ThermoPower™ 30 Tube Vacuum Direct Flow Solar Collector

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Get peace of mind with the 10-year SunMaxx warranty and 1/2″ NPT connections of our high-quality solar water heater. Our product is OG-100 certified, making it eligible for solar tax credits, and has been manufactured since 2006. Featuring a 30 tube evacuated tube with direct flow, it is perfect for both commercial and residential use. Invest in an efficient and reliable solar water heating system today.

  • 10 Year SunMaxx Warranty
  • 1/2″ NPT Connections
  • Manufactured since 2006
  • OG-100 Certified – Certified for Solar Tax Credits
  • 30 tube evacuated tube with direct flow
  • Suitable for commercial or residential use
SKU: ThermoPower-VDF30 Category:


Evacuated Tube Solar Collector VDF Series

The Vacuum Direct Flow Solar Collector from SunMaxx Solar is an ideal choice for an efficient and easy to install solar hot water heating system. This pre-packaged system requires minimal assembly and features a vertical mounting design which makes it easy to install and maintain. With fewer components and lightweight, durable aluminum construction which eliminates the need for heavy frames, mounting this system shouldn’t be a problem.

Additionally, the Vacuum Direct Flow Solar Collector has an incredibly low start-up temperature and low pressure drop, meaning you can get up and running with your solar hot water heating system in no time! SunMaxx Solar strives to make renewable energy products more affordable, so you can be sure you’re getting the best value for your money!

Optimum Performance, Remarkable Versatility

The newest and most advanced solar collector on the market, the ThermoPower™ 20 Tube Vacuum Direct Flow Solar Collector, is the perfect choice for anyone looking to reduce their energy costs and increase their home’s efficiency. This revolutionary technology quickly and efficiently harnesses the sun’s energy, providing an abundance of free hot water for your home or business. With its unique design and collection properties, the ThermoPower™ 20 Tube Vacuum Direct Flow Solar Collector is exceptionally efficient even in low-light conditions and with its freeze protection, it performs with an efficiency of over 70% even in freezing temperatures.

When it comes to investment and performance, you can’t go wrong with the ThermoPower™ 20 Tube Vacuum Direct Flow Solar Collector. Its cutting-edge design and high-quality materials ensure optimal performance over a long lifespan, while its affordable price makes it the perfect choice to maximize your return on investment. Enjoy the benefits of renewable energy while paying less on your energy costs with the ThermoPower™ 20 Tube Vacuum Direct Flow Solar Collector.

Features & Benefits

  • High operational safety
  • 92% coating absorbance
  • Simple integration into building structure.
  • VDFs Can be mounted vertically, horizontally or at any angle in-between
  • Adjusted to mount and connect to large solar installations
  • Ready mounting system provided
  • 10 years performance warranty
  • 25-30 years expected lifetime
  • SRCC & Solar Keymark Certified
  • Free technical support

Quick Sizing
Calculators & Guides

Technical Details


  • Weight: 170 lbs (without crating)
  • Dimensions: 1.65 in H x 2.22 in W
  • Packaging: Ships via freight on pallet or available for local pickup (1 pallet is available for residential or commercial delivery)
  • Assembly Time: A single collector can be assembled in 1.5 hours
  • Manufacturer: SunMaxx Solar
  • Warranty: 10 years collector warranty
  • Expected Lifetime: 25-30 years
  • Fitting: 1/2 NPT


  • Complete Flush and Tilt Mounting Frame
  • Manifold (header)
  • 30 Revolutionary SunMaxx Vacuum Tubes
  • 30 Vacuum Direct Flow Heat Pipes
  • Hardware required for collector assembly

ThermoPower™ VDF Series Details:

