RF destroys Nest Thermostat

Discussion in 'General Technical Questions and Answers' started by W3KDK, Jun 20, 2016.

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  1. W3KDK

    W3KDK Ham Member QRZ Page

  2. W3KDK

    W3KDK Ham Member QRZ Page

    Ugh really? What the heck. Well mine is about 4 years old, and probably way out of warranty. But this is a pretty nasty issue.

    It failed at 100 watts on 40 meters. 40 meters seems to be the magic band that causes issues.
    Last edited: Jun 20, 2016
  3. W3KDK

    W3KDK Ham Member QRZ Page

    After looking around the internet, I can't believe how widespread this issue is. If you own a nest, and transmit on 40 meters, be very careful.
  4. N0IU

    N0IU Ham Member QRZ Page

    With all due respect, it has to be something you are doing. I am still using the first version of the Nest that hit the market several years ago shortly after they came out. I also transmit on all HF bands and I have NEVER had any RF related issues with the Nest. Granted, I only use 100 watts into a vertical for 10-40 meters and a folded terminated dipole for 80-160 but for some strange reason, none of the electronics in our house suffer any ill effects due to my amateur radio activities.
  5. W3KDK

    W3KDK Ham Member QRZ Page

    Here are 3 other accounts of the exact same issue:



    Including the guy on this forum thread who mentioned his friend, that brings the total cases that I have found up to 5.
    Not exactly a huge sample size, but it's pretty odd that at least 5 people have had the issue, all on 40 or 80 meters, all with the same symptom (HVAC running uncontrollably).
    One even mentioned that the problem proceeds even when the nest CPU is disconnected from the wall, which is exactly the symptom I am seeing.
    Seems like a little too high of a coincidence for me.

    You may also have certain variable that protect your system. Control cables running through the duct work? aluminum siding? Shielded control wires?
    Maybe your control wires are not long enough to be resonant at the critical frequencies that kill the nest.

    I tore the nest apart earlier looking for answers. Although the CPU potion is heavily shielded from RFI using metal casing, the outside power/mounting ring is not. The nest CPU itself continued working without any issues, it's actually the outside mounting/wiring bracket that failed.

    I have been transmitting at 10, 15, and 20 without any problems at all. Literally my first transmission at 40 meters killed the nest instantly, and it was for half a second. The evidence speaks for itself.
    Found another
    Last edited: Jun 20, 2016
  6. N0IU

    N0IU Ham Member QRZ Page

    And so does my evidence! I also participate in contests on all modes on all bands (except for the WARC bands of course!), but especially using FSK RTTY on 40 meters. Even though we try to keep contest exchanges as short as possible, an exchange can last for several seconds at full duty cycle at full power and this can go on for an entire weekend. None of this has any effect on my Nest.

    I also see a lot of posts from people who complain about how their amateur radio gear messes up various electronic items in their homes. But who knows how they ground their equipment (if at all!) or how and where they run their cables?

    With all due respect, I see that you got your Technician license on May 18 (just over a month ago) and your General 6 days ago on June 13. This plus the fact that you only have 30 callsign lookups here indicates that you are a brand new ham. Of course I don't know anything about your background in radio electronics, but given the extremely short time you have been licensed, I maintain that the most likely cause of your problem is with the way your station is set up and not a problem with the Nest thermostat. Sorry.
    Last edited: Jun 20, 2016
    KC9UDX likes this.
  7. KC9UDX

    KC9UDX Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    How to avoid $200?

    You can get a really nice 7-day programmable thermostat that doesn't have these issues for less than $100.
    AE7RZ likes this.
  8. KC4YLV

    KC4YLV Ham Member QRZ Page

    Ooh, do me next! I got my ticket in '91.

    The Nest absolutely does have an issue. The issue is exacerbated by HVAC control line routing. Your antenna is probably more orthogonal and farther away from the HVAC lines than the other antennas at stations that have had problems. That doesn't mean that the Nest is blameless or that it's acceptable that a $300 thermostat is killed by quite honestly some of the most common HF RF around. I suspect they under-suppressed the control terminals from an RF standpoint but haven't torn one down to peer further.

    It'd be one thing if the Nest went into an error mode or stopped working _while_ RF was out and about. But permanent kill is unacceptable.
  9. K4SAV

    K4SAV Ham Member QRZ Page

    Reminds me of the time many years ago that I decided to fire up an end fed wire on 160. I blew out the horizontal drivers in a big projection TV. Not a good antenna choice.

    Jerry, K4SAV
    KC9UDX likes this.
  10. AE7RZ

    AE7RZ Ham Member QRZ Page

    Honeywell TH8732WF5018 Lyric WiFi-Enabled Thermostat (Contractor version)
    KC9UDX likes this.

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