[Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

Tue Oct 13 16:37:06 PDT 2015

Mark,
I’d stick with Bill’s original suggestion. Run the model with “zero” OA and compare to the “proposed” case. Seem’s close enough to me… As Joe notes, in the end there can be some ambiguity about exactly how the total hourly coil  load should be apportioned. If you are curious about how the model works on an hourly basis, generate some hourly AHU reports (coil loads, MA and SA conditions), from the two runs. Do not just compare L- and S- loads reports. L- reports are at a constant temp, and in addition to OA, do not include any “false” loads from overcool/reheat, fan heat… I’m sure there are more.

One thing to check first; make sure your coil capacity with the OA is large enough to fully condition the air at each timestep. Also, for models that use it, set the “cooling coil/cool control range” to 0.1F or so to avoid possible small changes in the coil leaving air temps between runs.

I think Trace and HAP provide a “ventilation load” in reports they probably do some intermediate calculation each hour for the AHU w/ and w/o OA. They may even allocate it per zone.

Food for thought: In buildings without high exhaust flows, some of the “OA ventilation load,” imposed by OA at the AHU, actually offsets some infiltration load that would occur throughout the building if that OA was not brought in, or ended up in an ERV somehow. “Simple” simulation programs attempt to account for this with schedules that are applied to infiltration based on initial AHU operating schedules, however those infiltration schedules are not directly linked to OA schedules. I’ve seen “efficient” buildings that were not adequately pressurized because the nifty heat recovery ventilator exhaust fan used up all the air that would otherwise kept the building pressurized.

Fred
Fred Porter, BEMP, LEED© AP
Principal Engineer
Sustainability Services
NORESCO
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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Tuesday, October 13, 2015 1:58 PM
To: equest-users at lists.onebuilding.org
Subject: [External] Re: [Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

There are so many differences between what's reported in the LS-D and SS-D that I would not use this method for anything more than an extremely crude look at the load attributable to OA.  In Loads,  all the heat flows are calculated at the reference temperature (TLOADS) and counted as Cooling if the net space load that hour is positive or Heating if it's negative.  In Systems, these loads are corrected to the actual zone temperature and the load from OA and interzone heat transfer added, while solving for the zone temperature. If the zone temperature is outside the thermostat deadband, a deficit would be considered a heating load and an excess as a cooling  load on the HVAC system.

There's a much better way to get the OA load, but it would take some work, either with a User-Function, which unfortunately is not available in DOE-2.2 (although I've heard that Expressions could do much the same thing...), or by post-processing hourly outputs.  Print out an Hourly Report with the following parameters: Outdoor Air Temp (To), Room Air Temperature (Trm), Outside Air CFM, and the Zone Load.  Then, use Excel or awk ( my favorite :-) :-) ) to calculate the load due to the OA as (Trm-To)*CFM*Cp of air .  This can then be compared to the Zone Load, but you'll notice some anomalies  such as during the swing season when the OA Load is actually "free cooling".   You'll then have to decide how to attribute the OA heat flows to the HVAC loads, which can be tricky.

Various people, including me, Dan Fisher, Jason Glazer, etc., have wandered into this area of deriving component loads, and have found that it ultimately raises philosophical questions.  :-) :-)

Joe

Joe Huang

White Box Technologies, Inc.

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On 10/13/2015 9:02 AM, Keith Swartz wrote:
Good point, David. The system report adds more than just ventilation load to the space load.

Keith Swartz, PE | Senior Energy Engineer
Seventhwave | Madison.Chicago.Minneapolis
608.210.7123 seventhwave.org

From: David Eldridge [mailto:DEldridge at grummanbutkus.com]
Sent: Tuesday, October 13, 2015 10:47 AM
To: Keith Swartz <KSwartz at seventhwave.org><mailto:KSwartz at seventhwave.org>; Mark.Hallman at rwdi.com<mailto:Mark.Hallman at rwdi.com>
Subject: RE: [Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

I’m not sure if that will exactly give the ventilation loads – the “L” reports are the building space loads, but the “S” reports will include other system effects such as fan heat, reheat, heat gain to the return air, so that the difference might not exactly be a ventilation load, and might be pretty far from an OA-only load.

If there is a preheat coil, you can set up a report to trend that coil’s load if you are after the heating loads. You could trend the cooling coil load as well, but this is a function of economizer operation and outside air temperature as well.

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Keith Swartz
Sent: Monday, October 12, 2015 8:55 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

Mark,

Look at the differences between values in reports LS-D and SS-D. SS-D includes ventilation. LS-D does not. (The first letter “S” stands for “system.” “L” is for “load,” the load in the space.)

Keith Swartz, PE | Senior Energy Engineer
Seventhwave | Madison.Chicago.Minneapolis
608.210.7123 seventhwave.org

From: Shaun Martin [mailto:smartin at shaunmartinconsulting.com]
Sent: Friday, October 09, 2015 12:13 PM
To: 'Mark Hallman' <Mark.Hallman at rwdi.com<mailto:Mark.Hallman at rwdi.com>>; 'Bishop, Bill' <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

Hi Mark,

You can use hourly reports to pull out the outside air volume (variable PO) plus the supply and return volumes and temperatures. Then off to a spreadsheet.

Or, if you’re feeling ambitious, you could write an input function (see Topics).

Shaun

Shaun Martin LEED-AP, BEMP
Principal
Shaun Martin Consulting
#90 – 425 Carrall Street
Vancouver, BC  V6B 6E3
p. 604-789-1095

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Mark Hallman
Sent: Wednesday, October 7, 2015 7:59 PM
To: 'Bishop, Bill' <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>>; 'equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>' <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: Re: [Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

Thanks Bill, nice tip.  Any way of parsing it out without running two simulations?

Tx!
Mark.

mark hallman
p.eng. leed ap bd&c
project engineer

mdh at rwdi.com<mailto:mdh at rwdi.com>
519 823 1311 x2494
RWDI:  the science of buildings, structures & the environment.  See what we do HERE<http://www.rwdi.com/#%21services3/c1h0m>.

From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com]
Sent: Wednesday, October 07, 2015 11:12
To: Mark Hallman; 'equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>'
Subject: RE: % LOAD ATTRIBUTED TO OA DELIVERY

One way would be to create a MIN-AIR-SCH with all hourly values set to 0 (or 0.001 to activate economizer), apply it to all SYSTEMs and use the difference in the outputs.

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Mark Hallman
Sent: Wednesday, October 07, 2015 10:59 AM
To: 'equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>' <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] % LOAD ATTRIBUTED TO OA DELIVERY

Hi there,

Is there a way to accurately parse out from the eQUEST output file the percentage of the cooling and heating load that is attributed to OA delivery?   Any advice would be appreciated.

Thanks in advance!
Mark Hallman.

mark hallman
p.eng. leed ap bd&c
project engineer

mdh at rwdi.com<mailto:mdh at rwdi.com>
519 823 1311 x2494
RWDI:  the science of buildings, structures & the environment.  See what we do HERE<http://www.rwdi.com/#%21services3/c1h0m>.

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