The ideal location for pad-mount transformer

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mehdi1351

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Location
New Zealand
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Electrical Engineer
Hello, I have two transformers, which are going to feed the two separate buildings. Each building has a dedicated main switch board (MSB). The question is:
1- Is it better to locate the transformer more close to the MSB, or its better to be more close to power pole connection point?
2- Do I have any authority to specify the location of the transformers, or this is something under POCO's decision?
3- The POCO is already ordered the two pad mount transformers and I have no idea on how they are going to feed them, i.e via radial feed or Loop feed. How could I know?
 
mehdi1351 said:
Hello, I have two transformers, which are going to feed the two separate buildings. Each building has a dedicated main switch board (MSB). The question is:
1- Is it better to locate the transformer more close to the MSB, or its better to be more close to power pole connection point?
2- Do I have any authority to specify the location of the transformers, or this is something under POCO's decision?
3- The POCO is already ordered the two pad mount transformers and I have no idea on how they are going to feed them, i.e via radial feed or Loop feed. How could I know?
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Meet with the poco engineer. Unless the customer owns the transformer, it is up to the poco engineer to approve the location of the transformer. The owner or their engineer usually meets with the poco engineer if a certain location is preferred.
 
Jim is spot on. Typically shorter low-voltage runs will be less expensive. Several utilities I have worked with don't allow the transformer to be more than 300' from your service equipment (probably your MSB in this case) due to voltage drop. Check with your PoCo and their guidelines for any additional transformer location requirements such as minimum distance from a building as well. Typically, you want your transformer to be at least 10'-0" from a combustible portion of the building (i.e. wood, windows, etc.).

As far as specifying location, for smaller projects, typically we will indicate where a transformer is desired on plans and submit to the PoCo for their approval. For larger projects, we usually have a meeting with the PoCo to determine those locations. To determine how the transformers are fed, I would recommend contacting the PoCo. The PoCo should assign an engineer to your project that would be tasked with determining that.
 
Regarding location, from my experience at least, more often than not the design team's architect has the strongest voice. To them, aesthetics outrank practical engineering, and for reasons that baffle me they don't think transformers are pleasing to the eye. Go figure!
 
jim dungar said:
In general you want to keep the low voltage run as short as possible, as you will have less voltage drop on the HV conductors.
The POCO will usually have extra charges for long primary circuits but they may be worth it.
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Very good point. This is exactly what I was looking to hear. So It needs a trade off between spending money on Secondary cabling (low voltage bigger conductor size) comparing with HV cabing (which is always part of POCO's scope of supply and installation).
 
Some of the rules of thumb I use for padmounts:

1) Away from parking traffic. Depends more on the nature of the business but if you expect a large parking lot like at a Target/mall then you might want to consider the flow of traffic and if it is likely someone will take it out. Similarly with shipping / receiving centers. Where trucks are larger and less likely to notice if they run through the bollard.

2) Location of the main switchgear(s) and trying to minimize the length of run. You can have heating issues in the UG runs if spaced too closely (typically at 2000A and up). You also get voltage drop to consider if it is far enough. More so depends on the secondary voltage.

3) If privacy to the company is a concern then put the padmount outside of the perimeter fence so the POCO doesn't need keys to get to the transformer. Then put the electrical room on the street side and a door to the street from the electrical room for their meter maid. Or outdoors with a gate for them.

4) Chemicals / air direction of refrigerants. Transformers are painted to protect their shell. That disappears with time in the sun and then you get the ammonia and other stuff creating rust. They will probably bill you for the replacement of it.

5) Sprinkler systems and related foliage. Same issue as the chemicals. The tree sap, leaf droppings, sprinkler water, etc. can increase harm and reduce the lifecycle. Roots can harm the pad. Some bushes and water systems that aren't pressured are fine. Like the drippers.
 
