Chiller Sequencing with Respect to Outdoor Temperature

Chiller Sequencing with Respect to Outdoor Temperature

I am currently modelling an adiabatic chiller for large commercial complex.


For this particular design, I need to do load management and chiller sequencing between air cooled and water cooled chiller on basis of outdoor air temperature.  


Please provide a suitable path for this modelling.

It’s gonna be a good week!

Sequencing chiller based on outdoor temperature.

Behold, a dummy model wherein I’ve entered detailed mode and changed the default names for a pair of chillers to something easy to copy a few times: CH-A and CH-B

1. Self Prompt:  I want CH-A to handle the loop for all conditions where the outdoor drybulb temperature is less than or equal to 85F.  I want CH-B only to handle the loop at all other times.

2. Looking downwards in my component tree, while in the water-side HVAC tab, I observe an empty component group entitled “Equipment Control.”  Right-click that, and “Create Equipment Control…”

3. At the prompt, give this Equipment Control a name that reflects your intent in the moment.  Choose the Control Type based on the kind of equipment you are trying to control (reference article pasted here for convenience), and select a Loop to which this applies if prompted as well:

4. Navigate to the Load Range 1 tab, select CH-A in the first dropdown, and enter nothing for the capacity (which is interpreted by the program to mean there is no limit on this first phase of operation.  Note that I did not also list CH-B, so this should effectively isolate operation to only CH-A while this EQUIP-CTRL is active.

5. A general aside:  For any other real-world sequence with more complex elements like multiple chillers/boilers/etc running at the same time… I can’t write a quick/simple guide for something that broad, but you’d be well advised to skim the reference materials under Volume 2: Dictionary > HVAC Components > EQUIP-CTRL … and specifically Volume 2: Dictionary > HVAC Components > EQUIP-CTRL > TYPE = COOLING for sequencing chillers

6. Now back out of these inputs, right click the freshly created EQUIP-CTRL in the component tree, and copy it.  Give it a distinct name and change the CH-A assignment to CH-B:

7. Now we just need to define under which circumstances we should use either EQUIP-CTRL.  Right click the empty component group “Load Management” in the component tree, and the first prompt will allow you to name and select a load management type.  If you select OA Temperature, you’ll be prompted to provide a temperature to correspond with your first sequence.  You can more descriptively think of this as “the maximum temperature for the first range of operation.”  Once again, if it’s initially unclear you can always change this stuff up later.

8. Click through your management sequence tabs, and select your EQUIP-CTRL intended for each range of temperatures.  Once again, there are a lot of input options available to accommodate a diversity of sequence intents, worthy of review pretty much anytime you are engaging these input dialogs, but for this prompt our lives are pretty simple:

9. We’re almost done!   This is probably the most universally important step.  Any time you mess with EQUIP-CTRL and LOAD-MANAGEMENT, I’d advise it’s easy enough for anybody to get turned around with the input options at-hand.  Set up a custom hourly report to track the operations of the targeted equipment, to help yourself verify intent and tweak inputs as necessary down the line.  I’m skipping through those steps as it’s something I and others have covered many times before on the lists (see archives if needed).  In this case, I’m just going to generate two columns of chiller loading alongside the hourly OADB conditions:

10. Simulate and export custom hourly report to confirm results/intent.  Spend a little time here to make the visual pretty / intuitive as it probably belongs in an imaginary report somewhere… this is where we earn our keep after all 😉

In this case I’m using pivot chart/table to quickly slice down to the first week of June, where I can observe weather conditions that should trigger between CH-A and CH-B.  Seems satisfactory to me!

I hope this helps you and others dipping your toes into sequencing with eQuest!   This is a relatively deep rabbit hole / skillset, but your prompt felt like an appropriately simple enough sequence to set up an introductory example for the community… Thanks for asking!

~Nick


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