  • Tube Length (in)/(m): 59/1.5
  • Outer Tube Diameter (in)/(mm): 1.77/45
  • Inner Tube Diameter (in)/(mm): 1.41/36
  • Tube Material: Borosilicate Glass
  • Tube Coating: Al-N/Al.
  • Thermal Expansion (in)/(mm): 3.310-6 / 8410-6
  • Coating Absorbance: > 94%
  • Coat Emissivity: < 7%
  • Vacuum (Pa): < 5×10-3
  • Heat Loss (W/m2.oC): < 0.7
  • Max. Pressure Thrust (MPa): 1.0
  • Flow Rate per Tube (gpm/lpm): 0.02 / 0.08
  • Tilt Angles (degrees): 0-90
  • Orientation: Portrait
  • Max of Tubes in series: 300
  • Operating Pressure (psi)/(bar): 20-70/1.4-4.8
  • Maximum Pressure (psi)/(bar): 87/6.0
  • Stagnation Temperature (F/C): > 457/236
  • Heat Transfer Fluid: Water
  • Heat Transfer Method: Direct Flow Pipe
  • Manifold Socket: Soldered Dry Socket
  • Glass to Metal Seal Type: Hermetic
  • Fittings: 1/2” NPT

Model Details:

  • Dimensions (in)/(m) (WxH): 87.4 x 64.9 /2.22 x 1.65
  • Gross Area (ft2/m2): 35.84/3.33
  • Net Aperture Area (ft2/m2): 28.84/2.68
  • Absorber Area (ft2/m2): 17.12/1.59
  • Weight (lbs/kg): 168/76.0
  • Fluid Capacity (gal/L): 0.7/2.60
  • Rated Flow Rate (gpm/lpm): 0.6/2.27
  • Minimum Flow Rate (gpm/lpm): 0.3/1.14
  • Maximum Flow Rate (gpm/lpm): 3.4/12.9
  • Storage Tank Size (gal/L): 50-60/189.3-227
  • SRCC Clear C Rating (kBTU/panel/day): 47.0


  • Domestic hot water: Normal hot water for a house
  • Radiant floor heating: Systems of any size
  • Pool and spa heating: Large and small pools
  • Residential hot water applications
  • Commercial hot water applications
  • Industrial hot water applications
  • Municipal hot water applications
  • Weight: The weight of the solar hot water collector without crating. It’s important to consider the weight when planning for installation.
  • Dimensions: The height and width of the solar hot water collector in inches. This specification is important for planning the installation location and the space required for installation.
  • Packaging: The way the product will be shipped. It can be shipped on a pallet via freight or can be picked up locally.
  • Assembly Time: The estimated amount of time required to assemble one collector. This specification can be helpful in planning the installation timeline.
  • Manufacturer: The company that produces the product.
  • Warranty: The length of time the manufacturer guarantees the product will function without defects. In this case, the warranty period is 10 years.
  • Expected Lifetime: The estimated lifespan of the solar hot water collector, which is 25-30 years in this case.
  • Fitting: The size and type of fitting used in the collector, in this case, a 1/2 NPT fitting.
  • Complete Flush and Tilt Mounting Frame: This is a part of the product that comes included, which is a mounting frame for the collector.
  • Manifold (header): A component in the collector that directs the flow of heat transfer fluid.
  • Revolutionary SunMaxx Vacuum Tubes: The type of tubes used in the collector to capture and transfer solar energy.
  • Vacuum Direct Flow Heat Pipes: The component that transfers heat from the tubes to the heat transfer fluid.
  • Hardware required for collector assembly: The necessary hardware for assembling the collector.

ThermoPower™ VDF Series Details:

  • Tube Length (in)/(m): The length of the vacuum tubes in inches and meters.
  • Outer Tube Diameter (in)/(mm): The outer diameter of the vacuum tubes in inches and millimeters.
  • Inner Tube Diameter (in)/(mm): The inner diameter of the vacuum tubes in inches and millimeters.
  • Tube Material: The type of material used for the vacuum tubes, which is borosilicate glass in this case.
  • Tube Coating: The coating used on the vacuum tubes, which is Al-N/Al. in this case.
  • Thermal Expansion (in)/(mm): The rate at which the vacuum tubes expand due to temperature changes.
  • Coating Absorbance: The percentage of solar energy absorbed by the coating on the vacuum tubes.
  • Coat Emissivity: The percentage of energy emitted by the coating on the vacuum tubes.
  • Vacuum (Pa): The level of vacuum in the tubes.
  • Heat Loss (W/m2.oC): The amount of heat lost in watts per square meter per degree Celsius.
  • Max. Pressure Thrust (MPa): The maximum pressure the tubes can withstand.
  • Flow Rate per Tube (gpm/lpm): The flow rate of the heat transfer fluid per tube in gallons per minute and liters per minute.
  • Tilt Angles (degrees): The angle at which the collector can be tilted for optimal performance.
  • Orientation: The orientation of the collector, which is portrait in this case.
  • Max of Tubes in series: The maximum number of vacuum tubes that can be connected in series.
  • Operating Pressure (psi)/(bar): The range of pressure at which the collector can operate.
  • Maximum Pressure (psi)/(bar): The maximum pressure the collector can withstand.
  • Stagnation Temperature (F/C): The temperature that the collector can reach when there is no heat transfer fluid flowing through it.
  • Heat Transfer Fluid: The fluid used to transfer heat from the collector to the hot water system, which is water in this case.
  • Heat Transfer Method: The method used to transfer heat from the collector to the heat transfer fluid, which is direct flow pipe in this case.

