Step-Down Step-Up Transformer Neutral to Ground Bonding

[Installer]

We have an an existing pair of 5 kva 600/120 Step Up Step Down Transformers feeding Transmitter 1 in a Field.
We want to dig a trench , install 400 feet of conduit, and extend that power to a new Transmitter Stand 2, again with 600/120 Step-Up Step-Down Transformers.
I'm trying to make sure I have my connections right and my Neutral and Ground bonded correctly. I don't know if my diagram can be read.

 

[synchro]

The neutral should not be bonded to ground again ahead of the 3KVA transformer, since it's shown being bonded to ground after the 5KVA one that feeds it. Otherwise, some neutral current will be flowing through the equipment ground conductors.

 

[texie]

The existing and new are not properly gronded/bonded.
The generator hookup-no transfer switch shown.
No over current shown.
Why are you feeding the new from the 120 side?

 

[Installer]

The existing and new are not properly gronded/bonded.
Could you please be more specific?
The generator hookup-no transfer switch shown.
There is none. They wheel one up and connect it
No over current shown.
Could you please be more specific?
Why are you feeding the new from the 120 side?
Its 240 at the Meter

Thank you for your comments

 

[augie47]

Two comments:
Your step down transformer appears to be as 240/120. X1-X4 will give you a 240 output, not the 120 shown.
That transformer (step down) will need a neutral-ground bond and a grounding electrode.

 

[LarryFine]

Why are you feeding the new from the 120 side?

My guess is for the generator.

 

[Installer]

Two comments:
Your step down transformer appears to be as 240/120. X1-X4 will give you a 240 output, not the 120 shown.
That transformer (step down) will need a neutral-ground bond and a grounding electrode.

augie 47,
Thank you for your comments. I was a staff engineer, got bored with the office, meetings and telcons, asked to move back to the field but I forgot one thing.
......I'm in my late 50's now and I need 8 hours of sleep and my mind just isn't as fast anymore.

This is the 3 KVA Acme Transformer information. Could the 5 KVA GE transformer be different or are they all the same?
BTW
1. I thought someone would give me a hard time because I thought the Neutral should not be switched.
2. Some of the switches are fused. Two are not. I read that too many fused switches is not too wise.

 

[MTW]

Is it possible to install your 2nd 600V transmitter feed, from the point of the first 600V step up transformer?
And eliminate the 2nd step up transformer.

Looks as if your starting branch circuit is 120V as labeled. But 1st step up transformer is shown wired for a 240V input.

If your starting with 120V, you could relocate the generator to that point, at the 120V branch circuit, install a manual transfer switch, and power both transmitters from the same point.

Less equipment, more versatility, same 600V extension system.

MTW Ω

 

[augie47]

augie 47,

This is the 3 KVA Acme Transformer information. Could the 5 KVA GE transformer be different or are they all the same?
BTW


View attachment 22961

They would alll be the same. Take a look at the Table in your post and you will see the configuration for a 120v(only) output.

 

[Installer]

What am I doing wrong. The table says: Tie X3 to X1; Tie X2 to X4; Connect Secondary lines to X1-X4 for 120

Of course when you're 50+ your energy goes, then your eyesight.

They would alll be the same. Take a look at the Table in your post and you will see the configuration for a 120v(only) output.

 

[Installer]

Thanks---redrawing it

Is it possible to install your 2nd 600V transmitter feed, from the point of the first 600V step up transformer?
And eliminate the 2nd step up transformer.

Looks as if your starting branch circuit is 120V as labeled. But 1st step up transformer is shown wired for a 240V input.

If your starting with 120V, you could relocate the generator to that point, at the 120V branch circuit, install a manual transfer switch, and power both transmitters from the same point.

Less equipment, more versatility, same 600V extension system.

MTW Ω

 

[kwired]

What am I doing wrong. The table says: Tie X3 to X1; Tie X2 to X4; Connect Secondary lines to X1-X4 for 120

Of course when you're 50+ your energy goes, then your eyesight.

I pointed this out in one of my PM's with you. Look closely at your two 5 kVA units on the 120 volt side, they should both be the same, your utility side unit is drawn as though it were connected to 240 volts but labeled as though it has 120 volts input.

I also mentioned in PM that the only "neutral" you have there is likely the one labeled "N" from the utility. All the other "N's" you have are not neutrals, if you ground them they are simply "grounded conductors".

Nothing wrong with switches in a grounded conductor - must simultaneously switch with the ungrounded conductors though. A circuit breaker with common trip will open both conductors at same time, you can not use a fuse in any grounded conductors though, if the fuse blows but the ungrounded conductor fuse doesn't you lose the grounded conductor.

 

[LarryFine]

What am I doing wrong. The table says: Tie X3 to X1; Tie X2 to X4; Connect Secondary lines to X1-X4 for 120.

It's a simple series or parallel connection, like a pair of batteries; do you want the higher voltage or the higher current?

 

[Installer]

Is it possible to install your 2nd 600V transmitter feed, from the point of the first 600V step up transformer?
And eliminate the 2nd step up transformer.
MTW Ω

Last week I was out with a backhoe operator and I got all the conduit and fittings in myself. Its true! 50 is the new 80.
Next week I'm meeting the electrician. I took your and Kwired's suggestion and redrew it with 3 transformers vice 4.
Ideally I think T1 should be 5 KVA and T2 and T3 should both be 3 KVA
Instead I have T1 at 5 KVA and T2 at 5 KVA and T3 at 3 KVA. due to logistics issues.
Will this cause a problem? Transmitter 1 draws 30 A and Transmitter 2 draws 10 A,
I guess I could do the math with all the transformer equations , but I'm thinking smarter people out there might know already.
I want to thank Kwired, Larry Fine and all for their help. I'm not a duffer, I'm a pretty hard worker and conscientious. I'm spending my own time to get this right.

