Student One On One Discussions

One of the benefits of the PEC program is that Ryan provides support for one on one work sessions to help students develop their system diagrams and projects. We I do one of the sessions, I try to remember to record it so that the attendee has it to refer to subsequently.

In some cases, I realize the information might be of general interest to other students in the class doing similar work, in which case, assuming the person I am working with is comfortable with it, I will place the video of that session here with a brief description of the discussion and any related resources that come up. Otherwise, I post the videos and related resources on a hidden page and send the link to the student afterwards so they can access it the information that way.

CHW Coil Temperature Rise; Coil Design Performance vs. Reality

Humidifiers; Hospital Codes

Functional Testing and Pump Tests for a HHW System

Parallel Pumps and Parallel Pump Curves

Thermal Storage System Assessments, the Ladder on Its Side Concept, and Triple Duty Valves

Flow Profile Assignment Discussion with Daniel's Team

CHW Coil Temperature Rise; Coil Design Performance vs. Reality

I forgot to click the record button for Brian's session (sorry about that), but one of the things we discussed that may be of broader interest is the design performance of a coil, in particular, a cooling coil relative to what it will do in day to day operation. Brian's building is served by a central chilled water system with a design temperature rise of 20°F. This can be challenging to achieve on a design day, especially for small coils like those you might find in a fan coil unit.

But even if you are able to make a selection that hits a 20°F Δt on the design day, you may find that it does

not do that on most other days due to the variations in entering air conditions it will see. If the system is a VAV system and/or has a discharge temperature reset, the performance will also be shifted by these factors.

If the performance achieved delivers less than the targeted temperature rise, which will frequently be the result, then the system will be driven into low delta t syndrome. In other words, most systems will enter the dreaded low delta t syndrome by design, even if nobody does anything wrong operationally.

The chart above is logged data from a 2.300 ton plant that serves approximately 60 nearly identical variable volume, integrated economizer equipped AHUs in the Seattle area. The plant and coils were selected for a 16°F Δt. But as you can see, even though the plant is well run, it seldom see's its design temperature rise. The resources below provide additional information on coil performance and low delta t syndrome.

coil_performance_from_u_of_w_load_dynamics_slides.pptx
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These slides are a subset of a presentation I use to discuss load profiles and illustrate how the performance of one of the coils in the Seattle project above varies as the entering conditions vary based on coil modeling.

cooling_coil_model_v6.xlsx
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This is the spreadsheet behind the charts in the PowerPoint. You can play with the filters to see how the coil performed with cool humid air vs. cool dry air, etc.

variable_flow_chiller_plants_v2.doc
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This is a white paper i wrote at PECI about variable flow primary/secondary plants and how they work and some of the issues (like low deltat t syndrome)

variable_flow_plants_v6.pptx
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This is a slide set I use sometimes to discuss different central plant configurations, including variable flow primary/secondary.

Humidifiers; Hospital Codes

I also forgot to hit the record button for my session with Austin yesterday. But there were two topics that came up that have come up with others so I thought I would post that information here.

humidifiers.pdf
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One was humidification and the file to the left is an article I wrote for HPAC on the topic a while back. It looks at the most common approaches and compares them.

hospital_design_performance_and__commissioning_issues_v1.pptx
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2017-01-12_mo_licensing_act_19c30-20.pdf
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Austin's building is a heath care setting and the codes governing those types of applications are more stringent than a typical office building code. The PowerPoint file to the left contains some code information I put together for a previous EBCx class regarding hospital codes and commissioning considerations.

Most hospital codes eventually come back to the Joint Commission for Hospital Accreditation (JCA) in terms of the enforcement requirements. The .pdf file is an example of a state hospital licensing act. It is for Missouri, which is where I did a lot of hospital design work. The mechanical system requirements and tables that you will find starting on page 21 are very similar for most jurisdictions, at least that has been my experience.

In California, OSHPD is the body that governs that sort of thing. I am not as familiar with their requirements but Tony Pierce, whom you will meet in May when he is a guest instructor, does a lot of hospital work in California. So if you have a California specific question, let me know and I will see he has time for a chat with you.

Functional Testing and Pump Tests for a HHW System

This session is a discussion I had with James about how to go about testing the hot water system he has targeted for his project. It includes a discussion of pump testing techniques, pump optimization strategies, and techniques that could be used to develop a load profile using trend data.

In the course of our discussion, I mention a number of resources so here they are.

