Cold Water Bond

[David Rogers]

I'm somewhat confused and could use some outside advise. I have a new building where we have a single electrical utility service feeding the building. There are two electrical services because one part of the same structure is a senior center and the other is a library. The senior center is fed with a 600 amp, 208v, 3 phase main breaker and the library is served with a 400 amp, 208v, 3 phase circuit breaker, but there is only one u.g. pull section and the main bus is rated for 1000 amps. The cold water entering the building is 80 feet away from the u.g. pull section and, therefore, the meters. There is only one entrance point to the building for water so the two factions will share the cost of the water bill and each will have their own electric bill.

We are having an in house discussion on the size of conductor to the water entrance point and the location where we will connect to the water pipe. We don't have the serving utilities wire size for using table 250.66 except that the representative of the serving utility said they were using 1000 aluminum. We installed 3-5" conduits for the secondary and we don't know if they are using 3 sets of 1000 or what. So, we are thinking we should base our water pipe bond on 1000 amps and come to our own conclusion.

Any input will be appreciated.

 

[pete m.]

Not sure I'm understanding your installation completely.

Are you saying that there are no service entrance conductors due to the utility supplying them?

If that is the case note 2 to table 250.66 may provide some guidance in sizing the GEC.

Pete

 

[David Rogers]

Cold water bond

Cold water bond

Thanks for the response. The building is not relative to 250-104, (2). We have a u.g. pull section and a meter/main and distribution for the senior center and one for the library. We don't know the feeder size because it is supplied by the serving utility and they have not completed their engineering so we don't have any drawings.

We were thinking we needed a #2/0 Cold water bond and we need to attached that bond within 10 feet of the point of entrance.

 

[pete m.]

Is there any way you can post a simple sketch?

It must be me, but in my mind it is sounding like the utility is bringing two laterals to the building.

Or, is the uitlity supplying one lateral to the UG handhole and then you take it from there to each meter/main combo?

Pete

If all else fails make your GEC 3/0 cu to the water line and call it a day.

 

[augie47]

With No service conductors you have to "guess".
If I understand you have one main section for service termination with a 600 and 400 amp service disconnect. In that case, your service conductors could be based on the calculated load.
If you were installing them and wanted to be anywhere close to a 1000 amp capacity you would end up with 1500 kcmil Cu or 2000 kcmil Al (depending on number of conductors, etc.)
POCO will no doubt use smaller conductors but you will probably end up close to a number requiring the maximum GEC of 3/0 Cu, ass Pete m notes.
If you need to install before POCO, you obviously will be safe with the 3/0 since it's the max.

Don't forget, if you building steel is a Grounding Electrode, you can connect service to steel and then steel to water and perhaps reduce the length of wire needed.