ERV exception for Baseline

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Hi eQuesters!

I am modeling a Laboratory building with Fume Hoods (Climate zone 4A).

Per ASHRAE 90.1-2007 Appx.G 3.1.2.10, the baseline laboratory AHUs should
be installed with Energy Recovery (SA>2400L/s & OA 70%).
However, there are 'Exceptions' and one of which says as follow:

*h. Systems serving laboratories wish exhaust rates of 2400 l/s or greater.*

Does it really mean that the Baseline AHU is not required to have ERV if
the AHU has an exhaust rate(Not return) of 2400 l/s or greater??

I don't know the reason under that exception(h), but anyhow, that
will be beneficial for my proposed model which has ERV(sensible HX) for the
laboratory AHUs.

Any comment on this?

Thank you !!

Kim

DongEun Kim's picture
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Joined: 2011-09-30
Reputation: 0

without looking at 90.1 right off i can't tell you, BUT i would be
careful about how you input your ERV. especially how it is controlled.
an uncontrolled ERV in your simulation will negatively impact your
simulation. i.e. add cost to your proposed case. i would suggest
setting up a couple of eers to check different delta t (or enthalpy, or
both) depending on your project and location & go with what gives you
the best return. that is if you're part of the design team and not
after fact impart the best control strategy for the erv to the design
team/construction documents so you can use that in the leed simulation.
i am referring to an uncontrolled ERV as one that is on whenever the
supply fan for the unit it is attached to is on - and by 62.1 that 'on'
position is whenever the space is occupied, which is typically business
hours.

Patrick J. O'Leary, Jr.'s picture
Joined: 2011-09-30
Reputation: 200