I have a transformer from 110v to 24v with ground isolation, my question is if I can connect both grounds, from primary and secondary side. I need to know if this is no going to damage the transformer. Please reply ASAP!

 

As is virtually always needed, post a schematic of what you're planning on doing -- it's much clearer than words...

 

Are you asking if you can connect the primary and secondary grounds together?

If so, the answer is no. And why would you want to? You lose isolation.
A schematic would clear things up, as someonesdad has said.

 

yes, retched this is what I meant. The issue is that I have an application circuit were I do not have a gnd/neutral present and a need to supply voltage to control it. I thought that probably connecting gnd/neutral of primary and secondary I can supply it. Hope this schematic explains a little bit.

 

Umm, no, that will not work.

Do you have a transformer with only one wire on the secondary?

The way it is shown, it will not operate. If you tie it to the other side, you will have 120v on the 24v side. so that wont work either.

 

no, the secondary has two wires but I have access to one wire only. I was just wondering that probably I can connect the primary and secondary gnd to have the loop I need, but it's not possible. Thank you so much, I have to keep searching another solution.

 

I'd cross check with your manufacturer docs, but if you only have one lead on the secondary, you may have an autotransformer. You can do a continuity check to see if your one lead is connected back to the primary side.

Connecting both primary and secondary to a ground common does not negate isolation (excepting above). It only adds a common reference point.

 

Connecting both primary and secondary to a ground common does not negate isolation (excepting above). It only adds a common reference point.

I believe this is a safety requirement as well.

 

As long as we are talking ground, and not neutral. Ground should not be involved with the high voltage side (Hot or Neutral) of the transformer in any way.

 

He is talking neutral.

He only has ACCESS to one of the two wires off of the primary.

So it has 2 wires, he just cant access the second.

 

As long as we are talking ground, and not neutral. Ground should not be involved with the high voltage side (Hot or Neutral) of the transformer in any way.

I agree, though let's get more specific - as I understand it the idea is that primary hot and neutral are both isolated from the chassis and ground while the ground is connected to the secondary neutral and chassis.

 

Rubi,

Your comment is still unclear - "The issue is that I have an application circuit were I do not have a gnd/neutral present and a need to supply voltage to control it. I thought that probably connecting gnd/neutral of primary and secondary I can supply it."

Do you access to the 'unconnected' output of the 24VAC winding?

You have not shown a mains earth anywhere. Is there one present. If not then is the transformer and the application suitable for an unearthed product - do you know or are you guessing?

Does your output need to be SELV rated?

Ciao, Tim

 

I agree, though let's get more specific - as I understand it the idea is that primary hot and neutral are both isolated from the chassis and ground while the ground is connected to the secondary neutral and chassis.

Yes, you are correct. Only the source is grounded, so your primary side, being a load for it's source, is not grounded. Your secondary, being a new source, is grounded.

Neutrals only occur in 3 or more wire systems (not including grounds). Neutrals are only bonded to earth at thier source, with a code spec'd wire. The rest of the system is 'bonded' to ground. The 'neutral' in a 2 wire system is more apt identified as the 'identified' conductor.

 

Common would have been a better term to use. Even though I used Neutral.

 

Continuity check the transformer including all wires and the case!

Some transformers have been designed so that bolting the transformer into a grounded chassis makes a necessary electrical connection.

Retched could be right; It is possible this is an autotransformer which will be easy to find out if there is continuity between the transformer output and input windings.

Chances of a reverse wired outlet being used make electrical connection to neutral or hot side of the primary the wrong way to go.