Garn Controller on WHS3200

jebatty Posted By jebatty, Jan 13, 2013 at 7:31 AM

  1. jebatty

    Minister of Fire 2.

    Jan 1, 2008
    Northern MN
    The new controller arrived and was installed yesterday. Installation is easy and straight-forward for anyone who has some basic low voltage wiring experience, such as with electronic thermostats or similar controls (Ranco, Johnson, etc.).

    Installation of only two probes is essential for the controller to work: the combined low water cutoff and tank temperature probe and the flue gas temperature probe. The flue gas probe sensor is a K-type. Also provided are sensors (appear to be Dallas DS18B20) for supply and return water and a sensor for outdoor temperature. These serve a reporting and not a control function.

    Initial operation was flawless. Quality by way of appearance and physical package is good. The controller box is the same size as the previous mechanical timer controller box, with the AC supply in the same location, which made it very easy to install the controller.

    This controller has a digital LCD screen with backlight, a push button to cycle through the readings of the probes/sensors, with a red LED low water signal light, and a green LED operating signal light. Also an on-off toggle switch and an electric/wood toggle switch (for Garn's with the electric option).

    As previously reported, the controller operates as an electronic differential controller with manual reset. After a fixed time of operation when flue gas is 5F or less than tank temperature, the draft fan is shut down, as this likely indicates a fire out situation -- a sensible setting.

    Would have wanted: longer leads for all the sensors. I had to splice in additional lead wire lengths for the combined low water/tank temperature probe and one of the supply/return sensors in order to reach the controller. Another 5 feet of lead length would have solved this. Perhaps the lengths of the lead wires is OK for the smaller Garns.

    Would have been really cool: 1) the ability to data log all temperature data rather than just display it. A card slot to record data on an SD card would have made this new controller a really useful device to allow users both to better understand how their Garns operate and to fine tune their Garn experience. 2) LED digital display, even multiple LED digital panel meters to display all sensor data.

    Useful information: 1) the tank temperature sensor measures water temperature at the top of the tank, which may be higher than water temp lower in the Garn due to stratification. But as has been reported elsewhere, when the Garn circulator is operating the Garn may may mix tank water fairly evenly (it does on the WHS3200 at 60+ gpm circulator flow). 2) the hot water supply and system return sensors will report actual temps of supply (top of tank) and return water (injection into bottom of tank). 3) the flue gas sensor does not report final exhaust flue gas temperature due to its point of measurement, and temperature at the measuring point probably is higher than final exhaust temperature.

    What else will the controller do? although pricey IMO, this controller could be used as an addition or replacement for other boilers to provide the same functions where the boilers do not have auto-shutdown and other temperature measuring features. The cost may be off-set by the design, ease of installation, and functions for those who have little experience putting together their own control and display systems. I don't see anything that uniquely ties this controller only to a Garn.

    More what else: the controller is a fine addition to update the Garn to the type of controls found on many other gasification boilers. The auto-shutdown will increase the efficiency of the Garn by not cooling down the stored hot water when the draft fan continues to operate when there is no fire.

    And finally: operational problems experienced in the future, if any, will be reported.
  2. bioman

    Feeling the Heat 2.

    Dec 25, 2010
    Central Missouri
    Just wondering where the flue gas measurement is located for this controller ? I can see a big improvement over burning different types of wood with a straight timer setup. sounds like a very good setup !
  3. heaterman

    Minister of Fire 2.

    Oct 16, 2007
    Falmouth, Michigan
    The flue gas sensor is threaded into the cleanout plate at the beginning of the last heat exchanger pass. If you look at a picture of a Garn it would be immediatly to the lower right of the draft motor. Actual exit temp of the flue gas will be 50-75* or so less than indicated on the read out.

    This is on the 1500/2000. Not sure where they are putting them on current production 3200's.
  4. Deere3720

    Member 2.

    Jan 18, 2012
    Southeastern MA
    Jim I just got my Garn in Nov. and I have the new controller. And I have been saying the same thing. I would love to know what the Max Flue temp was. I would love to know what the max water temp got to. To take all the information in put it into a spread sheet and plot the graph of all the temps would be very useful. Do you know if there is any talk of them doing this?
  5. Sawyer

    Minister of Fire 2.

    May 17, 2008
    Northern WI
    Thanks for the report Jim. I will look forwar to future reports. I have resisted updating to the new controller due to the cost.

Share This Page