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  1. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    80
    Views
    3,095

    No need because I'm not selling it. In fact, the...

    No need because I'm not selling it. In fact, the system was later converted back as part of an A-B-A test procedure (intended to rule out external factors), which turned it back into a normal R22...
  2. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    80
    Views
    3,095

    Big difference between selling a unit containing...

    Big difference between selling a unit containing hydrocarbons (or a building containing such a unit) and merely testing one for research purposes.
  3. Turn down the airflow to enhance dehumidification.

    Turn down the airflow to enhance dehumidification.
  4. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    80
    Views
    3,095

    Some Dell servers have the option to disable PFC...

    Some Dell servers have the option to disable PFC right in the BIOS. Even in a commercial setting, it's sometimes a disadvantage to have PFC when there's a UPS that's acting as the PFC.

    VFDs are...
  5. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    80
    Views
    3,095

    If you understand how active PFC works, the EMI...

    If you understand how active PFC works, the EMI coming off the switching stage at 50-100kHz or so is far more problematic than the low frequency harmonics coming off a rectifier. FCC considers...
  6. Replies
    5
    Views
    286

    On the electrical side, EEVblog is one of the...

    On the electrical side, EEVblog is one of the best resources out there. Aussie50 has more random electrical and mechanical stuff, including a few compressor teardowns.
  7. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    80
    Views
    3,095

    EMI is actually reduced with the active PFC...

    EMI is actually reduced with the active PFC disabled. What was the PFC inductor became an EMI choke. PFC in residential is an unnecessary cost for most applications. The main exception being EV...
  8. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    80
    Views
    3,095

    Do you sell those "power factor correction" boxes...

    Do you sell those "power factor correction" boxes to your residential customers? The reputable techs won't because it doesn't help residential customers. It does in commercial and industrial, but it...
  9. Replies
    8
    Views
    292

    I'm still more impressed by the EV:...

    I'm still more impressed by the EV:
    http://www.plasmaboyracing.com/whitezombie.php
  10. Replies
    2
    Views
    257

    If it's old, just replace the whole thing.

    If it's old, just replace the whole thing.
  11. Replies
    7
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    449

    Actually had that problem at a company I used to...

    Actually had that problem at a company I used to work at. They were expanding the lab and added a few rows of test racks, right against the wall where one of the temperature sensors was! It was bad...
  12. Replies
    12
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    412

    I heard that as well, but the gasoline engine...

    I heard that as well, but the gasoline engine predates the CRT.
  13. It is working properly.

    It is working properly.
  14. Replies
    12
    Views
    412

    An inductor resists change in current. If you...

    An inductor resists change in current. If you abruptly break the circuit, it will try to output as much voltage as needed to keep the current going. It then approximates a current source.
  15. Replies
    74
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    3,518

    The high pitched whining is the inverter PWM...

    The high pitched whining is the inverter PWM (carrier) frequency. Rule of thumb says that 4-5kHz gives the best efficiency on most VFDs if noise is not an issue, which is often the case for the...
  16. The relay coil is such high impedance that it has...

    The relay coil is such high impedance that it has basically no effect on efficiency.
  17. Try connecting your meter across a fan motor cap...

    Try connecting your meter across a fan motor cap (a compressor would start too quickly), preset it to the 400V (or nearest higher) AC range (autorange will miss the first split second), and turn the...
  18. Replies
    12
    Views
    412

    Fun fact: the flyback converter was the first...

    Fun fact: the flyback converter was the first switching power converter used in a consumer product - the automobile. The name apparently originated when a mechanic got zapped and promptly jumped...
  19. Replies
    8
    Views
    394

    And make sure the fan is going in the right...

    And make sure the fan is going in the right direction before you call it done!
  20. That's a sign the installer was too cheap to...

    That's a sign the installer was too cheap to oversize the supply ducts.
  21. Replies
    11
    Views
    467

    Not the same, just close friends. HVAC and power...

    Not the same, just close friends. HVAC and power electronics just happen to be topics that she and I share interest in. HVAC is the #2 fastest growing application for power electronics (automotive is...
  22. Replies
    12
    Views
    412

    In a flyback converter (which most ignition...

    In a flyback converter (which most ignition circuits are based off of), when the switch (usually a MOSFET or IGBT) turns off, the magnetic field in the transformer (really a coupled inductor)...
  23. Put the unit on a VFD. It won't eliminate the...

    Put the unit on a VFD. It won't eliminate the noise but it will reduce it. It would also mostly throttle down instead of cycling on and off, making the noise less apparent. When the load is small...
  24. Replies
    11
    Views
    467

    That's just an inside joke relating to power...

    That's just an inside joke relating to power electronics. It basically states that UVLO (undervoltage lockout) is a very good idea in gate drivers and to use gate drivers with plenty of current...
  25. Replies
    74
    Views
    3,518

    I once worked in a (semiconductor testing) lab...

    I once worked in a (semiconductor testing) lab that had dozens of chip cooler machines, each one with a built in VFD driving a reciprocating compressor. The VFD is actually one of the most reliable...
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