The ability to convert solar energy into thermal energy is expressed by the optical efficiency of the system (ŋ0). The global solar radiation varies considerably from region to region. On a clear summer day approximately 850 W/m2 (270 Btu/ft2)can be expected, whereas clouds can reduce it to 400 Btu/ft2 (127 Btu/ft2)

Both Flat Plate and Vacuum Heat Pipe collectors are insulated to prevent heat loss, but due to extremely good insulation properties of the SunMaxx Vacuum heat pipe Solar Collectors, the “only” heat loss is via the SunMaxx Manifold with its small surface area and thick layer of high-quality polyurethane foam

SunMaxx Evacuated Heat Pipe Solar Collectors can supply heat at temperatures significantly higher than those achieved by Flat Plate Collectors. This comparison is particularly relevant in cold, windy and cloudy climates. The following explanations are for installations of up to 90 tubes (4 Flat Plates).

How to Size your Solar Hot Water System (DHW):

On average a homeowner uses approximately 20 gallons of hot water per day per person. Using this figure you can calculate which size prepackage system is suitable for your heating requirements.

If you are looking to utilize a solar hot water heating system for space heating needs please contact our solar hot water sales department so we may provide you with an accurate assessment of your heating requirements. Typically we are able to offset between 40-80% of your home heating needs with a payback period of less than 8 years.


Need Assistance?
If you have questions need help or simply feel uncomfortable placing your order online feel free to contact the product representative at 1-800-786-0329.

While both types of collectors capture the suns energy and convert it to hot water each have there own advantages.

Evacuated Tube Collectors are best used in northern climates where freezing can occur and can be utilized in areas where temperatures drop down to -60°F. Evacuated Tubes are are extremely efficient by virtue of the Tubes themselves. Each Evacuated Tube is hermetically sealed meaning it is highly insulated due to the fact that it is a sealed atmosphere nearly impervious to outside temperatures. Evacuated tubes can also be replaced if damaged, simply by plugging it in, no need to replace the whole unit.

SunMaxx Flat Plate collectors use a highly efficient flat absorber material called Tinox which transfer heat to a series of copper tubes which circulate a 50% glycol/water mix. The collectors themselves are in essence a a sealed insulated box which captures the suns energy and transfers it via the Tinox, then through the pipes filled with glycol and into  the storage tanks.

Yes you can. Collectors can be attached to our ballast system, which uses the weight of standard patio blocks to hold the collectors in place. Wind load calculations must be done by an engineer to conform to local building codes. With the proper weight attached, collectors will stay in place without putting any holes in the roof. This has been done with our evacuated tube collectors and our flat plates. Flat plates obviously have a much higher wind resistance, and therefore require greater weight to hold them in place. Our ballast system will work with photovoltaic panels as well.

There are no guarantees with rafters when it comes to distance apart or consistency. The easiest way to deal with this problem is using the ConnectMaxx rail system. Our roof mounts can be secured where the rafters are, and then our rails can be secured to the roof mounts. All of our collectors can then be secured anywhere along the rails using sliding blocks. When using SunMaxx rails, you can worry less about where the rafters are and more about where you want your collectors!

This answer depends on what you are trying to accomplish. For simple Domestic Hot Water systems you should try and position you collectors at the same angle as your latitude. For systems that are tied into the home heating system, as in a combisystem, you should position you collectors 15 degrees higher than your latitude. For summertime use only systems, as in a pool system, you should position your collectors at your latitude minus 15 degrees.

