Home » OSO Delta GeoCoil DGC250L 250 Litre Heat Pump Unvented Cylinder
SKU: 11009122
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OSO Delta GeoCoil DGC250L 250 Litre Heat Pump Unvented Cylinder

OSO Hotwater
£2,100.00 Inc. VAT £1,750.00 Exc. VAT
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The OSO Delta GeoCoil DGC250L is a 250 litre indirect unvented heat pump cylinder engineered for maximum energy efficiency in renewable heating systems. Built from EVERLAST™ titanium-alloyed stainless steel and insulated with OSO's award-winning combination of NANOPUR foam and Vacuum Insulation Panels (VIP), the DGC250L achieves an ErP A energy rating — making it one of the most efficient heat pump cylinders available in the UK market. The large 2.6 m² smooth scale-resistant coil is optimised for heat pumps up to 15 kW, while the built-in 2.8 kW INCOTEC™ immersion heater provides backup boosting capability. Compatible with both S-plan and Y-plan systems, the DGC250L includes a digital dual cylinder thermostat with anti-legionella and holiday mode functions as standard, and is backed by OSO's 25-year warranty on the stainless steel tank.

250 L
Nominal Capacity
A
ErP Energy Rating
2.6 m²
Primary Coil Area
2.8 kW
Immersion Heater
25 Years
Tank Warranty
≤15 kW
Heat Pump Capacity
🔴 Building Regulation G3 – Unvented Cylinder Installation
This unvented hot water cylinder must be installed by a competent person holding a current G3 unvented hot water storage qualification, in full compliance with Building Regulation G3, EN 12897:2016, and all current legislation in force at the date of installation. The discharge pipework must be routed to a safe, visible position with continuous fall to drain.
🟢 Vacuum Insulation Panel (VIP) Technology
OSO's proprietary Vacuum Insulation Panels work alongside NANOPUR high-performance foam to deliver class-leading thermal retention. OSO states that the VIP + NANOPUR combination can reduce heat loss by approximately 400 kWh per year compared to conventional insulation, helping housebuilders meet stringent SAP energy requirements and potentially saving enough energy to pay for the cylinder over its lifetime.
🟢 EVERLAST™ Corrosion Protection
The DGC250L tank is manufactured from EVERLAST™ titanium-alloyed stainless steel using OSO's ULTRAWELD™ welding system and advanced passivation process for class-leading corrosion resistance. OSO stainless steel cylinders are over 40% lighter than equivalent enamelled products, and the INCOTEC™ immersion heater uses ultra-high-grade Incoloy 825 stainless elements with DZR brass and zinc-free soldering for maximum durability in hard water areas.
Key Features
Heat Pump Optimised Coil Design
The 2.6 m² smooth tube heat exchanger is specifically engineered for low-temperature renewable heat sources. Its large surface area ensures efficient heat transfer even at the lower flow temperatures typical of air source and ground source heat pumps up to 15 kW, maximising system COP and reducing reheat times.
Award-Winning VIP + NANOPUR Insulation
The dual-layer insulation system combines Vacuum Insulation Panels with NANOPUR high-performance foam to achieve the lowest standing losses in the heat pump cylinder market. This ErP A-rated thermal performance helps meet Part L building regulations and contributes to superior SAP scores for new-build projects.
INCOTEC™ Immersion Backup
The factory-fitted 2.8 kW INCOTEC™ immersion heater positioned above the coil acts as an emergency backup or boost element. Using Incoloy 825 stainless steel with carefully calculated surface loads, it resists scale build-up in hard water regions and raises the upper portion of stored water to full temperature quickly when needed.
Digital Dual Thermostat with Legionella Protection
The electronic dual cylinder thermostat provides precise temperature control with a clear LCD display. The built-in anti-legionella function delivers an automatic weekly boost to above 60°C, adjustable from 1 to 7 days or fully disabled. Holiday mode shuts down all heating during extended vacancy to save energy.
Complete G3-Compliant Kit Included
The DGC250L ships with a full G3 accessory kit including multibloc valve (with line strainer, PRV, expansion relief, and balanced cold take-off), tundish, drain cock, Honeywell V4043H motorised valve, and a 24 litre expansion vessel — reducing the need for additional site-sourced components and simplifying installation.
EVERLAST™ 25-Year Tank Warranty
The titanium-alloyed stainless steel tank with ULTRAWELD™ welded construction and advanced passivation delivers exceptional corrosion resistance. OSO backs this with a 25-year warranty on the stainless steel vessel — among the longest in the UK cylinder market — reflecting confidence in their Norwegian manufacturing quality (ISO 9001 / ISO 14001 certified).
Technical Specifications
Product Identification
Manufacturer OSO Hotwater AS (Norway)
Product Name Delta GeoCoil DGC250L
MPN 11009122
International Product Code DGC 250 – 2.8 kW / 1×230V + HX 2.6 m²
EAN / Barcode Not publicly listed — contact OSO UK
Capacity & Dimensions
Nominal Capacity 250 litres
