Forum discussion
NC-2009 EAp2: Minimum Energy Performance
Hello Everyone,
Our resort project has 25 walk in freezers for food storage. After an inquiry I have a ruling stating that a door control sensor is not acceptable as an auto shut off mechanism under ASHRAE 90.1-2007 9.4.1.1. The light is set to shut off 7seconds after it closes in the current design. An occupancy sensor was suggested. Is anyone aware of other options that might fit the requirement for 9. 4.1.1?
Thanks for your help.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5915 thumbs up
February 9, 2017 - 11:12 am
A ruling from whom?
When people enter the cooler does the door stay open while they get (or put in) what they need and then leave? If so I would argue that your door sensor qualifies under 9.4.1.1 (c). It would probably save more energy than a motion sensor since the sensors typically have a longer delay.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
February 9, 2017 - 11:32 am
It should be considered that that the lighting type matters here. LEDs don't use the same start up currents and energy usage than T5 lights, for example and better sustain on off cycles.
Another problem is that walkin coolers' doors are often self closing, so a light that goes out when the person is still inside (because the door swings closed behind him) is not a good design. This would lead to users jambing the door open while they are in there, wasting the cooling energy.
An infra-red occupancy sensor should be robust enough, right?
John Covello
Senior Sustainability ManagerUL Solutions
9 thumbs up
February 14, 2017 - 2:48 am
Hi Marcus & Jean,
Thanks for your feedback.
I got my interpetation from ASHRAE on a Request for Interpetatiopn form. I has hoping someone had dealt with this before and might have heard of other alternatives than occupancy sensor. The ASHRAE Interpetation states:
Background: Our project is using door sensors for lighting controls for Walk in Freezers and Room Chillers. Do these qualify as an occupant sensor (Section 9.4.1.1b)? They would turn the light on when someone is inside, and turn off the light when it is closed. No one will be inside with a closed door.
Interpretation: A door operated sensor for a freezer room counts as an occupant sensor for Section 9.4.1.1b of ASHRAE/IESNA Standard 90.1.
Question: Is this interpretation correct?
Answer: No
Comments: A door sensor (switch) does not meet the intent or specific language/definition in the standard because it only senses whether the door is open or closed and not whether the room is occupied or vacant.
Also this comment from ASHRAE rep:
In a chiller space – such as a walk-in freezer – there needs to be an occupancy sensor or timer to control the lighting. The fact that it’s not regularly occupied highlights the reason for it.
Say someone leaves the lights on when they walk out of the freezer. If it’s unoccupied for 176 hours until the next person walks in, the lights will have been on the entire time.
Preventing that sort of un-needed illumination is why the requirement is written the way it’s written.
So the example of “no one will be inside with a closed door” isn’t always true. If there’s mechanisms to allow people to exit, then there must be times when people are in a freezer with the door closed.
We are looking into specialized occupancy sensors for freezers. There are some available on the market.