Jul 09, 2018
Written by: Ben Calendine, P.E., Parsons Electric
This article was written in June 2018 for the 2018 Quarter Three Newsletter.
The MN Energy Code is a new set of codes that focus on lighting and plug load control. There are currently two different standards for the MN Energy Code, IECC 2012 and ASHRAE 90.1. The Engineer of record is allowed to choose the code that best suits them. The IECC tends to steer towards new construction and has more stringent standards for mechanical systems while ASHRAE 90.1 steers more towards remodels but focuses more on lighting controls. Typically, in remodel situations, office buildings tend to follow the ASHRAE 90.1 because changes to the mechanical systems can be too intrusive and expensive. As I understand it, you can use either code in either situation, it's just that IECC has more expensive mechanical requirements while ASHRAE has more expensive electrical requirements. Electrical and Mechanical systems that remain largely unchanged do not need to adhere to new guidelines. Therefore choosing whether to use IECC or ASHRAE needs to be thought of from both an Electrical and Mechanical perspective.
With regards to lighting controls, they must be updated when you alter more than 10% of the existing lighting in a space whereas IECC 2012 has that number set at 50%. Both codes require vacancy sensing (manual on/auto off) for office, open office storage rooms, conference and multipurpose rooms, break rooms and training rooms. This can be accomplished by wall switches and ceiling sensors or by combination wall switches and ceiling sensors.
Daylight harvesting is also required in both codes. This requirement is that all lights within a certain distance from an exterior window, including skylights, dim or turn off with the level of brightness of the daylight. This is required in most rooms greater than ~200 square feet in a typical office space with the exception of specialty rooms. Also in ASHRAE 90.1 daylight harvesting is not required in private offices.
The last piece of the energy code is plug load control. This requirement is only found in ASHRAE 90.1 and it states that 50% of the receptacle loads in open and private offices need to be either controlled by occupancy or by time clock. This is a code that makes very little sense to us contractors. Workers can just use plugstrips to bypass the receptacles that turn off, which negates the purpose of minimum receptacle requirements within workspaces. I believe at some point this could get removed from the code for this reason.
As of right now, there is no entity specifically tasked with enforcing the energy code, every AHJ looks at it differently. Keep in mind, like smoke detectors and exit lights, energy code is a building code and not a part of the National Electric Code even though electricians are responsible for their installation. What I've found is the local city inspectors will look at it and enforce more strictly than the state inspectors will. Most state inspectors will say it is not their responsibility to enforce the code, unless the city specifically tells them to start enforcing energy code.
In the future, I don't see much changing with the energy code. I believe it's a good thing that keeps energy costs down even with equipment and lighting becoming more energy efficient. It takes a lot of the simple waste out of the equation. It is more expensive up front than normal switching, but the electrical savings over time and the company and the employees knowing they are trying to do their part in energy conservation make it worth the upfront cost. One thing I do think that could change is the elimination of the plugload controls. This can be easily bypassed by using a plugstrip in the receptacle that doesn't get automatically shut off.