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Misc vs plug loads

asked 2023-03-16 06:24:31 -0500

jferamo89's avatar

updated 2023-03-16 06:27:46 -0500

Hi there,

I am currently carrying out an energy model for an office building. I would like to include the receptacle loads for the equipment but I am unsure which could be the right approach. I have found two main sources that are recommended in many cases but in some cases, they contradict each other. I would like to understand If I am interpreting these two concepts wrongly and if they refer to different loads, or are just the same. The sources I am referring at are the ASHRAE 90.1 Addendum Schedules and Loads and COMNET appendix B available here:

In the ASHRAE 90.1 the term Misc loads is being used, for offices a value of 0.75 W/ft2 is being set, which I belive it is quite reasonable considering the actual standards. I COMNET the term Plug Loads is being used. I have always thought receptacle, plug, equipment and misc loads refer to the same thing. In COMNET appendix B offices appear to have 1.67 W/ft2, which is much higher than those considered by ASHRAE. Furthermore, if I use the plug loads tsd calculation I obtain 2.2 W/ft2, which is an even larger number. But I would like to double check this interpretation and have your feedback. I am a bit confuse on which could be more certain, mainly due to the large difference between them and the terms used. Since this is a warm shell office space, I will not know the number of equipment that will be installed there, and therefore I have to make an assumption. Have you faced this issue before? which could be the best approach for these cases? is there any difference between these terms which explains the large difference? is ASHRAE misc loads at a building level (including storage, lobby, parking,...) and COMNET at a zone level?


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answered 2023-03-16 09:15:13 -0500

Keigo's avatar

First of all, plug loads depend on projects. They are normally designed by MEP engineers. You can use those reference plug loads only when they are not designed yet e.g. projects in conceptual design phase.

The difference between 0.75W/ft2 and 1.67W/ft2 is that 1.67W/ft2 includes server loads in a office building.

Please refer to the Scorecard of Large Office for ASHRAE90.1 in the following website.

Prototype Building Models

image description

In "Zone Summary" sheet, you can see that the plug loads for office zones are 0.75W/ft2, and there are another loads of 20W/ft2 and 40W/ft2 for data center zones. The average loads for the whole office building are 1.661W/ft2 ≈ 1.67W/ft2.

image description

Therefore, 0.75W/ft2 is considered appropriate for office space without servers or office space with servers in a different location of the building. 1.67W/ft2 is considered appropriate for office space with servers in the same space Or for an office building as a whole if your model is a simple shoe box.

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Asked: 2023-03-16 06:24:31 -0500

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Last updated: Mar 16