 

[Installer]

Still confused on H. G, N on a transforner

Still confused on H. G, N on a transforner

I'm just being overly cautious I guess. And possibly I still don't understand.
This is my (incorrect?) thinking:
On the secondary side of each transformer, there's X1 and X4. You have to pick one as the neutral and ground it or you don't establish 120 VAC across X1 to X4.
However I don't think you have to do that on the H1 and H4 600 V side since you're not pulling a Load at that point. I drew Neutral to Ground bonding in Red because I don't think its needed.
How far out in left field am I?

I also mentioned in PM that the only "neutral" you have there is likely the one labeled "N" from the utility. All the other "N's" you have are not neutrals, if you ground them they are simply "grounded conductors".

N

 

[Installer]

Service Entrance Switch downstream of Utility

Service Entrance Switch downstream of Utility

This is the very first switch after the Utility and the 240/600 Transformer after that. Inside the switch there are Two Blacks and One White. Each of the two Blacks is switched, and the White bypasses the Switch. I didn't get a chance to pull the cover on the Transformer downstream of the Switch but I certainly will look at it very closely before we start. I think the two Blacks go to X4 and X1 on the transformer. I can't wait to pull the cover and see where the White goes.
Am I correct in expecting the White to be tied to ground along either X4 or X1 to establish 240?
I'm in my 50's but this kind of reminds me when I was twenty and I took part my first engine. Still like to learn new stuff and tinker

 

[MTW]

Pointers on the grounding and bonding connections.

Your red bonding jumpers on the drawing should be removed. For the transformer input coils, they should be provided a equipment grounding conductor with the incoming circuit. The EGC supplied with the circuit, will conduct fault currents from the input coil, and the transformer case if a fault were to occur in the input side. Bond the EGC to the transformer case, but not to the input coil. The supply side of the circuit, should already be bonded to ground at its source.

In your photo, at the beginning of the circuit, it appears that your EGC in the disconnect is provided by the enclosure, conduit, and a bonding bushing on the conduit. With all the nests in the disconnect, and the cropped view, it's hard to tell for sure what's in there. At any rate, you need to be sure you have a solid and proven EGC at the beginning of the circuit from the utility system. The downstream bonding and grounding depends on it.

The secondary coil is isolated or floating, it needs to be bonded to the supply circuit EGC, and a Grounding electrode system installed, for a earth reference. Two ground rods are the norm on an isolated outdoor installation. With equipment mounted on a strut rack, out in the field, I would bond that to the grounding electrode system as well. From this newly established grounding electrode system, you would then connect the next downstream transformer input ground, just like the first one. And would need another grounding electrode system installed at the 2nd transmitter transformer location

A white conductor is not needed or wanted, there is no neutral on a 240V 1Φ 2W transformer supply circuit. You need a green conductor for the equipment grounding conductor. White is not an acceptable substitute for an equipment grounding conductor, when using individual conductors.

In my 2013 GE catalog, they list two transformer models in your voltage use case 120/240 - 600V. One with taps, like your Acme drawing, and one without taps. You need to check yours to be sure what you have. Your transformer sizes appear to be adequate for the load values you gave.



For your transmitter #2, T3 transformer, I would put the disconnect at the transformer location, not 500' away, or both locations if you need that.

MTW Ω

 

[LarryFine]

On the secondary side of each transformer, there's X1 and X4. You have to pick one as the neutral and ground it or you don't establish 120 VAC across X1 to X4.

Not quite. You will have 120v between X1 and X4 no matter what, as long as the primary is energized.

What you accomplish by grounding one of them is establishing 120v between one of them and ground.

And, by extension, establishing 0v between the 'neutral' and ground, "stabilizing" the circuit voltages.

An internal short in a transformer could otherwise send much higher voltage into the secondary circuit.

However I don't think you have to do that on the H1 and H4 600 V side since you're not pulling a Load at that point. I drew Neutral to Ground bonding in Red because I don't think its needed.
How far out in left field am I?

You definitely should not have that bond in place! What if L1 is hot relative to ground? hmy:

It's up to the source of your power to determine which, if any conductor is to be grounded.

You bond (at) sources, not (at) loads. The same way you don't re-ground a neutral at a sub-panel.

 

[Installer]

Thanks all

Thanks all

GE part number 9T21B1016G02.
Thanks all for everything. In time. I'll be able to help others on this forum.

Not quite. You will have 120v between X1 and X4 no matter what, as long as the primary is energized.

What you accomplish by grounding one of them is establishing 120v between one of them and ground.

And, by extension, establishing 0v between the 'neutral' and ground, "stabilizing" the circuit voltages.

An internal short in a transformer could otherwise send much higher voltage into the secondary circuit.


You definitely should not have that bond in place! What if L1 is hot relative to ground? hmy:

It's up to the source of your power to determine which, if any conductor is to be grounded.

You bond (at) sources, not (at) loads. The same way you don't re-ground a neutral at a sub-panel.

 

[Installer]

This is the corrected version

This is the corrected version

The green bubble shows what I'm adding. Everything else is existing, although I am replacing the 3 KVA transformer with a 5KVA transformer on the existing stand at the Utility. At the new location I got some 4/0 and got the biack hoe operator to trench and somehow I got the 4/0 in there and I used a Hilti to drive 4 rods in.
50 is the new 80, as I said before