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Re: [TRNSYS-users] Control of on active layer
Arnaud,
I was thinking that by "pre-heat" you meant this was the air input to an
air handler, then the output of the air handler (to the zone) is
constant and stability is not an issue. But if this air goes directly to
the zone, then yes, Jeff's recommendation of type 2 is better. Any kind
of control where you want to both *read* and *influence* zone
temperature needs a real controller with deadbands of some kind for
stability.
-Cramer
-----Original Message-----
From: Jeff Thornton [mailto:thornton@tess-inc.com]
Sent: Monday, July 13, 2009 11:24 AM
To: Cramer Silkworth; a.thome-08@student.lboro.ac.uk;
trnsys-users@engr.wisc.edu
Subject: Re: [TRNSYS-users] Control of on active layer
<I would like to pre-heat the inflow of the ventilation during the
heating period to see the impact that this would have on the heating
bill.
To do so I would like find a controller to model:
if Tzone>20°C then Tinflow=Toutside_amb
if Tzozne<20°C then Tinflow=35°C
Do you know wich controller should I use?>
<All you need is an equation:
Tinflow = gt(Tzone,20) * Toutside_amb + not(gt(Tzone,20)) * 35
the GT and LT functions return either 0 or 1, so this contruction gives
you, in effect, an in-else statement.>
While that seems like the ideal solution, using a simple equation to
watch the zone temperature and control the heating temperature will
likely result in a non-convergence situation. During one timesteps, the
zone will likely rise above 20 C when the heating temperature is 35 and
fall below 20 C when the heating temperature is ambient - causing an
unstable solution. I would suggest you use either the thermostat model
or the Type
2 controller - they're made to handle situations like this.
Jeff
Jeff Thornton
President - TESS, LLC
22 North Carroll Street - Suite 370
Madison WI 53703 USA
Phone: 608-274-2577
Fax: 608-278-1475
E-mail: thornton@tess-inc.com
Web: www.tess-inc.com