Questions and Answers about Wood Burning or Corn Burning Outdoor Furnace - Also Referred to As an Outdoor Boiler or Hydronic Heater

A: No. When tested by the U.S. Environmental Protection Agency (EPA), Central Boiler’s non-qualified outdoor wood furnace was found to have similar emissions as wood stoves.

After testing a Central Boiler non-qualified outdoor wood burning furnace, EPA reported that these furnaces produce similar PM as wood stoves. EPA said: “Compared to a wide range of residential heating options, these furnaces’ emissions were of the same order as other stick wood burning appliances.” (EPA report: EPA/600/SR-98/017, February 1998)

Furthermore, when comparing data from this report and data from a report on EPA certified phase 2 wood stoves (EPA report: EPA/600/SR-00/100 December 2000), the comparison shows emissions from the Central Boiler wood furnace and EPA certified phase 2 wood stoves both average 10 grams of particulate matter per kilogram (g/kg) of wood consumed. (Emissions Comparison from Two EPA Reports)

To provide even cleaner, more efficient energy, Central Boiler has created the E-Classic 1400, E-Classic 2300, E-Classic 2400, E-Classic 3200 outdoor wood furnace and the Maxim M250 outdoor pellet furnace. Central Boiler makes significant investments in research and development to create and bring to market new and innovative designs that increase efficiency and environmental performance of outdoor furnaces.

The E-Classic and Maxim are next-generation outdoor wood and pellet furnaces that are EPA Phase 2 Program Qualified.

Central Boiler's Phase 2 Qualified White Tag Models

Manufacturer	Model Name & Number	Heat Output Rating ⁽¹⁾	Annual Average Emission Rate	Heat Output Annual Average Emission Level⁽²⁾	Highest Individual Test Run	Fuel Type
Central Boiler	Maxim M250	212,453 BTU/hr	1.6 grams/hr 0.07 grams/hr/ 10,000 BTU heat output	0.06 lbs/million BTU output	4.9 grams/hr	wood pellets; continuous feed
Central Boiler	E-Classic 3200	261,506 BTU/hr	3.3 grams/hr 0.02 grams/hr/ 10,000 BTU heat output	0.08 lbs/million BTU output	7.3 grams/hr	stick wood; batch load
Central Boiler	E-Classic 2400	186,453 BTU/hr	3.3 grams/hr 0.03 grams/hr/ 10,000 BTU heat output	0.12 lbs/million BTU output	5.4 grams/hr	stick wood; batch load
Central Boiler	E-Classic 1400	107,459 BTU/hr	5.5 grams/hr 0.08 grams/hr/ 10,000 BTU heat output	0.27 lbs/million BTU output	8.5 grams/hr	stick wood; batch load
Central Boiler	E-Classic 2300	160,001 BTU/hr	6.4 grams/hr 0.06 grams/hr/ 10,000 BTU heat output	0.31 lbs/million BTU output	17.6 grams/hr	stick wood; batch load

1 - Based on 8-hour test for stick wood models and 4-hour test for continuous feed models.
2 - EPA Phase 2 qualified level is 0.32 pounds of fine particles per million BTU of heat output (weighted average representing the range of burn rates expected in a year) and a maximum individual test run of 18.0 grams per hour. Typically, the maximum individual test run is the maximum heat output burn rate.

Several States including Oregon and Minnesota use EPA’s below graphic labeled “Relative Emissions of Fine Particles” in lbs/MMBtu heat output to illustrate average particulate emissions from some wood heating appliances. The graphic on the right labeled “Average Emissions of EPA Phase 2 Qualified Models” was added to demonstrate the particulate emission averages from two classes of wood heating appliances in the EPA Hydronic Heater Phase 2 Program compared to particulate emissions from other wood heating appliances as depicted in EPA's graph.

According to EPA, “most current EPA-certified woodstoves emit 0.8-1.5 lbs/million Btu heat input.” According to EPA most current EPA-certified woodstoves emit an average of 1.4 lbs/million Btu heat output and most EPA certified pellet stoves emit and average of 0.49 lbs/million Btu heat output.

Comparatively, the average emissions from both “stick wood” and “wood pellet” EPA Phase 2 Qualified Models are less than the averages for other wood heating appliances when compared in lbs/million Btu heat output.

Q: Is the Unites States Environmental Protection Agency (USEPA) planning to include outdoor wood furnaces in the revised New Source Performance Standards (NSPS)?

A: Yes. The USEPA is currently revising the NSPS and will include outdoor wood furnaces and a host of other wood heating appliances including indoor wood furnaces.

Residential Wood Heaters - New Source Performance Standards (NSPS)

Current Draft Revisions

EPA 2010 Phase 2 Voluntary Program Qualifying Level

0.32 lb / mmBTU heat output
23 EPA-qualified models already
Typical State 2010 regulatory level
0.32 lb / mmBTU heat output

Draft NSPS limits for PM

0.32 lb / mmBTU heat output for outdoor HH in 2013 and indoor in 2014

Q: How cost effective are outdoor wood furnaces?

A: Outdoor furnaces are a cost-effective source of heating energy for many owners who cut their own wood, or can obtain free or reasonably priced wood as fuel. Often, owners can entirely eliminate their heating bills. Over a 10-year period, a homeowner or business may save $10,000 to $50,000 or more on heating costs. In addition, some insurance companies prefer outdoor wood burning furnaces over indoor wood stoves because they remove the fire hazard from the home.

