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OSO Saga Charge 250 S2S Supercharged Smart Direct Unvented Cylinder | 250L
Smart Energy Appliance (ESA)S2S Supercharged250L Direct CylinderTime-of-Use Tariff ReadyOSO InCharge App3 kW Titanium Immersion25-Year Cylinder Warranty
The OSO S Charge 250 (internally the S2S 254L) is an Energy Smart Appliance (ESA) — a direct electric unvented hot water cylinder that actively connects to time-of-use electricity tariffs, automatically scheduling its heating to the cheapest available 30-minute pricing windows. It is fully pre-plumbed and wired using OSO's patented S-DESIGN, with all pipework, expansion vessels, and cabling concealed behind a removable lid. Heated by a 3 kW titanium-grade immersion heater (TITANIUM IMMERSION — durable in hard water), the S Charge 250 stores water at 75°C for maximum hot water availability and Legionella compliance. The integrated OSO InCharge system connects to the cloud, reads day-ahead energy prices (e.g. Octopus Agile), and heats during the lowest-cost periods — OSO projects average savings of around £200 per year. Three internal temperature sensors provide precise control. The cylinder is built from stainless steel using ULTRAWELD laser-welded Duplex steel construction, carries a 25-year cylinder warranty, and meets Building Regulations G3 with a factory-fitted G3 kit including integral expansion vessels, PRV, strainer, tundish, and drain cock.
Key Features
- Energy Smart Appliance (ESA) — meets UK government smart appliance standards 3 years ahead of mandate
- Connects to time-of-use tariffs (e.g. Octopus Agile) — heats during cheapest 30-minute periods automatically
- OSO InCharge app: monitor live temperature, available hot water, historical usage, and set holiday mode
- Machine learning AI adapts to your daily hot water usage patterns to ensure availability at lowest cost
- Projected saving of ~£200/year by avoiding peak electricity pricing
- 3 kW TITANIUM IMMERSION heater — superior durability in hard water conditions
- 75°C thermostat setpoint — maximises effective hot water capacity through temperature stratification
- Effective hot water capacity at 40°C: 464L — 250L cylinder delivers significantly more usable hot water than nominal volume
- S-DESIGN — all pipework, expansion vessels, cables concealed under lid for a clean, tidy installation
- NANOPUR high-grade insulation — excellent standing heat loss performance
- ULTRAWELD — laser-welded Duplex stainless steel cylinder with 25-year warranty
- Fully pre-plumbed and wired — up to 70% labour saving vs traditional cylinders
- Integral G3 Building Regulations kit: 2 × 8L expansion vessels (factory-fitted), PRV, strainer, expansion relief, drain cock, tundish
- Mixing valve preset to 60°C at draw-off point for user safety
- XL tapping profile — suitable for family homes with high hot water demand
OSO Technology Advantages
S-DESIGN — All Connections HiddenNANOPUR — High-Grade InsulationULTRAWELD — Superior Corrosion ResistanceTITANIUM IMMERSION — Hard Water DurabilityTARIFF-READY — Smart ESA
What's Included
S Charge 250 (S2S 254L) direct cylinder
3 kW TITANIUM IMMERSION heater (factory-fitted)
Mixing valve — preset 60°C
P&T safety valve (10 bar / 90–95°C)
2 × 8L integral expansion vessels (factory-fitted)
Inlet control valve (strainer + PRV + expansion relief)
Drain cock
Tundish
Fitting template
Installation manual
ℹ️ Smart Tariff Connectivity: The S Charge 250 is an Energy Smart Appliance certified to work with flexible time-of-use tariffs. It knows energy prices 24 hours in advance and uses AI to learn your household's hot water demand, heating at the lowest-cost periods while always ensuring adequate hot water availability.