Elect117 said:
Some of the rules of thumb I use for padmounts:

1) Away from parking traffic. Depends more on the nature of the business but if you expect a large parking lot like at a Target/mall then you might want to consider the flow of traffic and if it is likely someone will take it out. Similarly with shipping / receiving centers. Where trucks are larger and less likely to notice if they run through the bollard.

2) Location of the main switchgear(s) and trying to minimize the length of run. You can have heating issues in the UG runs if spaced too closely (typically at 2000A and up). You also get voltage drop to consider if it is far enough. More so depends on the secondary voltage.

3) If privacy to the company is a concern then put the padmount outside of the perimeter fence so the POCO doesn't need keys to get to the transformer. Then put the electrical room on the street side and a door to the street from the electrical room for their meter maid. Or outdoors with a gate for them.

4) Chemicals / air direction of refrigerants. Transformers are painted to protect their shell. That disappears with time in the sun and then you get the ammonia and other stuff creating rust. They will probably bill you for the replacement of it.

5) Sprinkler systems and related foliage. Same issue as the chemicals. The tree sap, leaf droppings, sprinkler water, etc. can increase harm and reduce the lifecycle. Roots can harm the pad. Some bushes and water systems that aren't pressured are fine. Like the drippers.
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Thank you very much for sharing your experience.
What I understand from all of the comments is to prepare the site location plan and place the two transformer in a location that is more beneficial for us (in terms of less low voltage cabling etc) and then send that drawing to the POCO to see what would be their comment.
How would I know whether the feeding into the transformers are radial type or looped type? Is this something that I, as a user, have to determine for the POCO?
 
mehdi1351 said:
How would I know whether the feeding into the transformers are radial type or looped type? Is this something that I, as a user, have to determine for the POCO?
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No, they will decide that.

Usually the POCO field rep will guide you thru all the requirements and you will meet on site and find a mutually agreeable location for the transformers. Note you may be responsible for installing the pad and sometimes they will have a secondary handhole that you may need to provide and install, and you will pull you cables to that not the transformer. Metering is another thing you will need to find out. Some will meter at the spades of the transformer which is real nice.
 
Elect117 said:
Some of the rules of thumb I use for padmounts:

1) Away from parking traffic. Depends more on the nature of the business but if you expect a large parking lot like at a Target/mall then you might want to consider the flow of traffic and if it is likely someone will take it out. Similarly with shipping / receiving centers. Where trucks are larger and less likely to notice if they run through the bollard.

2) Location of the main switchgear(s) and trying to minimize the length of run. You can have heating issues in the UG runs if spaced too closely (typically at 2000A and up). You also get voltage drop to consider if it is far enough. More so depends on the secondary voltage.

3) If privacy to the company is a concern then put the padmount outside of the perimeter fence so the POCO doesn't need keys to get to the transformer. Then put the electrical room on the street side and a door to the street from the electrical room for their meter maid. Or outdoors with a gate for them.

4) Chemicals / air direction of refrigerants. Transformers are painted to protect their shell. That disappears with time in the sun and then you get the ammonia and other stuff creating rust. They will probably bill you for the replacement of it.

5) Sprinkler systems and related foliage. Same issue as the chemicals. The tree sap, leaf droppings, sprinkler water, etc. can increase harm and reduce the lifecycle. Roots can harm the pad. Some bushes and water systems that aren't pressured are fine. Like the drippers.
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Walmart violates rule #1, they put the transformer at the top of the truck dock ramp! Have replaced many a service conductor when a trucker hits the transformer knocking it off the pad! Thought I was going to get a good YouTube video when a small poco tried to lift the transformer three different times. Each time, the truck wasn’t big enough, so they would bring out another. They finally hired a local crane company!
 
charlie b said:
Regarding location, from my experience at least, more often than not the design team's architect has the strongest voice. To them, aesthetics outrank practical engineering, and for reasons that baffle me they don't think transformers are pleasing to the eye. Go figure!
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