-out rated for in-cylinder operation. It provides an independent electric heating capability when the boiler is offline, and can be wired to an off-peak tariff timer or a solar PV diversion device (such as myenergi Eddi or iBoost) to use free surplus solar generation for water heating. The 250 L and 300 L models are supplied with two immersion heaters for independent top and bottom zone control.

3kW immersionThermal cut-outSolar PV ready2× on 250/300L

Secondary Return on 210 L, 250 L and 300 L

The three larger models include a 22 mm secondary return tapping, allowing a pumped secondary circulation loop to be connected. A secondary return ensures hot water is available immediately at every outlet in a larger property, eliminating the wait and reducing water waste at distant taps. The 180 L model does not include a secondary return tapping.

22mm secondary return210/250/300L modelsInstant hot water at outlet

Open-Vented and Sealed Primary Systems — Gas, Oil or LPG

The primary coil circuit is compatible with both sealed (pressurised) and open-vented (F&E cistern) primary systems. Maximum primary working pressure is 3 bar for the horizontal models. Compatible boiler types include gas (natural and LPG), oil, and biomass conventional heat-only and system boilers. Not suitable for combi boilers (which do not use a storage cylinder).

Sealed primaryOpen-vented primaryGas / oil / LPGMax 3 bar primary

Technical Specifications

Cylinder Construction
Type	Horizontal indirect unvented (boiler-heated coil + immersion backup)
Vessel material	Duplex stainless steel
Coil type	High-efficiency corrugated stainless steel
Orientation	Horizontal (lying on side on factory cradle supports)
Manufacture	Made in the United Kingdom
Fixed Dimensions (All Models)
Height (standing on cradles)	585 mm
Diameter	550 mm
Per-Model Data
180 L – IDEPROIN180H	Floor length: 1,306 mm \| Actual vol: 172 L \| Heat loss: 78 W \| Heat-up: 27 min \| 1× immersion \| No sec. return \| 29 kg empty / 201 kg full
210 L – IDEPROIN210H	Floor length: 1,494 mm \| Actual vol: 206 L \| Heat loss: 82 W \| Heat-up: 27 min \| 1× immersion \| 22mm sec. return \| 31 kg empty / 237 kg full
250 L – IDEPROIN250H	Floor length: 1,744 mm \| Actual vol: 244 L \| Heat loss: 86 W \| Heat-up: 36 min \| 2× immersions \| 22mm sec. return \| 35 kg empty / 279 kg full
300 L – IDEPROIN300H	Floor length: 1,990 mm \| Actual vol: 288 L \| Heat loss: 91 W \| Heat-up: 32 min \| 2× immersions \| 22mm sec. return \| 46 kg empty / 334 kg full
Secondary Circuit (Mains Water Side)
Operating pressure	3 bar (after PRV in inlet group)
PRV setting	3 bar
Expansion relief setting	4.5 bar
T&P relief valve	89 – 96°C / 6 bar
Min. recommended mains supply	1.5 bar static, 25 L/min
Cold supply pipework	22 mm minimum recommended
Primary Circuit (Boiler Side)
Max. primary working pressure	3 bar
Compatible heat sources	Gas, oil, LPG, biomass (conventional or system boiler)
Primary system types	Sealed pumped or open-vented (F&E cistern)
Immersion Heater
Power	3 kW
Connection	1¾″ BSP
Rating	16 A / 250 V AC
Thermostats	Integral control thermostat + thermal cut-out
ERP and Compliance
ERP hot water efficiency rating	C
Building regulations	G3 (England & Wales) / P3 (Scotland) / P5 (NI)
Warranty
Vessel	25 years (subject to T&Cs; registration required)
Parts & labour	2 years
Expansion vessel and controls	2 years

Frequently Asked Questions

Why is the primary working pressure only 3 bar on the horizontal model?

This difference comes from the cylinder orientation. In a vertical cylinder, the primary coil sits at the bottom where mechanical support is greatest. In a horizontal cylinder, the geometry limits the maximum primary working pressure to 3 bar. This is still more than adequate for a typical domestic sealed primary circuit (which operates at 1 – 1.5 bar) and for an open-vented F&E system. If your system operates above 3 bar primary pressure, the vertical Pro is required.

Can I use this cylinder with a combi boiler?

No. A combi boiler produces hot water instantaneously on demand and does not use a storage cylinder. The Ideal Pro Horizontal is an indirect unvented storage cylinder, designed for use with a heat-only (conventional) or system boiler that heats water in a primary circuit, transferring heat to the stored water via the corrugated coil. If your property currently has a combi boiler and you wish to switch to stored hot water, you would need to replace the combi with a heat-only or system boiler at the same time.

Why does the 300 L heat up faster than the 250 L?

This is not an error. The heat-up time depends on both the volume of water and the coil surface area. The 300 L model has a larger corrugated coil than the 250 L, which increases the rate of heat transfer from the primary circuit to the stored water. In the 300 L, the coil improvement more than compensates for the larger volume, resulting in a 32 minute heat-up time versus 36 minutes for the 250 L. Both figures assume adequate boiler output and a start temperature of 15°C.

What is the actual storage volume versus the nominal capacity?

The nominal capacity (180 L, 210 L etc.) is the headline marketing figure. The actual usable storage volumes are slightly lower due to the space occupied by the internal coil, immersion heater boss, and fittings: 180 L = 172 L actual; 210 L = 206 L; 250 L = 244 L; 300 L = 288 L. This is normal across all unvented cylinder brands and does not affect sizing decisions.

The cylinder will be installed in a loft — what special considerations apply?

Loft installations require attention to several factors. Frost protection: insulate all exposed pipework in the loft. Floor loading: the 300 L model weighs 334 kg when full — verify the loft floor structure can support this distributed load. Discharge pipework: the T&P valve discharge must fall continuously at a minimum 1:200 gradient to a safe visible discharge point. Plan the discharge route before installation in a confined loft space.

Do I need to buy any additional components?

In most standard installations, no. Every G3-compliant component is included: combination inlet group, expansion vessel and bracket, T&P valve, motorised energy cut-out valve, tundish, thermostats, immersion heater(s), and cradle supports. You will need to provide the discharge pipework from the tundish to the safe discharge point (site-specific), and the primary circuit pipework connecting to your boiler. In hard water areas, Ideal Heating recommends fitting an in-line scale inhibitor on the cold feed.

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