how could the compact HVAC be get started?

llyces1985 · Posts: 32

Hi,
I want to use the 'compact HVAC' programe to define my hvac systems. But I don't know how to get the programe started in the 'Model Data Tabs/HVAC Tab',so could you tell me how to do it because I failed to find the way. And could the pumps and cooling tower be simulated in DB by 'compact HVAC'? Thanks! Best regarts!

AJ Lester · Posts: 72 Location: Auckland

Hi,

If you go to the "model options" dialogue and under the 'data' tab change 'HVAC' slider from simple to compact, the model data - HVAC tab will change allowing access to the more complex functions of the compact HVAC systems.

As to pumps, these should be added automatically as necessary. If the system you have requested requires pumps they should be automatically generated as part of the system. Certainly I have never had any problems with this, and have had pumps created by DB that have ended up, as appropriate, in my .idf files.

I am not sure about cooling towers. It is possible to model these within EnergyPlus, but I am not sure whether DB has these implemented. Hopefully someone from DB support can confirm this with a yes/no.

If you ever wish to model a non-DB standard system, you can always export an .idf file and modify it to include the necessary EnergyPlus objects.

All the best,

Andrew Lester

bhandari · Posts: 86

Hi,
If you select Condense Type as 2- water Cooled, DB will create cooling tower (Cooling Tower:Single Speed)..
Mahabir

llyces1985 · Posts: 32

Hi
I set the HVAC data as 'compact' type in the 'Model Options Data'.Then I turned back to 'Model Data Tabs', I choosed 'Constant volume' in the 'HVAC Template' tab. I want to know that the type is 'compact' or not? If it is ,but I found the 'Auaxiliary energy' in the 'HVAC templates data' of the ''Constant volume' . Does the 'energy' would effect the result of the simulation? Thanks! Best regards!

llyces1985 · Posts: 32

Hi,
Thank you for your help! But I failed to find the 'Condense Type' in DB! Could you tell me how to define it in a few more detailes? Thanks! Your help will be appreciated! Best regards!

bhandari · Posts: 86

Hi,
You can use one of the VAV systems to model your constant volume system. You would need to assign the Turndown ratio (supply air min flow fraction)as 1.0. You can then set Condenser type as Water cooled..
Mahabir

llyces1985 · Posts: 32

Hi,
I followed your way, but I failed to find the 'Condenser type' in the VAV system. Maybe I took a mistake(please look at the attachment), but I don't know where is wrong.Could you help me further? Sorry to bother you again! Thanks! Best regards!

bhandari · Posts: 86

Hi,
Please see the attached figure..
regards,
Mahabir
PS: Sorry, I had trouble uploading jpeg file so I put it in Word file..

llyces1985 · Posts: 32

Hi
I found where was wrong about my problem. I selected the 'VAV system' in the zone level, so I could not find the 'Condenser type' in the cooling. But, if I turned bact to the building level, I got it! I don't know why. It says"If you select Unitary multizone, CAV or VAV at zone level, then the same selection must be made at building level. " in the 'help file' of DB. And what I want to say is that only some zones or block take the 'Constant volume' system( could be used instead if I want to simulate the cooling tower) and the other takes the 'fan coil units system in my model. Does it means that if I take the 'VAV system', the fan coil units could not be used in the same model? However, the 'two system' must be used in my model, how to deal with such probem? Could you give me some important advice? Thanks! Best regards!

bhandari · Posts: 86

Hi,
I apologize for not mentioning that you could select it at building level only. You can select unitary single zone or FCU at the zone level. ["If you select Unitary multizone, CAV or VAV at zone level, then the same selection must be made at building level. "] means you cannot select other of the two systems at the zone level. For example, if you select VAV at building level then you cannot select multizone or CAV at the zone level. You can, however, select unitary single zone or FCU at the zone level. I hope it helps..
Best regards,
Mahabir

llyces1985 · Posts: 32

Hi,
Thank you for your help, Mahabir! I want to discuss with you again! And I will definitely appreciate that other people could join in and give some precious advice! I rechecked the 'HVAC system' of my model, and I selected 'Constant volume' system at the building level, then I also got the 'condenser type', so I could select FCU at zone level. You say that " If you select Condense Type as 2- water Cooled, DB will create cooling tower (Cooling Tower:Single Speed).. " But in my simulation results, I failed to find some obvious results about the 'cooling tower'. How to get it? And I want to affirm that, if I select 'Constant volume' at the building level, is the 'constant volume' at the zone level same as the building level? I want to get some energy saving strategies by analysing the variables of the supply and return chilled water temperatue and volume, and the variables of enter and outer water temperature of FCU and, volume of the chilled water of FCU. Could DB supply such ways? Thanks!
Best regards,
Esong

bhandari · Posts: 86

Hi Esong,
Yes, it should select the same system at zone level. You can double check it. I think the best you to analyze the individual variables you mentioned in your email is to export the idf file and run it independently and report these variables. You may not see all the reporting variables in idf file first time but simulating the file once and opening it again lists the variables.
regards,
Mahabir

llyces1985 · Posts: 32

Hi Mahabir,
I exported the idf file of my model by 'File > Export > EnergyPlus IDF file > Simulation', then I tried to open it in EP-launch. But surprising results, it warned that I had errors. I don't know why, maybe I take mistakes in my model in DB or other reasons. And I tried to think up the way to "run it independently and report these variables. You may not see all the reporting variables in idf file first time but simulating the file once and opening it again lists the variables" as you say, but I failed. Maybe I don't understand completely though I try to. So, could you give me some advice about the 'run it independently and report these variables'? Thank you very much!
All the best,
Esong

AJ Lester · Posts: 72 Location: Auckland

Hi Esong,

Although I cannot speak for Mahabir, I will try and answer your questions in the meantime.

If EP-Launch is reporting error 'warnings', then this is not too surprising. It is relatively common to get some small warnings in particular in relation to ground temperatures etc. as these ground temperatures are set to a default value that is not really appropriate. (This particular warning has been extensively discussed in other posts on this and the EnergyPlus forum.)
If EP-Launch is reporting more severe errors, it would be helpful if you could post the nature of these errors here, so that we can work out together where they have come from.

I believe what Mahabir meant by the phrase "run it independently and report these variables. You may not see all the reporting variables in idf file first time but simulating the file once and opening it again lists the variables" is that you first need to get the simulation running correctly in EnergyPlus. Initially the HVAC definitions are all compact definitions, which are not always explicit in terms of the outputs available. After the file has been run once, an expanded version of the file (.expidf) is created. In this file, all the reports should be visible. You can then look at each of the available reports to find the ones you need.

As far as I can see, this would be roughly what Mahabir meant and what you would need to go forward. If you could post here again, detailling what errors you are experiencing, that would be helpful.

All the best,

Andrew Lester

llyces1985 · Posts: 32

Hi Andrew,
Thank you for your great help! I tried to understand and solve the errors as I exported the idf file independently, but I failed. I will appreciate you could have a look at my attachment, and I hope I can work out together with you. And I want to ask another question, why it comes out such errors when I have exported the idf and try to open it in EP-launch even though I could get simulation results in DB? Thanks a lot!
Best Regards,

Esong

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