[Equest-users] VFD vs constant pump

[Pramod .D via Equest-users]

Hi Melissa,

This makes sense. There's only small amount of energy usage increased in dhw with vfd pump. Thanks for your help.

Pramod
________________________________
From: Melissa Crowe<mailto:MCrowe at engsolutions.com>
Sent: ‎29-‎04-‎16 ಅಪರಾಹ್ನ 07:11
To: Pramod .D<mailto:d.pramod at setty.com>
Subject: RE: [Equest-users] VFD vs constant pump

Hi Pramod

Pump energy to the water, heats the water (there is a temperature rise across the pump).    When pump energy is reduced more boiler energy is required to maintain the same water temperature.  For the same reason when going from constant flow to VFD flow in CHW systems this results in a small cooling savings.

Melissa

From: Pramod .D via Equest-users [mailto:equest-users at lists.onebuilding.org]
Sent: Thursday, April 28, 2016 5:21 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] VFD vs constant pump

Hi All,

I am simulating a model to see the savings provided by VFD pump connected to the DHW plant loop. The energy used by the VFD pump is less compared to constant volume pump. The problem is the energy usage of DHW increases if constant volume pump is changed to VFD. Is this correct or am I missing anything?  How does VFD pumps increases DHW usage?

Thanks!
Pramod
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