For an outside wood furnace connected to a forced-air system, the products below are water-to-air heat exchangers, also called hot-water coils. The best choice depends on the available duct opening, required heating capacity, and the furnace’s water connections. The 22-by-22-inch AB Store model is listed with the highest stated capacity, while the 10-by-10-inch model suits buyers comparing a smaller coil. Furnace Supply’s listings provide 1-inch copper connections but less performance detail, so confirm sizing before buying.
| Product | Listed size | Useful distinction |
|---|---|---|
| Furnace Supply hot-water coil | 18 x 18 inches | 1-inch copper connections |
| AB Store heat exchanger | 10 x 10 inches | 42,000 BTU capacity stated |
| AB Store HTL15x20 | 15 x 20 inches | 110,000 BTU capacity stated |
| AB Store heat exchanger | 22 x 22 inches | 190,000 BTU capacity stated |
| Furnace Supply hot-water coil | 22 x 24 inches | 1-inch copper connections |
Furnace Supply 18 x 18 Hot-Water Coil
This Furnace Supply coil is an 18-by-18-inch water-to-air heat exchanger for an outdoor wood furnace. Its listed feature is 1-inch copper connections. In a forced-air setup, hot water circulates through the coil while the system’s blower moves air across it to distribute heat through ductwork.
Best for: Buyers whose installation calls for an 18-by-18-inch coil and 1-inch copper connections. It was selected as a middle-size option between the smaller 10-by-10-inch exchanger and the larger listed models.
Limitation: The supplied product information does not state a BTU capacity, number of tube rows, or fin details. Confirm those specifications and the required water flow with the seller or installer before choosing it for a particular heating load.
AB Store 10 x 10 Compact Heat Exchanger
The AB Store 10-by-10-inch model is the smallest listed exchanger in this selection. Its product information states a 42,000 BTU capacity and describes 1-inch copper ports, 12 aluminum fins, and three rows of 3/8-inch seamless copper tubes. The listing also says the fin surfaces are wavy and epoxy-coated, and that the exchanger has a steel shell with brazed edges and contact points.
Best for: Buyers who need a smaller exchanger and whose heating requirements and duct opening suit its stated capacity. Its compact listed dimensions make it a useful option to compare where a larger coil may not fit.
Limitation: Do not assume that the listed 42,000 BTU capacity guarantees a particular output in your system. The listing also mentions output of up to 360,000 BTU per hour depending on application, so confirm how that figure applies to this model and your operating conditions.
AB Store HTL15x20 Heat Exchanger
The AB Store HTL15x20 is a 15-by-20-inch water-to-air coil with 1-inch copper ports. Its listed capacity is 110,000 BTU. Product details describe three rows of 3/8-inch seamless copper tubes, 12 aluminum fins, a steel shell, brazed edges and contact points, and epoxy-coated fins. The manufacturer also describes it as usable with water-based heat sources such as boilers and solar panels.
Best for: Buyers looking for a medium-to-large coil with a stated capacity between the 10-by-10-inch and 22-by-22-inch AB Store options. It offers more listed capacity than the smaller model while occupying a smaller face size than the 22-by-22-inch exchanger.
Limitation: Confirm the actual dimensions, duct fit, water-flow requirements, and heating output for your installation. The listing’s “up to 360kBtu” statement is application-dependent and should not be treated as a guaranteed output for every system.
AB Store 22 x 22 High-Capacity Coil
This 22-by-22-inch AB Store exchanger is listed with a capacity of 190,000 BTU and 1-inch copper ports. Its feature description includes 12 aluminum fins, three rows of 3/8-inch seamless copper tubes, a steel shell, brazed edges and contact points, and epoxy-coated fins. It is the highest-capacity model among the products here with a stated model-specific BTU figure.
Best for: Buyers whose heating-load calculations call for a larger coil and whose plenum or duct opening can accommodate a 22-by-22-inch unit. It is a better capacity comparison than the smaller AB Store models when substantial output is required.
Limitation: A larger exchanger is not automatically the right choice. Verify the available installation space, airflow, water temperature, and circulation capacity; the listing’s stated capacity should be checked against actual system conditions.
Furnace Supply 22 x 24 Hot-Water Coil
This Furnace Supply product is a 22-by-24-inch hot-water coil for an outdoor wood furnace. The supplied feature information specifies 1-inch copper connections. Compared with the 18-by-18-inch Furnace Supply option, its listed face dimensions are larger, which may suit a system designed around a wider coil.
