Re: [EnergyPlus_Support] Tracking down temperatures too high

On Tue, Mar 8, 2016 at 10:05 AM, Jeremiah Crossett <jcrossett@xxxxxxxxxx> wrote:

My main question for the list is: Has anyone modeled a Thermally active slab system with tap water supply before or have any suggestions for objects that could be used to model this system? (It seemed rather easy at first with the temperature source object but has been rather problematic to get it to work as expected or to track down the issue so I am thinking to go back to the drawing board of sorts)Â

Many ThanksÂ

Jeremiah Crossett | Chief Technological OfficerÂ | NRGSIM INC.Â | www.nrgsim.comÂ |Â 7409 SW Capitol Highway Portland OR, 97219Â | 503-688-8951Â

On Mon, Mar 7, 2016 at 11:33 PM, Jeremiah Crossett <jcrossett@xxxxxxxxxx> wrote:
Hi, Jean,Â

Yes, it has been a bit difficult, but I have never met a model that can not be done!Â

When I last posted on this model you sent an example that used a chiller and boiler. I looked at it and followed your logic in a similar workflow as I have used in the past to use node and branch configurationsÂ but change out the plant object. This time however, it does not seem to be working as expected. I am fine with nodes and branches and have managed to setup systems without issues in the past, but for this project I am having a difficult time----->

Deciding the best objects to model the water plumbing line as the supply, near constant water temperatures from the water as a low temperatureÂ direct cooling supply and also as the source for heating with a heat pump.Â

I did notice that theÂ Â lowtemperatureradiant object and it was my first choice to use theÂ CentralHeatPumpSystem with aÂ ChillerHeaterPerformance:Electric:EIR object, however, oddly theÂ CentralHeatPumpSystem, in V8.1 dd not seem to work when properly setup, Â even the node manager in IDF editor did not find nodes- I figure it was just an IDD error but then extra warnings showed theÂ CentralHeatPumpSystem was an unused object so I gave up on that route and decided to get the cooled slab floors working with the outside air system and to do a separateÂ model for the heating season.Â Now it seems that the outside air system has issues with not having a controller that does not control a coil, so attempted to add a cooling coil on the same supply and the model has fatal errors, while the model with no cooling coil runs but has too hot of supply temperatures. How it has too hot of supply temperatures is the issue I am trying to track down in my model, as I do not see any issues, but do see very high temperatures. I first figured there was too small of a flow rate somewhere in the system, next looked for anywhere that there could be heat added and now have concluded that the issue must be with some type of system component, controler or availability manager but am having trouble tracking it down and would like to either rethink what objects to use or find the issue behid the too hot supply coming from the temperature source object supplyingÂ a constantÂ 17C autosizedÂ flow rate.Â

Attached is a svg from the last working version (no cooling coil, only TABS system as designed) and a doc from the client on the building. Below is a diagram of the active slab and the building. I am open to any work around or proper method, so long as it allows the thermal mass to be cooled and heated from the fluid loops and am very thankful for any insight anyone may have that will result in a resonable model. Thanks---->Â

They intend to use aâ??TABS-Thermally-Active Building Systemâ??Â https://www.ashrae.org/resources--publications/periodicals/ashrae-journal/features/using-building-mass-to-heat-and-cool-thermo-active-building-systemsÂ for heating and cooling and a mechanical ventilation.Â

Building in glass, 5 floors offices (OBj.A)! In Switzerland, Bioggio near Lugano.
Flat roof, U=0.373 W/m2K
(concrete slab + 20cm insulation U = 0.029 W/m2K)
Floor against outside - garage, Â U = 0.16 W / m2KÂ
(screed, insulation 4 cm, slab BA + under slab insulation: rock wool 15 cm
Glass facades, U =0.13 W/m2K
light transmittance = 24%
(Qbiss.Air, ref: QATT6: 6 chambers (5-chamber core
+ additional IGU, krypton)

Jeremiah Crossett | Chief Technological OfficerÂ | NRGSIM INC.Â | www.nrgsim.comÂ |Â 7409 SW Capitol Highway Portland OR, 97219Â | 503-688-8951Â

On Mon, Mar 7, 2016 at 9:42 PM, Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Â

Hi Jeremiah,

this sounds like a nightmare model. From what you say I should point out
- you can't have two lowtemperatureradiant objects in the same surface.
- you CAN both heat and cool with THE SAMEÂ lowtemperatureradiant object but not at the same tinestep.

Could you post an svg of your preferred HVAC setup?

Best regards,

Jean