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aedg office hvac wshp doas - measure problems

asked 2014-11-03 11:03:13 -0600

jdunn gravatar image

updated 2015-11-12 15:37:24 -0600

Simulation community -

I'm having trouble using the "aedg office hvac wshp doas" measure. After creating a fairly simple model (5 zones, 5 stories) with pretty much all ASHRAE 90.1-2009 defaults, I attempted to use the aedg wshp whole building HVAC measure. It appears to work and specifies all of the equipment successfully, and even runs successfully, but my cooling unmet hours during occupied times are 4000+. Looking through the errors, it looks like these five are responsible:

* Warning * GetSpecificHeatGlycol: Temperature is out of range (too high) for fluid [WATER] specific heat * * ~~~ * ..Called From:CalcHPCoolingSimple:SourceSideInletTemp,Temperature=[228.47], supplied data range=[0.00,125.00] * ~~~ ** Environment=NEW ORLEANS LAKEFRONT AP ANN CLG .4% CONDNS DB=>MWB, at Simulation time=08/21 00:00 - 01:00

* Warning * GetDensityGlycol: Temperature is out of range (too high) for fluid [WATER] density * * ~~~ * ..Called From:FindCompSPLoad,Temperature=[234.74], supplied data range=[0.00,100.00] * ~~~ ** Environment=NEW ORLEANS LAKEFRONT AP ANN CLG .4% CONDNS DB=>MWB, at Simulation time=08/21 00:00 - 01:00

* Warning * CoolingTower:SingleSpeed "COOLING TOWER SINGLE SPEED 1" * ~~~ * Cooling tower water outlet temperature (-0.24 C) is below the specified minimum condenser loop temp of 1.00 C * ~~~ * Environment=RUN PERIOD 1, at Simulation time=01/02 16:00 - 17:00

* Warning * GetSpecificHeatGlycol: Temperature is out of range (too low) for fluid [WATER] specific heat supplied values * * ~~~ * ..Called From:PlantLoopSolver::UpdateAnyLoopDemandAlterations,Temperature=[-0.24], supplied data range=[0.00,125.00] * ~~~ ** Environment=RUN PERIOD 1, at Simulation time=01/02 16:00 - 17:00

* Warning * GetDensityGlycol: Temperature is out of range (too low) for fluid [WATER] density * * ~~~ * ..Called From:FindCompSPLoad,Temperature=[-0.24], supplied data range=[0.00,100.00] * ~~~ ** Environment=RUN PERIOD 1, at Simulation time=01/02 16:00 - 17:00

Upon looking at the cooling tower outlet temperature, see image below, it spikes in February and stays in the unreal 200 deg celsius range. I'm not sure what is causing this, and I've even tried it on a single zone, even simpler model, and I get the same error and results. So I'm not sure if its something on my part or if there is an issue with the script.

I've ran the "aedg office VHAC VAV with DX Cooling" and it works properly without any crazy temperature spikes or unmet hours.

image description

Any help is greatly appreciated! Here is a link to a zipped folder with the osm and run files in case it's helpful.

https://drive.google.com/file/d/0B6aA...

Cheers,

-jake

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ASHRAE 90.1-2007 or 2010?

Did you mean five zones per floor?

DancingDavidE gravatar image DancingDavidE  ( 2014-11-03 14:15:09 -0600 )edit

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answered 2014-11-03 14:51:07 -0600

Hey Jake,

I have had this issue before as well. Mine was fixed by changing the setpoint manger on the HP loop. I assume right now the boiler and cooling tower are in parallel with scheduled setpoint managers after each on. Try setting up the boiler and cooling tower in series, with a dual setpoint manger on the outlet node of the loop. This is a new object in OS and in my experience it controls the HP loop better then the way it is done in the AEDG measure. See the link to when I asked this question for more information.

https://unmethours.com/question/580/o...

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Thanks a ton for your comment! I tried to change the boiler/cooling tower configuration from in series to parallel in OS, and I also added a dual setpoint manager on the loop exit node (heating setpoint = 20 C, cooling = 30 C). However, i still get the same temperature out of range error. Not sure if I'm modeling it correctly in OS, but here's a picture of the configuration. I've also tried to run it without the single set point managers right after the cooling tower and boiler, still to no avail.

jdunn gravatar image jdunn  ( 2014-11-05 09:31:10 -0600 )edit

That configuration looks correct, and you shouldn't need the setpoint managers at the exit nodes for the boiler and cooling tower. The only other thing I can suggest is to try a different cooling tower, maybe one of the variable speed ones.

TaylorRoberts gravatar image TaylorRoberts  ( 2014-11-05 09:50:50 -0600 )edit
1

answered 2014-11-03 15:42:01 -0600

I had this in draft all afternoon, and now I like the prior answers that came before. But just in case those don't solve it...

The real-world scenario (obviously breaking down before reaching 200C!) is that the system can't reject enough heat that is being added to your system.

1) Can you also trend flow rate in addition to the tower's temperature?

2) What internal loads did you assume for the spaces? Could there be an error that is way overloading the space with heat gain'? You said the building ran with a VAV system though and the results were reasonable, so this probably isn't the fix.

3) Check your equipment capacities to be reasonable for this size building - cfm/sf, square feet per ton (add up all the heat pumps), square feet per ton of cooling tower, etc. Do these match up with the VAV system case?

4) The system seems to take a drastic turn for the worse at the beginning of February, are there any changes in occupancy schedules or equipment availability around that time?

5) Does the system have a boiler? If so, maybe get rid of the glycol.

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answered 2014-11-03 14:42:23 -0600

If you haven't already make sure you check the plant loop temperature inputs - max, min, exit, difference. The default temps are for a HHW loop.

image description

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Thanks for the help! I changed the min max to reflect the mixed water loop operating range, i.e. 30 C for cooling, 18.3 for heating. When I run the simulation it gives me the severe error:

* Severe * Plant temperatures are getting far too hot, check controls and relative loads and capacities * PlantLoop Inlet Node (SupplySide) does not have a Setpoint. * PlantLoop Inlet Node (DemandSide) does not have a Setpoint. * PlantLoop Outlet Node (SupplySide) does not have a Setpoint. * PlantLoop Outlet Node (DemandSide) does not have a Setpoint etc. etc.

jdunn gravatar image jdunn  ( 2014-11-05 09:41:47 -0600 )edit

Nice, sounds like you're closer to eliminating the errors...and maybe you need a setpoint manager.

MatthewSteen gravatar image MatthewSteen  ( 2014-11-05 09:53:31 -0600 )edit

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Asked: 2014-11-03 11:03:13 -0600

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Last updated: Nov 03 '14