24v Transformer Blows when Cooling is On - HVAC Low Voltage Short

Tools used in this video
Fieldpiece Expandable Stick Multimeter Hs33 - amzn.to/4cJOum1
3 amp resettable fuse for low voltage short troubleshooting -amzn.to/4aKf0Kk
3 amp fuses - amzn.to/4aEakpL
Wire Crimping Tool - amzn.to/4cMqYVh
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[@AaronPowellvox]

Great teaching tool. I hope your other techs are taking notes from you.

[@zekenzy6486]

Great Video. Thank you for sharing. Have a nice weekend

[@fisforfriendship6093]

so when you disconnected the y and c the (A/c wires coming from its contactor)you were reading the ohms of the wires and contactor from the terminal block indoors. since the resistances of those tiny wires although long wont give that many ohms your essentially reading the ohms of the contactor its connected to. i wonder if water corroded the contacts since the cover was off or if it was welded some what. wish we knew what caused the contactor to go bad i can only guess overheated

[@ApartmentMaintenancePro]

Ya about 10 floors of that wire running accounted for almost 2 ohms. I couldn’t visually see anything on the coil that would make it bad as I did take it apart and start unwinding the wire because I was curious about the failure

[@eddiepulido9571]

I have an hvac question. A resident is complaining about humidity being high but they have a furdown. I know it could be a dirty cool issue but it’s a hassle to take down and clean. Is there another way to lower their humidity without doing that?

[@ApartmentMaintenancePro]

Where are you located? To solve this issue you have to figure out where the humidity is coming from. Dryer vent hooked up and sealed? Do they have a bunch of aquariums? Are they using humidifiers? etc. What's your delta t split? Supply air vs return air. If it's above 20 you have an airflow issue.

[@eddiepulido9571]

@@ApartmentMaintenancePro it’s usually the first floor units. I’m in Texas and this usually happens during warm weather. I just wanted to help my assistant. We’re learning as we go. Thanks for your help!

[@patbiat929]

Hey, did you connect the fuse to the 120v wire or the 24v ones. And did you disconnect the wire to the roof for ever. Here, I have 2wires(black and white) are showing 120v on multimeter and I got yellow and blue showing nothing. Probably the transformer blew up. How can I connect the fuse on my transformer?

[@danielshepherd4436]

0:53

[@klarnorbert]

Wonder why manufacturers don't install a fuse in the secondary side of a transformers...

[@ApartmentMaintenancePro]

Some do 👍

[@klarnorbert]

@@ApartmentMaintenancePro There are no regulations over there to do so?

[@benjamintimmins1656]

No...a lot of 75va xfmrs have a fuse switch on the side of the transformer secondary....you can also add a 1amp fuse for the primary side since that has and will burn up just as often...that's why its good to ohm out the xfrmr to tell which side burned up. Cause your always gonna have 120v or 240v to the transformer from the whip...won't know how it burned up unless you ohm it out...and primary windings are smaller which means they burn up easier and can actually happen through the secondary👍

[@hectorcarrasco3394]

Usually when the transformer burns out on you its a bad contactor

[@ApartmentMaintenancePro]

I get it all at the places I work. Mostly for me its wires rubbing to ground. Just trying to show the steps of verifying without a doubt that in this case it was the contactor. So many maintenance techs just blindly waste time by replacing parts without verifying anything is wrong.

[@hectorcarrasco3394]

@@ApartmentMaintenancePro ofcourse, I actually Love that you do that, troubleshooting that is, and you are right most maintenance technicians do just replace the parts without truely knowing for a fact where the cause of a failed component is actually happening, Great video!