Establishing electricity

I kept busy at the U.S. Green Building Conference and Expo, which was in town. While I was cruising the tradeshow floor looking for the latest developments in sustainable technologies, a young man walked up to me and said: “You are behind on your blog.”

Was I surprised? Hell yes! Did I get the hint? Let’s say yes to that one too.

Two weeks ago I talked about the service desert. The subject for today is about another service, the electrical main service.


The old main service into the house was a 100 amp line feeding three meters and subsequently three breaker panels in the basement.

The wiring in the panels was – let’s say – creative, and not necessarily safe. I had everything disconnected relatively early on. Later on, Cathy discovered the wire that was not running through the meters or breakers, but came directly from the main service.

electrical-main-service-01It’s time to replace the existing setup with a new main service to a bank with four meters (garden unit, 1st floor, 2nd floor and public areas) and new breaker panels.

There was some confusion to whether we need a 200 amp or 400 amp main service to the meters. The electrician recommended a 400 amp main service for three 100 amp panels and one 60 amp panel for the public areas (totaling 360 amp).

The design documents specified a 200 amp main service, as it is highly improbable that the users in all three units would ever get enough appliances going to get close to a 360 amp load. This is particularly true since our goal is that of energy efficiency and conservation.

The case was quickly settled by the building inspector, who has the last say in these things. I learned that 100 or 200 amp service to buildings like ours is typical. If anyone would like to install a main service larger than 200 amp, the building department requires a load schedule that lists all points of electrical use for each unit and their estimated electrical load.

With that clarification at hand and our goal of minimizing our electricity consumption we eventually got the 200 amp main service installed.

Moving on into the basement, we have the panel for the garden unit and the public circuits located right behind the electrical meters on the outside.


The other two panels are placed on the 1st and 2nd floor for easy and convenient maintenance access.

electrical-main-service-03 electrical-main-service-04

This layout does require us to install two disconnects to the 1st and 2nd floor in the basement (see image above).

We now have established electricity to the breaker panels. The next step is to run conduit and cables through each unit.

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

One thought on “Establishing electricity

  1. I’ve just been through this with my 3 flat:

    If you work through the full process, sizing the electrical service is an impressively complicated process. But the end result is that in Chicago (where we have natural gas for heating, cooking and clothes drying), for a 1, 2 or 3 residential unit (sanely sized) building, you’ll probably end up with a 200A service from ComEd.

    Technically, the 2008 Edition of the NEC (National Electric Code) made some changes, but this is still a very useful worksheet for practical, real-world sizing of a residential electrical service:

    Even treating each floor of the 3 flat as though it was a small, free-standing single-family house, and totaling them up, adding some basement and outdoor lighting loads, then adding two potential plug-in cars, I didn’t get anywhere near 200A. (From my research, the Volt, Leaf and Tesla are assuming that charging at 240v will draw something like 20A.)

    If you want a more extensive discussion for a single-family home calculation:

    There’s a link on the above page that discusses multi-family sizing based on NEC code requirements.

    The big idea with sizing the service is the simple reality that not everything in the house will be used simultaneously. That’s part of why “3 panels at 100A and one at 60A says you need a 400A service” is off.

    Also, keep in mind that the service is 200A at 240v. Most of the equipment/lighting in a residence is at 120v. A 100W lightbulb at 120v draws 0.83A. (That’s 100/120=0.83) But if that lightbulb was drawing 100W at 240v, then it would be pulling 0.42A. It’s confusing, but you always have to think about “how many Amps at what Voltage”.

    About those disconnects – when planning your electrical service, keep this in mind: you must have a disconnect within 5′ of where the service enters the building. That’s why there are those two disconnects – because the panels are distant from the “service entrance”, they have to be located just inside from the meters. When the meter feeds the panel as the other two do, the main breaker in the panel serves as the require disconnect.

    Finally: the panels themselves. I can’t make out which panels you used. Almost all electricians go with the cheapest electrical panels available from the reputable manufacturers for residential applications. They wouldn’t put that equipment into a commercial installation. I’m not sure why – the electrons don’t know if they are in a house or in an office.

    There is a long and unhappy history of using aluminum instead of copper for electrical conductors. AL is still the best conductor in certain circumstances, but in most CU is better. All the electrical equipment manufacturers have a “residential” grade line of breaker panels that use AL for the main bus. SquareD has it’s “Homeline” series, Cutler-Hammer has their “BR” series, and Siemens has one. (The AL is typically CU plated.) They also have a step up: for SquareD, it’s the “QO” series, for Cutler-Hammer, it’s the “CH” series and for Siemens, it’s the “Ultimate Load Center” line. These typically have a solid copper bus – often with an anti-corrosion tin plating. Also, these “better than bare minimum” panels use a better-built quality of circuit breakers.

    So – the better quality solid copper bus gets a tin anti-corrosion plating, but… the cheaper aluminum bus gets exposed copper plating? Hmmmm….

    These panels typically cost about $50 more than the bottom-of-the-line panels (and the breakers cost a bit more as you fill the panel). Yes, it’s probably overkill, but to me, it’s worth it to reduce the odds that I’ll have to track down corrosion in the panel or a failed breaker sometime in the next 10 or 20 or 50 years. Particularly when the panel is in the somewhat-damp conditions of an old house basement…

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