Existuje no universal rule that a 100L solar tank needs 10 heat-pipe tubes, a 300L tank needs 30, or a 500L tank needs 50. Those are real configurations published by one manufacturer, but other manufacturers publish 36 tubes for 300L and 60 tubes for 500L.
The correct sequence is to calculate the hot-water energy load, choose a target solar fraction for the project location, select a collector from tested area and thermal-performance data, and only then confirm how many tubes that collector contains.
This distinction matters in procurement. A tube is not a standardized unit of useful heat. Tube diameter, length, absorber construction, aperture area, efficiency curve, manifold loss, operating temperature and complete-system design can all differ. Comparing quotations only by tube count can reward the wrong system.
Direct Answer: What Three Manufacturers Actually Publish
The table below compares complete, forced-circulation heat-pipe system configurations published by SolarMaster, JinYi and Zantia. It is evidence of market variation, not a recommendation to copy any one row.
| Nominal tank capacity | SolarMaster | JinYi | Zantia |
|---|---|---|---|
| 100L | 10 tubes × 1 collector | Not listed | Not listed |
| 150L | 15 tubes × 1 | 18 tubes × 1 | Not listed |
| 200L | 20 tubes × 1 | 24 tubes × 1 | 20 tubes × 1 |
| 300L | 30 tubes × 1 | 36 tubes / 2 collectors | 30 tubes × 1 |
| 500 l | 25 tubes × 2 = 50 | 60 tubes / 2 collectors | 30 tubes × 2 = 60 |
At 300L, the published range is 30–36 tubes, a 20% difference relative to 30. At 500L, it is 50–60 tubes, also a 20% difference relative to 50. If litres alone determined the answer, those differences should not exist.
Důležité: each row belongs to that manufacturer’s own collector, tank, heat exchanger, pump station and design assumptions. Do not combine one company’s tank with another company’s tube-count table without recalculating the system.
Why Tank Capacity Cannot Determine Tube Count by Itself
1. Tube dimensions are not always the same
Twenty tubes of one diameter and length do not necessarily have the same absorber or aperture area as twenty tubes from another series. Even when the external dimensions look similar, the absorber coating, vacuum quality, heat-pipe condenser and manifold interface can change performance.
Start by comparing: tube outside diameter and length, number of tubes, collector gross area, aperture or lighting area, certified efficiency parameters, heat-loss coefficient, and specified output at stated test conditions. If a quotation lists only “30 tubes” and no area or tested performance, it is incomplete.
2. The same tank can serve a different heat load
A 300L tank in a warm climate with 25°C mains water requires less energy to reach 55°C than the same tank with 5°C incoming water. A hotel preheating tank, a villa cylinder and a process-water buffer may also have completely different draw schedules.
| Tank volume | Assumed temperature rise | Ideal heat added |
|---|---|---|
| 100L | 40°C | 4.65 kWh |
| 300L | 40°C | 13.95 kWh |
| 500 l | 40°C | 23.26 kWh |
These figures exclude tank loss, piping loss, heat-exchanger approach, draw profile and control losses. Their purpose is to show why an energy calculation is required before a tube count.
3. Buyers choose different solar fractions
One project may ask solar thermal to cover 30% of the annual hot-water load; another may target 60% or more. The U.S. Department of Energy’s Federal Energy Management Program calculator explicitly sizes solar hot-water systems from solar resource and the percentage of load to be met.
A larger solar fraction normally requires more collector capacity, but oversizing for the best month can create summer stagnation and poor economics. The design must examine monthly demand and solar availability, not only an annual average.
4. Collector output changes with operating conditions
Published peak or specified power is tied to test conditions. Actual useful output changes with: solar irradiance, ambient temperature, collector inlet temperature, flow rate, tilt and orientation, shading and soiling, wind, pipe and manifold loss, heat-exchanger performance, and storage temperature and stratification.
A 30-tube collector operating with cold return fluid on a clear day is not equivalent to the same collector trying to maintain a high storage temperature in cold wind.
5. Complete-system architecture changes the pairing
The number of tanks, number of coils, collector banks, hydraulic layout, expansion vessel, controller and backup source all influence the final system. JinYi’s published 300L configuration uses two collectors and 36 tubes; SolarMaster and Zantia publish a single 30-tube collector for 300L. At 500L, all three use multiple collector modules, but the total count still varies.
This is why a capacity-to-tube table is useful for market comparison but unsafe as a universal design chart.
What SOLETKS Currently Publishes for Its HPC Collectors
SOLETKS’ HPC technical guide publishes five heat-pipe collector models. The verified table below compares each collector as a component; it does not assign a tank capacity to any model.
| SOLETKS HPC model | Vakuové trubice | Lighting area | Specified power |
|---|---|---|---|
| HPC182 | 12 | 1.20m² | 0.72kW |
| HPC240 | 16 | 1.60m² | 0.96kW |
| HPC298 | 20 | 2.00m² | 1.20kW |
| HPC370 | 25 | 2.50m² | 1.50kW |
| HPC442 | 30 | 3.00m² | 1.80kW |
The published range uses Φ58 × 1,800mm evacuated tubes, has a 0.6MPa working pressure and a 120°C maximum operating temperature. The guide also lists a peak efficiency of 0.724 and a total heat-loss coefficient of 2.453W/(m²·K).
Those values allow a qualified designer to compare models and build a collector field. The 1,000W/m² power row is an instantaneous test-condition reference, not a daily-energy promise. Daily and annual yield still require local irradiation, temperature and loss inputs.
Most importantly: SOLETKS does not currently publish a verified table saying 100L = a specific HPC model or quantity, 300L = a specific HPC model or quantity, or 500L = a specific HPC model or quantity. Until such a table is issued and technically approved, buyers should request a project calculation rather than treat a competitor’s 10/30/50 pattern as a SOLETKS recommendation.
