• Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • CONTRACTORS
  • ENGINEERS
  • RADIANT & HYDRONICS
  • INSIGHTS
  • MEDIA
  • RESOURCES
  • EMAGAZINE
  • SIGN UP!
cart
facebook instagram twitter linkedin youtube
  • CONTRACTORS
  • BATH & KITCHEN PRO
  • BUSINESS MANAGEMENT
  • HIGH EFFICIENCY HOMES
  • TECHNOLOGY
  • WATER TREATMENT
  • PMC COLUMNS
  • PMC COLUMNS
  • Dave Yates: Contractor’s Corner
  • John Siegenthaler: Hydronics Workshop
  • Kenny Chapman: The Blue Collar Coach
  • Matt Michel: Service Plumbing Pros
  • Scott Secor: Heating Perceptions
  • ENGINEERS
  • CONTINUING EDUCATION
  • DECARBONIZATION | ELECTRIFICATION
  • FIRE PROTECTION
  • GEOTHERMAL | SOLAR THERMAL
  • PIPING | PLUMBING | PVF
  • PME COLUMNS
  • PME COLUMNS
  • Christoph Lohr: Strategic Plumbing Insights
  • David Dexter: Plumbing Talking Points
  • James Dipping: Engineer Viewpoints
  • John Seigenthaler: Renewable Heating Design
  • Lowell Manalo: Plumbing Essentials
  • Misty Guard: Guard on Compliance
  • RADIANT & HYDRONICS
  • RADIANT COMFORT REPORT
  • THE GLITCH & THE FIX
  • INSIGHTS
  • CODES
  • GREEN PLUMBING & MECHANICAL
  • PROJECT PROFILES
  • COLUMNS
  • SPONSOR INSIGHTS
  • COLUMNS
  • Codes Corner
  • Natalie Forster: Editorial Opinion
  • Guest Editorial
  • MEDIA
  • PODCASTS
  • VIDEOS
  • WEBINARS
  • RESOURCES
  • INDUSTRY CALENDAR
  • DIRECTORIES
  • EBOOKS
  • PM BOOKSTORE
  • CE CENTER
  • MARKET RESEARCH
  • CLASSIFIEDS
  • EMAGAZINE
  • EMAGAZINE
  • ARCHIVE ISSUES
  • CONTACT
  • ADVERTISE
  • PME EMAGAZINE ARCHIVES
search
cart
facebook instagram twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • CONTRACTORS
    • BATH & KITCHEN PRO
    • BUSINESS MANAGEMENT
    • HIGH EFFICIENCY HOMES
    • TECHNOLOGY
    • WATER TREATMENT
    • PMC COLUMNS
      • Dave Yates: Contractor’s Corner
      • John Siegenthaler: Hydronics Workshop
      • Kenny Chapman: The Blue Collar Coach
      • Matt Michel: Service Plumbing Pros
      • Scott Secor: Heating Perceptions
  • ENGINEERS
    • CONTINUING EDUCATION
    • DECARBONIZATION | ELECTRIFICATION
    • FIRE PROTECTION
    • GEOTHERMAL | SOLAR THERMAL
    • PIPING | PLUMBING | PVF
    • PME COLUMNS
      • Christoph Lohr: Strategic Plumbing Insights
      • David Dexter: Plumbing Talking Points
      • James Dipping: Engineer Viewpoints
      • John Seigenthaler: Renewable Heating Design
      • Lowell Manalo: Plumbing Essentials
      • Misty Guard: Guard on Compliance
  • RADIANT & HYDRONICS
    • RADIANT COMFORT REPORT
    • THE GLITCH & THE FIX
  • INSIGHTS
    • CODES
    • GREEN PLUMBING & MECHANICAL
    • PROJECT PROFILES
    • COLUMNS
      • Codes Corner
      • Natalie Forster: Editorial Opinion
      • Guest Editorial
    • SPONSOR INSIGHTS
  • MEDIA
    • PODCASTS
    • VIDEOS
    • WEBINARS
  • RESOURCES
    • INDUSTRY CALENDAR
    • DIRECTORIES
    • EBOOKS
    • PM BOOKSTORE
    • CE CENTER
    • MARKET RESEARCH
    • CLASSIFIEDS
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • CONTACT
    • ADVERTISE
    • PME EMAGAZINE ARCHIVES
  • SIGN UP!
Plumbing & Mechanical ContractorThe Glitch & The Fix

The Glitch & The Fix: Mixed results

The Glitch - April
The Fix
The Glitch - April
The Fix
April 22, 2021

The Glitch:

An installer is asked to connect a single speed geothermal water-to-water heat pump to a highly-zoned low temperature hydronic distribution system. The installer realizes that when a single speed heat pump is connected to such a distribution system, it is essential to use a buffer tank, so one is installed, as shown in Figure 1. 

