RE: [EnergyPlus_Support] need help E+ in verify and modifying IDF

Hi, Aditya

You may be getting unusual results, because the Building Surface Ground temperature is too high. The range should between 18°C to 25°C.

==============
Site:GroundTemperature:BuildingSurface,
27.5, !- January Ground Temperature {C}
27.4, !- February Ground Temperature {C}
27.5, !- March Ground Temperature {C}
27.5, !- April Ground Temperature {C}
29, !- May Ground Temperature {C}
29.9, !- June Ground Temperature {C}
30, !- July Ground Temperature {C}
30.1, !- August Ground Temperature {C}
30.1, !- September Ground Temperature {C}
29.2, !- October Ground Temperature {C}
27.7, !- November Ground Temperature {C}
27.6; !- December Ground Temperature {C}
==================

These values are for building exterior surface temperatures. The ground temperature is much lower. The deep ground temperature is at 18°C all the year around at any location.

I have not completed looking at your IDF, as the building entry also may not be correct.

The others warnings are schedule syntax errors. The error file is attached. Use simple schedules to start with and then change them to more complex one.

Timestep 4 is sufficient for your design. More timestep will need more simulation time. Do the DesignDay sizing simulation first, and then the annual weather file simulation in order to save time. You may not notice this if you have a fast PC.

The other comments are below.
Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: adityaravi87@xxxxxxxxx
Date: Mon, 11 Jul 2011 10:26:49 -0700
Subject: [EnergyPlus_Support] need help E+ in verify and modifying IDF

Hello,

I have attached an IDF,which I created few days back. I am a beginner with E+. I wanted to check if I have done it properly or not. There are no errors on running the simulation. There are a few warnings which come up since I have not used all day types, I think. However I assume that this does not affect my simulation results. Please go through and let me know if its correct.

There are 12 day types, you can display these using:
Output:Variable,*,DayType Index,hourly; !- Zone Average []
When you are not sure, you can use 'alldays' for all the 12 days and use 'allOtherDays' to cover any days which may have been left out. DesignDays are included in the 'allDays'.

Coming to what I want: I need to run a simulation for a 3 bedroom house. I assumed it to be under a single zone, since only one thermostat is to be used to regulate the temperature throughout the house. Firstly is this assumption correct?
When you need three rooms, you should declare them as three zones with three thermostats.

Use one AHU to feed the three zones with air distrubution units. One thermostat will be used as he master to control the system and the other two thermostat will not be used.
Next, I have PTAC with electric heating coil. Is this enough for performing both heating and cooling? Also please look into the output. I find that during winter, at certain time of the day, cooling occurs which sounds not correct. Can you kindly explain why? Am I making a mistake in the scheduling?

I am not sure whether PTAC will provide both heating and cooling. DX coil provides cooling and Heating coil may be heated with electricity or gas.

The resean why your example was not getting the proper control, because there are different ways to use the thermostat control.

You did not declare two seasons in your schedules and the thermostat types.

Please verify my file and if changes are to be made, please help me out with it.

I had emailed earlier inquiring about this and got few replies. However I did not understand them very clearly. So here it is again: I need the HVAC to cut off on reaching the cooling or heating set point. This is automatically done by the thermostat control, using the heating setpoint and cooling setpoint values. You did not define these in the IDF.

In other words, I do not want the HVAC to be running continuously and trying to maintain the set point. Zone/room temp = set point, HVAC should turn off. Then once the room/zone temperature rises or falls by 1 deg C, I want the HVAC to once again kick ON to cool or heat the room. And I want the heating and cooling to be electric. This is what we normally observe in our houses.

With seasonal control, the cooling will happen from a high temperature to the set point and stop. When the building is heated up by a degree or so, the cooling will start again. This is know as the set back of the type 2 thermostat.

In Winter, the heating will start from a low temperature and stop at the heating set point value, as in the type 1 thermostat.

With type 4 thermostat, the seasons are not defined. There is a band of temperature values that neither the cooling nor heating will come on. This is dual band control with a dead band.

Heating and cooling can be electric, but in EPlus heating can be a electric heater. The electric cooling system is actually, a compressor, an evaporator, a condenser and a fan. The evaporator is mounted in the AHU or the zone as the DX coil, in the PTAC. A split unit has two fans. A window unit has two fans on the same motor.

A heat pump blows the condenser air into the room for heating. However, it will not work well with outdoor temperature below 5°C.

So basically, it will be a cycle of cooling in case of summer and a cycle of heating in winter. Can this be done in E+, if so, can you explain in detail how to do this. It will be really helpful, since I am working on my thesis based on this. In of the replies which i had got earlier, I was asked to look into the part load ratio and I was told that the HVAC operation is
dependent on the load and is not about reaching the set point. It makes sense and I agree speaking technically, but with this software, how do I get to the part load ratio?

As I explained above, the start stop of the system is controlled by the thermostat in one room. The real system is a mercury switch mounted on a bi-metal coil. The temperature change tilt the switch to turn on and off the compressor or heater. When the fan is set to 'auto', it turns on and off with the compressor.

The PLR tells you whether the system is of the correct capacity. If the PLR is too low, the system is switch off most of the time. Therefore, the capacity is too large. So you turn the fan speed lower. PLR is calculated and listed as a variable.

Once again I request you to go through the IDF and verify if its correct and suggest modifications to improve it or in case its wrong help me correct it. Also please explain in detail on how to go about to achieve the HVAC operation like I have mentioned.

I think you whould look at the following in the exampleFiles directory:

HVACTemplate-5ZonePTAC.idf

HVACTemplate-5ZoneFanCoil.idf

OutdoorAirUnitwithAirloopHVAC.idf

=================

Sincerely,

Aditya

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