Utility pad mounted transformers (75-500KVA), is there a particular distance that they need to be from the building service (commercial)?

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Cartoon1

Cartoon1

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Florida
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Electrical Engineer
Hello. I have seen all kinds of distances of utility pad mounted transformers being installed from buildings main services. My understanding is that the maximum secondary length before first over-current device is 25 feet, unless it is outdoors. My question is there a maximum distance for utility exterior transformers to main service? Below is from my local utility standards and as shown highlighted it says 25 feet maximum, am i misreading this for something else? Thank you

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It's ahead of the meter, so it's pretty much up to the utility. Who will pull in the cable? Voltage drop could be a consideration. But regardless, if you need or want more than 25 feet, you will need to request this variance from the utility.
 
synchro said:
It looks to me like 25 feet is the maximum wire length between the CT's and the meter.
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You mean if the CT was in or by the transformer then meter on the building can be a maximum 25feet? if i understood that correctly.
 
Cartoon1 said:
You mean if the CT was in or by the transformer then meter on the building can be a maximum 25feet? if i understood that correctly.
Click to expand...
Not a very good document but I take as if the CTs are in the transformer or in a CT cabinet the CTs can't be more than 25' from the meter in any configuration.
 
Last edited:
From JEA's "Rules and Regulations for Electric Service 2021":

7.10 RACEWAYS FOR INSTRUMENT TRANSFORMER SECONDARIES
The customer shall provide a raceway from the instrument transformer cabinet to the meter
enclosure.
The raceways shall be 1½ inch or larger SCH 40 PVC (UV rated gray electrical). Conduit must
be effectively bonded to meter socket/enclosure. Electrical SCH 80 PVC (UV rated gray
electrical) is required where exposed to physical damage. The raceway shall be used solely for
the installation of instrument transformer secondaries. The raceway shall not exceed 125 feet
in length from the instrument transformer terminals to the meter test block terminals. This
distance is reduced to 25 feet when the CTs installed in padmounted transformer. All raceways
must have a pull wire in them strong enough to pull eight #12 AWG solid copper wire and one
#10 AWG stranded wire. A bond, connected from the customer’s single point bonding system,
must be supplied by the contractor at the CT location on overhead and underground services.
All bonding must be done in accordance with the National Electrical Code and local inspection
authority requirements.
 
synchro said:
From JEA's "Rules and Regulations for Electric Service 2021":

7.10 RACEWAYS FOR INSTRUMENT TRANSFORMER SECONDARIES
The customer shall provide a raceway from the instrument transformer cabinet to the meter
enclosure.
The raceways shall be 1½ inch or larger SCH 40 PVC (UV rated gray electrical). Conduit must
be effectively bonded to meter socket/enclosure. Electrical SCH 80 PVC (UV rated gray
electrical) is required where exposed to physical damage. The raceway shall be used solely for
the installation of instrument transformer secondaries. The raceway shall not exceed 125 feet
in length from the instrument transformer terminals to the meter test block terminals. This
distance is reduced to 25 feet when the CTs installed in padmounted transformer. All raceways
must have a pull wire in them strong enough to pull eight #12 AWG solid copper wire and one
#10 AWG stranded wire. A bond, connected from the customer’s single point bonding system,
must be supplied by the contractor at the CT location on overhead and underground services.
All bonding must be done in accordance with the National Electrical Code and local inspection
authority requirements.
Click to expand...
Well, the details always count. One needs to always study the entire document before drawing conclusions. Thanks for the research.
 
synchro said:
From JEA's "Rules and Regulations for Electric Service 2021":

7.10 RACEWAYS FOR INSTRUMENT TRANSFORMER SECONDARIES
The customer shall provide a raceway from the instrument transformer cabinet to the meter
enclosure.
The raceways shall be 1½ inch or larger SCH 40 PVC (UV rated gray electrical). Conduit must
be effectively bonded to meter socket/enclosure. Electrical SCH 80 PVC (UV rated gray
electrical) is required where exposed to physical damage. The raceway shall be used solely for
the installation of instrument transformer secondaries. The raceway shall not exceed 125 feet
in length from the instrument transformer terminals to the meter test block terminals. This
distance is reduced to 25 feet when the CTs installed in padmounted transformer. All raceways
must have a pull wire in them strong enough to pull eight #12 AWG solid copper wire and one
#10 AWG stranded wire. A bond, connected from the customer’s single point bonding system,
must be supplied by the contractor at the CT location on overhead and underground services.
All bonding must be done in accordance with the National Electrical Code and local inspection
authority requirements.
Click to expand...
This makes a lot more sense now, Section 7 it is. Thank you!!!
 
Cartoon1 said:
Hello. I have seen all kinds of distances of utility pad mounted transformers being installed from buildings main services. My understanding is that the maximum secondary length before first over-current device is 25 feet, unless it is outdoors. My question is there a maximum distance for utility exterior transformers to main service? Below is from my local utility standards and as shown highlighted it says 25 feet maximum, am i misreading this for something else? Thank you

View attachment 2568501
Click to expand...
That maximum length is just for the CT cable and not the secondary service conductors. The secondary service conductors can be as long as you want them, but we try and keep them as short as possible for cost to the owner.
 
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