A Two-Stage Method for Choosing the Collector
Define the Thermal Requirement
- Project location and monthly solar resource
- Daily hot-water volume and busiest-hour draw
- Cold-water temperature by season
- Required storage and delivery temperatures
- Target monthly or annual solar fraction
- Tank, pipe, recirculation and heat-exchanger losses
- Backup-heater type, capacity and operating window
Select Tested Collector Area & Quantity
- Use aperture or lighting area consistently
- Use the certified efficiency curve at expected conditions
- Estimate useful monthly energy, including losses
- Check roof area, structural load, wind, snow, spacing
- Check pressure drop, branch balance, pump/exchanger duty
- Confirm stagnation, freeze protection, expansion volume
- Convert the selected model and quantity into a tube count
Calculate the hot-water energy load and the portion intended to come from solar. For commercial work, use a time series or recognized simulation method rather than one daily average.
Worked example — SOLETKS HPC442 concept estimate
Daily hot water: 5,000L · Cold inlet: 15°C · Target preheat: 50°C · Temperature rise: 35°C
This is only an early concept estimate. Final sizing must consider local irradiation, seasonality, tilt, pipe loss, tank size, backup heating, operating temperature, pump strategy and solar-fraction target.
This method may produce 30, 36, 50 or 60 tubes for a system in the capacities discussed here. The defensible answer is the one tied to stated inputs and tested performance.
What Certifications Can and Cannot Tell You
Solar Keymark distinguishes certified solar collectors, factory-made systems and custom-built systems. That distinction matters because a certified collector result does not automatically certify every tank-and-collector combination assembled around it.
Ask the supplier to identify:
- the exact certified product or family
- whether the certificate applies to the collector, the factory-made system or both
- the tested aperture area and performance parameters
- whether the quoted tank/collector combination is included
- the current certificate and test-report revision
Certification supports comparable performance evidence. It does not eliminate the need for site sizing, hydraulic design or local code review.
A Procurement Comparison That Is Better Than “Price per Tube”
Use a normalized quotation table:
| Procurement field | Why it is required |
|---|---|
| Tank model & actual usable volume | Nominal litres may not equal drawdown volume |
| Collector model & quantity | Links the quote to a verified product |
| Tube diameter, length & count | Confirms the physical configuration |
| Gross & aperture/lighting area | Enables like-for-like area comparison |
| Efficiency curve & heat-loss coefficient | Supports output calculations beyond peak efficiency |
| Specified output with test conditions | Prevents an unqualified power claim |
| System or collector certificate | Shows what was independently evaluated |
| Heat-exchanger type & area | Confirms that collector heat can enter the tank |
| Pump, design flow & pressure drop | Supports hydraulic performance |
| Expansion vessel & safety valves | Supports closed-loop safety |
| Backup heater & recovery time | Shows how demand is met when solar is insufficient |
| Freeze & stagnation strategy | Protects the system at both temperature extremes |
| Monthly energy estimate & assumptions | Makes solar-fraction claims auditable |
Price should be compared only after these fields are aligned. A system with fewer tubes may have a larger effective area or stronger tested output; a system with more tubes may be compensating for a smaller collector module or a more demanding design target.
Common Mistakes When Interpreting Tube-Count Tables
Treating litres per tube as a physical constant
“Ten litres per tube” is a product-family pattern, not a law of solar thermal design. It does not replace an energy balance.
Comparing heat-pipe and direct-flow systems by count
Collector construction and fluid path differ. Keep the comparison within the same technology class and use tested area and output.
Ignoring the number of collector modules
A 500L row may say “50 tubes,” but the physical system can be two 25-tube collectors, affecting piping and layout.
Using peak power as daily energy
Kilowatts describe power at a moment. Kilowatt-hours describe energy over time. Daily yield requires irradiance and condition data.
Assuming a competitor configuration is a SOLETKS configuration
The comparison table documents how other manufacturers package systems — it does not fill the missing SOLETKS capacity-to-HPC mapping.
Frequently Asked Questions
How many heat-pipe tubes are needed for a 100L solar water heater?
How many tubes are needed for a 300L tank?
How many tubes are needed for a 500L tank?
Does SOLETKS recommend 10, 30 and 50 tubes for 100L, 300L and 500L?
Is a higher tube count always better?
Request a Load-Based Heat-Pipe System Proposal
Send the project location, daily hot-water demand, inlet and target temperatures, load schedule, target solar fraction, roof information and backup source. SOLETKS can then propose the HPC model quantity, storage, heat exchanger, hydraulic components and controls as one engineered system.
Kontakt SOLETKS EngineeringContinue the Heat-Pipe Selection Topic Cluster
HPC Heat Pipe Solar Collector — Full Verified Specifications
SOLETKS Heat Pipe Solar Water Heater — Integrated Product Line
Compact Heat Pipe Solar Water Heater: Cold-Climate Selection
For verified component data, see the SOLETKS HPC Heat Pipe Solar Collector Guide. For the current integrated-product range, see the SOLETKS Heat Pipe Solar Water Heater. The existing Compact Heat Pipe Solar Water Heater guide covers cold-climate selection and remains the destination for that broader intent.
Zdroje
- SolarMaster — Split Pressurized Solar Water Heater product range
- JinYi — Heat Pipe Solar Water Heating System
- Zantia — Heat Pipe Forced-Circulation Kits
- U.S. Department of Energy FEMP — Solar Hot Water System Calculator
- Solar Keymark — Information for Manufacturers
- SOLETKS — HPC Heat Pipe Solar Collector Guide
- SOLETKS — Průvodce návrhem solárních systémů pro ohřev vody