Technical Specifications
| Specification | Unit | Value |
|---|---|---|
| Product Number | OSO | 11014148 |
| Internal Model Name | S2S 254 | |
| Nominal Volume | L | 254 |
| Effective Capacity at 40°C | L | 464 |
| Dimensions (H × Ø) | mm | 1645 × 595 |
| Weight (empty) | kg | 53 |
| Weight (full) | kg | 304 |
| Thermostat Setpoint | °C | 75 |
| Heat Loss (EN 12897) | W | 69 |
| Heat Loss / 24 hrs | kWh/day | 1.66 |
| Annual Energy Consumption | kWh/year | 4349 |
| Energy Efficiency | % | 38.5 |
| Energy Rating | C | |
| Tapping Profile | XL | |
| Immersion Power | kW | 3 |
| Electrical Supply | V | 240 V single-phase |
| Max Operating Pressure | bar | 6 |
| Expansion Vessels | 2 × 8L factory-fitted | |
| Mixing Valve Preset | °C | 60 |
| P&T Valve Rating | 10 bar / 90–95°C | |
| Cylinder Material | Stainless steel — ULTRAWELD Duplex laser-welded | |
| Immersion Type | TITANIUM IMMERSION | |
| Cylinder Warranty | 25 years |
Installation Overview
⚠️ Qualified installer required: This is an unvented hot water cylinder. Installation must be carried out by a qualified installer holding a current G3 Unvented Hot Water Systems certificate (or equivalent). All electrical connections must comply with BS 7671.
- Pre-installation check: Confirm the cylinder will fit in the installation location — dimensions are 1645mm (H) × 595mm (Ø). Ensure the floor can support the full loaded weight. Allow 400mm clearance above the unit and 150mm at the rear for pipe connections.
- Use the fitting template: Fix the supplied fitting template to the rear wall. This locates the pre-cut pipe tails in the exact positions required for the S-DESIGN rear connection system. Drill and fix accordingly.
- Connect incoming cold mains: Connect the mains cold water supply to the integrated inlet control valve (strainer, PRV, expansion relief already factory-fitted). Ensure supply pressure is within system limits — install a PRV upstream if mains pressure exceeds 6 bar.
- Connect hot water outlets: Connect the hot water outlet to your distribution pipework. The factory-fitted mixing valve is preset to 60°C — do not alter without re-calculating downstream scalding risks.
- Connect tundish discharge: Connect the tundish outlet to a safe and visible discharge point in accordance with BS 6700 / Building Regulations Part G. Use an indirect discharge pipe with the correct air gap.
- Electrical connections: Connect the immersion heater to a dedicated 240V 13A fused connection unit (FCU). The smart ESA connectivity requires a broadband internet connection — follow the OSO InCharge app setup guide to pair the cylinder with your Wi-Fi network and energy tariff.
- Fill, commission and test: Fill the cylinder slowly and check all connections for leaks. Open hot water outlets to bleed air. Switch on and allow the cylinder to heat to operating temperature. Confirm the mixing valve is correctly set. Complete the G3 commissioning record and hand it to the customer.
💡 Smart energy tip: The S Charge 250 works best with a dynamic time-of-use tariff such as Octopus Agile or Octopus Flux. Once paired via the OSO InCharge app, it will automatically shift its heating to off-peak periods. A £200/year saving is projected based on typical usage patterns.
Frequently Asked Questions
What makes the S Charge different from a standard electric cylinder?
The S Charge is an Energy Smart Appliance (ESA). Unlike a standard cylinder that heats on a fixed timer, the S Charge connects to the internet, reads 30-minute ahead energy prices from your tariff provider, and automatically heats during the cheapest periods. It uses AI/machine learning to learn your household's hot water patterns and always ensures hot water is available when you need it — at the lowest possible cost.
Which electricity tariffs does the S Charge work with?
The S Charge is designed for dynamic time-of-use tariffs where the unit price of electricity changes every 30 minutes in response to grid demand and renewable generation. Octopus Agile is the most common example in the UK. The unit retrieves 24-hour ahead pricing data via its internet connection and schedules heating accordingly.
How much can I save with the S Charge?
OSO projects an average saving of around £200 per year for a typical household, achieved by consistently heating during the cheapest tariff windows and avoiding peak periods. Actual savings depend on your tariff, hot water usage, and local energy prices.
Can I still control the cylinder manually if needed?
Yes. The OSO InCharge app gives you full manual control — you can override the smart schedule, boost the temperature immediately, set holiday mode (to prevent unnecessary heating while away), and view live temperature readings and historical usage data.
How much usable hot water does the S Charge 250 actually provide?
Because the cylinder stores water at 75°C, blended down to 60°C at the mixing valve, the effective usable hot water volume (at 40°C comfort temperature) is 464 litres — significantly more than the nominal 254L. This means you can often install a smaller cylinder than with a competitor product.
