[Equest-users] ASHRAE 90.1 Appendix G Proposed Model

[Bruce Easterbrook]

I would not include the large unit.  It is a specific 
purpose/intermittent unit.  I would however investigate how it is going 
to be used.  Normally you try to segregate the truck loading areas from 
the rest of the plant to limit the area exposed to the exhaust fumes and 
to make it easier to remove them.  Sometimes though, making large items, 
this is not possible.  Typically these units are connected to CO/CO2 
sensors and also have an exhaust fan.  If you use the MUA unit to blow 
the exhaust fumes out it won't work when the doors are closed.  This is 
why an exhaust fan works better with the MUA unit.  The way the loading 
normally happens is the trailer is backed in first and the tractor comes 
in last, the door is closed and the truck is shut off for the loading 
period.  That puts all the truck exhaust on the ceiling by the loading 
doors.  That is where you put the exhaust fans.  The MUA unit is placed 
across from the exhaust to push the truck exhaust to the exhaust fans.  
The unit only runs until the sensor is satisfied.  As Bill mentioned you 
don't have to bring that MUA up to plant temperature either, that would 
depend on where you are dumping it and how much air there is.  You may 
not have to heat it at all.  I have used systems which bring in air 
unheated and use fabric tubes to spread it at ceiling level in the hot 
stratified air next to the ceiling.
I don't consider these events in the general system for heating the 
building but you do have to consider the event and how to mitigate it's 
impact on the plant and meet all the safety rules. You generally have 
unit heaters near large roll up doors as they are leaky and not as well 
insulated as the rest of the building. This comes in handy when you open 
the doors or when you have 10 tons of cold steel sitting in the loading 
bay.  Don't forget floor drains.
Bruce Easterbrook P.Eng.
Abode Engineering

On 08/10/2012 08:52 AM, Bishop, Bill wrote:
>
> Pete,
>
> Before increasing the proposed design heating capacity, I would 
> consider other changes you can make to the model:
>
> ·Increase the process/plug loads (after all, it is a manufacturing 
> facility)
>
> ·Decrease the heating thermostat setpoint (70F or less)
>
> ·If you have nighttime setback, create a morning warm-up period
>
> ·Increase the thermostat throttling range a few degrees (reflecting 
> less "comfort" but resulting in fewer unmet hours; IMO a last resort 
> before adding heating capacity)
>
> Note that you would make the same changes in the baseline for any/all 
> of these suggestions.
>
> Regards,
>
> Bill
>
> Senior Energy Engineer 28Jun2012 <mailto:wbishop at pathfinder-ea.com>
>
> *From:*equest-users-bounces at lists.onebuilding.org 
> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Peter Baumstark
> *Sent:* Friday, October 05, 2012 10:54 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] ASHRAE 90.1 Appendix G Proposed Model
>
> I have a high bay manufacturing facility with two100% OSA, CV, low cfm 
> but high air velocity heating only units. These are intended for 
> comfort heating.
>
> The building also has one 100% OSA, CV make-up air (MUA) unit, with a 
> gas furnace.  The MUA is only used when one or more roll-up doors are 
> open with trucks inside and unloading.  This blows the diesel fumes 
> out of the building.  The MUA has almost 3x the air volume capacity as 
> the two comfort heating units combined.
>
> When I model the proposed design, with just the two units intended for 
> comfort heating, I end up with almost 700 unmet heating hours.  I add 
> the capacity for the MUA unit and schedule it for the purpose of 
> comfort heating, and my unmet hours go down to less than 10.
>
> Also in 90.1, App G, if unmet load hours exceed 300, heating capacity 
> can be added incrementally until unmet load hours are reduced to below 
> 300.
>
> So would it be fair to not include the MUA unit for heating, but 
> simply add one or two more of the comfort heating units to get the 
> unmet hours down?  It seems like it may be over-kill to include the 
> MUA unit for the purpose of comfort heating.
>
> Any guidance would be appreciated.
>
> Thank you,
> Pete
>
>
>
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