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  1. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    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
    82
    Views
    4,653

    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
    82
    Views
    4,653

    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
    82
    Views
    4,653

    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
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    336

    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
    82
    Views
    4,653

    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
    82
    Views
    4,653

    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
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    366

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

    I'm still more impressed by the EV:
    http://www.plasmaboyracing.com/whitezombie.php
  10. Replies
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    294

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

    If it's old, just replace the whole thing.
  11. Replies
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    554

    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
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    538

    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
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    538

    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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    4,424

    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. Replies
    16
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    1,166

    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. Replies
    16
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    1,166

    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
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    538

    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
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    515

    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
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    589

    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
    538

    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
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    589

    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
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    4,424

    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...
  26. Replies
    18
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    989

    Actually, she didn't teach me that. I don't even...

    Actually, she didn't teach me that. I don't even think she knows that since she always insists on using valve core removers.

    And she says hi back to you.
  27. Replies
    11
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    589

    If you look up a guide on how to convert a window...

    If you look up a guide on how to convert a window unit into a PC chiller, do it in reverse (condenser coil in tank) and you have a water cooled unit. A little 5000BTU/hr unit would be more than...
  28. Replies
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    554

    It will work just fine. What is problematic is if...

    It will work just fine. What is problematic is if it was installed where the supply air hits it, causing short cycling.
  29. Replies
    18
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    989

    On a smaller system, the valve cores won't have...

    On a smaller system, the valve cores won't have much effect unless there's a lot of moisture inside.
  30. Replies
    11
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    589

    She's a good HVAC friend of mine (I have to admit...

    She's a good HVAC friend of mine (I have to admit I had to look that up!) and she taught me a lot about HVAC. However, the idea of water cooled air conditioning is far from new. Water transports heat...
  31. For those who don't know, there is no such thing...

    For those who don't know, there is no such thing as a "drop in" replacement except the refrigerant that was there to begin with. When changing over to any replacement, the system design must be...
  32. Replies
    11
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    589

    If the water is fixed rate, look into a water...

    If the water is fixed rate, look into a water cooled unit. Then you only need a pair of relatively small tubes to the nearest sink.
  33. Replies
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    283

    Lock the disconnects and give the keys to the...

    Lock the disconnects and give the keys to the owner. Far from foolproof but pretty cheap.

    If the thefts seem to happen at night, you could set up some strobes (visible only from roof level) to...
  34. Hydrocarbon refrigerants are commonly used...

    Hydrocarbon refrigerants are commonly used overseas. Somehow, they do just fine without corporate interests from the fluorocarbon industry discrediting it...
  35. Would you prefer I call it a proprietary R22...

    Would you prefer I call it a proprietary R22 replacement? (Not "drop in" because there is no such thing...) Also, there's a big difference between research and production.
  36. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    Researchers rarely start completely from scratch....

    Researchers rarely start completely from scratch. When they agree to use work from others, it often comes under some form of agreement not to disclose (too much of) the details, though it's often OK...
  37. Replies
    7
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    1,038

    Check the subcooling. It will be way low if the...

    Check the subcooling. It will be way low if the unit is low on charge. If the subcooling appears normal but the superheat is higher than expected, look for a restriction or bad/improperly adjusted...
  38. The (new) evaporator is designed with more...

    The (new) evaporator is designed with more surface area per ton so it works more efficiently. I have a R433b (similar pressures to R22) research unit that runs nearly 90PSI suction (though the...
  39. Replies
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    5,452

    Recently, I was working on a server (recovering...

    Recently, I was working on a server (recovering from failed firmware upgrade) and found some paper looking thing with a bit of ribbon cable going to the motherboard. Unwrapped it and it turns out it...
  40. If it's really that old (doubt it, I suspect he...

    If it's really that old (doubt it, I suspect he mistook some other number for a date code), he'll be better off using a few window units.
  41. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    I do benefit from improvements in energy...

    I do benefit from improvements in energy efficiency, but looking broader, everyone benefits. Maybe you just don't care about the environment...

    There is nothing that says that setting it to...
  42. Replies
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    18,608

    He might as well get that EPA certification and...

    He might as well get that EPA certification and actually learn how to do it. Maybe that's what he's doing...
  43. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    Call it marketing if you want, but the intent...

    Call it marketing if you want, but the intent isn't really personal gain. Instead, I'm pushing for advancements in energy efficiency, particularly through technology that isn't used much but is...
  44. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    I do not manufacture products for sale. Research...

    I do not manufacture products for sale. Research is my field.

    Samlex (a big name in inverters for off grid applications) does in fact make inverters that have a very limited built in VFD function....
  45. The ambient temperature was given, at 90F. The...

    The ambient temperature was given, at 90F. The liquid line temperature (not condensing temperature) should be only a few degrees above ambient. So 95-100F liquid line would be reasonable for 90F...
  46. The superheat looks fine. Try cleaning the coils...

    The superheat looks fine. Try cleaning the coils since the liquid line temperature is on the high side.
  47. Replies
    2
    Views
    224

    Leave it downstairs, then just use a fan (in the...

    Leave it downstairs, then just use a fan (in the window) to cool down the bedrooms at night.
  48. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    Maybe nit picking, but an inverter that outputs...

    Maybe nit picking, but an inverter that outputs 100V/50Hz would not fall under UL 458. In reality, the output would vary depending on cooling demand, possibly as low as 60V/30Hz or so under light...
  49. Thread: Enviro-Safe

    by NiHaoMike
    Replies
    82
    Views
    4,653

    What about the specific case of a VFD designed...

    What about the specific case of a VFD designed such that the fridge or whatever just plugs into it with no modification? It won't work as well as one that does require rewiring, but you can buy...
  50. What's your location? Variable speed is great for...

    What's your location? Variable speed is great for better dehumidification, though using a humidity switch to switch between two speeds can work almost as well in practice.
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