Hybrid System - Definition?

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Trying to track down the definition of a hybrid system according to ashrae.
Does anyone know where that definition can be found?

Chris Flood

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Joined: 2011-10-02
Reputation: 400

Hi Chris,

I have a document that submitted to ASHRAE with a clear definition of an
hybrid system.


I hope that help.

Luc Delestrade

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Joined: 2011-10-02
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I've tried to find a specific definition before with not a whole lot of
luck. We've taken it as pretty much anything at is not purely sourced
from the electrical grid. The example that I always run into is primary
heating using a heat pump with a natural gas fired boiler as
backup/supplemental heat. So it would be an electric/fossil hybrid. If
anyone comes across an official definition I would be interested in
seeing it.

Brendan Hall, M.Sc.

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Joined: 2011-09-30
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That's how we've interpreted it also. Pretty much if it's not completely electric heat, it's hybrid (in terms of ASRHAE 90.1 App G)

William Mak, LEED AP BD+C

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Joined: 2011-09-30
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If this is for LEED Energy modeling baseline selection there are a few CIRs that allow you to model some types of Hybrid systems with an electric baseline if the gas heat source is not predominant.
For example if the OA unit is as heating and everything else is perimeter electric heating, the OA can be treated as preheat gas as long as it is consistent in both baseline and proposed design.


Arvinder Dang's picture
Joined: 2011-10-02
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Another hybrid system type common out here in the northwest is Packaged VAV with natural gas furnace preheat and electric zone reheat at the terminal units. It has always been accepted as a hybrid system through many LEED reviews/certifications.


Andrew Craig PE, LEED AP

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