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  1. #14
    Join Date
    Feb 2003
    Location
    S.W. PA
    Posts
    3,298
    Originally posted by hvac hero
    I heard a story one time about a condenser not having a ground on it. The compressor went to ground, which wasnt there. This made the outside casing energized. A boy was playing hide n seek in the backyard & hid behind it, put his hand on it & was electrocuted.

    So is this just some BS story that someone made up or would this happen if a condenser wasnt grounded???

    i would say it is possible if condensor was sitting on rubber pads or something similar

  2. #15
    Join Date
    Feb 2006
    Posts
    1
    Yes that could happen, down in the basement do you ever see any nominal copper pipes with an earth ground on them running back to the main panels ground bar? Thats a precaution- because if a wire was nicked and the insulation was exposed to touch the copper pipe (copper to copper connection) and it wasn't properly grounded every metal pipe in your house could potentially become energized i.e. faucets, tubs wherever the pipes run to- its essential that everything is properly grounded to provide an alternate path for current to flow.

  3. #16
    Join Date
    Jul 2004
    Location
    midwest
    Posts
    2,868
    Originally posted by dhvac
    Originally posted by hvac hero
    I heard a story one time about a condenser not having a ground on it. The compressor went to ground, which wasnt there. This made the outside casing energized. A boy was playing hide n seek in the backyard & hid behind it, put his hand on it & was electrocuted.

    So is this just some BS story that someone made up or would this happen if a condenser wasnt grounded???

    i would say it is possible if condensor was sitting on rubber pads or something similar
    And the coil had a plastic drain pan.

  4. #17
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    2,013
    Originally posted by hvac hero
    I heard a story one time about a condenser not having a ground on it. The compressor went to ground, which wasnt there. This made the outside casing energized. A boy was playing hide n seek in the backyard & hid behind it, put his hand on it & was electrocuted.

    So is this just some BS story that someone made up or would this happen if a condenser wasnt grounded???
    Ever watch the show MYTHBUSTERS? Sounds like this would make a good show for those guys to see if they could fry one another.

    As to the story... Murphy's Law was written just for instances like this one and so were the electrical codes. Would it happen? Maybe Could it happen? If nothing else connected to the condenser via ..... say the line set were grounded (that would trip the fuse/breaker) then the potential for someone to complete a ground path at the condenser is 100% possible

  5. #18
    Join Date
    Oct 2003
    Location
    southern mo.
    Posts
    323
    i've been shocked by cond.units&duct work, and the other day the cover of a breaker box,older mobile with a dgat that woudnt stay lit,{allready upgraded} the home wasnt grounded right and had wireing problems somewhere,read 12vac to the earth off side of home,furnace would only stay lit if i turned off all the other breakers in the home,at the furnace read 9vac to ground off the neutral,as they turned on other circuits it slowly went up to 12vac,told them to call an electrition out before the place burned.i guess it couldnt sense flame with an energized neutral...

  6. #19
    Join Date
    Nov 2005
    Posts
    576
    What about floating grounds on generators? Is the whole metal frame ground and neutral.

    There are lots of generator service disconnect switches that do not disconnect ground and neutral.

  7. #20
    Join Date
    Feb 2004
    Location
    Pacific NW
    Posts
    567
    hvac hero:

    No myth, and numerous other scenarios. Did an insurance company file search a few years back for a safety review for a high voltage class being taught at the time.
    The worst scenario is when the case is not grounded and there is a case short to the junction of the run capacitor to the compressor winding. This results in the higher voltage (300 volts on 115 Vac circuit, due to winding/capacitor reactances) at that point being applied to the case.

    Here is a specific reference to a window unit electrocution due to that type short and the case being ungrounded.

    [T. Bernstein, “Investigation of Alleged Appliance Electrocutions and Fires Caused by Internally Generated Voltages”. IEEE Transactions on Industry Applications, July/August, 1989.]

  8. #21
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    Originally posted by cyro
    What about floating grounds on generators? Is the whole metal frame ground and neutral.

