reducing unmet hours with thermostat settings/controls

4 posts / 0 new
Last post

Christopher,

* Which PNNL manual are you referring to and can you provide a link?
* What modeling applications do you use it for (LEED, code compliance, other baselines etc.)?
* Is dual maximum control the same as TWO-POSITION in DOE-2/eQUEST?
* What THERMOSTAT-TYPE would you recommend for a baseline if different from a proposed design (and is there language anywhere that supports/allows it)?
Thanks,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP
Senior Energy Engineer

[Pathfinder-EA-logo-2]T: (585) 698-1956 F: (585) 325-6005
bbishop at pathfinder-ea.com www.pathfinder-ea.com
134 South Fitzhugh Street
Rochester, NY 14608 [cid:image011.png at 01D4E482.692A7AA0] Ask me why Carbon Fee & Dividend may be right for you.

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

Hi Bill,
The PNNL document is, ASHRAE Standard 90.1-2010 Performance Rating Method Reference Manual, May 2016. The manual addresses 90.1-2010 Appendix G.

Dual maximum control is achieved using THERMOSTAT-TYPE = REVERSE-ACTION. The baseline model would use Single Maximum (PROPORTIONAL). See page 124 in the document.
https://www.pnnl.gov/main/publications/external/technical_reports/PNNL-25130.pdf

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

[cid:image003.png at 01D4E534.01DDF310]

Jones, Christopher2's picture
Joined: 2017-10-12
Reputation: 0

All,
Does anyone have a different suggestion on addressing unmet hours in VAV systems that best meets the intent of 90.1 simulation?
As Christopher points out, the PNNL 90.1-2010 PRM Reference Manual (linked below ) requires ?single maximum? thermostat control for VAV zones (PROPORTIONAL in DOE-2/eQUEST). The heating airflow is not permitted to increase above 30% minimum flow (ZONE:MIN-FLOW-RATIO = 0.3). I have never interpreted G3.1.3.13 this way and have been using REVERSE-ACTION thermostats with ZONE:HMAX-FLOW-RATIO = 1.0 to address unmet heating hours in both Baseline and Proposed models. (HMAX-FLOW-RATIO = 0.5 or 0.6 is often sufficient.) This is easy to implement through zone defaults and minimizes adjustments to individual zones. If you have to use PROPORTIONAL thermostat control, I think you would need to increase the ZONE:HMIN-FLOW-RATIO above 0.3 or increase the SYSTEM:SIZING-RATIO.
Thanks,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP
Senior Energy Engineer

[Pathfinder-EA-logo-2]T: (585) 698-1956 F: (585) 325-6005
bbishop at pathfinder-ea.com www.pathfinder-ea.com
134 South Fitzhugh Street
Rochester, NY 14608 [cid:image006.png at 01D4E556.80F253E0] Ask me why Carbon Fee & Dividend may be right for you.

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

Bill,
I typically adjust the heating min air low to reduce unmet hours. I have never had an issue under review.

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

[cid:image001.png at 01D4E56C.24678620]

Jones, Christopher2's picture
Joined: 2017-10-12
Reputation: 0