What is the cylinder made from and what warranty applies?
The S Charge cylinder is made from stainless steel using OSO's ULTRAWELD Duplex laser-welded construction for superior corrosion resistance. The cylinder carries a 25-year warranty against material and manufacturing defects. The immersion heater and electrical components carry a 2-year warranty.
Does the S Charge work if my broadband goes down?
Yes. If the internet connection is lost, the cylinder falls back to its last-known heating schedule or a default schedule. You won't lose hot water — you just lose smart tariff optimisation until connectivity is restored. The app will notify you of connectivity issues.
Is the S Charge suitable for hard water areas?
Yes. The TITANIUM IMMERSION heater is specifically designed for use in hard water areas, offering significantly better durability than standard stainless steel or incoloy elements. The stainless steel cylinder construction also provides inherent scale resistance.
Does the S Charge come with everything needed for Building Regulations compliance?
Yes. The G3 kit is factory-fitted, including two 8L integral expansion vessels (one on 150L models), PRV, strainer, expansion relief, drain cock, and tundish. Your G3-qualified installer will complete the commissioning checklist and issue the relevant documentation.
Can the S Charge work with solar PV?
Yes. The OSO InCharge app supports solar panel integration, allowing the cylinder to prioritise heating when your solar PV is generating excess electricity. This maximises self-consumption and can further reduce running costs beyond the tariff optimisation savings.
$955.16
Original: $2,729.03
-65%OSO Saga Charge 250 S2S Supercharged Smart Direct Unvented Cylinder | 250L—
$2,729.03
$955.16More Images
OSO Saga Charge 250 S2S Supercharged Smart Direct Unvented Cylinder | 250L
Smart Energy Appliance (ESA)S2S Supercharged250L Direct CylinderTime-of-Use Tariff ReadyOSO InCharge App3 kW Titanium Immersion25-Year Cylinder Warranty
The OSO S Charge 250 (internally the S2S 254L) is an Energy Smart Appliance (ESA) — a direct electric unvented hot water cylinder that actively connects to time-of-use electricity tariffs, automatically scheduling its heating to the cheapest available 30-minute pricing windows. It is fully pre-plumbed and wired using OSO's patented S-DESIGN, with all pipework, expansion vessels, and cabling concealed behind a removable lid. Heated by a 3 kW titanium-grade immersion heater (TITANIUM IMMERSION — durable in hard water), the S Charge 250 stores water at 75°C for maximum hot water availability and Legionella compliance. The integrated OSO InCharge system connects to the cloud, reads day-ahead energy prices (e.g. Octopus Agile), and heats during the lowest-cost periods — OSO projects average savings of around £200 per year. Three internal temperature sensors provide precise control. The cylinder is built from stainless steel using ULTRAWELD laser-welded Duplex steel construction, carries a 25-year cylinder warranty, and meets Building Regulations G3 with a factory-fitted G3 kit including integral expansion vessels, PRV, strainer, tundish, and drain cock.
Key Features
- Energy Smart Appliance (ESA) — meets UK government smart appliance standards 3 years ahead of mandate
- Connects to time-of-use tariffs (e.g. Octopus Agile) — heats during cheapest 30-minute periods automatically
- OSO InCharge app: monitor live temperature, available hot water, historical usage, and set holiday mode
- Machine learning AI adapts to your daily hot water usage patterns to ensure availability at lowest cost
- Projected saving of ~£200/year by avoiding peak electricity pricing
- 3 kW TITANIUM IMMERSION heater — superior durability in hard water conditions
- 75°C thermostat setpoint — maximises effective hot water capacity through temperature stratification
- Effective hot water capacity at 40°C: 464L — 250L cylinder delivers significantly more usable hot water than nominal volume
- S-DESIGN — all pipework, expansion vessels, cables concealed under lid for a clean, tidy installation
- NANOPUR high-grade insulation — excellent standing heat loss performance
- ULTRAWELD — laser-welded Duplex stainless steel cylinder with 25-year warranty
- Fully pre-plumbed and wired — up to 70% labour saving vs traditional cylinders
- Integral G3 Building Regulations kit: 2 × 8L expansion vessels (factory-fitted), PRV, strainer, expansion relief, drain cock, tundish
- Mixing valve preset to 60°C at draw-off point for user safety
- XL tapping profile — suitable for family homes with high hot water demand
OSO Technology Advantages
S-DESIGN — All Connections HiddenNANOPUR — High-Grade InsulationULTRAWELD — Superior Corrosion ResistanceTITANIUM IMMERSION — Hard Water DurabilityTARIFF-READY — Smart ESA
What's Included
S Charge 250 (S2S 254L) direct cylinder
3 kW TITANIUM IMMERSION heater (factory-fitted)
Mixing valve — preset 60°C
P&T safety valve (10 bar / 90–95°C)
2 × 8L integral expansion vessels (factory-fitted)
Inlet control valve (strainer + PRV + expansion relief)
Drain cock
Tundish
Fitting template
Installation manual
ℹ️ Smart Tariff Connectivity: The S Charge 250 is an Energy Smart Appliance certified to work with flexible time-of-use tariffs. It knows energy prices 24 hours in advance and uses AI to learn your household's hot water demand, heating at the lowest-cost periods while always ensuring adequate hot water availability.
