[Bldg-sim] Residential System for High Ceiling house
Guillaume Jolly
gjolly at gfbris.com
Wed Feb 4 19:41:47 PST 2009
Hussein,
Best practice for building configurations that involve temperature stratification (atriums, high ceiling spaces etc...) is to design them using CFD for load and air distribution. If you regularly come across this configuration, it might be worth it to get a proper CFD study done on it. It must include heat transfer by radiation which become very important as the difference in temperature increase between the house sufaces.
It will clarify how the air distribution performs in the space, it will show what capacity you need and where you should locate the sensors. By helping to visualise what's happening in the house and comparing it with heat loads calcs, it will give you a feeling for things that you will be able to apply to your next projects.
Best Regards
Guillaume Jolly
George Floth Pty. Limited
CONSULTING ENGINEERS BRISBANE OFFICE
Ground Floor, 42 Doggett Street
Fortitude Valley, Brisbane. 4006
p +61 7 3252 0977
f +61 7 3252 2499
e gjolly at gfbris.com <mailto:gjolly at gfbris.com>
w www.gfbris.com <https://mail.gfbris.com/exchweb/bin/redir.asp?URL=http://www.gfbris.com/>
________________________________
From: Abaza Hussein [mailto:ahussein at spsu.edu]
Sent: Wed 04/02/2009 06:57
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Residential System for High Ceiling house
Hi all;
Can any one advice on the best HVAC system configuration for a house with a high ceiling in the great room (other than installing a fan in the ceiling). I have faced this problem many times. The way I was doing it is by over sizing the AC unit for the second floor, and over sizing the furnace for the first floor. But still, the thermostat in the second floor will not help in making the lobby of the first floor much cooler that what it should be. The same thing applies for the heating. Another way I was doing it is by having one system for the entire house and run the fan continuously, but this system is also in efficient, because I can not zone the house. Is there a better way to do it and is there any research in this area?
Thank you.
H. Abaza
________________________________
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Xiaobing Liu
Sent: Tuesday, February 03, 2009 11:41 AM
To: 'Bereket Nigusse'; bldg-sim at lists.onebuilding.org; Jeff Haberl
Subject: Re: [Bldg-sim] Residential System Sizing
Bereket:
There are many other reasons could explain the differences:
1. "System-Sizing-Ratio". For many system, eQUEST uses 1.15 "System-Sizing-Ratio".
2. Fan power. Different from space load calc, the system cooling capacity has to account for fan power heat as part of the cooling loads.
3. How about latent cooling? Have you accounted for latent cooling in your comparison?
4. Make sure the zones in LS-B and SV-A report are exactly the same. Has the loads from roof/ceiling be accounted for in the LS-B report?
I am surprised to see in your results that Minneapolis, MN has slightly higher cooling loads (20.3 kBtu/hr in LS-B) than Houston, TX (20.2 kBtu/hr in LS-B).
Jeff:
In your e-mail, you mentioned that "DOE-2 is known for doing a very bad job of sizing for residential". Is there any report/paper detailing this?
Xiaobing
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org]On Behalf Of Bereket Nigusse
Sent: Tuesday, February 03, 2009 5:32 AM
To: Joe Huang; Ellen Franconi; bldg-sim at lists.onebuilding.org; Jeff Haberl
Subject: Re: [Bldg-sim] Residential System Sizing
Hi All,
I am modeling a residential building with RESYS as a system, and using auto sizing for system sizing.
The space temperature (space design temperature) for load calculation is set at 75 oF while the Design-Cool-T is set at 78 oF. I believe that this has the effect of decreasing the system cooling capacity. There is no set-back or set-up applied. No ventilation outdoor air is specified. Infiltration, which is already captured in the building load calculation, is part of the building load.
How does the system cooling capacity increases by more than 50% (in the case of Minneapolis and Duluth, Minnesota) compared to the building peak load in the absence of any out door air load for ventilation?
Thanks,
Bereket
________________________________
From: Joe Huang <joe at drawbdl.com>
To: Ellen Franconi <EFranconi at archenergy.com>; bldg-sim at lists.onebuilding.org; Jeff Haberl <jeffhaberl at tees.tamus.edu>; Bereket Nigusse <nigusse_ba at yahoo.com>
Sent: Tuesday, February 3, 2009 2:16:32 AM
Subject: Re: [Bldg-sim] Residential System Sizing
Ellen,
Not exactly. What you wrote is definitely true during the SYSTEMS simulation and peak loads reported in SS-F (?), but Bereket was referring to the SV-A, which is the systems sizing report. Assuming that he's doing "auto-sizing", the DOE-2 sizing routine will take the peak loads from LOADS and compute the design cooling capacity at the COOLING-DESIGN-TEMPERATURE. (I may have the keyword wrong, since I don't have a DOE-2 manual handy). Thus, the termperature discrepancy between the single LOADS temperature and the COOLING-DESIGN-TEMPERATURE does exist, as you've mentioned, but transient loads due to tempeature set-up or set-back or interzone heat flows are not reflected. That's why an autosized SYSTEM will often still result in a few undercooled or underheated hours.
