How many little fuses do you have to blow...
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  1. #1
    Join Date
    May 2005
    Location
    South
    Posts
    580

    How many little fuses do you have to blow...

    How many little fuses do you have to blow before you figure out that you should find another way to trouble shoot?

    I don't get it.
    I had to follow up on a guy today, said it was a bad circuit board, the boss had me look at it. Found a pile of fuses on top of the airhandler.

    What I do is take out my premade 3 amp circuit breaker and plug it into where the fuse was.

    Disconnect and seperate all low voltage wires.
    Touch red to green, red to yellow, red to white. Does it work? Yes? Ok theres nothing wrong with the airhandler controls. Or circuit board.

    Then start connecting the thermostat and cond unit wires, yes you have to do this live.

    Once you connect the shorted wire the breaker trips. Pretty simple.

    If it's the cond unit wire disconnect it at the unit and try again.
    If it's the thermostat wire disconnect that at the t-stat and try again.

    When you find it, follow it down and inspect the wire, or just replace it. Pretty simple.
    If it stops tripping when you disconnect the cond unit or t-stat then look there for the problem.
    Fuses wasted 0. Tools needed: nut driver, wire cutters, transformer breaker.

  2. #2
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,325
    Quote Originally Posted by truck12 View Post
    How many little fuses do you have to blow before you figure out that you should find another way to trouble shoot?

    I don't get it.
    I had to follow up on a guy today, said it was a bad circuit board, the boss had me look at it. Found a pile of fuses on top of the airhandler.

    What I do is take out my premade 3 amp circuit breaker and plug it into where the fuse was.

    Disconnect and seperate all low voltage wires.
    Touch red to green, red to yellow, red to white. Does it work? Yes? Ok theres nothing wrong with the airhandler controls. Or circuit board.

    Then start connecting the thermostat and cond unit wires, yes you have to do this live.

    Once you connect the shorted wire the breaker trips. Pretty simple.

    If it's the cond unit wire disconnect it at the unit and try again.
    If it's the thermostat wire disconnect that at the t-stat and try again.

    When you find it, follow it down and inspect the wire, or just replace it. Pretty simple.
    If it stops tripping when you disconnect the cond unit or t-stat then look there for the problem.
    Fuses wasted 0. Tools needed: nut driver, wire cutters, transformer breaker.
    Or invest in a meter that reads low amperage. I take my Fluke 179 or 87V and go across the fuse holders with the alligator ends. I can monitor amperage as I energize components.

    Your method is nice and easy on a residential split.......but when you dealing with a unit that might have 20+ loads on a circuit.......it's alot easier to monitor amperage and when it spikes, narrow it down to what just was called for or pulled in.

  3. #3
    Join Date
    May 2005
    Location
    South
    Posts
    580
    Quote Originally Posted by ascj View Post
    Or invest in a meter that reads low amperage. I take my Fluke 179 or 87V and go across the fuse holders with the alligator ends. I can monitor amperage as I energize components.

    Your method is nice and easy on a residential split.......but when you dealing with a unit that might have 20+ loads on a circuit.......it's alot easier to monitor amperage and when it spikes, narrow it down to what just was called for or pulled in.
    I see your point, but thats just it, this is residential not rocket science.
    Someone could just as easily put a 10 amp fuse in it and judge by the arc of flicking the two wires together.

  4. #4
    Where was the short? Did someone get out of control with the weed wacker near the line-set?

  5. #5
    Join Date
    Mar 2007
    Location
    NW AR
    Posts
    2,478
    Quote Originally Posted by truck12 View Post
    I see your point, but thats just it, this is residential not rocket science.
    Someone could just as easily put a 10 amp fuse in it and judge by the arc of flicking the two wires together.
    Ill stick with my 3 amp breaker.

  6. #6
    Join Date
    May 2005
    Location
    South
    Posts
    580
    Quote Originally Posted by HVAC/R-Wizard View Post
    Where was the short? Did someone get out of control with the weed wacker near the line-set?
    It was at a romex connector where the low voltage wires went through the airhandler case. One of our installers overtightened it. Honestly I was surprised they didn't just shove it through the knock out as usual.

    New install, 2 1/2 months ago.

  7. #7
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,627
    I carry 2 of the 3A mini breakers. One for testing as mentioned and on the rare occasion that a transformer gets smoked because there is no fuse the mini gets left in.

  8. #8
    Join Date
    Apr 2012
    Location
    Cleveland
    Posts
    605
    I use the 3a Lil popper and find them every time... Or use 10 or 20a fuse method and replace whatever component blows jk.

  9. #9
    Join Date
    Feb 2006
    Location
    USA
    Posts
    4,381
    Quote Originally Posted by Hvac216 View Post
    I use the 3a Lil popper and find them every time
    Yep, me too ......


    Sent from my HTC Sensation 4G using Tapatalk 2

  10. #10
    Join Date
    Feb 2012
    Location
    Toronto Canada
    Posts
    1,090
    Can you Please post a Picture of your Mini breaker and clips?

  11. #11
    Join Date
    Apr 2012
    Location
    Cleveland
    Posts
    605
    hope this upload works
    Attached Images Attached Images  

  12. #12
    Join Date
    Feb 2010
    Location
    Calgary, Alberta
    Posts
    1,076
    Lennox sells 3a resettable circuit breakers for their newer furnaces and air handlers for about $2
    32w47 is the part number I think

  13. #13
    Join Date
    Aug 2010
    Posts
    2,300
    Quote Originally Posted by ascj View Post
    Or invest in a meter that reads low amperage. I take my Fluke 179 or 87V and go across the fuse holders with the alligator ends. I can monitor amperage as I energize components.
    Controls is my forte and Fluke meters use a special 11A fuse with 20,000A interruption capacity on the high-A range (as opposed to mA range). That fuse is such that it can safely interrupt up to 20,000A of fault current should you accidentally try to measure voltage across phases on 480v bus bars without the meter turning into a fireball but it would just as easily blow if you were to accidentally try to measure current across a cordless drill battery too.
    All that safety is great... but the catch is, that fuse cost like $13/piece.

    I would use two automotive 1156 bulbs(12v 2A or so) wired up in series so that you'd end up with a 24v 2A bulb, simply because 24v bulbs are hard to find. You could leave it connected in a short indefinitely and no harm would be done. The bulbs would simply remain lit indefinitely.

    You know there is a short when the bulbs come on brightly. If you can't be near it, have another person tell/radio you that bulbs lit up.

    It might barely glow with pilot, turn a bit brighter with call for main valve (and might actually drop out with bulbs in place) and light up bright if there's a short.

    If the two bulbs glow like you hooked them up directly to the transformer, there's a short.

    It is more productive than resetting breakers over and over since there's no resetting ever and there is a visual indicator. If it flickers, you've got a chaffed wire in a conduit or something.

    Use it for a while and you'll learn how to eyeball abnormal draw by looking at how bright the bulbs glow.

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