Technical Specifications
| Specification | Unit | Value |
|---|---|---|
| Product Number | OSO | 11014148 |
| Internal Model Name | S2S 254 | |
| Nominal Volume | L | 254 |
| Effective Capacity at 40°C | L | 464 |
| Dimensions (H × Ø) | mm | 1645 × 595 |
| Weight (empty) | kg | 53 |
| Weight (full) | kg | 304 |
| Thermostat Setpoint | °C | 75 |
| Heat Loss (EN 12897) | W | 69 |
| Heat Loss / 24 hrs | kWh/day | 1.66 |
| Annual Energy Consumption | kWh/year | 4349 |
| Energy Efficiency | % | 38.5 |
| Energy Rating | C | |
| Tapping Profile | XL | |
| Immersion Power | kW | 3 |
| Electrical Supply | V | 240 V single-phase |
| Max Operating Pressure | bar | 6 |
| Expansion Vessels | 2 × 8L factory-fitted | |
| Mixing Valve Preset | °C | 60 |
| P&T Valve Rating | 10 bar / 90–95°C | |
| Cylinder Material | Stainless steel — ULTRAWELD Duplex laser-welded | |
| Immersion Type | TITANIUM IMMERSION | |
| Cylinder Warranty | 25 years |
Installation Overview
⚠️ Qualified installer required: This is an unvented hot water cylinder. Installation must be carried out by a qualified installer holding a current G3 Unvented Hot Water Systems certificate (or equivalent). All electrical connections must comply with BS 7671.
- Pre-installation check: Confirm the cylinder will fit in the installation location — dimensions are 1645mm (H) × 595mm (Ø). Ensure the floor can support the full loaded weight. Allow 400mm clearance above the unit and 150mm at the rear for pipe connections.
- Use the fitting template: Fix the supplied fitting template to the rear wall. This locates the pre-cut pipe tails in the exact positions required for the S-DESIGN rear connection system. Drill and fix accordingly.
- Connect incoming cold mains: Connect the mains cold water supply to the integrated inlet control valve (strainer, PRV, expansion relief already factory-fitted). Ensure supply pressure is within system limits — install a PRV upstream if mains pressure exceeds 6 bar.
- Connect hot water outlets: Connect the hot water outlet to your distribution pipework. The factory-fitted mixing valve is preset to 60°C — do not alter without re-calculating downstream scalding risks.
- Connect tundish discharge: Connect the tundish outlet to a safe and visible discharge point in accordance with BS 6700 / Building Regulations Part G. Use an indirect discharge pipe with the correct air gap.
- Electrical connections: Connect the immersion heater to a dedicated 240V 13A fused connection unit (FCU). The smart ESA connectivity requires a broadband internet connection — follow the OSO InCharge app setup guide to pair the cylinder with your Wi-Fi network and energy tariff.
- Fill, commission and test: Fill the cylinder slowly and check all connections for leaks. Open hot water outlets to bleed air. Switch on and allow the cylinder to heat to operating temperature. Confirm the mixing valve is correctly set. Complete the G3 commissioning record and hand it to the customer.
💡 Smart energy tip: The S Charge 250 works best with a dynamic time-of-use tariff such as Octopus Agile or Octopus Flux. Once paired via the OSO InCharge app, it will automatically shift its heating to off-peak periods. A £200/year saving is projected based on typical usage patterns.
