RE: [EnergyPlus_Support] an idf model question

Hi, Felix

I do not recognize the end of simulation message format. It is possible that you were using some third party software.

I have identify that you have one air loop feeding one zone, with a cooling plant.

The order of the branches are definately not in the order normally used by EPlus. There is a warning to this effect in the eroor file.

The missing controller is in the air loop object. The field was left blank.

Until this is fixed, the IDF would not run. I used empIDF in my last reply, it should be expIDF. The first one, empIDF, is from Macro expansion.

Do not try entering cooling only, if you will be using heating later on.

For the weather in Hanzhou, type4 thermostat type may be more suitable, because the Winter and Summer seasons are not well defined. The heating and the cooling plant may be left on all the time, or make unavailable during the Spring and Autumn season to save energy. The dead band region save energy. (economizer operation)

You have used the maximum air flow rate for the zone and the fan, with a minimum ration of 1. If this number is low, the zone set point may not be reached. You may autosize these fields.i

If you can use templates for heating and cooling in the air loop used that. Use set point or thermoratat to turn the heating or cooling off, if necessary. Set point manager is more difficult to use.

Do not sort the expIDF and change it, if you cannot export the template IDF.

You have 150 people in the zone. It could be a shopping centre or a class room. There must be diffusers in the room. You should divide the room into five zones as in the example file 5zone arrangement to study the solar load from the windows.

The location of the system in the zone does not mean that there is only one air terminal.

Please use the node names suggested by the template. Do not remove the spaces. I suggested using under-score, for Zone related names only.

If you are not using template, but using the expIDF from the template example, then you may be doing the wrong thing.

You said that you were converting it from a non EPlus simulation program. What program were you using? Can you send me the file, before it was converted.

In order to get efficient with e+ simulation, I revised my modelling job into several steps. 1 Establish a simple construction (1 zone with internal mass This is not necessary and not the bestg way to learn. ) and simple hvac (without outdoor air and heating device   To do this you have left many fields not used, and ended up with more possibility for errors.  ). Simulate only cooling period.  &

Dr.Li,

It's Strange.

Plz try the two idf attached. One with controller and the other without.

They are both working well on my computer, whether there is a controller or not, as you have informed me. I tried the idf with and without the controller. My ep version is 6.0.0.023, is it the problem?

It's working well except the cooling consumption is always zero while it does has an autosized design load.

There is a design cooling load according to the output. It means that the internal load and building surface are resonable.

But the monthly cooling consumption is always 0 according to the output file. It should have cooling consumption at least in the month which design day exists. What kind of errors could give such output?

This is what confused me the most, I can't find anything wrong with the input within my knowledge.

You are definitely good at e+, but I am not. I have read many examples in the spread sheet and tried the examples in the gettingstarted book. I can understand some basic rules but not all of them. So I am trying to master it by simulate my previous project that are not simulated by e+.  By this stage, I could establish a building zone, plant loops efficiently. That a great progress I think. But the air side is still a problem sometimes.

Indulge me that I am using such an example, but this is the best way you can help me the best, I think.

Thank you very much.

Leebye

From: YuanLu Li <yli006@xxxxxxxxxxx>
To: EnergyPlus_Support <energyplus_support@xxxxxxxxxxxxxxx>
Sent: Saturday, September 3, 2011 1:13 AM
Subject: RE: [EnergyPlus_Support] an idf model question

Hi Felix

I am not sure what you are going to do.

If you are are trying to learn how to write an good EPlus IDF, open one 3Zone or 5Zone example oand see how the objects are arranged.

Choosing a one zone problem does not make it easier to learn EPlus. You do not know what is a zone equipent and what is a system equipment. Why do you need a system and cooling plant plant? Yes, the room is large. That was why asked you last time is such a building arrangement pracital?

If you have a large room and with good insulation and no internal load, you would need any cooling.

However, the simulation error was due to you formet of IDF was not complete. A controller list is required with your water coil controller object.

