3ph - 1ph question

Discussion in 'General Electronics Chat' started by anocsparky, Aug 5, 2009.

  1. anocsparky

    Thread Starter New Member

    Aug 5, 2009
    Hi there, im new here. Just one quik question. I HOPE:)

    Ok here it goes. My church just bought a used modular building for class room use, they have asked me to hook it up for them. it currently has a 200A 120/240V 3ph 4 wire panel. On site all we have is 1ph. so what do i Need to do to make this work? Im assuming that ill need to change out the guts in the panel to start off. Ive been an electrician for 14 years now and have never run into this situation before so any advise would be greatly appreciated.

    Thanks in advance.
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    Given you are an electrician I don't want to be telling you things that are already obvious to you but I guess a few points to consider would include

    1. Can the existing single phase supply to your church facility accommodate the added maximum demand load of the new modular building?[#]
    2. Could you not simply cable across the 1-phase supply to the new sub-board and loop the same phase across what would normally be the 3 individual phases + neutral (+earth) input terminals? That would save you re-hashing the board in any significant manner.
    3. Comply with your supply authority's earthing requirements for the modular building - e.g. do you require a separate earth stake or can you just bring the earth across from the main board as well? [#]

    [#]That's the stuff you would probably know anyway.
  3. PRS

    Well-Known Member

    Aug 24, 2008
    I believe your new service has 240 volts between phases and 120 volts from a single phase to neutral/ground. There should be no problem when it comes to using the 120 volt outlets I assume are available. or the single phase lighting at 120 volts either for that matter. If you need to test this with a simple drill or lamp or something of the sort.
  4. GetDeviceInfo

    AAC Fanatic!

    Jun 7, 2009
    Code and your local inspector will have you replacing the panel. Will your code not call for a new service run as well?
  5. alim

    AAC Fanatic!

    Dec 27, 2005
    Hi jumping in here, you should familarise your self with the 3phase system you have to work with.There are two types of 3 phase systems DELTA AND WYE. In a delta system the phase voltage is the same as the line voltage, and has a neutral tap on one leg to provide 120 volts. In the WYE system the line voltage is 1.732 * the phase voltage,or the phase voltage is 0.577 times the line voltage, thus for a 240 v line voltage, the ph. voltage is 138 volts. for 120 volt phase the line voltage is 208 volts