Frequently Asked Questions
What makes the S Charge different from a standard electric cylinder?
The S Charge is an Energy Smart Appliance (ESA). Unlike a standard cylinder that heats on a fixed timer, the S Charge connects to the internet, reads 30-minute ahead energy prices from your tariff provider, and automatically heats during the cheapest periods. It uses AI/machine learning to learn your household's hot water patterns and always ensures hot water is available when you need it — at the lowest possible cost.
Which electricity tariffs does the S Charge work with?
The S Charge is designed for dynamic time-of-use tariffs where the unit price of electricity changes every 30 minutes in response to grid demand and renewable generation. Octopus Agile is the most common example in the UK. The unit retrieves 24-hour ahead pricing data via its internet connection and schedules heating accordingly.
How much can I save with the S Charge?
OSO projects an average saving of around £200 per year for a typical household, achieved by consistently heating during the cheapest tariff windows and avoiding peak periods. Actual savings depend on your tariff, hot water usage, and local energy prices.
Can I still control the cylinder manually if needed?
Yes. The OSO InCharge app gives you full manual control — you can override the smart schedule, boost the temperature immediately, set holiday mode (to prevent unnecessary heating while away), and view live temperature readings and historical usage data.
How much usable hot water does the S Charge 250 actually provide?
Because the cylinder stores water at 75°C, blended down to 60°C at the mixing valve, the effective usable hot water volume (at 40°C comfort temperature) is 464 litres — significantly more than the nominal 254L. This means you can often install a smaller cylinder than with a competitor product.
What is the cylinder made from and what warranty applies?
The S Charge cylinder is made from stainless steel using OSO's ULTRAWELD Duplex laser-welded construction for superior corrosion resistance. The cylinder carries a 25-year warranty against material and manufacturing defects. The immersion heater and electrical components carry a 2-year warranty.
Does the S Charge work if my broadband goes down?
Yes. If the internet connection is lost, the cylinder falls back to its last-known heating schedule or a default schedule. You won't lose hot water — you just lose smart tariff optimisation until connectivity is restored. The app will notify you of connectivity issues.
Is the S Charge suitable for hard water areas?
Yes. The TITANIUM IMMERSION heater is specifically designed for use in hard water areas, offering significantly better durability than standard stainless steel or incoloy elements. The stainless steel cylinder construction also provides inherent scale resistance.
Does the S Charge come with everything needed for Building Regulations compliance?
Yes. The G3 kit is factory-fitted, including two 8L integral expansion vessels (one on 150L models), PRV, strainer, expansion relief, drain cock, and tundish. Your G3-qualified installer will complete the commissioning checklist and issue the relevant documentation.
Can the S Charge work with solar PV?
Yes. The OSO InCharge app supports solar panel integration, allowing the cylinder to prioritise heating when your solar PV is generating excess electricity. This maximises self-consumption and can further reduce running costs beyond the tariff optimisation savings.
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
Smart Energy Appliance (ESA)S2S Supercharged250L Direct CylinderTime-of-Use Tariff ReadyOSO InCharge App3 kW Titanium Immersion25-Year Cylinder Warranty
The OSO S Charge 250 (internally the S2S 254L) is an Energy Smart Appliance (ESA) — a direct electric unvented hot water cylinder that actively connects to time-of-use electricity tariffs, automatically scheduling its heating to the cheapest available 30-minute pricing windows. It is fully pre-plumbed and wired using OSO's patented S-DESIGN, with all pipework, expansion vessels, and cabling concealed behind a removable lid. Heated by a 3 kW titanium-grade immersion heater (TITANIUM IMMERSION — durable in hard water), the S Charge 250 stores water at 75°C for maximum hot water availability and Legionella compliance. The integrated OSO InCharge system connects to the cloud, reads day-ahead energy prices (e.g. Octopus Agile), and heats during the lowest-cost periods — OSO projects average savings of around £200 per year. Three internal temperature sensors provide precise control. The cylinder is built from stainless steel using ULTRAWELD laser-welded Duplex steel construction, carries a 25-year cylinder warranty, and meets Building Regulations G3 with a factory-fitted G3 kit including integral expansion vessels, PRV, strainer, tundish, and drain cock.