For systems that have a high solar fraction, i.e. 75% or greater, you should increase the angle of incline in order to decrease your summertime production slightly.

Do you want to make this system perform to its highest ability or should it look nice and fit the architecture of the house?

We have all seen those albatrosses on the roof that are cantilevered at a compound angle to get a few extra BTU’s at the cost of aesthetic appeal. Here are some guidelines to consider when deciding what is most important in determining collector orientation and inclination.

For most collectors, tubes or flat plates, the angle of inclination has a 30 degree window of variation and the performance will still be within 95% of the expected maximum. That is, if your collectors should be mounted at 55 deg then you can mount them between 40-70 while losing only a small fraction of energy gain.

As for the collector orientation, that window is 60 degrees for Evacuated tubes and 30 degrees for flat plates. These considerations allow you to fit the collector to most homes’ pitch and orientation without losing too much energy gain.

Obviously you want your client to get the most out of it, but you are more likely to get additional jobs if the collectors are mounted in a way that takes into account the aesthetic appeal. Ask your Sunmaxx Representative for a copy of the Inclination and Orientation performance Chart so you can make informed decisions.

Yes it is. Depending on your type of collector, you can program your controller to manually activate the circulator which will bring heat from your storage vessel and into the collectors, which will radiate that heat back out thus melting the snow. This method only works for FLAT PLATES however and will usually take as much energy as it makes. When the sun is out in full force, the rays passing through thge snow are typically enough to create substantial heat that in turn, melts the snow on flat plates.

For Evacuated tubes however, there is very little you can do to melt the snow. If your collectors are sitting at a tilt off from the roof pitch, you should be okay because the snow will pass between the tubes onto the roof. But for flush mount EVT systems, snow can and will build up. However, in my experience, this will only affect the output for a day or two. Becuase if the sun is out enough to make any amount of BTU”S then there will be enough heat wasted at the roof/collector interface that begins to melt the snow alowing it to slide down from the top of the tubes. With only minimal exposure to the direct sunlight, the small amount of exposed tube will begin to yield significant amount of BTU’s, even though they are mostly covered. So for tubes, dont sweat it, you are not going to lose much unless of course they get covered by a couple feet or so then perhaps you’ll want to sweep them off if you can.

This will be a debate well in to the future. For an more in-depth review please watch this Click here to watch this 1/2 hour webinar. Your decision should be based primarily on the following considerations:

  • Temperature demand– What is you existing application? EVT’s will outperform FP’s at higher temp load.
  • Climate location- In a general sense, flat plates have more value than evacuated tubes in warmer climates and EVT’s will do better in cold, cloudy climates.
  • Aesthetics appeal– This is where there is no “right” answer. Instead, each person has their own personal view. We recommend that you go with it. If they prefer flat plates for that reason then you install flat plates and if they prefer evacuated tubes for their aesthetic appeal, then by all means, you should install Evacuated tubes.

The point is, you really CANT GO WRONG. Each type will yield significant value and in the end, the differences will be negligible.

Fortunately, solar thermal collectors are not nearly as sensitive to light conditions as PV collectors. As for performance, you have roughly a 60 degree window of opportunity to mount the collectors toward south before you begin losing a small bit of total production. In other words, your house can be situated 30 to the east of true south or 30 degrees to the west of true south and your performance will still be at or above 95%.

As far as tilt angle goes, this window opportunity is slightly smaller but still you can have a roof pitched about 20 degrees plus or minus of your particular latitude angle and you will still see results at or above 95% of expected.

Ask a SunMaxx rep to run a Polysun report for your particular conditions to be sure, you will be happy you did and pleasantly surprised.

SunMaxx Solar collectors have the below certifications and standards.

  • SRCC OG-100
  • USEC UL 1703
  • ASHRAE Std 93-1986
  • ASTM E 330 (Wind Load Rating)

SRCC OG-100 Certification

Replacement Evacuated Solar Tubes

We recommend the below accessories.

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Replacement Evacuated Solar Collector Parts

We recommend the below accessories.

Collector Connection Accessories

We recommend the below accessories.

