Hotel Electrical System

[Spanish Engineer]

Thanks in advance for your help again.
I am making a project about hotel under spanish rules and USA rules. I have many doubts about american project and I need your point of view.
In my installation I consider a transformer at the beginning of electrical system "transformer 1".This transformer is 480Y/277 volts. This transformer feeds motors and other heavy loads (these loads have a supply voltage of 480 V 3 wire). After ot this, I have other dry transformer ("transformer 2") that is fed from "transformer 1". This last transformer is 208Y/120 volts for lightning loads and outlets.
I have tree questions:
1 - Is correct this diagram?
2 - can I take a 4 wire from "transformer 1" for a load where I need a neutral conductor?
3 - I need a emergency supply system (generator). where would the generator be placed? .I think parallel to "transformer 1".
Sorry for my bad english and thanks again for your replies.

 

[augie47]

Thanks in advance for your help again.
I am making a project about hotel under spanish rules and USA rules. I have many doubts about american project and I need your point of view.
In my installation I consider a transformer at the beginning of electrical system "transformer 1".This transformer is 480Y/277 volts. This transformer feeds motors and other heavy loads (these loads have a supply voltage of 480 V 3 wire). After ot this, I have other dry transformer ("transformer 2") that is fed from "transformer 1". This last transformer is 208Y/120 volts for lightning loads and outlets.
I have tree questions:
1 - Is correct this diagram?
2 - can I take a 4 wire from "transformer 1" for a load where I need a neutral conductor?
3 - I need a emergency supply system (generator). where would the generator be placed? .I think parallel to "transformer 1".
Sorry for my bad english and thanks again for your replies.

1. I believe so. On US installations your "transformer 1" is often suppled by the power company.
2. Yes 277 volt equipment would be supplied off "Transformer1" & neutral.
3. Depends on what equipmet you need to supply. Many generator installations do not supply the HVAC and other "heavy" loads to allow a smaller generator. You would need to size the genrator based on the load and voltage of the equipmemt you wish or are required to supply.

 

[wirenut1980]

3 - I need a emergency supply system (generator). where would the generator be placed? .I think parallel to "transformer 1".

The only thing I have to add to augie's post is:

Yes, your thinking is generally correct. The generator would probably supply loads fed from the "transformer 1" secondary. However the transformer and generator would not operate in parallel. For a hotel, you would generally have an open transition transfer (or a "break before make") switch between transformer 1 and the generator. In the US, there are also some specific rules for grounding depending on if the transfer switch switches the neutral or not.

 

[Spanish Engineer]

thanks for your help

thanks for your help

Thanks for your help.

 

[Spanish Engineer]

Specific Rules

Specific Rules

The only thing I have to add to augie's post is:

Yes, your thinking is generally correct. The generator would probably supply loads fed from the "transformer 1" secondary. However the transformer and generator would not operate in parallel. For a hotel, you would generally have an open transition transfer (or a "break before make") switch between transformer 1 and the generator. In the US, there are also some specific rules for grounding depending on if the transfer switch switches the neutral or not.

Please, where can I read the specific rules that you say me about grounding?.
Thanks again.

 

[wirenut1980]

Please, where can I read the specific rules that you say me about grounding?.
Thanks again.

You're welcome:smile:

The code book that specifies minimum wiring practices for safety, and that is legally adopted in most areas of the US is the National Electrical Code - NFPA 70.

 

[Spanish Engineer]

You're welcome:smile:

The code book that specifies minimum wiring practices for safety, and that is legally adopted in most areas of the US is the National Electrical Code - NFPA 70.

Thanks for all. In this moment, I am reading NEC 2005.

 

[Spanish Engineer]

Other question about Voltage Drop.

Other question about Voltage Drop.

Good day at all,

I continue with my questions, sorry for my insistence.
In other question, I asked about voltage drop. A person say me that voltage drop is in 210.19 a) FPN No.4 and other places. Under this text I think that the drawing is correct. Please if it?s correct you say me. In other case, please correct me.

|----------------MAXIMUM VOLTAGE DROP IS 5%---------------------|

--TRANSFORMER 1 --------TRANSFORMER 2 --SWITCHBOARDS -----LOADS
|
------------------SWITCHBOARDS ----- LOADS

|-----------MAXIMUM VOLTAGE DROP IS 5%--------|

For other hand, in Spain when we have for example one machine, I have four wires (phase R, phase S, phase T) and Neutral Conductor, and other wire that is protection conductor (ground). I think that in USA the neutral conductor and ground conductor is the same. Is correct?.
Thanks for your help again.

 

[augie47]

For other hand, in Spain when we have for example one machine, I have four wires (phase R, phase S, phase T) and Neutral Conductor, and other wire that is protection conductor (ground). I think that in USA the neutral conductor and ground conductor is the same. Is correct?.
Thanks for your help again.

This would be true for SERVICE conductors. Look at 250.24. Any panel other than the service panel may not have a grounded-grounding connection.
(There will also be a grounded-grounding connection on seperately derived systems such as your "transformer 2".)

 

[augie47]

Good day at all,

I continue with my questions, sorry for my insistence.
In other question, I asked about voltage drop. A person say me that voltage drop is in 210.19 a) FPN No.4 and other places. Under this text I think that the drawing is correct. Please if it?s correct you say me. In other case, please correct me.

|----------------MAXIMUM VOLTAGE DROP IS 5%---------------------|

--TRANSFORMER 1 --------TRANSFORMER 2 --SWITCHBOARDS -----LOADS
|
------------------SWITCHBOARDS ----- LOADS

|-----------MAXIMUM VOLTAGE DROP IS 5%--------|

.

Yes
Look at FPN 4 on 210.19 (a)(1)

 

[Spanish Engineer]

Thanks again.

Thanks again.

This would be true for SERVICE conductors. Look at 250.24. Any panel other than the service panel may not have a grounded-grounding connection.
(There will also be a grounded-grounding connection on seperately derived systems such as your "transformer 2".)

I think that I understand it. The SERVICE conductors would be the conductors before transformer 1. At the rest of the system, a grounded-grounding connection are not made. But, you say me that in transformer 2 is needed a grounded-grounding connection, but where?, from transformer 1 to transformer 2?.
Please Augie47 if you dont mind, please give me your mail and I send to you a good drawing about my installation. ok? and you help me about this.
I can help you about any information or books that I have get.
Thanks again for your help.

 

[augie47]

I think that I understand it. The SERVICE conductors would be the conductors before transformer 1. At the rest of the system, a grounded-grounding connection are not made. But, you say me that in transformer 2 is needed a grounded-grounding connection, but where?, from transformer 1 to transformer 2?.
Please Augie47 if you dont mind, please give me your mail and I send to you a good drawing about my installation. ok? and you help me about this.
I can help you about any information or books that I have get.
Thanks again for your help.

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