Confusion of AutoSizing

[haoyuf]

Hello,

I am modeling a commercial building, which has lots of thermal zones. I know how to establish the HVAC network, but there is one thing that confuses me regarding autosizing. There is tutorial online showing that he autosizing is following the steps like set system schedules, set system parameters, zone level sizing, system level sizing. As I understood, you can only set one schedule, one set of system parameters there. However, different type of rooms may have different schedules and different thermal requirements. The schedule and system parameters we input can not cover all the conditions and may conflict with the controller settings I previously establised. How can we autosize in this case?

Hope someone could help me and appreciate your help~

Best
Haoyu

[PCully]

Hi,

If you follow the autosizing process then you can create different sets of profiles etc for use in the model, it is important to use the tools provided in the navigator to ensure the links between the model, systems and spreadsheet are maintained.

You can see on System schedules and setpoints that you can create sets of profiles for different schedules and via this dilaog they can be assigned to different prototype systems or groups of rooms.

It's worth looking at your project before and after doing this to see where the assignments are done and you will get a better feel for how the models have to be constructed for autosizing to work. It may even allow you to identify efficiency improvements for when you are building future projects (e.g. for zoning, grouping, project management etc)

Phil

[JohnLloyd]

Is there a simple tutorial anywhere that walks you through the Autosizing feature? It would be a useful thing to get my head around but at the moment I'm scared!

[Megan]

Don't be scared!!

The ApHVAC User Guide (section 9) walks through all of the steps in a fair amount of detail. It's not the simple tutorial you're looking for, but that's great feedback! We cover the autosizing steps in training but will have to look into developing a tutorial that walks through the basic process.

[JohnLloyd]

One of your youtube videos would be ideal

[JohnLloyd]

In order to use the Autosize features do you have to be using one of the prototype systems? Or can you autosize things (like radiators, for example) with a HVAC network created entirely from scratch?

Also, can you only use Autosize if you've got an ASHRAE Loads license? At the moment I only have access to a CIBSE Loads license.

[Megan]

Yes - you have to be using one of the prototype systems for Autosizing to work. Custom systems are not autosizeable.

I'm not sure about the licensing as I've only used ASHRAE Loads here in the US! I'll have to do some research or hopefully someone from the UK can chime in.

[JohnLloyd]

Thanks Megan, that's interesting. Has that always been the case? From my notes of my Apache HVAC training which I sat about two and half years ago I don't mention anything about Prototype systems.

[Megan]

The System level sizing still works without using a prototype system, but the ASHRAE Loads/Room level sizing only works with the prototype systems.

System level autosizing will size components such as fans, cooling & heating coils, and room radiators. Zone level sizing determines airflow to the zone and populates flow & temperature controllers, for example. If you manually populate these values, you can still use the system level sizing.

[JohnLloyd]

Thanks Megan, I'm trying to use it for radiator sizing so it sounds like it should be working. Tried it. Can't get it to work. Still scared.

I've sent a request into the tech support guys so hopefully they can point out where I'm going wrong.