[porto_products use_simple="" ids="21418, 18446, 21419"]

Evacuated Tube Collector Accessories

We recommend the below accessories.

[porto_products use_simple="" ids="18817, 13063, 18815, 18804"]

Evacuated Tube Collector Accessories

[porto_products use_simple="" ids="21622, 21625, 21626, 21634, 21631, 21633, 21635, 21640, 24013"]

Collector Warranty: 10 years

Extended Warranty: Available for purchase with qualified SunMaxx Solar installer.

SunMaxx Solar Collectors Warranty

How to Order:

If you are confident with your solar hot water heating requirements you can place your order online by clicking on the add to cart button which is located above. All orders are reviewed by our solar hot water heating department and the customers are contacted in order to ensure that you have ordered the correct merchandise for your application. In the event you have any questions our sales staff are available from 8:30AM to 5:30PM EST.

Silicon Solar Inc ships products internationally please ask your sales representative for a shipping rate to your destination.

Need Assistance?
If you have questions need help or simply feel uncomfortable placing your order online feel free to contact the product representative at 1-800-786-0329.

Learn more about SunMaxx Direct Flow Solar Hot Water

Direct flow evacuated tube collectors are a type of solar thermal collector, gaining popularity for their high efficiency and versatility in various applications. These collectors harness solar energy by converting it into heat, which can then be used for domestic hot water, space heating, and other purposes. This article provides an in-depth look at the technology behind direct flow evacuated tube collectors, as well as their advantages and disadvantages.

Description of Direct Flow Evacuated Tube Collectors

Direct flow evacuated tube collectors consist of multiple glass tubes, each containing an absorber plate and a heat transfer fluid. These tubes are aligned in parallel to form a collector array, which is mounted on a frame and angled towards the sun to maximize exposure. The absorber plate, typically made of a selective coating material, efficiently absorbs sunlight and converts it into heat. The heat transfer fluid (usually a mixture of water and glycol) flows directly through the tubes, absorbing the heat generated by the absorber plate.

The tubes are vacuum-sealed, creating an insulating barrier that minimizes heat loss due to convection and conduction. This vacuum insulation ensures that the direct flow evacuated tube collector can achieve high efficiencies even under unfavorable weather conditions, such as low temperatures or cloudy skies. The design of these collectors allows for individual tubes to be replaced if damaged or malfunctioning, without affecting the performance of the entire collector array.

Advantages of Direct Flow Evacuated Tube Collectors

  1. High Efficiency: Direct flow evacuated tube collectors have a higher efficiency compared to other solar thermal collector technologies, such as flat plate collectors. The vacuum insulation reduces heat loss and the selective coating materials used for the absorber plate enable effective heat absorption. This allows these collectors to achieve higher temperatures and maintain optimal performance even during cloudy or cold days.
  2. Versatility: These collectors can be used for various applications, including domestic hot water, space heating, solar cooling, and industrial process heat. They can be easily integrated into existing systems or used as a stand-alone solution, making them suitable for both residential and commercial applications.
  3. Easy Installation and Maintenance: The modular design of direct flow evacuated tube collectors allows for straightforward installation and maintenance. Individual tubes can be replaced in case of damage or malfunction, without the need to replace the entire collector array.
  4. Durability: The vacuum-sealed tubes and high-quality materials used in direct flow evacuated tube collectors contribute to their long lifespan and resistance to corrosion, making them a cost-effective choice in the long run.

Disadvantages of Direct Flow Evacuated Tube Collectors

  1. Initial Cost: The high efficiency and advanced technology of direct flow evacuated tube collectors come with a higher initial cost compared to other solar thermal collector technologies. However, the long-term savings due to reduced energy bills and maintenance costs can offset this initial investment.
  2. Aesthetic Concerns: Some homeowners may find the appearance of evacuated tube collectors less visually appealing compared to flat plate collectors, which have a more streamlined design. This is a subjective factor, but it is worth considering when choosing a solar thermal collector.
  3. Size and Weight: Direct flow evacuated tube collectors tend to be larger and heavier than flat plate collectors, which might make installation more challenging in certain situations or locations.

Additional information

Weight68 lbs
Dimensions99 × 7 in