PTAC Baseline - low heat rejection use

7 posts / 0 new
Last post

Hello,

I am working on a Trace model that will eventually be a LEED submission.  My baseline system is PTAC (considered a residential building).  I believe I set up the system correctly in Trace, however the energy usage was not as much as I would have expected, compared to my proposed case(s).

Digging a little deeper, the PRM summary report breaks out the energy use for different catagories, and the "Heat Rejection" catagory is much much less on the baseline case.  This strikes me as quite odd, considering the heat rejection equipment is nothing more then an air cooled condenser.  I used the 90.1 minimum air cooled condenser in Trace.

I was wondering if there were any words of wisdom from the Energy Models braintrust on this.  I have hosted my model below.  Do I have the PTAC baseline set up correctly?

Garasaki's picture
Offline
Joined: 2011-02-16
Reputation: 1

Hello-

 

Hate to break it to you, but that link does not work for your file. I removed the link from the website since that was one of the most malicious sites I have been to in a while.

Anyway, you can attach the file directly to the forum (below where it says "attach new file") and I will check it out.

First thing I would say without looking at the file is that you should select the 90.1-07 min PTAC for equipment (which uses the condenser as mentioned). You probably did this already.

Bob's picture
Bob
Offline
eQUEST UserLEED AP BD+CTRACE 700 User
Joined: 2010-06-30
Reputation: 475

Boy I think I've looked everywhere and can't find a way to attach the file directly.  I can attach an image directly but not any other files.


But yes, I selected PTAC (90.1 07 min, new construction, greater then 15 mbh) as the equipment type.  I am just now looking more deeply into some other reports, and the building is maintaining the correct temperature, and has a reasonable cooling load.  Comparing all the usage figures, the only thing that sticks out as being unreasonable is the heat rejection usage, in particular the condenser fans.

Garasaki's picture
Offline
Joined: 2011-02-16
Reputation: 1

Hey Garasaki,  looks like we didn't have upload enabled for all users, now you should be able to upload the file.  Let us know if there are any issues.  Thanks

Joe's picture
Joe
Offline
eQUEST UserTRACE 700 User
Joined: 1969-12-31
Reputation: 400

Yay!  Ok here it is.


Where'd I go wrong on this baseline...

Garasaki's picture
Offline
Joined: 2011-02-16
Reputation: 1

Without looking at your file, I'm finding descrepencies with the PRM fan breakout in general. Not sure if I trust Trace700 in this manner yet, so I've been going oldskool with the PRM (csv) file Trace creates. Are you letting Trace do the PRM-2007 PRM calc's?

Be Sustainable -- Never let today use up tomorrow!.

Bobba_Fett's picture
Offline
eQUEST UserLEED EA Credit 1 TrainingTRACE 700 User
Joined: 2010-10-01
Reputation: 229

Hey Bobba-

Have you checked out the new fan report? It's based on the oldschool csv report you mentioned. I myself still like the csv, but new fan report is good.

I'd be interested if you have bounty hunted down any discrepancies!

Regarding the model itself; it isn't fully completed so it will have a number of difficulties in determining actual numbers at the moment.

Joe's picture
Joe
Offline
eQUEST UserTRACE 700 User
Joined: 1969-12-31
Reputation: 400