[Equest-users] High throttling setting and KW/CFM calc

[MatthewRLarson at Eaton.com]

The virtual rate is a straight $/unit rate for each utility, so $/kWh and $/therm for electricity and natural gas.  The reason they are different in this case is due to a monthly charge that is applied to each utility no matter the amount of energy used.  You can see this in the utility rate properties.  So your charge to units is not exactly proportional because of that monthly charge.  Having a demand charge for kW would also have an effect on your virtual rate.

 

Regarding the Pumps and Aux usage, this is coming from your Crankcase Heat that is associated with your DX cooling for each system.  This input is under Cooling, Unitary Power, Crankcase Power.  There are a number of these kind of parameters that end up in the Aux part of Pumps and Aux usage.

 

Thanks,

 

Matthew Larson, LEED AP BD+C
Project Engineer

Energy Solutions Group

E M C Engineers, Inc.
Eaton's Electrical Services & Systems 
143 Union Blvd, Suite 350
Lakewood, CO 80228
tel: +1 303 328-3419
mobile: +1 303 668-2511
fax: +1 303 974-1239

MatthewRLarson at Eaton.com 
www.eaton.com/energysolutions  

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Travis Miller
Sent: Tuesday, March 08, 2011 2:07 PM
To: Greg Collins; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] High throttling setting and KW/CFM calc

 

Greg, it looks like it was all in the zoning. Designating the trouble areas with their own system allowed me to reduce the throttling range to a more reasonable number (I left it at 2°). Thanks for your help.

 

I have a couple of other issues that I can't figure out. Looking at the ES-D report, it looks like the virtual rate between the proposed and baseline case are different. Why would that be? Everything is set to the local energy company and nothing has been changed in the utility and economics tab. Not exactly sure what a virtual rate is to be honest. 

 

The other question I have is with regards to some energy usage showing up on the baseline model under pumps and aux. The baseline model does not have any pumps associated with it. Any thoughts on what exactly the auxiliary load is accounting for? 

 

Thanks again for your help.

 

Travis

 

 

 

From: Greg Collins [mailto:GCollins at glumac.com] 
Sent: Tuesday, March 08, 2011 12:58 PM
To: Travis Miller; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] High throttling setting and KW/CFM calc

 

Travis,

 

Bumping your throttling range up will definitely reduce your unmet cooling/heating hours, but it's not usually the correct approach to do so.  You're basically saying that the system is trying to maintain 75°F in cooling (hypothetically), but the cooling demand is met as long as it's less than 75 + 8°F = 83°F.  Is 83°F a comfortable temperature for your occupants?  Probably not.

 

I'd check to make sure you have adequate zoning by looking at the SS-R report and seeing if the unmet hours are similar between the spaces in your zone.  What can happen is your system will maintain temperature in the control zone (where the thermostat is) and the other spaces can suffer.  If all of the spaces have unmet hours, your system capacity might off.  There are lots of things that could be wrong, but the reports are your best friend while troubleshooting..

 

Regarding your kw/cfm calc - I didn't look at it, but the number looks reasonable if you're modeling a 90.1 baseline system.  If you're modeling an actual design, you want to use the kW (from bhp) your fan is operating at during the design condition.

 

Greg Collins
GLUMAC | (949) 833-8190

 

From: Travis Miller [mailto:tmiller at dcengineering.net] 
Sent: Tuesday, March 08, 2011 11:14 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] High throttling setting and KW/CFM calc

 

I am looking for a little help in trouble shooting a couple of setpoints on the attached model. 

 

The first concern I have is my throttling setpoint. I have it 8 degrees right now. The reason for that was to eliminate unmet cooling hours. Is this a feasible approach? Is there something else that I should be looking at?

 

Second - Fan design KW/CFM - after reading through the archives I have figured out that I just need to restore the defaults in the static in WG box to allow the KW/CFM box to become active. Is the next step just to calculate the bhp for each unit per table G3.1.2.9, then calculate fan power from section G3.1.2.9? 

 

I did this for my first unit and got a value of .000768318 KW/CFM. This was for system S1 with a baseline "design" (from the air side summary report) CFM of 1,986 CFM.  Does that seem like a reasonable #? I have attached my calc spreadsheet for reference, it is a little crude but I think it is correct. 

 

Thanks again in advance.

 

Travis

 

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