Best Popular Wood Fired Hot Tub Coil Heat Exchanger – Model D2
Price range: $8.00 through $358.00 Free shipping
Offer Smartclima`s patented food-grade stainless steel wood fired hot tub coil heat exchanger, our best selling type. Off-grid thermosiphon heating for DIY barrels, stock tanks & small pools. Modular kits with ash collector, wood fire holder and rotatable BBQ grille , saltwater resistant. Free global shipping.
The Smartclima stainless steel coil heat exchanger for wood fired hot tub use is a food-grade, off-grid heating coil that converts any ordinary tub, barrel, stock tank, or Dutch-style tub into a wood-fired hot tub without electricity, gas, or a water pump. Built from a single continuous 25mm stainless steel tube wound into an 8-turn spiral, the Model D2 coil uses natural thermosiphon gravity circulation to heat water passively while you burn wood in the integrated fire holder. It is Smartclima’s best-selling wood fired hot tub coil kit, shipped as a complete modular package with the coil, fire holder, ash collector, rotatable BBQ grill, ground support, and a stainless steel hose fitting kit.
TL;DR: A food-grade stainless steel coil heat exchanger that heats any tub or barrel with wood fire alone, no pump or electricity required. The Model D2 kit includes the 8-turn spiral coil, fire holder, ash collector, BBQ grill, and hose fittings for tub walls 1 to 50mm thick, with custom sizing available for thicker or non-standard tubs.
What the Stainless Steel Coil Heat Exchanger Does
A coil heat exchanger for hot tub use works by transferring heat from a wood fire into the water inside the tub through a closed loop of stainless steel tubing. Cold water from the bottom of the tub enters the coil, travels through the heated spiral where it absorbs heat from the fire, and rises back into the tub as hot water. This continuous thermosiphon cycle is driven entirely by the density difference between hot and cold water, so it needs no pump, no electricity, and no moving parts.
The Model D2 is an external wood-burning coil heat exchanger, meaning the fire burns outside the tub in a dedicated fire holder while the coil sits in the water. This keeps ash and embers out of your bathing water and lets you load wood without reaching into the tub. The same fire that heats your water can also cook on the included rotatable BBQ grill, so a single wood fire heats water and grills food at the same time.
Why Food-Grade Stainless Steel for the Heating Coil
The coil material determines how long the heat exchanger lasts under repeated high-fire use. Smartclima uses food-grade stainless steel rather than copper for three reasons verified in long-term outdoor testing:
- Corrosion resistance: Copper corrodes rapidly under sustained high-fire heat and in saltwater or mineral-heavy water. Food-grade stainless steel resists rust, scaling, and saltwater corrosion for multi-year outdoor service.
- Structural integrity at high temperature: Copper has a lower melting point that risks pipe deformation and warping under continuous fire. Stainless steel holds its spiral shape through repeated heating and cooling cycles.
- Freeze tolerance: A fully drained stainless steel coil survives winter freezing without cracking, where copper tubing can split from ice expansion.
The result is a coil heat exchanger that stays in service for years on rural cabins, camping sites, and off-grid properties without replacement.
Model D2 Coil Heat Exchanger Specifications
| Product | Model D2 Wood Fired Hot Tub Coil Heat Exchanger (previous Model X) |
| Brand | Smartclima |
| SKU | SC18060113 |
| Material | Food-grade stainless steel |
| Coil structure | 8-circle spiral heat exchange design |
| Tubing diameter | 25mm |
| Coil outer diameter | 35cm |
| Coil height | 30cm (±1 to 3cm tolerance) |
| Number of turns | 8 |
| Power source | Wood burning |
| Working principle | Natural thermosiphon gravity water circulation, no pump |
| Type | External heating system for tub, barrel, or container |
| Weight | 9 kg |
| Package dimensions | 53 × 36 × 30 cm |
| Price range | $8.00 to $358.00 USD (kit and accessories) |
| Shipping | Free delivery to US, CA, AU, NZ, UK, Ireland, EU, Japan, and most global regions |
What Is Included in the Model D2 Kit
The kit ships as a complete modular package so you can install it on a tub the same day it arrives:
- 1x stainless steel heater coil (8-turn spiral, 25mm tubing, 35cm outer diameter)
- 1x rotatable BBQ grill
- 1x wood / fire holder
- 1x hot ash collector
- 1x ground supporting system (3 pieces)
- 1x hose kit containing:
- 2x hose, 100cm long each
- 2x stainless steel tub fittings for tub wall thickness 1 to 50mm
- 4x ergonomic stainless steel clamps, tool-free installation
How to Install the Coil Heat Exchanger on a Tub or Dutch Tub
The Model D2 is designed for tool-free installation on most wooden barrels, stock tanks, plastic tubs, and Dutch-style tubs with walls between 1mm and 50mm thick.
- Choose two mounting points on the lower side of the tub wall, spaced to match the two hose fittings. The lower fitting draws cold water from the bottom of the tub, the upper returns heated water.
- Drill or cut two holes matching the fitting diameter at your chosen points.
