Technical Service Bulletins

This webpage is intended to be viewed by GARN® Wood Heating Systems’ Owners and Operators.  Its purpose is to present technical service bulletins to current customers of GARN® Wood Heating equipment.  Each technical service bulletin addresses a specific topic.  A technical service bulletin may arise out of conversations with customers about specific issues and resolutions and is intended to provide official company correspondence regarding such issues.  Technical service bulletins may also give supplementary or additional information that may not be specifically addressed in the GARN® Owners Manual or other such documentation.

Update 10/17/2019

PVC Plug Issue – DECTRA CORPORATION is issuing this service bulletin related to a potential component quality issue. Since January 1, 2018 about 20 GARN WHS 2000 H and 2000 V models may have had a 1.5” schedule 40 PVC NPT plug accidentally installed in lieu of a steel plug.

Update 11/24/2015

Anode Rod Quality Issue – Part 3 (Solution) – Anode rods are no longer available for purchase nor will they be provided with the purchase of a new GARN unit.  In this document, we discuss the solution to the problem with electric isolation and specific grounding procedures.

Update 11/12/2015

Anode Rod Quality Issue – Part 2 (Background and Research) – Background information, research, and progress updates.  Anode rods will no longer be supplied with new GARN units and will no longer be available for purchase at our online store.

Update 10/23/2015

Anode Rod Quality Issue – Part 1 (Awareness) – If you purchased a new GARN® WHS unit or ordered replacement anode rods from our online store in 2014 or 2015, please read this bulletin.  The bulletin talks about assessing the condition of the anode rods and if they exhibit signs of having a quality issue.


Q: Is there a way to test for undirected current?

Answer: Not Easily

Testing for undirected current is difficult. But, if desired, should be completed by a qualified electrician. A local co-op or utility may be able to provide this service. If testing for undirected current is carried out, the electrician must follow all suggestions and recommendations in the GARN Owner’s Manual, and these technical service bulletins.

Q: Are there customers who have removed their anode rods and isolated their units?

Answer: Yes

There are existing GARN customers who have already removed anodes rods from their tanks and have fully electrically isolated their units at the recommendation of their local co-op/utility.  These customers have operated their systems successfully without any damage caused by electrolysis/un-directed current for several decades.

Q: Is there a way to test if my unit is properly electrically isolated?

Answer: Yes

When full electrical isolation work has been completed, a simple check can be done to see if the unit has been successfully isolated. Only proceed if you are comfortable and competent checking electrical connections with a volt-meter. Otherwise, contact a licensed electrician.

Take a volt meter and touch one lead to a metal part of the GARN tank. Take the other lead and touch it to a ground path (such as the ground socket of the receptacle of the WHS digital controller). If there is a voltage reading, then the unit is isolated. There is no telling what the exact voltage reading might be, but something on the order of 0.1 to 2.0 Volts may be expected.

If there is still a ground path that exists in contact with the GARN unit, then the voltage reading will be a steady 0.0 Volts.

Q: Is there a warranty against corrosion in my GARN unit?

Answer: No

While there is no corrosion warranty, we endeavor to give our customers the best recommendations for protecting their GARN unit. In addition, GARN WHS equipment is designed to be fully cleanable and repairable, so any corrosion problem that may be encountered can be fixed.

Q: Why can't I purchase anode rods?

Answer: Anode rods can no longer be sourced to meet the requirements for use in GARN units.

Please read the above technical service bulletins Part 1 to 3 for further explanation.

Q: Does this apply to all GARN units from 1985 to Present?

Answer: Yes

Electric isolation will be required for all GARN units from 1985 to Present. Please read the Anode Rod Quality Issue – Part 3 for more detail.

Q: Do I have to isolate the electronic combustion air intake damper?

Answer: No

The combustion air intake damper uses a brushless 24VAC motor.  It is also a 2-wire motor with no ground wire.  Because if these two items, the motor and casing is effectively isolated from the controller and GARN unit.