Key Features
- Energy Smart Appliance (ESA) — meets UK government smart appliance standards 3 years ahead of mandate
- Connects to time-of-use tariffs (e.g. Octopus Agile) — heats during cheapest 30-minute periods automatically
- OSO InCharge app: monitor live temperature, available hot water, historical usage, and set holiday mode
- Machine learning AI adapts to your daily hot water usage patterns to ensure availability at lowest cost
- Projected saving of ~£200/year by avoiding peak electricity pricing
- 3 kW TITANIUM IMMERSION heater — superior durability in hard water conditions
- 75°C thermostat setpoint — maximises effective hot water capacity through temperature stratification
- Effective hot water capacity at 40°C: 464L — 250L cylinder delivers significantly more usable hot water than nominal volume
- S-DESIGN — all pipework, expansion vessels, cables concealed under lid for a clean, tidy installation
- NANOPUR high-grade insulation — excellent standing heat loss performance
- ULTRAWELD — laser-welded Duplex stainless steel cylinder with 25-year warranty
- Fully pre-plumbed and wired — up to 70% labour saving vs traditional cylinders
- Integral G3 Building Regulations kit: 2 × 8L expansion vessels (factory-fitted), PRV, strainer, expansion relief, drain cock, tundish
- Mixing valve preset to 60°C at draw-off point for user safety
- XL tapping profile — suitable for family homes with high hot water demand
OSO Technology Advantages
S-DESIGN — All Connections HiddenNANOPUR — High-Grade InsulationULTRAWELD — Superior Corrosion ResistanceTITANIUM IMMERSION — Hard Water DurabilityTARIFF-READY — Smart ESA
What's Included
S Charge 250 (S2S 254L) direct cylinder
3 kW TITANIUM IMMERSION heater (factory-fitted)
Mixing valve — preset 60°C
P&T safety valve (10 bar / 90–95°C)
2 × 8L integral expansion vessels (factory-fitted)
Inlet control valve (strainer + PRV + expansion relief)
Drain cock
Tundish
Fitting template
Installation manual
ℹ️ Smart Tariff Connectivity: The S Charge 250 is an Energy Smart Appliance certified to work with flexible time-of-use tariffs. It knows energy prices 24 hours in advance and uses AI to learn your household's hot water demand, heating at the lowest-cost periods while always ensuring adequate hot water availability.
Technical Specifications
| Specification | Unit | Value |
|---|---|---|
| Product Number | OSO | 11014148 |
| Internal Model Name | S2S 254 | |
| Nominal Volume | L | 254 |
| Effective Capacity at 40°C | L | 464 |
| Dimensions (H × Ø) | mm | 1645 × 595 |
| Weight (empty) | kg | 53 |
| Weight (full) | kg | 304 |
| Thermostat Setpoint | °C | 75 |
| Heat Loss (EN 12897) | W | 69 |
| Heat Loss / 24 hrs | kWh/day | 1.66 |
| Annual Energy Consumption | kWh/year | 4349 |
| Energy Efficiency | % | 38.5 |
| Energy Rating | C | |
| Tapping Profile | XL | |
| Immersion Power | kW | 3 |
| Electrical Supply | V | 240 V single-phase |
| Max Operating Pressure | bar | 6 |
| Expansion Vessels | 2 × 8L factory-fitted | |
| Mixing Valve Preset | °C | 60 |
| P&T Valve Rating | 10 bar / 90–95°C | |
| Cylinder Material | Stainless steel — ULTRAWELD Duplex laser-welded | |
| Immersion Type | TITANIUM IMMERSION | |
| Cylinder Warranty | 25 years |
Installation Overview
⚠️ Qualified installer required: This is an unvented hot water cylinder. Installation must be carried out by a qualified installer holding a current G3 Unvented Hot Water Systems certificate (or equivalent). All electrical connections must comply with BS 7671.
- Pre-installation check: Confirm the cylinder will fit in the installation location — dimensions are 1645mm (H) × 595mm (Ø). Ensure the floor can support the full loaded weight. Allow 400mm clearance above the unit and 150mm at the rear for pipe connections.
- Use the fitting template: Fix the supplied fitting template to the rear wall. This locates the pre-cut pipe tails in the exact positions required for the S-DESIGN rear connection system. Drill and fix accordingly.
