[Equest-users] Cooling tower - Two-speed vs VFD fan, bug?

Jason Millheim jason at rhtenergy.com
Tue Jun 4 13:27:45 PDT 2013


Energy savings in cooling tower fans are a result of the ability for
turndown when heat loads are less than the full capacity of the cooling
tower.  You will not see any savings if the heat load in the condenser water
loop does not vary.  In a similar manner, if the heat load does decrease but
the fans remain running at full speed in order to drive down the condenser
water temperature, there will not be any savings.  You may want to check if
there is a condenser water temperature reset which is not being utilized.

 

Jason Millheim, P.E., LEED AP

Mechanical Engineer

Commercial + Industrial

 

Working with Energy Trust of Oregon

 

541.770.5884 DIRECT

541.842.0120 CELL

541.770.7477 FAX

 <http://www.energytrust.org/> energytrust.org

 

This email is intended for its addressee(s) and may contain confidential
information.  If you receive this email in error, please notify me and
delete it promptly.  Thank you.

 

+ Please consider the environment before printing this email.

 

From: R B [mailto:slv3sat at gmail.com] 
Sent: Tuesday, June 04, 2013 9:57 AM
To: RobertWichert; eQUEST Users List
Subject: Re: [Equest-users] Cooling tower - Two-speed vs VFD fan, bug?

 

The default on vfd is 40%. I see savings compared to every other option -
one-speed, discharge damper etc. None of them use the fan-speed vs power fan
curve except two-speed and vfd options. So, basically both are working in
the same way with a penalty of vfd losses in the vfd case? I would think
that the two-speed option will not need a curve.

Thanks, 

-Rohini

 

On Tue, Jun 4, 2013 at 8:37 AM, RobertWichert <robert at wichert.org> wrote:

I recall having to pick the "minimum speed ratio" box or something like that
before the VFD would show savings.

Have you set that?





Robert Wichert P.Eng. LEED AP BD&C
+1 916 966 9060 <tel:%2B1%20916%20966%209060> 
FAX +1 916 966 9068 <tel:%2B1%20916%20966%209068> 
 
 
 
 
 
 
 
===============================================

On 6/3/2013 7:22 PM, R B wrote:

Hi all, 

Has anyone tried to see the savings associated with upgrading two-speed fan
to VFD in a cooling tower? I see increased energy use due to the vfd. on
further digging, it looks to me that both two-speed and vfd fans use the
same fan performance curve. Is this the case or am I missing something?

Thanks in advance,

-Rohini

 

_______________________________________________
Equest-users mailing list
http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
To unsubscribe from this mailing list send  a blank message to
EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130604/3661a046/attachment-0002.htm>


More information about the Equest-users mailing list