I thought no one would use a 2 pipe system with Type4 theremostat operation. It usually takes two days to switch over the chiller to the boiler system in a building. The water to water heatpump can change over quickly at the system level, but will be for a smaller installation where the pipe and coil volume are relatively small.
For transition period, most two pipe fan coil unit has an electric heater to bridge over the cold nights, after the system has been switched to cooling mode.
I said that the EPlus does not simulate the pipe system because they are usually entered as Pipe:adiabatic. The suggestion of using a storage tank is a work around, so that the volume and environment can have some values. What I had in mind was to place the tank in a core zone. The heat will exchange with the zones as the pipes, and when all the zones are off, the plant will cycle this tank on and off.
This will simulate the condition in a building with the pipes in a riser.
If you do use the detailed Pipe:Indoor, then all the risers and feed length would need to be modelled. I do not think any one would like to do that.
Once you have estimated the pipe and coil volume, the thermol storage tank model can provide some reasonal number. The tank can be left in the simulatin in a suitable core zone as an parasitic heat source which will change the PLR of the fan coil unit as in a real building.
The water temperature of a real zone 2 pipe system is not from 12.5°C to 90°C. The range is much narrower. I do not know the preferred design values.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Date: Wed, 8 Aug 2012 06:17:10 -0500
Subject: RE: [EnergyPlus_Support] Multiple HVACTemplates Per Zone Error
As I read Dr. Li?s comments, I am thinking in more detail about 2 pipe systems.
The principal problem with 2 pipe systems, other than inconvenience and inflexibility, is that the water volume must be warmed or cooled to the new mode?s temperature (i.e., ~90C water must be cooled to 12C and then back to 90C as the system changes from heating to cooling and back).
It seems doubtful, but possible that the energy loss for changing the water volume?s temp will be accounted for by E+, but you will need to make sure the water volume is correct in the PlantLoop object. This seems like an exercise that is a bit outside E+?s normal capability ? I think I?d consider your spreadsheet as good as you need!
Contrary to Dr. Li?s comment, E+ apparently can model heat transfer from a pipe (Pipe:Indoor), but it certainly does not simulate the dynamic transfer that you are interested in ? it appears to be a constant rate only.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of YuanLu Li
Sent: Tuesday, August 07, 2012 9:51 PM
To: EnergyPlus_Support
Subject: RE: [EnergyPlus_Support] Multiple HVACTemplates Per Zone Error
You have a two pipe fan coil unit in each zone. This is a zone unit, and does not need an AHU. The OA mixer may be included in the unit.
You need two water plants, one for HW and one for ChW.
EPlus does not switch plant loops, so you will connect them as a four pipe system.
In Summer, the chiller is turned on. In Winter the boiler is turned on. The change over days are assigned by you with a schedule.
How much energy are wasting? I think, you are referring to the days that the system is on and the fan coil units are not running.
In Eplus, the plant would be turned off when there is no demand.
EPlus does not simulate pipe loss (all specified as adiabatic). The tank, if used, may have a conduction loss to the environment. Therefore the annual simulation would not give you the idle energy wasting values.
In a real system, you will observe the PLR when idle, and use that to estimate the energy usage.
For example the chiller may cycle between 12.5 and 7.5°C. Start at 12.5°C run till the water is at 7.5°C and then turn off. The energy wastage is entirely on the tank and pipes, and the power is for the pump and the fan at the EIR. These cannot be easily simulated, because the location and environment for these pipes are not known. You may simulate the effect with an equivalent storage tank. The plant will keep this tank at the designed water loop temperature when the demand is zero.
The direct answer to you question on the EPlus template usage is that the set of templates must be for the appropriate application..
You will use the HVACtemplate:Zone: for the fan coil unit. and the HVACtemplate:plant for the water plant, boiler and chiller.
VAV for the zone is an adjustable damper for an air duct, which is to be used with a HVACtemplate:system. (two templates) to form the DOAS (AHU system).
An additional fan coil unit in the zone is still possible, but not easy to specify, because one zone thermostat cannot control two sets of equipment..
You can only specify one HVACtemplate:Thermostat for each zone.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: matthew.sverre.anderson@xxxxxxxxx
Date: Tue, 7 Aug 2012 22:04:32 +0000
Subject: [EnergyPlus_Support] Multiple HVACTemplates Per Zone Error
Hey Everybody,
So I have a system that has central handlers feeding 5 zones, 1 basement, 2 north/south for the 1st and 2nd floor. It then has a room fancoil system that heat/cools the same zones. The fancoil system is two pipe with a switch over where we can only heat or cool at any given time.
I would like to get to the point where I can correctly model the amount of energy we are wasting in switch overs, I have done this in excel already but I would like to figure this out in E+.
In trying to put both a fan coil and a VAV air handler into a zone I received an error regarding the DSOA systems where it is trying to tell me I can't have more than one HVAC Template per system. Is this true?
Any work arounds here?
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
__,_._,___