At BIG RED DOG we often receive questions about utility transformers and how they interact with the footprint of a new, and sometimes existing, building. To aid our BIG RED Blog readers, we’ve put together a few of the more common questions regarding pad mounted transformers, and their associated answers.
Question: How big are they and what footprint do I need to design around?
Answer: Depending on the size and requirements of your building, transformers come in a variety of sizes. However, when it comes to placing your transformer, Austin Energy requires that your pad mounted transformer sit on a ten foot by ten foot concrete pad, regardless of size. Regarding footprint, Austin Energy also requires a 5’ clearance on three sides of the transformer pad and 10’ clearance on one side. That clearance footprint ends up being a 20’ x 25’ rectangle that no other service can go underneath or above. That is a significant amount of real-estate, so plan your building accordingly!
Question: Does Austin Energy prefer any specific locations for pad mounted transformers?
Answer: Austin Energy has a few guidelines that need to be followed when placing pad mounted transformers. For starters, it must be located within 6’ of a traffic or parking area so that an Austin Energy truck can easily access it for maintenance. In addition, the transformer pad must be stationed a minimum of 5’ from the building, 5’ laterally from any window or door, 20’ laterally from any fire escapes and 12’ vertically from any windows or ventilation ducts. Below is an example, included in the Austin Energy Design Criteria, to help display these required clearance spaces.
Question: What about other utilities? What do I need to know?
Answer: Pad mounted transformers don’t play nicely with other utilities. The 20’ x 25’ footprint clearance box extends both infinitely skyward and underground. This means, when placing a pad mounted transformer in a site’s footprint, no other utilities can cross underneath the transformer, including but not limited, to sanitary/domestic water, gas and telecom. As well, it’s important to consider the utilities potentially running overhead such as overhead electrical lines. For safety reasons, Austin Energy will not allow a transformer to be placed below overhead power or telecom lines. But don’t forget to also ensure nothing else impedes the transformer’s clearance, such as cantilevered buildings, mechanical equipment overhangs, etc. It is important to understand the existing utilities on the site before attempting to locate pad mounted transformers as well as understand where the transformer might go during building shape design.
Remember these are only some of the more frequently asked questions regarding pad mounted transformers in the City of Austin. For a comprehensive design guideline, Austin Energy issues a design criteria manual that addresses the many requirements to locating, procuring, setting and completing installation of a pad mounted transformer. Here is a link to that manual: Austin Energy Design Criteria 2015