The best wood stove copper coil depends on the air-duct opening and the water-loop connections in your system. These five Furnace Supply products are water-to-air hot water coils listed for outdoor wood furnaces, each with 1-inch copper connections. The 12-by-12-inch model is best for a smaller opening; the 22-by-24-inch model is the largest listed option. Check the product’s exact dimensions and system requirements before choosing, because the supplied product details do not state heating capacity, flow rate, or operating limits.
| Product | Listed face dimensions | Best suited to |
|---|---|---|
| 12×12 Water to Air Heat Exchanger | 12 x 12 inches | Smaller duct openings |
| 12×15 Water to Air Heat Exchanger | 12 x 15 inches | A narrow, taller opening |
| 16×20 Water to Air Heat Exchanger | 16 x 20 inches | A medium-size opening |
| 18×18 Water to Air Heat Exchanger | 18 x 18 inches | A square opening |
| 22×24 Water to Air Heat Exchanger | 22 x 24 inches | A larger opening |
Furnace Supply 12×12 Water-to-Air Coil
This Furnace Supply heat exchanger is listed as a 12-by-12-inch water-to-air hot water coil for an outdoor wood furnace. Its stated connection feature is 1-inch copper connections. The compact listed dimensions make it the best fit among these five choices when the available opening is small and close to square.
Best for: Buyers whose measured installation space suits a 12-by-12-inch unit and whose system design calls for 1-inch copper connections. It is selected as the smallest square-format option in this group.
Check before buying: The listing information provided does not specify heating output, water flow requirements, coil depth, or the precise dimensions needed for mounting. Avoid choosing it based on face dimensions alone; verify the full installation measurements and system specifications.
Furnace Supply 12×15 Water-to-Air Coil
The 12-by-15-inch Furnace Supply model is a water-to-air hot water coil listed for an outdoor wood furnace. It has 1-inch copper connections. Compared with the 12-by-12-inch option, its listed face is taller while retaining a 12-inch width, so it may be a better match for an opening with that shape.
Best for: Buyers who need a narrow, taller listed size rather than a square coil. It is selected because it offers a distinct face dimension in the product group while keeping the same stated connection size.
Check before buying: The available details do not include coil depth, airflow requirements, heat output, or water-flow data. Confirm those points with the seller or an HVAC professional, and compare the complete unit dimensions with the duct or plenum opening.
Furnace Supply 16×20 Water-to-Air Coil
This 16-by-20-inch model is a Furnace Supply water-to-air heat exchanger described as a hot water coil for an outdoor wood furnace. The listed connection feature is 1-inch copper connections. Its face dimensions are larger than the 12-by-12 and 12-by-15 options, making it a middle-size choice in this selection.
Best for: Buyers whose measured opening suits a 16-by-20-inch coil and who want a rectangular format. It is selected as a step up in listed face size without moving to the largest option here.
Check before buying: A larger listed face does not, by itself, establish a particular heating capacity or airflow performance. The supplied details do not state those ratings or the full mounting dimensions. Confirm the product’s specifications against the furnace, ductwork, and hydronic system before ordering.
Furnace Supply 18×18 Water-to-Air Coil
The 18-by-18-inch Furnace Supply unit is listed as a water-to-air heat exchanger and hot water coil for an outdoor wood furnace. It has 1-inch copper connections. Its square listed face offers a different size from the compact 12-by-12-inch square model and the rectangular alternatives.
Best for: Buyers with a square installation opening that measures for an 18-by-18-inch unit. It is selected for people who need a larger square format rather than a wider or taller rectangle.
Check before buying: Product details supplied here do not state heating output, depth, water temperature limits, or required flow. Do not assume the square shape alone guarantees a fit. Verify all dimensions, connection placement, and system requirements before purchase.
Furnace Supply 22×24 Water-to-Air Coil
This is the largest listed face size in this selection: 22 by 24 inches. Furnace Supply describes it as a water-to-air hot water coil for an outdoor wood furnace, with 1-inch copper connections. The larger listed format makes it the best candidate here when the installation opening is correspondingly large.