If you only have a single zone fan coil unit there is not controller required. The fan coil is controlled directly by the thermostat.   Cooling alone does not reduce the controlling requirement.

I suggest that you run the examples in the Getting Started document and read the instructions on how to use the templates and controls.

Do not copy some unknown examples and try to make it work. If you are using the template, stay with the template and make changes in the template IDF.

From the IDF's I have seen so far, there are a lots of un-necessary holidays, schedules declarations. A file with names such as 1FCCCWINLETNODE is very difficult to debug.

I can make the IDF work simply by copying your building into a working example. But that will not help you learning how to write a good IDF.

According to the error file, your IDF was not working. The controller list was not present. You may have deleted it.

Dr. Li.



To: EnergyPlus_Support@xxxxxxxxxxxxxxx
CC: yli006@xxxxxxxxxxx; leebye2008@xxxxxxxxx
From: leebye2008@xxxxxxxxx
Date: Thu, 1 Sep 2011 20:07:54 -0700
Subject: Re: [EnergyPlus_Support] an idf model question

Dr.Li,

Thanks a lot for your previous information.

In order to get efficient with e+ simulation, I revised my modelling job into several steps. 1 Establish a simple construction (1 zone with internal mass) and simple hvac (without outdoor air and heating device). Simulate only cooling period. 2 Add out door air to the model. 3. Add boiler to the system. 4 Add any other equipment and controls to derive further output.

For the 1st step, I established a model with simple zone and system definition only in cooling period.

The system has only one big fan, one cooling coil, one chiller and one tower, no outdoor air. It's a great progress that it works and runs five months simulation and gives me some basic understanding of the e+ syntax. Summer design outputs make some meaning.

But the cooling consumption is always zero and there are a lot of hours does not meet temperature requirement.

I changed the internal gains and eliminated ground heat transfer, but still no cooling consumption only fan and pump consumption.

Could please help to check the idf and see what's wrong with the model.

thank you very much and best regard

leebye

From: YuanLu Li <yli006@xxxxxxxxxxx>
To: EnergyPlus_Support <energyplus_support@xxxxxxxxxxxxxxx>
Sent: Friday, August 19, 2011 2:02 AM
Subject: RE: [EnergyPlus_Support] an idf model question

My comments in red below.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
CC: yli006@xxxxxxxxxxx; leebye2008@xxxxxxxxx
From: leebye2008@xxxxxxxxx
Date: Wed, 17 Aug 2011 23:49:51 -0700
Subject: Re: [EnergyPlus_Support] an idf model question

Thank you for your information, Dr.Li.

I think I need some basic understanding of the rules of EP HVAC system input.

Now I have got that the pump should be the first branch in supply side.

Let me explain my problem one by one so that you could help me cracking them.

---------------------------------------------------------------------------------------------------------

The hvac system in this case is not a good one, but it's a real system already in operation that I have to simulate.

If you are simulating a real system, you should mention the duct, diffusers, etc. I am sure you are using two big fans for the whole floors, blowing in from one corner.

The original envelop is downloaded from somebody else's case without any hvac input. That is an DesignBuilder output exactly. I added hvac component to the original file and developed my idf file. I haven't used any templates.

If this is your first EPlus simulatioon, you should try the template, You are doing quite well without it.

I do not intend to have 3 air loops in one zone. Just OAU sys and AHU sys. The exh fan is designed for the OAU. The input of OutdooeAirUnit asks for an exhaust fan. Is the OutdoorAirUnit and Exhaust fan input correct? I am not clear how to set the exhaust air node. The OutdoorAirUnit input do not asks for exh. air node, but the ZoneHvac:EquipmentConnection needs an exhaust air node. And the fan object also should have inlet and outlet air node. I think the ZoneHvac:EquipConnection object is not related to the OutdoorAirUnit. So how to relate the fans to the oau and the zone?

The OA mixer box may be connected to either the OAU or the AHU. If you are not using separate ducts to feed the fresh air, OAU is not required.

Move the OA mixer box to the main branch of the air loop. Because you do not have duct to feed other zones, the thermostat for the zone can be used to control the AHU.