    There are lots of generator service disconnect switches that do not disconnect ground and neutral.
    Generators are a little different. First, if the transfer switch doesn't break the neutral, the neutral and ground of the generator should be unbonded. When it is connect to your house, the main utility panel has the neutral and ground connected. This same point acts to bond the generator neutral and ground together.

    If you happen to use a generator like this in a portable fashion (unbonded, and not connected to a house), then it will be running with an ungrounded neutral. This isn't so bad in a generator because it isn't connected to the earth anywhere. The power utility is, so if you lose the ground at your house, there is still unfortunatly a voltage difference between the earth and the hot wires. This isn't so with an unbonded portable generator (but there are still some things that could happen so its better to rebond it internally if using it in portable configuration).

  9. #22
    Join Date
    Feb 2004
    Posts
    2,458
    We have lots of 2 wire services (120 volt) around here & no grounds.. Of course these are very old homes.

  10. #23
    Join Date
    Jul 2004
    Location
    midwest
    Posts
    2,868
    Originally posted by mike3
    We have lots of 2 wire services (120 volt) around here & no grounds.. Of course these are very old homes.
    There are a few of those around here also. Do you ever see them go through a double fuse holder that includes the neutral?

  11. #24
    Join Date
    Feb 2004
    Posts
    2,458
    Originally posted by trane
    Originally posted by mike3
    We have lots of 2 wire services (120 volt) around here & no grounds.. Of course these are very old homes.
    There are a few of those around here also. Do you ever see them go through a double fuse holder that includes the neutral?
    Yes we see a lot of those..Both are fused. Actually we see them fused on both sides of meters at times

  12. #25
    Join Date
    Oct 2005
    Location
    Omaha, NE
    Posts
    309

    Grounding ...the most poorly understood even among electricians

    Household current is basically:

    a. GROUND: connects to plumbing piping and/or earth; therefore "Ground".
    Ground is connected by Utility company outside of the house
    (but do not trut that this true, there is a 1% chance (or more) that this does not happen).

    b. NEUTRAL (WHITE wire): At main panel it connects to ground through the "Bus Bar".

    c. HOT (BLACK wire): This word refers to the fact that it is "Hot", i.e., if you touch the BLACK wire while holding a ground subject, you will get a good shock.

    Get a Volmeter and measure:

    a-b: 0 volts
    a-c: 110 volts
    b-c: 110 volts

    NEUTRAL (b) is created inside the Main Panel by grounding the bus bar to the WHITE wiring).

    Actually from the Utility to the house, there are:
    - 1 GROUND
    - 2 BLACK wires (measure across these 2 BLACK wires will give you 220 Volts. This is the circuit used in the house for Electrical Oven-Ranges or Electric Cloth Dryer). Let'sc all each of these BLACK wires "c1" and "c2".

    So:
    a-c1 = 110V (this is each SINGLE circuit breaker in your house)
    a-c2 = 110V (this is each SINGLE circuit breaker in your house)

    But... c1-c2: 220V (this is each DOUBLE circuit breaker in your house for Electrical Oven or Dryer)

    The best way to understand how Household Electricity works is here:

    http://www.achrnews.com/FILES/IMAGES/5223.gif

    http://www.mikeholt.com/onlinetraini...13835748_2.jpg

    (The 2 "Blac" wires are c1 and c2 in my example; the third wire from utility is grounded; then each 110-V circuit is powered by EITHER c1 or c2).

    If you have an OPENED GROUND, you can get some of these:

    http://www.mikeholt.com/graphics/touch.gif

    http://www.mikeholt.com/instructor2/...1080685011.jpg


    Hope this helps.

    cn



    My advice to all servicemen: Before touching anything electrical, check the GROUND by:
    - using a circuit checker ($6-7 at Home Depot)
    - measure the above values.


  13. #26
    Join Date
    Aug 2002
    Location
    manitowoc wisconsin
    Posts
    4,943
    It could give you fits with flame rectification circuits.Last year I found an unbonded main box that was causing 200 mv. potential between ground & neutral.The boiler locked out on flame failure intermittently for a few years before I got there & bonded the box for the guy......The bonding screw was still in the bottom of the box uninstalled haha!
    Take your time & do it right!

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