#816 AHU WG: Proposals

Jay Herron Tue 26 May

Hi community, the AHU working group has had a few discussions recently and has finalized a proposal for some tagging changes. Please find the proposals below. We'd love to hear your feedback!

Distinguish minimum outside air dampers and economizing dampers

Prompted by Cory Mosiman here

  • Adds ventilation tag which indicates outside air that is used for ventilation. This would represent minimum outside air dampers.
  • Adds economizer tag which indicates outside air that is used to reduce conditioning energy requirements.
  • Adjusts outside tag to specify that if ventilation or economizer tag are not included, it is implied to perform both operations.

dxHeating/heatPump interactions

Prompted by Cory Mosiman here

  • Adjusts heatPump to specify that heating and cooling processes are dxHeating and dxCooling respectively.

Dedicated outside air system VS makeup air unit

Prompted by Annie Mroz here

  • Adds new doas equip which is a an ahu subType, and indicates an AHU that brings in 100% outside air and no recirculated air.
  • Changes mau to a subType of doas, and adjusts definition to specify that it provides replacement air for a separate, dedicated exhaust system.

Cory Mosiman Fri 29 May

Just wanted to confirm my understanding. We will basically have 3 potentially different dampers:

  1. {outside damper actuator equip} Refers to a single outside air damper which is used for economizing and ventilation purposes.
  2. {economizer outside damper actuator equip} Denotes a damper in an outside duct that is used to reduce conditioning requirements.
  3. {ventilation outside damper actuator equip}. Denotes a damper in an outside duct used for ventilation purposes, not economizing.

This does get us to the point where on queries, if people are looking for dampers that do both economizing and ventilation (but not single purpose dampers), they will need to exclude these on filter: outside and damper and actuator and equip and not economizer and not ventilation.

Just wanted to point that out as its probably important for others to consider. Would people weigh in on whether or not they think these exclusionary principles will make a difference to them?

Leroy Simms Sat 30 May

In these scenarios should we address the fact that often a point will control an outside air damper and a return air damper inversely to each other, however, sometimes they are independent. When both are controlled should the mixed tag be added?

Jay Herron Mon 1 Jun

Leroy, typically it would be tagged {mixed, damper} in that case. Another alternative could be to split the reading into two points: {outside, damper} and {return, damper}, which would also allow you to adjust the value to represent a 0-100% open reading on both.

Great point Cory. There are a few tagging schemes, each with benefits and drawbacks:

  1. The proposed situation, where we use economizer and ventilation alongside outside and having neither economizer or ventilation implies both.
    1. Benefits:
      1. Most existing outside point tagging won't change
      2. Most existing outside queries will still work (although multiple-result situations may arise)
      3. Avoids adjusting the existing AHU outside, return, discharge, exhaust duct scheme
    2. Drawbacks:
      1. The not query format Cory identified
  2. We use economizer and ventilation alongside outside and any outside point must have one or both.
    1. Benefits:
      1. Avoids the not query issue
      2. Most existing outside point queries will still work
      3. Avoids adjusting the existing AHU duct scheme
    2. Drawbacks:
      1. Existing outside point tagging must be changed
  3. We determine a new third tag to denote an outside section that does both ventilation and economizing. This is functionally the same as option 2.
  4. We define economizer and ventilation not as subtypes of outside, but rather as their own AHU duct.
    1. Benefits:
      1. Avoids the not query issue
    2. Drawbacks:
      1. Adjusts the existing AHU duct scheme
      2. Existing outside point tagging must be changed
      3. Existing outside point queries must be changed

From our AHU WG deliberations, we decided to propose Option 1, but I think Option 2 is also a decent solution.

What do you guys think?

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