[Equest-users] Baseline HVAC Single Zone Furnace Operation.

[Mark Darrall]

Hi!

G3.1.2.1 is pretty clear that for the baseline model you're supposed to use the minimum equipment efficiencies shown in Section 6.4. In other words, the single zone gas furnace you reference would be baseline-modeled per Table 6.8.1E, so a small gas furnace (<225 MBH) would be 78% AFUE.

So your equipment EEM in your design case would be the 94% furnace.

The only way I know this is because I'm working on a building with 6 of these little guys.

Good luck!

MARK DARRALL, AIA, LEED AP BD+C, NCARB
Senior Project Manager

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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol Gardner
Sent: Wednesday, March 30, 2011 8:59 PM
To: Kathryn Kerns
Cc: equest-users at lists.onebuilding.org; Steve Butros
Subject: Re: [Equest-users] Baseline HVAC Single Zone Furnace Operation.

Sorry I accidentally hit the send button.

I was saying, my take on modeling systems that Appendix G and the rest of Standard 90 don't supply specific requirements for is to make them reasonably inefficient. I say reasonably because it has to be within reason, so that you can't be accused of gaming the system. In this case you have further justification for using the modulating baseline as you truly don't have any information about staging,

Cheers,

Carol
On Wed, Mar 30, 2011 at 5:53 PM, Carol Gardner <cmg750 at gmail.com<mailto:cmg750 at gmail.com>> wrote:
Hi Kathryn,

Thanks for sharing your solution to the Georgia project. It sounds like a really good idea, simple yet effective. It's funny I don't think I would have thought of using 2 DOAS units, but why not?

WRT to the furnace. My ta
On Wed, Mar 30, 2011 at 1:59 PM, Kathryn Kerns <kathryn.kerns at bceengineers.com<mailto:kathryn.kerns at bceengineers.com>> wrote:
Everyone, I may have asked this before, but has anybody run across a section of ASHRAE 90.1 or LEED describing the operation of a baseline furnace in a PSZ unit? Do we assume the heating modulates or does it stage? And if it stages, how many stages? I have been modeling baseline furnace heating as modulating since that is what naturally appears in eQuest, but I wonder. I know in reality that a lot of small furnace heaters cycle to maintain space heat.

Also, I promised I would share results of my struggle to model dehumidification for a project in Georgia. I was sort of successful, I think. What I ended up doing was attaching 2 DOAS in series. The first DOAS had a cooling only heat pump and the second unit had heating only heat pump. The first unit handled the outside air and passed space/return air to the second DOAS.  The second unit supplied space/return air to the terminal units. This way I got to define set points for the first DOAS cooling supply temperature (space/return temperature) and the second DOAS heating supply (space/return temperature). The amount of energy consumed and size of each unit was adjusted to approximate a horseshoe dehumidification unit. It seemed to work.




Kathryn Kerns

Systems Specialist

BCE Engineers, Inc.

| Ph: 253.922.0446<tel:253.922.0446> | Fx: 253.922.0896<tel:253.922.0896> |



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--
Carol Gardner PE



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Carol Gardner PE
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