One is the link to the BACnet Testing Labs site, where you can look up the PICS (Protocol Implementation and Conformance Statement) for a BACnet certified product to get a sense of what objects are made visible, and the nature of those objects. The vendors should have that information in their manuals, but sometimes it is faster to go straight to the source, at least as a first pass. The image to the left is a screen shot of what showed up when I picked ALC from on the Tested Products page.

I also referenced several blog posts/web pages.

This link is the blog post about measuring pipe surface temperatures and the subsequent one shows you how to install a surface temperature sensor for a data logger in order to get viable data if you don't have a well you can use.
This post is the first in a series of posts about how 4-20 ma current loops work and how you can use a data logger to monitor them. The monitoring part is specific to using Onset loggers and their 4-20 ma cable but would generally apply to other loggers. And you can do a similar thing for transmitters that generate a 1-5 vdc or 2-10 vdc signal using a voltage divider able that Onset has.
This link takes you to a video where I do a pump test on the chilled water pump at the PEC. We have a tach and a power meter set up on the pump and you can see all of those parameters change as I throttle the pump and it unloads. So pretty darned exciting.

Parallel Pumps and Parallel Pump Curves

tab_18.1_-_pump_ineractions_and_the_affinity_laws_v3.pptx
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The file to the left contains slides that I use in the U of W DDC class that I help support and focus on different interactions that can happen between pumps in parallel, including how shutting one of two identical pumps that are in parallel down does not reduce the flow by 50%, why running

two redundant parallel pumps at reduced speed instead of one at full speed will likely not save energy, how pumps sharing a long common header will move around on their pump curves depending on which pumps are running, and how dissimilar pumps in parallel interact in potentially adverse ways.
You will find information on how to construct a parallel pump curve in the slides from the Pumps and Piping; Design, Performance and Commissioning Issues class in the module titled Parallel Pumps and Pump/Motor Interactions. You will also find additional information on pumps and parallel pumps in the two Energy Design Resources design briefs that have the word "pumps" in their title.

Thermal Storage System Assessment, the Ladder on Its Side Concept, and Triple Duty Valves

ice_storage_system.zip
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Energy storage, demand management, and energy recovery strategies are complex in terms of how to assess their cost benefit, partly because they can be physically complex, but also because their value in terms of saving dollars and/or energy is not only related to their efficiency, it is also related to the rate schedules behind them.

For example, in a project I was involved with where we recovered energy using a water source heat pump in a hospital's central chilled water plant. We would load a water source heat pump to match the heating demand (primarily reheat and domestic hot water during the times of year when we did this) by resetting the mixed air temperature up and down in one of the major air handling systems to false load (or not) the chilled water coil in the unit.

Every year or two, we would need to adjust the control sequence in terms of when we allowed the strategy to work and what the temperatures were on the reset schedule based on the cost of gas and the cost of electricity. When electricity was cheap and gas expensive, we could afford to allow the heat pump to recover energy to much higher hot water temperatures (less efficient heat pump operation) than when the opposite was true.

A similar concept applies to the ice storage system at the PEC. When we upgraded the controls, Ryan asked me to look at the sequence and set points because the electric rates and demand periods were much different now than when the system was installed. We also suspected that the chiller performance was not "as advertised".

It turned out that it simply was not a good plan to make ice currently unless you need the capacity to peak on a day when it will be hot outside and there is a big event in the building. I believe that is how Ryan operates the system currently.

The files in the zip file above are my analysis, my discussion of it, and an NCBC presentation done by one of the EBCx students at the time who focused on testing the system to validate or not my theories. While specific the the PEC, the concepts can be generally applied, so those of you working with energy recovery, thermal storage, and demand shifts may find them useful.
Another concept that came up during my system diagram meeting with Dallas was how to manage the Ladder On Its Side concept when you have a really big system. I cover that in a set of slides I use when I did the system diagram workshop in the past and you will find them on the System Diagram Workshop materials page in the Basic Concepts module, starting around slide 11.

Finally triple duty valves came up in a number of discussions, including how to read them. You will find information on how to read them in Slack discussion I had with Thomas. You will find additional information, including some pictures of different types and what one looks like inside in the slides from the Pumps and Piping; Design, Performance and Commissioning Issues class in the module titled Pipe, Valves, and Fittings starting around slide 31. You will also find additional information the two Energy Design Resources design briefs that have the word "pumps" in their title.

Flow Profile Assignment Discussion with Daniel's Team

degrading_chw_plant_delta_t_-_ashrae-d-6996-20020403.pdf
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This is a recording of a web meeting I had with Daniel and his team to discuss their results for the assigment where you used logged data from the chillers and plant to create a flow profile.

The files below are files that came up in the course of the discussion.

It turns out the coil model spreadsheet I open up is already uploaded above.