Therefore all those setpoint manager/controllers for the OAU are not required.

The fresh air inlet is the inlet of the OA mixer, and this is the actuator node of the OA box. If you wanted to have variable OA intake, a controller need to be used to calculate the air flow in accordance to a schedule.

Because the AHU is defined as a system, an ATU is needed to feed the Zone. The zone return air or exhaust air node would be connected to the return air node of the OA mixer box. It is not necessry to provide an exhaust fan, because the relief node of the OA box will send air out to balance the intake volume.

The OA intake can be zero. 100% of the zone return air is circulated.

The OA intake equals to the fan volume, 100% OA is fed to the zone. All zone return air would leave the OA relief node.

By the way the Fig93 ( OutdoorAirUnit) of Input Output Reference is something wrong in the four nodes caption. The node numbering are wrong.

And should the outdoor air unit branches stated in the NodeBranchManagement object? I think it's not necessary. You need to insert the OA mixer as a component in the main branch. A conponent in the system equipment list. In the connection, the mixed air node should be connect to the coil or fan, in the correct sequence. The zone return ai would be connected to the air loop inlet and the return air node of the OA box. The air loop supply and air loop demand nodes are duplicated, I think, in a primary loop object.

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For the thermostat and controller, I have two coils in each AHU, one heating and one cooling. They both respond to the zone return air temperature. If I set two setpoint manager for the two coils the reference the same setpoint node: RA Node, there are errors then. But if I delete one setpoint (ie heating coil), errors asking for an setpoint appears.   You have not declared that the AHU is the zone equipmet (four pipe fan coil unit) It is still a system equipment. But because you onlyhave one zone, this is not clear. There is field in the AHU for you to declare the theremostat location.

If this field is not present, then you may be using a different object which is set point controlled.

What confused me much is that the ZoneEquipment is an Uncontrolled object (AirTerminal:SingleDuct:Uncontrolled), and how the thermostat could respond and control. So I think the thermostat is not necessary in this case. Just controllers are enough.? This ATU does not require thermostat control. The first listed zone with this ATU gives up the thermostat to the system AHU. This is know as the master zone and will have the zone temperature controlled to the thermostat value. All the other zone, if available, will have HVAC proportional to the damper setting.

In your case, only one damper, the damper setting would be one. All the fan volume flow to this zone.

----------------------------------------------------------------------------------------------------------------------------------

I agree with you in the performance and simulation of The absorption chiller heater. Dividing into one chiller and one boiler should have the same performance.

What I do not understand is that point in your email " In fact, if the chiller is entered in two places, all the branches will be in correct order." What do you mean by "entered in two places"

In your schematic, the absorption chiller has three sections. CW loop, HW loop and Condenser loop. In fact there are only two loops, hot and cold.

For cooling the cold end is connected to the CW loop and the hot end is connected to the condenser loop. The hot water loop does not exist, unless you use the HW loop as the condensor loop. When the HW water tank get too hot. the condenser loop should take over. This is not the arrangement.

Therefore you need to use two section absorption chiller. Hot and cold ends only, used in two different heat flow direction.

-------------------------------------------------------------------------------

Input logic is not fully and clearly stated in the reference files, I think, that's where the difficulties come from. I think the programe is developed by many different universities, so we have to input some variables for more than once in different groups different subroutines. Really difficult to understand the input syntax.

You need to define your sistem first, and then the EPlus moduls. EPlus id developed as a mathematical engin to carry out heat related calculations. It defines the solar condition using the weather file for external coditions. Use OA wind velocity for convection calculation. CTF for heat transfer across the wall. Convection and radiation from window to zone air heat balance. Exchange of cold and hot zone air for HVAC control.

Each module is defined, and each sentence of the IDF is the input to each of these functions. Therefore, you must define the zone, what equipment you wanted to use, and how they should be connected.

You cannot ask EPlus "what HVAC shall I use for this building?".

Thank you again. And may god bless you helping so much EPfreshpeople allover the world. That should be a hard work.