Best for: Buyers who need a 22-by-24-inch coil and 1-inch copper connections. It was selected to provide a larger Furnace Supply size option alongside the AB Store models with published capacity figures.
Limitation: The supplied details do not list a BTU rating, tube layout, fin count, or other performance data. Confirm output and installation requirements before comparing it directly with models that have stated capacities.
Buying Guide: How to Choose an Outdoor Wood Furnace Coil
What is an outside wood furnace forced-air system?
An outdoor wood furnace heats water outside the home and circulates that hot water to a heat exchanger installed in a building’s forced-air duct system. The home’s blower moves air over the coil, transferring heat to the air before it travels through the ducts. The products above are heat exchangers, not complete outdoor furnaces or standalone forced-air furnaces.
Buyers should check that the chosen coil works with their specific hydronic system, ductwork, and blower. A qualified HVAC or hydronic-heating professional can help assess the installation, controls, circulation, and applicable code requirements.
How should I compare coil size and BTU capacity?
Start with the heating load and the physical opening where the coil will go. A larger face size may provide more surface area, but it must fit the plenum and leave the airflow arrangement appropriate for the system. Compare the listed dimensions with the actual coil measurements, rather than relying on a model name alone.
Among the AB Store products in this list, the stated capacities are 42,000 BTU for the 10-by-10-inch model, 110,000 BTU for the 15-by-20-inch model, and 190,000 BTU for the 22-by-22-inch model. The Furnace Supply listings do not provide a capacity in the information supplied. Ask how a manufacturer’s capacity figure was determined and whether it applies at your water temperature and airflow.
Which connections and construction details matter?
Check connection size and orientation against the piping plan before purchase. The listed models specify 1-inch copper connections or ports, but the supplied details do not describe every fitting or installation dimension. Confirm the connection type, placement, pressure requirements, and needed accessories with the seller or installer.
The AB Store descriptions specify copper tubes, aluminum fins, and steel shells, with epoxy-coated fins and brazed contact areas. Furnace Supply’s provided information identifies 1-inch copper connections but does not provide comparable construction details. Treat missing specifications as questions to resolve, not as evidence that a product has or lacks a feature.
Will the coil work with my blower and ductwork?
Coil fit and air delivery are separate checks. The exchanger must fit the duct opening, and the system must move air across it at a suitable rate. Ask an HVAC professional to verify the coil’s external dimensions, available plenum space, airflow direction, and any effect on the existing blower. A coil that fits physically may still need system changes to operate properly.
What does “up to 360,000 BTU per hour” mean?
Some AB Store descriptions state that output may reach up to 360,000 BTU per hour depending on the application, while also listing a separate capacity for the specific model. Because the supplied wording does not explain the conditions behind that higher figure, do not use it as a guaranteed model output. Request the performance data for the exact exchanger and operating conditions being considered.
What should I verify before ordering?
- Confirm the coil’s actual width, height, depth, and connection locations.
- Match the exchanger’s stated capacity to a calculated heating load.
- Check required water flow, water temperature, and system pressure with the installer or manufacturer.
- Verify duct opening dimensions and whether the existing blower can move air across the coil.
- Ask for missing performance details, especially when the listing does not state a BTU capacity.
- Plan installation and controls with an appropriately qualified professional.
Frequently Asked Questions
Are these products complete outdoor wood furnaces?
No. They are water-to-air heat exchangers or hot-water coils intended to transfer heat from circulating water to forced air. The supplied product information does not identify them as complete outdoor furnaces.
Which listed product has the highest stated capacity?
The AB Store 22-by-22-inch heat exchanger has the highest model-specific capacity stated in the supplied information: 190,000 BTU. Actual performance depends on system conditions, so confirm the rating for your application.
Which model is the smallest?
The AB Store 10-by-10-inch exchanger is the smallest listed by face dimensions. It is stated to have a 42,000 BTU capacity, but buyers should confirm fit and output for their system.
Do all five products list a BTU rating?
No. The supplied details give specific capacity figures for the three AB Store models. The Furnace Supply listings specify 1-inch copper connections but do not provide a BTU rating in the information provided.
Can I choose a coil based only on its dimensions?
No. Dimensions help determine whether a coil can fit, but capacity, water flow, water temperature, duct airflow, and connection requirements also matter. Check these details before purchase with the manufacturer or a qualified installer.