Forced Air Waterless Furnace

A Forced-air furnace is often considered a water-less furnace because there is no water…duh…

It is a good choice if you are looking for a maintenance-free furnace!

NO WATER, so NO RUST and no anti-rust chemicals are needed nor are annual water tests!

ThermoWind (water-less) models will only heat one building and will not heat your domestic hot water like a boiler can.

It is a very simple furnace with off-the-shelf parts available anywhere; nothing proprietary that you have to get from us.

This is a very simple furnace to install; requiring only a power wire, a thermostat wire and ductwork to connect to your existing ductwork under your home. Nothing could be easier. In fact, 95% of our customers install these themselves.

We recommend a pad that is 50 inches wide and at least 9 1/2 feet long; giving you about 3 feet to stand at the furnace and load it on solid ground. If you want to add concrete to the rear, where the dog house is with the two fans, you can certainly do so. About 2 feet extra would be ample.

Cast-iron grates (versus standard steel grates) are available at a nominal cost, starting at $65 for the ThermoWind 1000 and they will last you a virtual lifetime!

Like the boiler, this firebox is formed using one piece of metal and is shaped with a 340 ton brake press which gives you similar qualities to the previous round firebox; less welds and more strength.

The main difference between this furnace and a water furnace, is that air circulates around the firebox, instead of water, so no pump is needed. However a fan is used to circulate the air (which is included, just like a pump is included on our boilers).

The forced-air furnace can only heat one building because there is only one thermostat hookup and cannot heat your domestic hot water like the boiler can. Any other building cannot be thermostatically controlled (only with a damper). A water furnace can heat virtually unlimited buildings and more than one hot water heater. A forced-air furnace has to be relatively close your home because of the expense of the pipe and the air flow losses, if it’s too far away.

One of the biggest differences is in the operation. A water furnace will only come on to heat up the water and it only does that every few hours and then will shut off when the water reaches temperature. The fire would not ignite again until the water temperature drops sufficiently to require it to be reheated.

By contrast, the forced air furnace operates just like an indoor furnace; it will likely come on for 20 +/- min. and then shut off for 20 min. and then come back on for 20 min. and repeat. This causes somewhat more smoke than a water furnace because that is the only time you have smoke; when it is building a fire.

Most people don’t care because you have your doors and windows closed in the winter and are rarely outside but I wanted to point that out, in case you have kids playing outside in the winter time frequently.

You can use less expensive pipe but then it may not look as good aesthetically (not hidden underground).

A forced-air furnace requires 2 ducts – supply and return; either standard inexpensive duct, or two buried insulated 12″ ducts. With the standard inexpensive duct, it normally runs through a wall or window and is visible, unless a chase is built to house the ductwork.

The underground duct is $20 a foot and you need two ducts plus you will usually need four elbows, which are $125 each. Clamps can be several hundred dollars ($50 each), depending on how many you need. Min of 10 per pack.

The only other items needed are 110V wire and a thermostat wire.

The furnace needs to be a min. of 5 feet from your home but no more than 40 feet from your existing ductwork.

Blue Duct should be buried below the frost line because it is always 50-55 F, no matter where you live, so that is like having the duct outside on a spring day instead of in frigid winter temperatures; saving you a lot of energy and wood.

In case you haven’t noticed, everyone says they are the best, so you have to look at the facts and decide for yourself.

Wadena / Hopsco Forced Air Furnace vs
Hyprotherm Forced Air Furnace

Hopsco who purchased Wadena Hyprotherm Manufacturing LLC
Firebox Thickness: only 3/16″
24/28″ deep
Firebox Thickness:
33.3% thicker at 1/4″
28-68″ deep!
ODF1500: 780 lb ODF2000: 950 lb TW1000: 1669 lb
TW2000: 2020 lb
TW3000: 2340 lb
TW4000: 3200 lb
Just 1500 CFM
34% bigger blower: 2010 CFM 
Heating area

ODF1500: 2,800 sq. ft.
ODF2000: 4,000 sq. ft.

TW1000: 4,375 sq. ft.
TW2000: 6,562 sq. ft.
TW3000: 8,600 sq. ft.
TW4000: 10,900 sq. ft.
This is loading it twice a day OR ONCE A DAY heating half of that square footage.

Note: There is no such thing as a furnace that is too big
because it is not like an air conditioner, where if you get one too big, it becomes inefficient.
This is like getting a bigger propane or oil tank!  You can load it with more wood (full rounds – no splitting!) and it will burn longer and therefore you will load it less often. No one has ever complained and said that I sold them one too big. In contrast, many people have said, “I wished that I listened to you!”
Duct Size 10″
20% bigger Duct Size; 12″
Flue must be purchased separately 87.5″ Flue included WITH a chimney cap²
Firebrick must be purchased! No Firebrick needed due to thicker firebox!
 I have never heard of this furnace until I saw this post so I checked out the website. The first thing I noticed was the tiny air ducts, then I saw only 500 cfm fan?! Those two items would make me walk away and not look back.
See review
COMPARE to our 20% bigger ducts AND our 34% bigger fan!

² OUR Flue drops down into the firebox 14 inches, trapping in the heat and the smoke but more importantly, the gases, due to this huge secondary burn chamber, which will be burnt off; valuable heat energy that would have been otherwise lost, up the flue. 

Note that many furnaces don’t have an ash pan, forcing you to clean the ashes out of the firebox – while the fire is burning (or you have to let it cool down).

There are no fancy (expensive) electronics or circuit boards to burn out at the first power surge or electrical storm.

Our fan (that feeds oxygen to the fire) is in the back and blows air up through the grate, feeding oxygen into the fire from the bottom, just like a blacksmith’s forge – the best way!  Many furnaces don’t have a fan at all and others have a fan on the front door, blowing air into the side of the fire, not in from the bottom where it’s needed.

Our chimney drops down in the firebox, trapping in the heat and gases, to maximize heat transfer and ensuring you’re not heating the outside air! This huge secondary burn chamber that is created, allows you to burn off all the gases that first ignite, when you throw in a new piece of wood. This is valuable heat, normally lost.

This design is one of the reasons that we achieved the high efficiency rating!

Most other manufacturers have their chimney right at the top of the firebox, allowing so much precious heat to escape!

Best regards,
WNC Stoves

828-683-0025 9 AM – 9 PM ET, 6 days a week

Remember, the 20 year parts AND labor ON-SITE warranty is probably the best feature because at least 80% of the manufacturers out there require that you ship the furnace back to the factory to get it repaired. Then they have to ship it back and while the repair may be free, they charge you for the shipping both ways AND you have to disconnect the furnace, and then reinstall it and be without it for 2-4 weeks