Actual Volume ~245 litres
Diameter (ø) 595 mm
Height (H) 1535 mm
Weight (Empty) ~60 kg
Adjustable Feet Range 0 – 40 mm (factory fitted)
Thermal Performance
ErP Energy Rating A
Insulation Type NANOPUR foam + Vacuum Insulation Panels (VIP)
Standing Heat Loss (EN 12897) Not separately published for UK VIP 250L — see amber callout above
Energy Saving vs Conventional ~400 kWh/year (OSO stated, VIP + NANOPUR)
Thermostat Set Point (Factory) 60°C
Primary Heating (Coil)
Primary Coil Surface Area 2.6 m²
Coil Type Smooth, scale-resistant tube heat exchanger
Compatible Heat Pump Output Up to 15 kW
Primary Flow Direction Bottom to top
Primary Connections 3/4" BSP female (flow & return)
Max Primary Flow Temperature 82°C
Immersion Heater
Immersion Power 2.8 kW (1-phase, 230 V)
Element Type INCOTEC™ (Incoloy 825, scale-resistant)
Immersion Thermostat Range Adjustable 18 – 70°C (preset 60°C)
Safety Cut-Out 85°C (manual reset)
Pressure & Water Supply
Max Operating Pressure 10 bar
Minimum Supply Pressure 2.5 bar (recommended)
Recommended Flow Rate 20 litres/min at 1 bar dynamic
T&P Relief Valve 10 bar / 90 – 95°C
Expansion Vessel 24 litre (3 bar pre-charge, included)
Controls & Safety
Cylinder Thermostat Electronic dual cylinder thermostat (25 – 65°C)
Limit Thermostat 80°C (concealed manual reset)
Anti-Legionella Function Weekly auto-boost to >60°C (adjustable 1 – 7 days)
Holiday Mode Yes — full shutdown for extended vacancy
Motorised Valve Honeywell V4043H1056C (2-port, included)
System Compatibility S-plan and Y-plan
Construction & Compliance
Tank Material EVERLAST™ titanium-alloyed stainless steel
Welding System ULTRAWELD™
IP Rating IP21
Pressure Vessel Standard EN 12897:2016
Safety Standard EN 60335-2-21
Certification UKCA marked
Directives LVD 2014/35/EU, EMC 2014/30/EU, PED 2014/68/EU
Tank Warranty 25 years
Country of Manufacture Norway
Frequently Asked Questions
What types of heat pump is the DGC250L compatible with?
The OSO Delta GeoCoil DGC250L is compatible with all thermostatically controlled air source heat pumps (ASHP) and ground source heat pumps (GSHP) with an output of up to 15 kW. The large 2.6 m² coil is specifically designed for efficient heat transfer at the lower flow temperatures typical of heat pump systems. The cylinder can also be connected to gas or oil boilers for faster reheat times if required.
Who can install this cylinder?
As an unvented hot water storage system, the DGC250L must be installed by a competent person who holds a current qualification in unvented hot water systems (Building Regulation G3). The installation must comply with all current building regulations, water regulations, and IEE wiring regulations. OSO cylinders are not suitable for gravity-fed primary systems or non-thermostatically controlled heat sources such as solid fuel stoves.
What is included in the box?
The DGC250L is supplied with a comprehensive accessory kit including: a multibloc valve (incorporating pressure reducing valve, line strainer, balanced cold take-off, check valve, and expansion relief valve), tundish, 3/4" × 22 mm elbow/drain cock, Honeywell V4043H motorised valve, 24 litre expansion vessel, and the installation manual with log book. The immersion heater, thermostats, T&P relief valve, and adjustable feet are factory fitted.
How does the anti-legionella function work?
The digital dual cylinder thermostat includes an automatic weekly legionella boost that raises the stored water temperature to above 60°C for one hour, killing any legionella bacteria. The interval can be adjusted from 1 to 7 days, or fully disabled during commissioning. OSO recommends keeping the cylinder thermostat set at 60°C in line with government guidelines to maintain adequate protection against bacterial growth.
What makes the VIP insulation different from standard cylinder insulation?
OSO's Vacuum Insulation Panels (VIP) use evacuated panels that dramatically reduce conductive and convective heat transfer compared to standard foam or fibre insulation. Combined with NANOPUR high-performance foam, the system delivers approximately 400 kWh per year less heat loss than conventionally insulated cylinders. This achieves an ErP A rating, helps meet SAP targets for new-build projects, and can save enough on running costs to recoup the cylinder cost over its lifetime.
Can I use this cylinder with a gas or oil boiler instead of a heat pump?
Yes. While the DGC250L is optimised for heat pump installations, the 2.6 m² coil can also be heated by a thermostatically controlled gas or oil boiler, which will deliver faster reheat times than a heat pump. The cylinder supports both S-plan and Y-plan system configurations. Note that non-thermostatically controlled heat sources (such as solid fuel or wood-burning stoves) must not be used with this unvented cylinder.
BTU & WATT Calculator
Room Dimensions
Room Type
Living Room
Bedroom
Kitchen
Bathroom
Conservatory
Hallway
Glazing Type
Single Glazed
Double Glazed
Triple Glazed
External Walls
0 Wall
1 Wall
2 Walls
3 Walls
4 Walls
Insulation Level
Poor
Average
Good (New Build)
Required Heating
0
Watts
0
BTUs

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