- Insert the stainless steel tub fittings through the holes from the inside, with the gasket seating against the inner wall. The fittings accommodate wall thickness from 1mm to 50mm.
- Secure the fittings with the included ergonomic clamps on the outside of the tub. No tools are needed for the clamps.
- Connect the coil to the fittings using the two 100cm hoses, clamping each hose connection.
- Position the coil and fire holder on the ground support beside the tub, with the coil sitting in the tub water and the fire holder on the ground.
- Fill the tub above the upper fitting before lighting the fire, so the thermosiphon loop is primed.
- Light the wood fire in the fire holder. Water circulation begins automatically as the coil heats.
For tubs with walls thicker than 50mm, or for non-standard shapes, contact Smartclima for custom fittings machined to your exact wall thickness.
Application Scenarios for the Wood Fired Hot Tub Coil
- Backyard DIY wooden hot tub and cedar barrel bath: Convert a standard empty wooden barrel into a self-heated soaking tub without any electrical hookup.
- Off-grid camping and remote wilderness use: Pair with a portable tub kit for seaside, mountain, and rural campsite hot water soaking where no utility power exists.
- Small commercial spa and tub manufacturer supply: Bulk coil kits for brands building custom wood-fired bath vessels for resort and outdoor hospitality facilities.
- Large stock tanks and small backyard swimming pools: The twin-coil variant heats higher-volume water containers for group soaking.
- Multi-functional outdoor leisure: Simultaneous hot tub heating plus BBQ grilling, stewing, or boiling water using the included rotatable stainless steel cooking grill.
Custom Manufacturing and OEM Coil Heat Exchangers
Smartclima manufactures the Model D2 in its own facility and offers custom coil heat exchangers for buyers who need dimensions, materials, or fittings outside the standard specification. As a China-based manufacturer with over 20 years of export experience (established 2001, Ningbo), Smartclima can produce:
- Custom coil diameters and heights for non-standard tubs and tanks
- Thicker wall fittings beyond the standard 50mm range
- Twin-coil configurations for high-volume containers
- OEM branding and packaging for tub manufacturers and spa brands
- Bulk production runs for commercial and hospitality buyers
For custom orders, send your tub dimensions, wall thickness, required coil size, and target quantity. Smartclima’s engineering team confirms feasibility and returns a quote. Custom fabrication is one of Smartclima’s three core business lines alongside HVAC parts and wood fired hot tub coil kits, so custom coil work is handled in-house rather than outsourced.
About Smartclima
Smartclima Co., Ltd. is a China-based exporter and manufacturer of HVAC, refrigeration, and climate-control parts, founded in 2001 and headquartered in Cixi, Ningbo, Zhejiang. The company ships worldwide, with free flat-rate delivery to the United States, Canada, Australia, New Zealand, the United Kingdom, Ireland, the European Union, and Japan. Smartclima’s wood fired hot tub coil designs are patent-protected, and the company has served over 10,000 customers across its three product lines: HVAC parts and materials, camping and eco products including wood fired hot tub coils, and custom metal, plastic, and rubber fabrication. Every coil heat exchanger is produced in Smartclima’s own facility under quality control before shipment.
Does this wood-fired coil heat exchanger require electricity or water pumps to work?
No pumps, electricity, or gas power are needed. The coil runs fully on natural thermosiphon gravity circulation, relying on the temperature and density difference between hot and cold water to cycle water through the heated coil automatically.
Why stainless steel instead of copper tubing for heating coils?
Copper corrodes rapidly under long-term high-fire heat, has a lower melting point that risks pipe deformation, and costs more. Smartclima’s food-grade stainless steel avoids rust, warping, and ice-burst damage for multi-year outdoor service life, including in saltwater.
Can I install this coil on thick-walled custom wooden tubs?
Standard connectors fit tub walls up to 50mm thick. For thicker wall structures, contact Smartclima’s support team for customized fittings machined to your exact wall thickness.
What maintenance does the stainless steel heating coil require after regular use?
Periodically clear ash from the fire holder, remove scale deposits from the coil pipe surfaces, inspect hose connections for minor leaks, and fully drain all water from the pipe before freezing winter nights to extend service life.
How long does it take to heat a tub with the Model D2 coil?
Heating time depends on tub volume, water starting temperature, and fire intensity. A typical 200 to 400 liter tub reaches soaking temperature in roughly 2 to 4 hours of steady wood fire. Larger stock tanks take longer and may benefit from the twin-coil variant.
Can the same coil be used in saltwater or mineral-heavy water?
Yes. The food-grade stainless steel construction resists saltwater and mineral corrosion, which is why the Model D2 is used in seaside and coastal off-grid setups where copper coils would corrode quickly.
Is the Model D2 coil available for bulk or OEM purchase?
Yes. Smartclima manufactures the coil in-house and supplies bulk orders and OEM configurations to tub manufacturers, spa brands, and hospitality buyers. Contact Smartclima with your specifications and target quantity for a custom quote.
Additional information
| Weight | 9 kg |
|---|---|
| Dimensions | 53 × 36 × 30 cm |
| Purchasing Options | Heater Coil Kit Model D2, Carrying Bag |
Reviews
There are no reviews yet.