- Connect incoming cold mains: Connect the mains cold water supply to the integrated inlet control valve (strainer, PRV, expansion relief already factory-fitted). Ensure supply pressure is within system limits — install a PRV upstream if mains pressure exceeds 6 bar.
- Connect hot water outlets: Connect the hot water outlet to your distribution pipework. The factory-fitted mixing valve is preset to 60°C — do not alter without re-calculating downstream scalding risks.
- Connect tundish discharge: Connect the tundish outlet to a safe and visible discharge point in accordance with BS 6700 / Building Regulations Part G. Use an indirect discharge pipe with the correct air gap.
- Electrical connections: Connect the immersion heater to a dedicated 240V 13A fused connection unit (FCU). The smart ESA connectivity requires a broadband internet connection — follow the OSO InCharge app setup guide to pair the cylinder with your Wi-Fi network and energy tariff.
- Fill, commission and test: Fill the cylinder slowly and check all connections for leaks. Open hot water outlets to bleed air. Switch on and allow the cylinder to heat to operating temperature. Confirm the mixing valve is correctly set. Complete the G3 commissioning record and hand it to the customer.
💡 Smart energy tip: The S Charge 250 works best with a dynamic time-of-use tariff such as Octopus Agile or Octopus Flux. Once paired via the OSO InCharge app, it will automatically shift its heating to off-peak periods. A £200/year saving is projected based on typical usage patterns.
Frequently Asked Questions
What makes the S Charge different from a standard electric cylinder?
The S Charge is an Energy Smart Appliance (ESA). Unlike a standard cylinder that heats on a fixed timer, the S Charge connects to the internet, reads 30-minute ahead energy prices from your tariff provider, and automatically heats during the cheapest periods. It uses AI/machine learning to learn your household's hot water patterns and always ensures hot water is available when you need it — at the lowest possible cost.
Which electricity tariffs does the S Charge work with?
The S Charge is designed for dynamic time-of-use tariffs where the unit price of electricity changes every 30 minutes in response to grid demand and renewable generation. Octopus Agile is the most common example in the UK. The unit retrieves 24-hour ahead pricing data via its internet connection and schedules heating accordingly.
How much can I save with the S Charge?
OSO projects an average saving of around £200 per year for a typical household, achieved by consistently heating during the cheapest tariff windows and avoiding peak periods. Actual savings depend on your tariff, hot water usage, and local energy prices.
Can I still control the cylinder manually if needed?
Yes. The OSO InCharge app gives you full manual control — you can override the smart schedule, boost the temperature immediately, set holiday mode (to prevent unnecessary heating while away), and view live temperature readings and historical usage data.
How much usable hot water does the S Charge 250 actually provide?
Because the cylinder stores water at 75°C, blended down to 60°C at the mixing valve, the effective usable hot water volume (at 40°C comfort temperature) is 464 litres — significantly more than the nominal 254L. This means you can often install a smaller cylinder than with a competitor product.
What is the cylinder made from and what warranty applies?
The S Charge cylinder is made from stainless steel using OSO's ULTRAWELD Duplex laser-welded construction for superior corrosion resistance. The cylinder carries a 25-year warranty against material and manufacturing defects. The immersion heater and electrical components carry a 2-year warranty.
Does the S Charge work if my broadband goes down?
Yes. If the internet connection is lost, the cylinder falls back to its last-known heating schedule or a default schedule. You won't lose hot water — you just lose smart tariff optimisation until connectivity is restored. The app will notify you of connectivity issues.
Is the S Charge suitable for hard water areas?
Yes. The TITANIUM IMMERSION heater is specifically designed for use in hard water areas, offering significantly better durability than standard stainless steel or incoloy elements. The stainless steel cylinder construction also provides inherent scale resistance.
Does the S Charge come with everything needed for Building Regulations compliance?
Yes. The G3 kit is factory-fitted, including two 8L integral expansion vessels (one on 150L models), PRV, strainer, expansion relief, drain cock, and tundish. Your G3-qualified installer will complete the commissioning checklist and issue the relevant documentation.
Can the S Charge work with solar PV?
Yes. The OSO InCharge app supports solar panel integration, allowing the cylinder to prioritise heating when your solar PV is generating excess electricity. This maximises self-consumption and can further reduce running costs beyond the tariff optimisation savings.
