480 Volt Delta System

fjsmith007

New member
Location
Connecticut
I'm hoping some one can help me with this - In the Northeast until about the 1970 most water and sewage pump stations were fed with either a 240 or 480 volt Delta voltage with the "B" phase being grounded. These systems are not being supported by the utilities any more and when they fail they are generally replaced with a wye system. We are doing a small upgrade in a water pumping station that has a 100 amp. 480 volt service with the "b" phase grounded.

The main circuit breaker is a 3 pole 100 amp unit in it's own enclosure that feeds a small Main lugs only distribution panel that is single phase. The center phase in grounded inside a CT cabinet (that is technically owned by the utility)that is located between the Main C/B and the distribution panel. The grounded phase is terminated on the neutral bar. The grounded phase wire has been color coded white.

My questions are:

What would be the most correct colors for the individual phases?

Inasmuch as this is a water pump station should the service be grounded to the water main as well as the existing driven ground?

Currently the branch circuit ground conductors are terminated on the neutral bar. Shouldn't they be installed on a separate ground bar?

Hopefully I got this into the correct forum.

Thanks for your help..
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
What would be the most correct colors for the individual phases?
If there are two system voltages then they need to be distinguished from each other. The NEC does not require us to use any color scheme but it does require us to identify the color scheme used for each system at the main service.

Inasmuch as this is a water pump station should the service be grounded to the water main as well as the existing driven ground?
If there is 10' of metal pipe in the ground it must be used as an electrode. If the metal pipe is used as an above ground piping system then yes it must be bonded also.

Currently the branch circuit ground conductors are terminated on the neutral bar. Shouldn't they be installed on a separate ground bar?
If this is the main panel (service equipment) then the neutrals and equipment grounds must be bonded together
 

augie47

Moderator
Staff member
Location
Tennessee
I'm hoping some one can help me with this - In the Northeast until about the 1970 most water and sewage pump stations were fed with either a 240 or 480 volt Delta voltage with the "B" phase being grounded. These systems are not being supported by the utilities any more and when they fail they are generally replaced with a wye system. We are doing a small upgrade in a water pumping station that has a 100 amp. 480 volt service with the "b" phase grounded.

The main circuit breaker is a 3 pole 100 amp unit in it's own enclosure that feeds a small Main lugs only distribution panel that is single phase. The center phase in grounded inside a CT cabinet (that is technically owned by the utility)that is located between the Main C/B and the distribution panel. The grounded phase is terminated on the neutral bar. The grounded phase wire has been color coded white.
IMO, to comply with Code you will need to do some updating. When POCO changes to a wye system, 250.24(C) requires you to bring a grounded conductor to the service disconnect point (and bond it).

My questions are:

What would be the most correct colors for the individual phases?
No particular color is required for the phases, however they can not be white, grey or green

Inasmuch as this is a water pump station should the service be grounded to the water main as well as the existing driven ground?
Yes, the grounded conductor should connect to a grounding electrode system, including the water pipe and driven ground rod



Currently the branch circuit ground conductors are terminated on the neutral bar. Shouldn't they be installed on a separate ground bar?
The neutral and grounding connection can only be made at the service disconnect. After that point they must remain separate.
Hopefully I got this into the correct forum.

Thanks for your help..
(sorry Dennis, you typed quicker)_
 

kwired

Electron manager
Location
NE Nebraska
I'm hoping some one can help me with this - In the Northeast until about the 1970 most water and sewage pump stations were fed with either a 240 or 480 volt Delta voltage with the "B" phase being grounded. These systems are not being supported by the utilities any more and when they fail they are generally replaced with a wye system. We are doing a small upgrade in a water pumping station that has a 100 amp. 480 volt service with the "b" phase grounded.

The main circuit breaker is a 3 pole 100 amp unit in it's own enclosure that feeds a small Main lugs only distribution panel that is single phase. The center phase in grounded inside a CT cabinet (that is technically owned by the utility)that is located between the Main C/B and the distribution panel. The grounded phase is terminated on the neutral bar. The grounded phase wire has been color coded white.

My questions are:

What would be the most correct colors for the individual phases?

Inasmuch as this is a water pump station should the service be grounded to the water main as well as the existing driven ground?

Currently the branch circuit ground conductors are terminated on the neutral bar. Shouldn't they be installed on a separate ground bar?

Hopefully I got this into the correct forum.

Thanks for your help..
Rules of grounding and grounded conductors do not change. A grounded service conductor of either system is brought to the service equipment. That conductor is required to be bonded to service equipment enclosure and a grounding electrode system is to be installed for either system. After the service point or disconnect for a separately derived system, the grounded conductor must be separate from equipment grounding conductors. What is different is the 4 wire system includes a neutral conductor.

In your installation you will need to install a fourth conductor between the point of supply and the service disconnect. You will need to reidentify the current grounded conductor if it becomes an ungrounded conductor.

Your single phase panel will need to be changed to a three phase panel if it is supplying three phase loads and a separate equipment grounding conductor will need to be run, as well as a separate grounded conductor if any load is added that requires a neutral. There will be no existing load that requires a neutral because you did not have a neutral originally - if there was any 120 or 277 volt loads (you did not specify which system you actually had) they would have had to be separately derived.

As Dennis mentioned - there is no color code requirement if only one voltage system exists. Grounded and grounding conductors are the only ones that require specific colors in all systems.

Utility company will have to rework their metering equipment and remove any bonding between any ungrounded conductors and the metering cabinet.

Grounding electrodes and other grounding requirements do not change other than a different system conductor is what gets grounded.
 

kwired

Electron manager
Location
NE Nebraska
IMO, to comply with Code you will need to do some updating. When POCO changes to a wye system, 250.24(C) requires you to bring a grounded conductor to the service disconnect point (and bond it).
That should have been done originally. The only difference with the change is a fourth conductor is needed (we now have a neutral to the system) and it will become the conductor that is grounded, the previously grounded phase if properly installed should only have been grounded at the service equipment. The (so called) neutral bar in his existing single phase panel should not have been bonded to the enclosure to be proper. The only way to make that panel work now will be to change it to a three phase panel as there will now be three ungrounded conductors and overcurrent protection will be needed for all those current carrying conductors that were on the grounded phase before.


One other thing that needs some consideration - if this was a 240 volt system before and will become 208 volts - motors will draw more current than they did before. If POCO does not want to replace with corner ground but offers 240 volt delta with a neutral (and wild leg) I would consider that if it will make some difference with what you have there.
 

kwired

Electron manager
Location
NE Nebraska
I'm unsure if that changes anything I said, but I agree with it.
People seem to be confused by corner grounded systems. The grounding rules are no different than for systems with a neutral. You have a grounded conductor (is typically current carrying if it is a grounded phase). You bond it and connnect a grounding electrode system to it at the service equipment. From the service equipment (or from main bonding jumper of a separately derived system) you keep the current carrying portions of that grounded conductor isolated from equipment grounding conductors to avoid possible objectionable current from flowing through unintended paths.

There was a grounded conductor brought to the service equipment to start with and it should have been bonded.
By changing to a system that utilizes a neutral - you still have a grounded conductor - just not A,B, or C anymore, and you should have needed to add one more conductor to the service entrance conductors. If things were done correctly to start with, beyond the service entrance little should need changed with the exception of the single phase panel used in the OP's situation.

Anyone want to bet on whether or not the breakers in the OP panel are straight 240 volt breakers or if they are 120/240 volt rated breakers? Remember in the corner ground system there is no 120 volt capabilities.
 
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