My suggestion to Bereket in making sense of the numbers is to compare the TEMPERATURE under SPACE-CONDITIONS for the LOADS reference temperature, to the COOLING-DESIGN-TEMPERATURE (I may have this keyword wrong) is ZONE-CONDITIONS in SYSTEMS. What kind of HVAC are you modeling? It sounds like a residential system (RESYS), but that system doesn't have any OUTSIDE-AIR, does it ?
Joe Huang
White Box Technologies, Inc.
----- Original Message -----
From: Ellen Franconi <mailto:EFranconi at archenergy.com>
To: bldg-sim at lists.onebuilding.org ; Jeff Haberl <mailto:jeffhaberl at tees.tamus.edu> ; Bereket Nigusse <mailto:nigusse_ba at yahoo.com>
Sent: Monday, February 02, 2009 7:50 PM
Subject: Re: [Bldg-sim] Residential System Sizing
Another reason that the results are different is that the space temperature may be different in the "loads" part of the DOE-2 program than in the "systems" part of the program. In "loads", the space temperatures are set equal to the space design temperate. In "systems", the space temperature is based on the zone setpoint schedule and whatever temperature is actually achieved in the space. Thus, if you have a set up or a setback from the design space temperature, it will be different.
Ellen
Ellen Franconi, Ph.D., LEED AP
Energy Analysis Group Manager
Architectural Energy Corporation
2540 Frontier Avenue
Boulder, CO 80301
tel. 303-444-4149
fax 303-444-4303
efranconi at archenergy.com
http://www.archenergy.com/
>>> Jeff Haberl <jeffhaberl at tees.tamus.edu> 2/2/2009 8:40 PM >>>
Bereket:
I would not expect the values in SV-A and LS-B to agree for most buildings. There are many reasons for this.
First, peak loads from LOADS do not include ventilation loads as would be the case in SYSTEMS, only infiltration.
Second, you may be looking at different days on the weather file between LOADS and SYSTEMS, so this would
need to be checked.
In addition, DOE-2 sizes for the absolute peak, whereas other methods, such as Manual J, have some undersizing
built into the procedures, hence you'll almost always get a much larger system size in DOE-2.
Both the SV-A and LS-B lists you show seem reasonable, with the exception of the MN #s, which I suspect that you
may have a fair bit of 24 hour infiltration in your input file...(i.e., low night time temps in MN?)
However, without looking at the file I can only guess.
There are 100s of reasons for the funny little differences you show. You're probabloy better off running a Manual J
calculation on the house if it is residential. DOE-2 is known for doing a very bad job of sizing for residential.
Jeff
8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) :=') 8=) 8=) 8=?
Jeff S. Haberl, Ph.D., P.E.............................jhaberl at esl.tamu.edu
Professor......................................................Office Ph: 979-845-6507
Department of Architecture.......................Lab Ph: 979-845-6065
Energy Systems Laboratory.......................FAX: 979-862-2457
Texas A&M University..............................77843-3581
College Station, Texas, USA.......................URL: www-esl.tamu.edu <http://www-esl.tamu.edu/>
8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) 8=? 8=) 8=) 8=)
________________________________
From: bldg-sim-bounces at lists.onebuilding.org on behalf of Bereket Nigusse
Sent: Mon 2/2/2009 5:59 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Residential System Sizing
Hello All,
I have a problem with DOE2.1E cooling system sizing. The cooling capacity reported by DOE2.1e in SV-A and LS-B reports are quite different and shows different sensitivity trends depending locations.
Question 1
For the case with out door air flow ratio input set to zero DOE2.1E calculated cooling capacity and the peak coolig load are shown below. I assume that the out door air contribution to the system load is zero for zero out door air fraction and with this assumption the system cooling capacity will be different from the peak cooling load only due to difference in ARI and the peak cooling load hour weather conditions. What else could cause the cooling capacity to be different from the peak load for zero out door air flow rate case? I have looked into to DOE2.1E manual but wasn't able connect the steps from the peak cooling load to the system capacity?
Question 2
Does the change from the peak cooling load to the system cooling capacity seem a reasonable for the different loacations given below?
The building is 2100 sqft conditioned floor area, two story, single family house. Each floor is modeled as a single zone.
Report AV-A Report LS-B
Locations Supply Flow, CFM Cooling Capacity, kBtu/hr Peak Cooling Load, kBtu/hr Outdoor DB Temp at Peak Load, oF Outdoor WB Temp at Peak Load, oF
Baltimore, MD 850.0 25.7 22.1 93 73
Houston, TX 813.0 27.0 20.2 93 78
Chicago, IL 1054.0 29.3 20.3 89 72
Minneapolis, MN 1226.0 33.5 20.3 89 79
Duluth, MN 1258.0 34.8 18.1 87 72
Phoenix, AZ 1281.0 37.4 31.6 114 71
Thank you in advance for the help,
Bereket
_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
________________________________
_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20090205/a48b3889/attachment-0001.htm>
More information about the Bldg-sim
mailing list