QU

From: YuanLu Li <yli006@xxxxxxxxxxx>
To: EnergyPlus_Support <energyplus_support@xxxxxxxxxxxxxxx>
Sent: Thursday, August 18, 2011 8:42 AM
Subject: RE: [EnergyPlus_Support] an idf model question

Hi, qutianfei

What ever your name meant.   Flying in the Autumn sky?

I do not understand why you have an OAU, an AHU and an exhaust fan in the same zone. You can split the office into zones, so that the air can be better distributed and controlled even if you do not have physical partition walls. (open office concept.)

You may have heard me saying VAV and reheat is not commonly used, and it is not new. What I really meant is referring to people using VAV rehet per room.

I have used VAV at the AHU main duct so that the East and West zone would get different amount of cooling supply during the morning and afternoon hours. (stepper motor controlled dampers, a timer and a couple of theremostat switches.)

We (the University engineering team) design the system to fit the different requirement of the building demand, with minimum capital and running cost. In tropical countries, the insulation requiements are not the same as the ASHRAE standard.

===============================
If your AHU feeds many diffusers, and the return air is normally via the false ceiling space, you should model the ceiling space as a plenum mixer for the air loop. You can channel lighting heat to the plenum and get better cooling efficiency.

If the AHU is the main cooling and heating source, then the thermostat of the zone should be assigned to this system.

The exhaust fan is not required, unless it is for the toilet or printing room, etc. It that case, they should have a separate zone defined and use zone mixing to control the air flow.

If the OAU is for providing the so called 100% fresh air, it can be part of the air loop, unless the quantity is so high that the flow must be separately heated or cooled. If the AHU air is ducted for distribution, the fresh air can be conditioned by the same sets of coils.

The zone thermostat can be used for either system, because you only have one zone.

I.e., one system, OAU or AHU has the use of the thermostat control. The other system can be uncontrolled or setpoint controlled. The outlet temperature will not follow the zone temperature value. This type of OAU is usually referred to as DOAS, which is not commonly used to feed a zone.
===============================
I have no hands on experience in running the absorption chiller. I assume it behave the same way as a heat pump, with the compressor replace by the heat source.

In that case, the component may need to be repeated in the separate cooling and heating plant loopss with the heating and cooling side properly connected.

When it is used as a chiller, the other hot side is connected to the condenser loop.

When used as a heater, the other cold side is the environment or auxiliary heat source.
======================
When you use the Controller:MixedAir there are two setpoints for cooling and one for heating, and one reference node. Two system would need six setpoint nodes. and two reference nodes.

These will not be required, if you use the AHU to feed the fresh air and save one fan.
=====================
I have already mentioned the branch ordering in the plant loops.

The absorption chiller is the on the supply side of the CW loop, the hot end is the demand side of the condenser loop, which is connected to the tower.

When it is used as a heating source, the hot end is the source of the HW loop, the cold end is to be exposed to a warm environment.
==============================
The above covers all those errors mentioned in the error file.

Because the file has been sorted, the branches are listed according to the object ty pe and ot by the system group. This is not so easy to sort out.

That is why I asked you whether you used the template in DesignBuilder. If you did, export the IDF without sorting if possible. It will then be easier to correct. In fact, if the chiller is entered in two places, all the branches will be in correct order.

The zone setpoint problem can be solved by moving the OA mixer to the AHU and delete the OAU. 100% fresh air can be injected with a Ventilation object with a schedule to control the quantity required.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx; yli006@xxxxxxxxxxx
CC: leebye2008@xxxxxxxxx
From: leebye2008@xxxxxxxxx
Date: Tue, 16 Aug 2011 19:53:58 -0700
Subject: [EnergyPlus_Support] an idf model question

Dr.Li,

I am working with a two floor office building, but always cannot pass the simulation compiling. Together with some of my understanding of EP, I attached this model dxf scheme file and idf file to this mail. It's really great help to get some right knowledge on EP. Hope that you could spent a few minutes on my problem. Thank you very much.

qutianfei

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