[TRNSYS-users] Modeling a hydronic heating coil

[Matt Fung]

Thanks, Jeff!  I took a rather crude approach to modeling a tankless (temporarily) by just passing water through an auxiliary heater and setting the output very high.  I have the TESS library.  Is the tankless model in that library?  If not, how can I get it?

Matt Fung
Associate Engineer



7407 Tam O'Shanter Drive
Stockton, CA 95210-3370
Phone: 209.473.5000 / Fax: 209.474.0817
MFung at ConSol.ws
www.ConSol.ws

-----Original Message-----
From: Jeff Thornton [mailto:thornton at tess-inc.com] 
Sent: Thursday, May 08, 2008 12:07 PM
To: Matt Fung; trnsys-users at engr.wisc.edu
Subject: Re: [TRNSYS-users] Modeling a hydronic heating coil

<I am trying to model a hydronic heating coil with a tankless water
heater.  The hydronic coil also has a separate DX cooling coil with it. 
These systems are being applied to a Type56 building.  Can anyone suggest
which Types that would accurately model this situation?  I am currently
using a Type 754 for the heating coil and Type 756 for the cooling coil.>

754 and 756 take a rather simplistic approach when they model coils.  The
assumption in these two models is that the specified outlet conditions
(setpoints etc.) are met by the device and the loads are then imposed upon
the fluid streams.  As you are likely aware, this isn't always the case -
especially if the fluid temperatures aren't sufficient to meet the cooling
or heating loads.  I would personally use the 508 cooling coil and the 753
heating coil which both represent a more accurate way of modeling coils.

How are you modeling the tankless water heater?  We have a new tankless
model that we developed late last year that is now available.  The model
accounts for many of the more interesting issues that define the current
tankless water heaters that are on the market (low limit flow cut-outs,
temperature instabilities etc.)

Jeff


Jeff Thornton
President - TESS, LLC

2916 Marketplace Drive - Suite 104
Madison WI 53719 USA

Phone: 608-274-2577
Fax: 608-278-1475
E-mail: thornton at tess-inc.com
Web: www.tess-inc.com