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Modifying a Cycleguard (TLDR; you can't)

thayesthayes Member Posts: 2
edited January 2015 in Strictly Steam
Like others I have the annoying Cycleguard LWCO on my boiler and the intermittent level test bothers me. There have been previous threads where people have speculated if it would be possible to modify it in some way to either eliminate this test or at least alter the timing parameters. Somebody even wrote to the company (and never received an answer I believe.)

I opened mine up and poked at the board myself, and unfortunately modifying it is not going to be something anyone without electronics and computer programming skill is going to be able to accomplish. The main control of the device is through a PIC microcontroller (12C508A) which is a one-time-programmable device (meaning you can program it once, but can't ever change that programming later...) Nor is it possible to extract the existing program from the chip. All the timing and state changes are controlled directly from this chip- the rest of the electronics on the board are for conditioning the logic signals into and out of the microcontroller for the sensors and relays.

If someone were skilled enough it would be trivial to develop a new program and replace the microcontroller (possibly even with a different device if desired- Arduino anyone?) The electrical design is pretty simple. The sense lines for the water level probe and "burner activation" input are conditioned into 5v signals and fed to the microcontroller's pins. Two other outputs from the controller run to relays for the burner power and water feeder. So with those 4 GPIO lines directly available it would be simple (for someone who knows microcontrollers) to replace the existing chip with something else.


  • wcs5050wcs5050 Member Posts: 126
    Just replace with Safegard 400/450. Some engineer had the best of intentions, but that Cyclegard is so aggravating. Just when the boiler gets some nice even steam going it shuts down. It would be great if had some interactivity with the pressure/temperature. I'm convinced it does no justice for efficiency either. Recently removed one, and heat performance is much better with the plain old Safegard. Boiler companies believe foaming and slanting water line while steaming put their iron at risk, hence Cyclegard.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 7,824
    It has been designed to protect the manufacturer against bad installations--NBC
  • thayesthayes Member Posts: 2
    I'm not sure I'm going to do anything with mine. My intent was to share the information with some of the others on the forum who I know are experimenting with creating their own controls with PLCs or whatever and so have the expertise necessary to modify the device.
  • jch1jch1 Member Posts: 186
    I wonder if all of the effort necessary to test and experiment with a solution is worth it in the end, when you could just spend a bit of money for the SafGard (which is what I did). Though it would be interesting to see someone else's results.
  • SWEISWEI Member Posts: 7,356
    Modifying devices in the safety string is a really bad idea. Replace it with something approved for the purpose.

    The PLC hackery here is being done to operating controls.
  • Captain WhoCaptain Who Member Posts: 452
    edited January 2015
    @thayes - Yeah I think I was the one doing the speculating most recently anyway. But to set the record straight I posted my discovery that it was a 12C508A microcontroller on Jan 14, so I guess I scooped ya on that :)

    There are still ways to trick the smartcycle by delaying the burner sense signal received by an appropriate amount or by simply sending it a false 24V AC burner on signal at regular timed intervals. Then it would effectively be a SafGard just to soothe any nannies that say you shouldn't hack a safety device.

    EDIT to add: If you look at the datasheet you see that they CAN be one time programmable (OTP) if the customer specially requests that. It doesn't say how to tell from the numbers on the chip if it is or not. So they are not necessarily all OTP.
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