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Re: [EnergyPlus_Support] Re: Zone Radiant HVAC Mass Flow Rate equal to 0 but system controlling the room temperature. How???
Another point to consider is that the lowtemprad object WILL use the thermostat if you are autosizing it.
My advice with lowtemprad objects is to make sure the surface temperatures are what you expect. This is the most crutial point for realistic modelling.
As an intresting side note, e+ support has assured us that lowtemprad objects can be used with subsurfaces (like doors). This opens an important tool to draw a subsurface representing only the active area on the base surface (by assigning it the same contruction as the base surface or other for example) so that the correct surface temps are considered for condensation analysis. It's perhaps more conveniant than spliting the base surface up.
Mit freundlichen Grü�en- Sent from my iPhone (excuse the brevity)
i. A.
Jean Marais
b.i.g. bechtold
Tel. +49 30 6706662-23
On 12.06.2014, at 22:16, "<mailto:franlozano2@xxxxxxxxx>franlozano2@xxxxxxxxx [EnergyPlus_Support]" <<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
>
>
> Hi Luke,
> Firstly again, a thousand thanks for your help, it has been crucial for seeing the problem from new different
points of view and I finally solved it.
> I think that one of the best ways to thank this kind of contribution is giving my feedback in order to get a better
understanding of EnergyPlus operation.
> 1. Effectively, it seems that "Zone List Sensible Cooling Energy" variable is not working with radiant
components, although I don't know if the scope of this variable is only reduced for airside. I had already
checked the "Zone HVAC Cooling Rate" variable but it was zero while I had the problem. I think that every
output variable related with the "ZoneHVAC:LowTemperatureRadiant:ConstantFlow" was set to zero or
default value due to the fact that the execution of this component in EnergyPlus was like locked, I mean,
like if EnergyPlus had jumped until the end of his zonehvac programming lines and had left everything in
zero. I explain at the end what I think was the problem.
> 2. I agree with you in that EnergyPlus is "something particular", but in this case it wasn't necessary to fill
the "pump efficiency" field given that it finally worked.
> 3. Regarding the point 1., through your mention of that no every variables are for every systems, I realized
that the "Zone Predicted Sensible Load to Cooling Setpoint Heat Transfer Rate (W)", which I was using in
order to see if there was a cooling load in the building, needs in an indispensable way the addiction to the
model the "ZoneControl:Thermostat" object since the "setpoints" used in "ZoneHVAC:LowTem...."
components are only schedules.
> So, I have the "ZoneControl:Thermostat" only for knowing the value of this variable as well as the schedules
of the radiant component using for the real setpoint of the system.
> PROBLEM CAUSED BY:
> As I had a radiant floor terminal unit for the winter season in an analogous model, I used the same model
only changing from the heating mode to the cooling mode. As the radiant floor is an inertial system I could
set the same control temperature for turning on (21 C) and turning off (21 C) the system, I mean, for example,
if the room temp. is lower than 21, heat the room, when the temperature has reached the 21, the system is
shut down but the temp. in the room continues increasing by means the heat storaged in the concrete, so
that, with radiant floor it can be used the same temperature for giving the order of turning on or turning off the
system.
> The problem was that unlike the radiant floor system, the turning on and turning off temperatures
for a non-inertial system can't be set equal, so, I changed the high control temperature to 25,5 C
and the low control temperature to 24,5 C instead of 25 and 25 C as I had previously. At least, this
is what I observed it.
> I hope my explanation to be useful.
>
> Thank you very much indeed.
>
> Fran.
>
>
>
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