Best for: Buyers who have measured a large opening and need a 22-by-24-inch face size. It is selected because it provides the largest dimensions among the five products compared.
Check before buying: Larger dimensions do not prove that this model is suitable for a particular furnace or deliver a specific amount of heat. No output, airflow, depth, or water-flow specifications were provided. Confirm these details and the available installation clearance before selecting it.
Buying Guide: How to Choose a Wood Stove Copper Coil
What does a water-to-air coil do?
A water-to-air heat exchanger transfers heat from hot water in a hydronic loop to air moved through or across the coil. In an outdoor wood-furnace arrangement, the water loop carries heat from the furnace toward the exchanger, while duct airflow distributes warmed air. These products are listed as water-to-air hot water coils, not as stand-alone wood stoves.
Confirm that this is the type of heat transfer your system needs. A water-to-water exchanger, a stove-mounted coil, and a water-to-air duct coil are not interchangeable simply because each may be described informally as a “copper coil.” Check the product’s intended application and the design of your existing system.
Which coil dimensions should you measure?
Measure the opening where the exchanger will sit, then check the full unit dimensions in the product specifications. The figures in the product names identify the listed face sizes, but the supplied details do not clarify whether those are exact outside dimensions or provide the coil’s depth. Allow for the frame, mounting method, connection location, and any service clearance required by the installation.
- Choose the 12×12 model for a small square opening, if its full dimensions fit.
- Choose the 12×15 model when a 12-inch-wide, taller format matches the space.
- Compare the 16×20 option with openings that suit a medium rectangular face.
- Consider the 18×18 model when the available space calls for a larger square face.
- Consider the 22×24 model only when the installation space can accommodate the largest listed face.
Do 1-inch copper connections match your system?
All five products list 1-inch copper connections. Check the connection size and type required by the piping layout, and confirm how the coil connects to the rest of the water loop. Connection diameter alone does not establish compatibility: the system’s piping, fittings, flow requirements, and installation arrangement also matter.
Do not assume that the word “copper” describes every part of the exchanger. The stated feature is specifically 1-inch copper connections. Review the complete product description or ask the seller about construction details if coil material is important to your decision.
What performance specifications should you confirm?
The product information provided for this comparison does not list heat output, water-flow rate, pressure limits, water temperature range, airflow requirements, or coil depth. Those details are important for determining whether an exchanger can serve a specific heating system. Ask the manufacturer or seller for the specifications and compare them with the requirements of your furnace, pump, ductwork, and heating load.
Do not treat a larger face size as a guaranteed performance upgrade. Dimensions can help establish whether a unit may fit, but they do not provide enough information to determine the heat it will transfer in a particular installation.
How should the coil be installed?
Plan for both the air side and the water side. The exchanger must fit the intended duct or plenum location, and its water connections must work with the hydronic circuit. The installation also needs to follow the product instructions and applicable local requirements. If you are unsure about piping, circulation, electrical controls, or duct modifications, consult a qualified HVAC professional or hydronic-heating installer.
Before ordering, confirm the exact model, all dimensions, connection details, and required operating conditions. The listed product descriptions are brief, so a fit decision should rely on the full specifications rather than the product name alone.
Frequently Asked Questions
Are these coils designed for a wood stove?
The listed products are described as water-to-air hot water coils for outdoor wood furnaces. Confirm the intended installation with the product documentation; the descriptions do not establish that they mount directly inside a conventional indoor wood stove.
Do all five products have the same connection size?
Yes. Each product’s supplied feature list states 1-inch copper connections. Verify the required connection details for your system before purchase.
Which model is the largest?
The 22×24 Furnace Supply model has the largest listed face dimensions in this selection. Its actual fit and performance still depend on the complete product specifications and installation.
Is the 12×12 coil automatically the best choice for a small system?
No. It is the smallest listed square option, but face size alone does not determine heating capacity or system suitability. Confirm the required output, airflow, water flow, and complete dimensions.
Can I choose a coil based only on the opening size?
No. Opening size is one consideration. Also check full unit dimensions, coil depth, connection placement, water-loop requirements, airflow, and the product’s stated operating specifications.