Re: [EnergyPlus_Support] frost/freeze error

Richard, thank you kindly.

Your explanations where very clear and useful..

A part of the problem was that I had used an HVAC system sized for one climate, and had moved it from one location to another, so the system was incorrectly sized...

Jeremiah D. Crossett

CleanTech Analytics

503-688-8951

www.cleantechanalytics.com

This document may contain valuable information proprietary to CleanTech Analytics which is private and confidential. It may not be shared, copied, stored or transmitted in any form without the prior written consent of CleanTech Analytics

On Tue, Mar 20, 2012 at 6:14 AM, Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Dear Jeremiah,
Your DX coil is trying to operate in cool weather. When it does, it applies its full capacity to the airstream and cools it down to freezing temperature.

This is the same error that Joe Huang posted about the other day (I think).
You?ll need to :

1.       Ignore it (after confirming that it?s not indicating some other problem)

2.       Turn off the coil during cold weather (after looking at the weather file to see when weather is below about 55-60F)

3.       Run an EMS script to turn off the coil whenever outdoor temp is lower than a set value

p.s., Certain ?baseline? systems (e.g., a heat pump serving an interior zone) don?t handle the situation well where an economizer is not used such as is the case in a warm climate zone. They need cooling in the cold weather, but the DX system doesn?t like operation then. (This is not a likely ?real? system, since engineers know these things. But a ?baseline? is not real?)

Here?s an EMS routine (grateful credit for which goes to Jean Marais and somebody at the Help desk a few months back):

DX coils that you want OFF via this routine must have their Unitary object specified with the same schedule which the EMS routine is turning on and off (?SchCpct_LowTempOFF? in this example)

The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of CleanTech Analytics
Sent: Monday, March 19, 2012 11:34 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] frost/freeze error

Dear List,

Any advise on how to approach this error?
Thanks

************* ===== Recurring Error Summary =====

************* The following recurring error messages occurred.
*************

************* ** Warning ** Coil:Cooling:DX:SingleSpeed "BLOCK1:ZONE1 AHU COOLING COIL" - Full load outlet temperature indicates a possibility of frost/freeze error continues. Outlet air temperature statistics follow:

************* ** ~~~ ** This error occurred 3849 total times;
************* ** ~~~ ** during Warmup 0 times;

************* ** ~~~ ** during Sizing 0 times.
************* ** ~~~ ** Max=1.999729 Min=0.701477

*************

Jeremiah D. Crossett
CleanTech Analytics

503-688-8951
www.cleantechanalytics.com

This document may contain valuable information proprietary to CleanTech Analytics which is private and confidential. It may not be shared, copied, stored or transmitted in any form without the prior written consent of CleanTech Analytics