Furnace works SFB3 - connecting correctly and replacing button style high limit and temp limit switches.

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.


New Member
Sep 20, 2023
Hello, glad I found this group. We bought a home last year and we have what appears to be very similar to the Furnace works SFB3 indoor wood boiler. The main difference is the unit is unbranded, almost identical design and size dimensions.

The unit is installed remotely in my garage and tied into my oil burning furnace by copper and 1” pex running about 30’ to the basement, partially buried underground through crawl space. It also is connected to a blower unit mounted in the shop, which has no thermostat or switch.

This unit has two button style controls, one has a temp dial on it, which I believe controls the electric damper on the front, and is tied into what appears to be a high limit switch.
Wiring is fried/ melted and appears to have several shorts the metal electrical boxes welded to top of unit, that hold the small controls.

The aquastat for the circ pump and the other controls are coming from a 24v transformer.

Can anyone advise on a wiring diagram on how to wire up the circ pump and the damper control correctly? I found replacement parts online and will replace, want to make sure the unit is safe and sound before using this winter.