From: Hirsch, Bruce R [mailto:Bruce.R.Hirsch@bge.com]

Sent: Wednesday, December 14, 2011 1:21 PM

To: 'Richard Parker'; Wes Patterson

Cc: Meyers, Aaron; Andrew Delaski; Alex Hofmann; Aris Marantan; Art Rosenfeld; Robert Berman; Brenda Edwards; Brian Coffey; Bob Smith; Chris Bold uc; Caitlin Johnson; Carlos Gaytan; Charlie Drexler;

Chris Brown; Simmons, Chuck; Clark Silcox; Charlie Stevens; Dan Cohen; Millure, Dave; David Flaten; Daniel Young; Emily Marchetti; Eric Peterson; Gary Fe rnstrom; Greg Rosenquist; Greg Coulter; James Lass; Jennifer Tiedeman; Freeman, Jeremiah; Jerry Corkran; Jerry Schoen; Jerry Hodge; Creevy, Jim; Jim Raba; Joanna Mauer; Caskey, John; John Cymbalsky; John Rossetti; Katie Coughlin; Ken Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Mich ael Hyland; Michael Rivest; Meg Waltner; Pamela Costello; Ryan, Paul; Phil Harter; Phil Hopkinson; Pu esh Kumar; Polinski, Raymond; Rob Greeson; Rick

Anderson; Bob Saint; Robert van Bu skirk; Robin Roy; Scott Beck; Steve Nadel; Steve Rosenstock; Tim

Ballo; Tom Eckman; Ted Johnstone; Thomas Petrosino; Zhimei Luo Subject: RE: Dry Type Transformers

Dry Type Transformers

– Commonwealth Edison uses dry type transformers in high rise buildings. I have

copied some of their comments and attached documents covering size and weight restraints as part of

this email. The issue is in the replacement market. If an existing transformer needs to be replaced, there

may not be room for a larger transfor mer or the ability to transport a heavier transformer to upper level

transformer rooms.

Bruce

ComEd installs medium voltage dry-type transformers in building vaults and building electrical closets as

follows:

 Single phase – 75 kVA – 833 kVA, 7200/12470GrdY – 120/240 V and 7200/12470GrdY –

277/480Y V

 Three phase – 112.5 kVA – 2500 kVA, 12470 – 208Y/120 V and 12470 – 480Y/277 V

The usage over the last five years is as follows:

 Single phase – 671 transformers (approx. 134 per year)

 Three phase – 454 transformer (approx. 91 per year)

I have attached an e-mail with a letter that ComEd subm itted earlier this year to the DOE regarding the potential impact of increased efficiencies. The followi ng is an excerpt from that letter regarding dry-type and network transformers installed in buildings. ComEd has very specific limiting dimensions and weights in its dry-type and network transformer specifications.



### The building vaults are designed on an individual basis. The equipment opening is designed to meet the cust omer's ultimate transfo rmer capacity requirement.

ComEd utilizes a table of dimensions and weights based on historical transformer designs of different sizes used as a guide to determine the size of equipment opening

needed to meet the ultimate tr ansformer capacity requirement.

The building vault structure is owned by the customer. The customer typically provides the smallest vault possible that still meets the ComEd requirements in order to reduce costs. The equipment opening is designed to meet the ultimate transformer capacity

### requirement with a typical clearance of only a few inches. Additionally, larger transformers may not be able to be m aneuvered through building hallways. A slightly larger transformer as a result of increased efficiency would potentially cause severe problems when replacing an existing transformer with respec t to the equipment opening. A slightly larger trans former as a result of incr eased efficiency installed in an existing building vault may violate certain co mpany operating clearances inside the vault and possibly be deemed a safety issue. A slight ly heavier transformer as a result of increased efficiency may cause severe problems if it exceeds the loading capacity of floors and elevators used to transpor t the transformer to the vault.

The customer would have the burden of pr oviding a larger opening and facilities (elevators and floors) needed to support a larger and heavier transformer which may result in an extended outage and a lar ge cost incurred by the customer.

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