Trouble replacing home alarm transformer

Thread Starter

dyelan

Joined Nov 6, 2015
4
I am attempting to replace the transformer that plugs into the wall outlet for my home alarm. The old transformer has 3 leads on it. I ordered the exact same model from Amazon and the transformer I received has only two leads. The lead for the ground is missing.

Is the ground necessary or is there a reason it is not present on the newer transformer?
 

dl324

Joined Mar 30, 2015
9,151
The old transformer has 3 leads on it. I ordered the exact same model from Amazon and the transformer I received has only two leads.
Can you post pictures of the power supply labels and plugs?

Wall wart type power supplies are isolated from line voltage, should have a ground, and wouldn't have an earth ground.
 

Hypatia's Protege

Joined Mar 1, 2015
3,197
I am attempting to replace the transformer that plugs into the wall outlet for my home alarm. The old transformer has 3 leads on it. I ordered the exact same model from Amazon and the transformer I received has only two leads. The lead for the ground is missing.

Is the ground necessary or is there a reason it is not present on the newer transformer?
If the missing lead is truly ground it may be tied to the core/jacket in the replacement -- if, on the other hand, it's missing a centertap, you've got hold of the wrong transformer...

Best regards
HP
 

Thread Starter

dyelan

Joined Nov 6, 2015
4
Can you post pictures of the power supply labels and plugs?

Wall wart type power supplies are isolated from line voltage, should have a ground, and wouldn't have an earth ground.

Old is the first. New is the second pic
20151107_124058.jpg 20151107_123957.jpg

Thanks for the help!
 

dl324

Joined Mar 30, 2015
9,151
Check for continuity between the center screw and ground connection on the plug. If you have continuity, you can connect the corresponding terminal on whatever you're powering with the grounding screw on the new adapter.

You could also check the device you're powering to see if it requires the center terminal to be connected.
 

dl324

Joined Mar 30, 2015
9,151
The green wire looks like it goes to the panel the lead is marked earth. To be honest I am not sure how to check continuity.
Use an ohmmeter to check for continuity from the center screw terminal to the earth ground pin on the plug.

To be safe, you could run a separate wire from the ground screw on the new adapter to the earth ground connection; and make sure you secure the screw in a properly grounded outlet.
 

MaxHeadRoom

Joined Jul 18, 2013
19,197
Check continuity with the Ohm meter range.
I would suspect that the only thing that would be reference to earth ground maybe would be any suppresion devices, for this reason it may be prudent to connect the Earth terminal/lead to an Earth Ground.
Max.
 
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