Q: What fuel is recommended for Central Boiler outdoor furnaces?

A: Depending on the model, Central Boiler outdoor furnaces burn seasoned wood, wood pellets, corn or other manufacturer's listed fuels like liquefied petroleum, natural gas or heating oil in the case of a dual fuel backup.

Q: Can you burn trash and scrap material in outdoor furnaces?

A: No. Central Boiler outdoor furnaces are designed to burn seasoned wood, wood pellets or corn. There are existing laws in some areas that prohibit the burning of trash that can be enforced against someone who burns trash in any device. Burning materials other than the fuels recommended by the manufacturer is not only bad for the environment, it is harmful to the furnace. Central Boiler forbids this practice and furnaces are posted with clear warnings not to burn trash. In addition, Central Boiler warns against burning materials such as plastics, gasoline, rubber, naphtha, household garbage, material treated with petroleum products (particle board, railroad ties and pressure treated wood), leaves, paper products and cardboard. Central Boiler works to educate distributors and users about Best Burn Practices.

Q: How is Central Boiler’s outdoor furnace more efficient than other outdoor furnaces?

A: Central Boiler outdoor furnaces are equipped with a water baffle that traps heat and gases at the top of the heavy-gauge steel firebox. The Ripple Top® firebox design creates a high-temperature secondary burn area for more complete combustion – the ability to collect more heat. It also allows for optimum heat transfer surfaces in the most intense heat collection area, so more heat can be transferred more efficiently to the water that is pumped to the building being heated. The firebox is enclosed in a water jacket to keep the metal from overheating or warping and it’s surrounded by waterproof, airtight urethane foam insulation.

The Central Boiler E-Classic models are the latest advance in clean wood-burning technology. They feature a three-stage combustion process that drastically reduces particulate emissions because they burn the wood so completely. The E-Classic’s controlled combustion delivers the proper amount of oxygen at optimal intervals, preventing the wood from burning too rapidly or from smoldering by burning too slowly. In addition, the E-Classic’s heat exchanger uses water to transfer heat from the extremely hot gases, producing exceptionally high thermal efficiency with low emissions per Btu of heat output.

Q: Can I use an outdoor wood furnace if I live in town?

A: Many towns allow the use of outdoor wood furnaces. Always check with all applicable laws and ordinances. Review Best Burn Practices and installation instructions for applicable models.

Q: Can outdoor furnaces explode?

A: Central Boiler outdoor wood furnaces are vented, non-pressurized systems, which eliminates this possibility. All Central Boiler outdoor furnaces are safety tested and listed. The listing placard is affixed to the exterior of every Central Boiler furnace.

Q: Are there regulations for outdoor furnaces?

A: EPA announced the EPA Outdoor Wood-fired Hydronic Heater Programs to promote the manufacture and sale of cleaner outdoor wood furnaces. Many of the States below have enacted regulations and laws based upon the particulate emission limits and test methods established in the EPA Outdoor Wood-fired Hydronic Heater Programs.

Central Boiler supports appropriate, effective ordinances that prevent and/or correct outdoor furnace misuse. Many communities throughout the United States have already implemented local regulations and Best Practice Ordinances. Central Boiler worked with EPA on its new testing standards and works with state and local governments on appropriate regulations to encourage cleaner burning wood furnaces and to implement Best Burn Practices.

Here are some States that have regulations on outdoor wood furnaces.

Q: What communities have implemented successful ordinances?

A: Many communities throughout the United States have already implemented local regulations and Best Practice Ordinances.

Q: Who can I contact to establish an outdoor furnace ordinance?

A: Central Boiler supports effective ordinances that promote proper installation and use, and prevent and/or correct outdoor furnace misuse. Information about how to establish smart and successful outdoor furnace regulations are outlined in the Best Practice Ordinances. For additional information, Contact Us at Outdoor Furnace Facts.

Q: Do outdoor furnaces produce four times as much fine particulate matter (PM) pollution as conventional wood stoves?

A: No. The New York AG’s report “Smoke Gets in Your Lungs” misleads the public, local government agencies, the press and other organizations about emissions from “Outdoor Wood Boilers” (OWBs). The information in the report makes improper comparisons using manipulated data.

The authors of the report took information from a United States Environmental Protection Agency report which reported conventional indoor wood stove emissions as 18.5 g/kg (grams per kilogram). However, the authors took the 18.5 g/kg information and incorrectly inserted it into the AG report as 18.5 g/hr (grams per hour). The author’s also manipulated data in their report regarding other wood heating appliances.

This misinformation is used to make the false claim that OWBs emit, “four times as much fine particulate matter pollution as conventional wood stoves.”

See: New York AG Report Fact Check

References to outdoor wood furnaces do not necessarily refer to all furnaces manufactured by any manufacturer; in many cases the available data relates to furnaces manufactured by specific manufacturers, including Central Boiler, Inc. Some of the information presented herein is, in part, based on the conclusions drawn by Central Boiler, Inc. from a variety of data and reports, including reports published by the United States Environmental Protection Agency.

Common Questions & Answers about Outdoor Furnaces