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  • Users: peebee
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  1. peebee

    PV Mounting Systems

    I understand that the optimal angle for PV system mounting is roughly equal to angle of latitude. For the northern US, that angle is about 40 degrees, implying a fixed PV panel mounting system of 40 degrees. Moreover, for max output on a fixed mount, you'd manually adjust that by +/- 15...
  2. peebee

    IEC - Central DC Battery Systems for Emergency Lighting?

    I've been directed to investigate the use of 220VDC (yes, DC) distribution for emergency lighting. It is unclear to me if such a beast exists. I have been unable to locate any ballast manufacturer offering an ac/dc ballast with a 220-240VDC input. Have I been sent on a wild goose chase?
  3. peebee

    IEC Equivalent to NEC 700-702 & 695?

    I'm trying to figure out if there's any IEC equivalent to the requirments of NEC 700-702 & 517, as well as related requirements in NFPA 20 & 110, for separate transfer switches to serve emergency, legally required, optional standby, and fire pump loads. So far, I haven't been able to find much...
  4. peebee

    UPS Input Power Factor

    Until recently, I suffered under the illusion that input power factor for a double-conversion UPS system would be near unity -- based on all power flowing through a DC bus, where power factor has no meaning. However, it has recently come to my attention that UPS power factor is actually much...
  5. peebee

    THHN vs RHW

    I have a project where THHN/THWN was specified for standard AC building wire, but RHW EPR was specified for a 125VDC system. Any guesses why? I'm not familiar with RHW EPR. Any particular advantages to this over THHN/THWN?
  6. peebee

    System Integrators for Web-Based Power Meters?

    I have a site where there are various existing power monitors connected to the Ethernet network. I need a vendor to pull that data off the LAN, perhaps do some simple number crunching (nothing more complex than add the kW's from a couple meters together), and display it (perhaps on an LCD...
  7. peebee

    Issues with adding high-resistance system ground

    We have been asked to review the possibility of adding high-resistance grounding to several 480-volt systems which were purchased, but not yet installed. Several potential issues come to mind, including: - breaker ratings - breaker ground current sensing - TVSS ratings - UPS ratings - method of...
  8. peebee

    Refrigerent-Cooled VFD's

    I'm hearing from one of the major chiller vendors that the only VFD's they offer are refrigerent cooled. I've never heard of this before, but he's saying they've been standard for this vendor since '98 or '99. (as an aside -- he did also state that all his competitors offer only water cooled...
  9. peebee

    #10 - #12 AWG Stranded Wire?

    NEC requires most conductors #8 AWG & larger to be stranded. For #10 & #12, stranded or solid can be used. However, I've never seen stranded used for #10 & #12 (only one exception ever to this). #10 & #12 are almost ALWAYS solid. I understand that there's essentially no cost difference...
  10. peebee

    Purpose of ANSI 21 Distance Relay?

    On an existing generator-utility full-time paralleling installation, there is an ANSI 21 Distance Relay monitoring the incoming utility MV feeder. This was specified to be provided for this customer-owned installation by the utility as a condition of operation of the system. Per the Red Book...
  11. peebee

    Fuel Cell as a Battery

    OK, so I'm pretty much of the opinion that if a hydrogen-based fuel cell serves any purpose whatsoever, it's pretty much as a replacement for lead-acid batteries. So my question is, how good a battery is a fuel cell? In terms of: 1. cost - my guess is batteries win, otherwise NASA wouldn't be...
  12. peebee

    Current Imbalance Definition

    Please confirm: Current Imbalance is defined as "(Imax-Imin)/Imax" ? Shoud Iavg be the denominator instead of Imax? Is the preferred term "Imbalance" or "Unbalance"?
  13. peebee

    Ground fault on 3-wire ATS transfer?

    We have experienced a strange problem at a new installation: We have a 3-wire ATS fed from a 3-wire grounded 3-wire 480-volt service, as well as a 3-wire grounded emergency generator source. ATS is reported to have midpoint-off position, although delay setting is unknown (currently being...
  14. peebee

    How does RGB create Yellow?

    How is it possible to get yellow from an RGB signal? Is "G" actually Yellow or Yellow/Greenish rather than Green? Can "B" go negative, subtracting Blue from Green to make Yellow? Just curious.
  15. peebee

    Sensing of Lamp vs. Ballast Failure (MH)

    Is anyone aware of any good/feasible method to sense lamp failures and ballast failures for metal-halide fixtures (sized anywhere from 70w to 1000w), including discrimination between which one has failed? I've heard rumors that a CT in the input of the ballast may be sufficient, either to...
  16. peebee

    Delamping & Ballast Damage

    Please see my question at thread659-69045 .
  17. peebee

    Delamping & Ballast Damage

    Does anyone know the reason why removing a fluorescent lamp can damage the ballast? Is this true with both magnetic & electronic ballasts? Do they have similar reasons for failing?
  18. peebee

    NEMA TP-1 Transformers

    I'm trying to determine if we should stick to general purpose transformers, consider NEMA TP-1/EnergyStar transformers, or standardize on NEMA TP-1 for all projects. Any insights, thoughts, observations, links, etc., would be appreciated. I'm primarily interested in dry-type transformers, but...
  19. peebee

    1080i YPrPb-->VGA Transcoder

    I'm interested in building or buying an HDTV YPrPb-->VGA transcoder, similar to the one from Key Digital, as sold at http://www.copperbox.com/lite/popinfo.php?lc_code=KD-CTCA2-OB&uneek=681850089 for $229. But that price seems incredible to me. Isn't this just three analog adders/subtractors...
  20. peebee

    Power Supply & Signal Grounding

    I posted this question ( thread240-50804 ) in the circuit engineering forum, but I figured some of you here might have some insights too. . . .

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