Process Exhaust rules

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What NACM Section(s) are relevant to this issue?
5.6.5.3 Zone Exhaust
5.7.3.4 Exhaust Fan Systems

A few questions for John and/or Roger:

1) The introduction indicates 'Energy is summed for the exhaust system level, 
not the thermal zone level.'  What is the intent of this statement in the 
context of the compliance software? My initial thought was to allow zone 
exhaust systems be either specified as ThrmlZn input -or- as a AirSystem if the 
exhaust system serves more than one zone. Is this approach to implementing in 
CBECC in contrary to the intent of the ACM?

2) As I understand it, the exhaust air flow rates are 'as designed', but there 
are specific rules for kitchen/lab SPACES.  This brings up the question: Should 
exhaust be a Spc or ThrmlZn level concept in the SDD?  If it is ThrmlZn 
concept, the I believe we should not allow combining of these space types with 
other space types. This is my preference, and tht the same limitation would 
apply to other, process-related space types.  Please let me know your thoughts.

3) The exhaust flow rate for labs is prescribed, based on whether it is 'hood' 
or 'load' dominated. Did you have a methodology in mind for making this 
determination?  If not, do you want me to propose one?

4) If the total process exhaust flow for the building is <5000cfm, does that 
mean the baseline exhaust systems (both process and non-process)  are same as 
the proposed?  

5) In 5.7.3.4, Fan Control Method, a option for 'Variable-flow, constant speed' 
is listed. The Fan Part-Flow Power Curve descriptor references Table 30, but 
there are many Variable-flow, constant speed options there. It doesn't acutally 
look like I can specify a Fan Curve for Fan:ZoneExhaust in E+, so this is a 
moot point for CBECC, but might be something to define for general completeness.

Original issue reported on code.google.com by da...@360-analytics.com on 18 Jun 2014 at 10:37

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Clarifications/updates to a few of the items (the number here corresponds to 
number in original post):

1) You can disregard this question.  I am now proceeding with SDD exhaust 
systems defined as ZnSys or AirSys objects.

2) You can disregard this question.  I am now proceeding with SDD exhaust flows 
defined at the Space, and then summed up to the ThrmlZn and system levels.

NEW 6) In the descriptor 'Exhaust Flow Rate', the NACM indicates 'Same as the 
proposed design but not above the maximum standard design flow rates listed in 
Appendix 5.4A.'  I do not see any maximum exhaust flow rates listed in the 
Appendix. Are you referring the minimum ventilation rates?

Original comment by da...@360-analytics.com on 21 Jun 2014 at 6:42

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GENERAL NOTE: while I have ACM rules in place, I expect a few updates needed 
for clarity or completeness, and will be reviewing what we have in place here.

3) I think the intent here is to allow the USER to specify hood-dominated or 
load-dominated, based on the application. Exhaust rates are prescribed (15 ACH 
or 6ACH) based on the user selection.  To be clear, the ACM should probably 
have another input as an entry of exhaust type/classification of hood-dominated 
or load-dominated.

4) For non-lab spaces, yes, I believe that is the intent. For lab spaces, 
exhaust cfm is prescribed.

5) Yes, I'll take a look at the options, to see if we can specify a curve so 
that it is not ambiguous.

Original comment by JohnJArent on 23 Jun 2014 at 6:40

• Changed state: Discussion

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Thanks John. 
Re 3) If you want to have specific criteria/guidance for determining hood vs 
load dominated, another ACM descriptor does make sense.  Please forward any 
specific criteria or more detail on this option once you have it available.

Can you also take a look at #6 in comment 1? 

Original comment by da...@360-analytics.com on 25 Jun 2014 at 6:13

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Regarding #3:

There is an existing ACM descriptor that already captures this input, 
"Laboratory Exhaust Rate Type".  

The user chooses "hood dominated" or "load dominated" for the zone that has any 
laboratory spaces.  CBECC should then set a fixed exhaust flow rate to 15 ACH 
or 6 ACH, based on the user input.  The user can apply whatever criteria he or 
she wants to determine hood-dominated or load-dominated; the software WILL NOT 
MAKE THIS DETERMINATION, regardless of the design.

Yes, regarding #6 in Comment 1:

The following language in the Standard Design:

"Same as the proposed design but not above the maximum standard design flow rates listed in Appendix 5.4A"

Should read: "Same as proposed design, but in spaces without covered processes (laboratory, commercial kitchen), the exhaust flow rate shall not exceed the minimum ventilation rate specified in Appendix 5.4A for the given space function type."

I assume this language is specific enough, but CBECC would have to interpret what "covered processes" means; for example, check if any of the user-defined space functions is a laboratory space or commercial kitchen, to implement this rule.

Changing status to RESOLVED. Please log comments, email or call me @ 415-970-6513 to resolve any issues. I have some time and would like to help close any outstanding issues out. Thanks!

Original comment by `JohnJArent` on 26 Jun 2014 at 7:37
* Changed state: **Resolved**

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Exhaust Air Flow Rate (comment #6):

Standard Design

Same as the proposed design but not above the maximum standard design flow 
ventilation rates listed in Appendix 5.4A for spaces that do not include 
covered processes. Exception for kitchen space types with over 5,000 cfm of 
exhaust: the baseline is a function of the Kitchen Exhaust Hood Length, Kitchen 
Exhaust Hood Style and Kitchen Exhaust Hood Cooking Duty, and is determined by 
Table 140.9-A.

Original comment by johnaren...@gmail.com on 15 Aug 2014 at 4:18

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Final Response to Issues:

#3: User-defined lab exhaust rate, as discussed. Ultimately the user defines 
whether it is "load dominated" or "hood dominated" through input of exhaust 
rate.

#4: For non-covered processes, exhaust flow of baseline is always same as 
proposed. For kitchen exhaust rates, the exhaust flow follows the procedures in 
the ACM RM, with some limits for the baseline exhaust cfm.

#5. I can specify one of the constant speed, variable curves for the baseline, 
and will make that ACM RM change for the next release, but it appears that ACM 
doesn't support this.

#6. See comment #5 above on August 15, 2014 for resolution.

Original comment by JohnJArent on 15 Oct 2014 at 5:56

• Changed state: DoneVerified

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The responses for #4 and #6 seem to contradict eachother.  #4 says baseline 
general exhaust rates are same as proposed, but #6 says they are same as 
proposed up to limit. I don't think there should be a limit on general exhaust; 
that is a design decision and the NACM does not provide enough resolution on 
this, so probably best to make it neutral at this time.

For lab systems, see issue 738 for what is currently implemented.

Original comment by da...@360-analytics.com on 16 Oct 2014 at 2:38

• Changed state: Discussion