[Equest-users] System-Level Exhaust??? How?

[Brian Fountain]

Nick,

DOE-2 enforces a mass balance at the system level.  Whatever OA that is 
not exhausted at the zone level must be returned to the central system 
and exhausted through your heat recovery device. By defining the OA 
volume flow rate, you are also defining the exhaust volume flow rate.

Nick Caton wrote:
>
> I need have an ERV which moves all the exhaust and supplies 
> conditioned OA to 2 of 3 FPVAV air handlers.  I've specified the 
> appropriate enthalpy wheel specifics at the two affected PIU systems, 
> maintaining identical efficiency properties and breaking down CFM's 
> and fan/auxiliary power figures by weighting each by the supplied OA 
> amount.
>
>  
>
> I understand from the help files that zonally-specified exhaust air 
> does not play into heat-recovery, when we specify energy recovery at 
> the system level (help section is copied below and highlighted for 
> reference).
>
>  
>
> I take it then I'm supposed to zero out all zonally entered exhaust 
> air flows, sum up the flows and add at the system level... but then 
> _how/where do I specify system-level exhaust CFM rates_? 
>
>  
>
> I've tried to enter     EXHAUST-FLOW     = #### under the systems in 
> question in the .inp file, but it introduces the following error:
>
>  
>
> *13131*    EXHAUST-FLOW     = 2550
>
> *ERROR********* ============ 
> *****************************************************************UNKNOWN 
> KEYWORD or PREVIOUS .. MISSING 
>
>  
>
> More errors ensue, and a long string of things appear to be 
> defaulted/lost when I continue to open the file... something is 
> obviously wrong with this approach.**
>
> * *
>
> cid:489575314 at 22072009-0ABB**
>
> * *
>
> *NICK CATON, E.I.T.***
>
> PROJECT ENGINEER
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> /Check out our new web-site @ /www.smithboucher.com_ _
>
>  
>
> *EXHAUST-FLOW*
>
> Flow rate of the zone's exhaust fan. This entry can be omitted if 
> there is no exhaust from the zone, if there is only central exhaust by 
> way of the system return, or if the exhaust tracks the supply flow 
> (see AIRFLOW-TRACKING). If specified, EXHAUST-STATIC should also be 
> entered. The exhaust fan may be either constant flow or variable flow.
>
> If exhaust air make-up is via the air handler (EXHAUST-SOURCE = 
> AIR-HANDLER), then the exhaust fan can operate only only when the 
> system supply and return fans operate (see SYSTEM:FAN-SCHEDULE or 
> SYSTEM:EXHAUST-FAN-SCH).
>
> The SYSTEMS program simulates heat recovery from central exhaust only, 
> not from zone exhaust. If heat is to be recovered, zone exhaust should 
> not be entered but rather allowed to default to the central system. 
> Return fan static should be adjusted, on a weighted average basis, to 
> reflect zone exhaust fan conditions.
>
> The program will not allow SYSTEM:MIN-OUTSIDE-AIR to be less than the 
> sum of EXHAUST-FLOWs for all zones divided by the sum of supply flows 
> for all zones. That is, MIN-OUTSIDE-AIR will not restrict the 
> operation of exhaust fans. The exception is when EXHAUST-SOURCE = 
> INFILTRATION, in which case zonal exhaust does not affect air handler 
> outside air requirements.
>
>  
>
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