[Equest-users] Air-Cooled EIR Curves

[Nick Caton]

Hi John,

 

Hmm… intuitively I think this makes sense, but I haven’t actually gone through creating a set of custom packaged DX curves before - lets’ first verify we’re looking at the same definition:

Volume 2: Dictionary > HVAC Components > SYSTEM > Cooling Equipment > DX Cooling

COOL-EIR-FT

Takes the U-name of a bi-linear or bi-quadratic curve that describes the Electric Input Ratio for cooling as a function of entering wet-bulb temperature and outdoor dry-bulb temperature (for direct expansion coils) or entering wet-bulb temperature and entering water temperature for a Water Loop Heat Pump (HP) system. At ARI conditions, the value of the curve should be 1.

I’m pretty sure the entering wet-bulb is that found entering the evaporator coil - the mixed air about to be conditioned.  If you check out a typical set of packaged DX unit performance tables (If you want a specific example to follow along, I’ve just cracked open an engineering guide for the Lennox LGH series <http://tech.lennoxintl.com/C03e7o14l/HS7CbNGGFw/ehb_lgh_abox_1010.pdf> * to page 21), you’ll find they’ve got OA DB along one axis (85/95/105/115) and Entering WB along the other axis (63/67/71).   It would appear the same tables could also be used to reference data for COOL-CAP-FT and COOL-SH-CAP curves.

 

Make sense now?

 

‾Nick

 

*Disclaimer: I have no particular ties or intent/business to advocate Lennox over their competitors - all of their major competitors publish similar reference/sizing tables, and this particular unit’s guide just happened to be near the top of my reference stack.

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John T. Forester
Sent: Wednesday, January 19, 2011 4:50 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Air-Cooled EIR Curves

 

Quick question,

 

When creating custom EIR fT and EIR fPLR curves for air-cooled packaged DX units with digital scroll compressors, what are the two independent variables?  The DOE2 help says to use entering wet-bulb and outside air dry-bulb.  Where is the entering wet-bulb temperature measured?  Intuitively, this doesn’t seem correct to me.

 

Thanks,

 

John

 

John T. Forester, P.E., LEED AP, Mechanical Design Engineer I BVH Integrated Services I 617.658.9008 tel I 617.244.3753 fax I One Gateway Center Suite 506, Newton MA 02458 I www.bvhis.com I Hartford ● New Haven ● Boston

 

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