Wiring transformer

Discussion in 'HVAC Heating & Cooling' started by hidden 1, May 23, 2019.

  1. hidden 1

    hidden 1 Member

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    I have a old trane heatpump an need to change out the transformer.

    On the new one the colors differ .

    The old one has a 230 60 hz /24vt 77va
    An 2 wires going in 1 black fused an a pair of blue wires .
    Coming out it has a hook up for the 2 red /white stripped. An a hook up for the other 2 blue w black striped.

    The new transformer has White as Common to wire to the incoming .. an beside it a Orange 240..to wire to incoming .

    Coming out the other side of new transformer 24vlts theres a blue an a yellow

    ..

    Do i wire the old incoming black fused wired to the New white[common] or to the New 240v Orange on transformer?

    And does the new 24v blue wire coming out go to the blue/black pair of wires or to the red white striped pair?
    The other new 24v wire coming out is yellow .
    Thanks
     

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  2. WorthFlorida

    WorthFlorida The wife is still training me.

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    Original post removed

    ALL unused pigtails must be cut down to the insulation of the wire and capped off with a wire nut. Don't trust electrical tape alone.
     
    Last edited: May 23, 2019
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  4. hidden 1

    hidden 1 Member

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    Ok so the new white Common off the new transformer goes to the 2 blue stripped wires..An the 240 Orange off the new transformer goes to the brown stripped 2 wires .?

    And the new blue 24v coming out of new transformer goes to the 2 light blue[1 goes to contactor ] wire .
    An new 24v yellow coming out of transformer goes to the old black wire that runs to the glass fuse?
    Yes i still am removing tbe ends ..
    pic shows black to glass fuse
     

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    Last edited: May 23, 2019
  5. WorthFlorida

    WorthFlorida The wife is still training me.

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    No, you changed color description.
     
  6. hidden 1

    hidden 1 Member

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    Heres diagram .
    Old transformer .
     

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  7. WorthFlorida

    WorthFlorida The wife is still training me.

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    looking at the wiring, the old transformer is a bit odd. Disregard my original post.
     
  8. hidden 1

    hidden 1 Member

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    This is 30 year wiring set up..Glass fused .

    No bells an whistles nor time delay either .

    Ill just test for the 240 an wire orange to the-240 ..an the common to the white ..

    An the 24v will be wired to last 2 ..

    Thanks
     
  9. hidden 1

    hidden 1 Member

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    Doing same thing with new transformer !
    I tested for the 240 ,an it read 240. an connected it up to new transformer 240 side to common white an 240 orange ,hooked the 24volts up also but no 24 volts coming out after turned on .It doea nothing..
    Heat Pump works when button on contactor is manually energised.

    New transformer has a reset button on it.but 2 wires only hooked up..
    Will those 2 of 5 wires still kick the reset,or does it use one of the capped off 3 wires? .

    Heres how its wired .
    What should i look at next ?
     

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    Last edited: May 24, 2019
  10. WorthFlorida

    WorthFlorida The wife is still training me.

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    For the input side only two wires are ever used. This breaker/reset button looks like it is on the 24v output side because of the amp rating and near the blue yellow output leads.

    Since the new transformer has a breaker, check the glass fuse and holder with an ohm meter. From the picture there is rust stains inside of it and it reads “dual element”. Possibly you can eliminate this fuse since the transformer has a built in breaker. It’s another weird thing with this. This type of fuse on the low voltage side. Are you sure it only thirty years old? I think it is older. How old is the compressor? They don’t last 30 years.

    Did you measure the 24v connected or disconnected? Should read it both ways. No connection it could read up to 29v, under load as low as 18v. Generally it’ll be ~22v under load. If still no output, with power off and the blue/yellow disconnected, read the ohms across them. Something other than infinity or zero should be read.

    The contactor is new so had there been other problems? This beast being over thirty years old is or less than SEER 10 and it must be costing a fortune to run it. It must be a R22 refrigerant that will no longer be available unless there is old inventory around and prices are through the roof. After this weekend heat we’re going to have it may convince you that it is time to retire the unit. A new SEER 16 unit may knock off $150-$200 a month off the electric bill in the summer months. It did for my son when an old unit was replaced.
     
  11. hidden 1

    hidden 1 Member

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    I measured it connected ..Yep back then they didnt have a fancy reset switch on transformers.
    No, my bills arent bad .A bit more in the summer yea but not bad .Im gonna put another unit in myself later but want to get this 24 volt issue fixed .I put in a goodman last year at my other place.
    Good cold air if contactor is engaged manually..
    I use a permanent gas heat i have in winter a lot too.
    Never had a issue with it over 10 yrs .The contactor replaced 8 mo ago due to old age an worn contacts.
    I changed out inexpensive capacitors an same contactor last week ,after it started ....those capacitors were OLD. ....again nothing changed as far as function ..
    Ill test it an see if reset got tripped an check wiring on the glass fuse.Im gonna ohms test old transformer off it too .
    Can a cut 24 volt wire to stat , maybe by rodent or weedeater cause the same issue ?
    I will do some ohms tests on several wires also.
    I will need to ohms test new transformer disconnected too .
    The Model # is. bwc030c100A0
     
    Last edited: May 25, 2019
  12. hidden 1

    hidden 1 Member

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    I see the VA 77 ..down to 75 on new is a tad lower .--does this factor it ?
     

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  13. hidden 1

    hidden 1 Member

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    On ohms.,meter set 200 The old trasformer,off, measured 18.1 then slowly went down to an stayed at 16.7ish on 240 side .
    And 7.4 going slowly down on the 24 side. To 1.8

    The new one ,disconnected ,measures 32 on high side an 3.3 on 24 side.
    Is this normal on new one ?

    Reset was not tripped on new one.

    Dual element time delay glass fuse showed 2.8.though its a 3.2..
     
    Last edited: May 25, 2019
  14. hidden 1

    hidden 1 Member

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    Power on..
    This time i did get 27 off low end
    An 240 on high ..
     
  15. WorthFlorida

    WorthFlorida The wife is still training me.

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    The new transformer, is right where the resistance is 10:1. Same as the voltage change. Not sure what is going on with the old one. Your last post? Do you now have 24v AC (27v with no load)?
     
  16. hidden 1

    hidden 1 Member

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    Yea .
    24 off transformer
    No 24 at contactor.

    Can still manually press it to start..not by stat .
    Inside stat shows the 24 v .
     
  17. WorthFlorida

    WorthFlorida The wife is still training me.

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    Since the transformer has a breaker, bypass that old glass fuse if it is just one circuit. The dual element may have been a replacement on hand unless the wiring diagram show a use of the second element.
     
  18. Reach4

    Reach4 Well-Known Member

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    Given that you have a schematic, you should be able to see what is stopping the voltage from reaching the contactor coil.
     
  19. hidden 1

    hidden 1 Member

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    Yea old systems must have used that set up before they were built on to them.
    Diagram shows it in line..Time delayed -dual function.writren on fuse..Is the one on the transformer time delay dual function ?

    I guess i can cut the black an red to ir an wire those together?..

    Yea im trying to go over diagram ..
     

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    Last edited: May 25, 2019
  20. Reach4

    Reach4 Well-Known Member

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    You have 24 volts at the transformer. Unless it is the fuse stopping the voltage from getting through, I would stop thinking about that fuse.
     
  21. hidden 1

    hidden 1 Member

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    WorthFloroda suggested it.
    I wasnt planning on changing it out...
     
    Last edited: May 25, 2019
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