Thanks David, at least some confirmation that there is a reason I am losing my mind on this project. I’m running 8.2, so I don’t think there has been a total
pump fix. My variable speed single pump (with zero minimum flow) seems to be with the variable flow program, but I have two headered pumps on heat exchangers that are not playing ball. Perhaps they need “fixing” as well. I’ll try to get someone on my team
to change them to variable speed with zero minimum flow and see if things improve.
Ned Lyon, P.E. (MA, WV)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Wednesday, February 11, 2015 10:58 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] RE: Loop Temperature Control With Heat Exchangers
Hi Ned,
In testing various PlantLoop applications (ChW, HW, CW for WSHPs), I've also observed unexpected pumping behavior when the min flow on the pump is set to a non-zero number. Basically, the pump runs continuously, regardless of load and even if operation is
set to Intermittent. I believe this bug was reported to the E+ dev team through various avenues, and is addressed in E+ v8.2. Not sure if this was exactly your issue, but based on your second post, it sounds it is related.
David
--
David Reddy
360 Analytics
Building Energy Analysis Consultants
mail: 9750 3rd Ave NE, Suite 405, Seattle, WA 98115
office: 206.557.4732 x 201
cell: 206.406.9856
web: www.360-Analytics.com
On 2/11/2015 6:01 AM, 'Edward G. Lyon'
eglyon@xxxxxxx [EnergyPlus_Support] wrote:
�to parrtially answer my own question, E+ apparently has a problem controlling loop temperature when the loop flow is greater than it needs (why bypass doesn’t seem to help I don’t know). Once I let my main loop pump slow to zero flow (I initially slowed to about 20% flow for typical VFD control) and autosize it instead of using the flows from the ME, loop temperature control improved�
I am uncertain if the control properly cascades through the heat exchanger isolations I am using.
Ned Lyon, P.E. (MA, WV)
Staff ConsultantSIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Tuesday, February 10, 2015 11:22 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Loop Temperature Control With Heat Exchangers
I am modeling a proposed design for a mixed loop water to air HVAC system. The cooling tower and boilers are connected to the mixed loop by heat exchangers. I’m having trouble controlling the mixed loop temperature and plant operation. For instance for the cooling tower, the mixed loop is pumping 300 gpm (minimum pump flow from a 1800 gpm variable speed pump) while the cooling tower side of the heat exchanger ramps all the way up to 1800 gpm full capacity (headered pump). The cooling tower is temperature controlled off the supply branch outlet and the mixed loop is temperature controlled off the mixed loop mixer for cooling and heating heat exchangers. The mixed loop also does not drop to the low temperature set point even though there is heating call to the boiler.
We also seem to have some issues with zone multipliers. We have plenty of mixed loop pumping capacity, but we have lots of unmet hours with the equipment we were given. When we autosize the zone equipment, we get 2-3 times equipment sizes, but still at minimum pump flow.
Any insight could be helpful.
Ned Lyon, P.E. (MA, WV)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
| Engineering of Structures and Building Enclosures
41 Seyon Street, Bldg. 1, Suite 500
Waltham, MA 02453
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
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Posted by: "Edward G. Lyon" <EGLyon@xxxxxxx>
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