Thermosyphon Solar Water Heater
Manufacturing & Supply

Solar Water Thermosyphon System

Millionsun specializes in OEM and ODM manufacturing of solar water thermosyphon systems for distributors, solar brands, EPC contractors, and installers worldwide.

Tank sizes range from 150L to 400L, with collector configurations from 1 to 3 units. We supply as complete systems, CKD/SKD kits, or fully customized solutions.

Key Features & Performance

Natural Thermosyphon Circulation

Natural convection operation, no circulation power or mechanical moving parts.

Open-Loop Direct System

Direct water heating without heat exchanger/antifreeze; lower cost & easy maintenance.

High-Efficiency Flat-Plate Collectors

95% absorptivity black selective coating, copper channels, ≥92% transmittance glass, laser welding for superior heat transfer.

Robust Storage Tank

1.5mm SUS304/SUS316L horizontal liner, painted steel shell, 50mm glass wool insulation.

Optional Electric Backup

1500W–3600W auxiliary heating for cloudy weather and nighttime hot water

Easy Installation

Complete all-in-one kit. Fits flat/sloped roofs, simple plumbing connection, no complicated commissioning.

Compact Integrated Structure

Slim integrated rooftop unit, saves valuable roof space.

Solar Water Thermosyphon System Specifications

Model C-TS150L/2 C-TS200L/2.5 C-TS300L/4 C-TS400L/6
Tank type M-ST/150L-TBP M-ST/200L-TBP M-ST/300L-TBP M-ST/400L-TBP
Tank volume 150L 200L 300L 400L
Collector type M-SBC/2.0-Black M-SBC/2.5-Black M-SBC/2.0-Black M-SBC/2.0-Black
Collector quantity 1 1 2 3
Collector Area 2.0m² 2.5m² 4.0m² 6.0m²
Suitable for roof Flat or Slope Flat or Slope Flat or Slope Flat or Slope
System weight 120 kg 150 kg 190 kg 240 kg
20GP / 40HQ 39 / 80 32 / 66 24 / 52 21 / 46
Number of persons 3–4 4–6 6–8 8–12
Main Components
Tank Tank type: Horizontal tank, volume from 150L to 400L. Inner material: SUS316L (1.5mm) or SUS304. Outer material: Painted steel or SUS304. Electric backup: Optional 1500W–3600W electric heating element.
Collector Size: 2000 × 1000 × 80mm (2.0m²) or 2000 × 1250 × 80mm (2.5m²) Cover material: 3.2mm low-iron patterned tempered glass. Absorber material: Black selective coating with aluminium sheet. Header tube: Φ22 × 0.6mm. Riser tube: Φ10 × 0.5mm. Insulation: Fiberglass wool. Backsheet: Aluminium plate.
Bracket Material: Aluminium alloy. Installation angle: 15°–60°.
Accessories T&P valve, air valve, copper fittings, circulation pipe and insulation.

What we offer?

OEM & ODM Manufacturing Support

Private Label Production

Electric Backup Options Available

Residential & Commercial Applications

Complete System or Component Supply

Technical Documentation & Engineering Support

Custom Project Solutions

Customized tank capacities and multi-collector configurations are available for OEM customers and commercial projects. Tank specifications, collector size, and backup heating can be specified per project requirement.

Recommended Applications:

Single-family homes

Villas

Holiday houses

Small residential projects

Business Value

Designed for Different Business Models
Your Business
How This Product Fits
Distributor
Stock one complete system for the residential market. High demand, fast turnover.
Brand
Put your label on it. Customize tank size, collector spec, and packaging.
EPC Contractor
Simple to specify and install. Ideal for large residential project rollouts.
Installer
No complex setup. Mount on roof, connect pipes, done.
Local Manufacturer
Source CKD/SKD kits. Assemble locally with simple tools.

Product Comparison — Why Thermosyphon Wins

The thermosyphon system is the simplest, most affordable solar water heating option. No pumps, no controllers, no moving parts — just free hot water from the sun.
Electric
Thermosyphon — Your Advantage
Energy source
Grid electricity
Sunlight — free
Monthly cost
Pay for every kWh
Save 55–85%
Lifespan
8–12 years
15+ years
Installation
Indoor tank
Single rooftop unit — no indoor space needed
Split System
Thermosyphon — Your Advantage
Circulation
Pump + controller needed
Natural circulation — no electricity, no pump, no controller
System type
Closed-loop (antifreeze + heat exchanger)
Open-loop direct — simpler, fewer parts
Installation
Collector on roof, tank inside, pipes between
Single rooftop unit — mount and connect
Cost
Higher (more components)
Lower — simplest design on the market
Maintenance
Pump and antifreeze need checking
Near zero — no moving parts
Heat Pump
Thermosyphon — Your Advantage
Energy source
Air + electricity
Sunlight — free
Noise
Compressor noise
Silent — no moving parts
Installation
Needs ventilated space
On the roof — no indoor space needed
Cold climate
Less efficient in winter
Simple — electric backup covers cloudy days
Cost
Higher equipment cost
Lower cost — simpler technology

How the System Works

1

Step 1
Sunlight hits the flat plate collector. The black selective coating absorbs the heat.

2

Step 2
Water inside the collector tubes heats up and becomes lighter.

3

Step 3
Hot water naturally rises into the storage tank above the collector.

4

Step 4
Cooler water from the bottom of the tank flows back down to the collector to be reheated.

5

Step 5
This natural cycle continues automatically throughout the day. The tank water gets hotter and hotter.

6

Step 6
If the sun is not enough, the electric heating element kicks in to keep the water at the desired

Manufacturing & Supply Capabilities

OEM Manufacturing

Millionsun makes solar water heating products for partners worldwide.

Our Factory

Supply Options

Frequently Asked Questions

Do you offer OEM service?

Yes. We make products for your brand. Tank size, collector spec, and packaging — all customizable.

150L, 200L, 300L, and 400L standard. Custom sizes available for projects.

A thermosyphon system uses natural circulation — no pump needed. The tank sits above the collector on the roof. A split system uses a pump and the tank is inside the building. Thermosyphon is simpler and lower cost; split is better for cold climates and larger buildings.
The solar heating works without electricity. The electric backup element needs power, but you can choose not to install it in sunny climates.
A qualified installer can complete a rooftop installation in half a day.
From 120 kg (150L system) to 240 kg (400L system). The roof must be able to support the weight.
Product documents, installation guides, engineering help, and project support.

Request OEM Quotation

Receive customized pricing based on your branding, configuration, and volume requirements.
No order too small, no project too complex. 20 years of OEM experience — your brand, our expertise.
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