[Bldg-sim] DOAS system

[Joe Huang]

I resisted jumping in on this discussion earlier, but Chris' comment 
motivated me to say that my experiences in China are very similar, and
that perhaps it's the US that's out of step with a lot of the world.

The standard HVAC system in Chinese buildings, i.e., at least 90% of
the time, are fan-coil units with a "DOAS" to provide conditioned fresh 
air. The "DOAS" are essential because of the high outdoor humidity
during the summe. Of course, they're not known as "DOAS"; I only learned 
that terminology when I explained the system to a US consultant.

It seems that when the US HVAC industry went to all-air systems in the
50's (?), fan-coil systems became stigmatized as archaic and their 
designs stagnated. That's not the case in other parts of the world.

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd. Suite 108D
Moraga CA 94556
(o) +925 388 0265
(c) +510 928 2683
yjhuang at whiteboxtechnologies.com
www.whiteboxtechnologies.com


Chris Yates wrote:
> This discussion has perhaps underlined the differences in terminology 
> between the US (where a significant part of development takes place) and 
> the rest of the world. 
> 
> For example, in the UK 90%+ of systems using an AHU are "DOAS" but I'd 
> never heard of the term before dealing with E+. 
> 
> Another thing we have come accross is the applcation of Fancoil systems 
> appears to vary significantly between the US and EU. In Europe most fan 
> coil systems are augmented by "DOAS". They can also be quite advanced 
> pieces of kit with electically commutated (EC) fan motors for efficiency. 
> 
> This is merely my observation from E+ where the Fourpipe fancoil object 
> is quite dumb (i.e. Single speed fan that doesn't modulate on/off with 
> the load).
> 
> I say quite dumb... It's obviously more clever than me!
> 
> Sent from my iPhone
> 
> On 27 Mar 2010, at 09:44, "James V Dirkes II, PE" <jvd2pe at tds.net 
> <mailto:jvd2pe at tds.net>> wrote:
> 
>> Dear Sambhav,
>>
>>  
>>
>> There is good information available from ASHRAE which you should read 
>> about DOAS.
>>
>>  
>>
>> A brief understanding is that certain HVAC systems, such as chilled 
>> beams, VRF and water-source heat pumps, are used to remove _zone_ 
>> sensible cooling or heating loads.  They are very effective at this 
>> function but do not provide _outdoor air ventilation_ for the zones.  
>> As a result, a separate HVAC system is provided for the express 
>> purpose of providing ventilation air.  This is called a Dedicated 
>> Outdoor Air System (DOAS).
>>
>>  
>>
>> *The Building Performance Team
>> **James V. Dirkes II, P.E., LEED AP
>> *1631 Acacia Drive NW
>> Grand Rapids, MI 49504
>> 616 450 8653
>>
>>  
>>
>> *From:* bldg-sim-bounces at lists.onebuilding.org 
>> <mailto:bldg-sim-bounces at lists.onebuilding.org> 
>> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *sambhav 
>> tiwari
>> *Sent:* Saturday, March 27, 2010 12:37 AM
>> *To:* 
>> <mailto:bldg-sim at lists.onebuilding.org>bldg-sim at lists.onebuilding.org 
>> <mailto:bldg-sim at lists.onebuilding.org>
>> *Subject:* [Bldg-sim] DOAS system
>>
>>  
>>
>> Hi All,
>>              I would like to know what is DOAS system for what purpose 
>> it is used .I have only heard about it but not used in any of the 
>> projects. It wil be so nice if anyone can tell for what applications 
>> it is used.
>>
>> Thanks
>> Sambhav Tiwari.
>>
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