The system uses a temperature setpoint controller to operate the heat pump so the buffer tank is maintained between 110° F and 130° F. It also uses a 4-way motorized mixing valve to control the supply water temperature to the distribution system based on outdoor reset control. At design load, the distribution system requires 125°. The heat pump is enabled to operate whenever any of the zone thermostats call for heat. The system has a 2 gallon expansion tank.

Can you identify several details that are wrong, and propose a better design?

The Glitch - April

The Fix:

The key to good performance with water-to-water heat pumps is keeping the load water temperature as low as possible. It makes no sense to maintain the buffer tank at a higher temperature than necessary, and then mix down to achieve the required supply water temperature to the heat emitters. The 4-way mixing valve, which is specifically intended to interface a conventional boiler to a low temperature load is completely unnecessary, and has been eliminated in Figure 2.

The Fix

Other Changes include:

  1. Set up the buffer tank in a 3-pipe configuration to allow direct-to-load heat transfer between the heat pump and distribution system when both are operating at the same time. Also avoid buffer tanks configurations where flow enters vertically at the top of the tank.
     
  2. Install a check valve between the heat pump and buffer tank to prevent reverse thermosiphoning when the tank is warm and the heat pump is off. Without this valve, which might be integrated into the circulator, warm water will slowly flow backwards through the inactive heat pump and its piping, unnecessarily dissipating heat to the surrounding space.
     
  3. Use an outdoor reset controller to turn the heat pump and its associated circulators on and off based on the temperature at a sensor located in a well at the mid-height of the tank.  This keeps the water temperature just warm enough to maintain comfort in the building while also allowing the heat pump to operate at the highest possible COP.
     
  4. Based on an estimated system volume of 120 gallons, an assumed system height of 10 feet, a maximum water temperature of 120°, the expansion tank needs to have a minimum volume of 4 gallons.
     
  5. The original system lacked any means of differential pressure control on the highly zoned distribution system. This has been corrected by using a variable-speed pressure-regulated circulator for the distribution system.
     
  6. The original system lacked a central air separation device. This has been added in Figure 2.
     
  7. The original system lacked a means of removing air from the top of the buffer tank. A float-type air vent has been added at the top of the tank in Figure 2.
     
  8. The original system shows a circulator, on the right side of the tank, pumping toward the point of no pressure change. This circulator is not necessary. Even if it were, it’s not in the correct location relative to the point where the expansion tank connects.
     
  9. The sensor for the mixing valve is shown very close to the outlet of that valve. Mixing may not be completed at this point and thus the temperature felt by the sensor may not be the true supply temperature to the heat emitters. Always locate the supply temperature sensor for a mixing valve downstream of the circulator (assuming that the circulator is on the supply side of the heat emitters).
     
  10. Notice that the expansion tank is connected to the buffer tank. Thus there will be very little change in the pressure within the buffer tank when these circulators operate. Both circulators in Figure 2 have been located so that they pump away from the buffer tank.
     
  11. A drain valve has been added to allow the buffer tank to be emptied if ever necessary.
     
  12. A pressure relief valve has been added near the expansion tank connection.

 

Download The Glitch & The Fix: April 2021 PDF

KEYWORDS: geothermal plumbers and pipefitters troubleshooting water-source heat pumps

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

Recommended Content

JOIN TODAY
to unlock your recommendations.

Already have an account? Sign In

  • Worker using the Milwaukee Tool SWITCH PACK drain cleaner

    Pipeline profits: Drain cleaning, pipe inspection create opportunities

    Drain cleaning and inspection services offer lucrative...
    Green Plumbing and Mechanical
    By: Nicole Krawcke
  • Uponor employee, Arturo Moreno

    The reinvestment in American manufacturing and training

    Plumbing & Mechanical Chief Editor Nicole Krawcke and...
    Plumbing News
    By: Nicole Krawcke and Natalie Forster
  • March 2024 Women in Plumbing hero image of woman engineer overlayed by circle of hexagon shapes with numbers from 1 to 10

    Celebrating 10 Influential Women in the Plumbing Industry

    Celebrating Women's History Month and Women in...
    Plumbing News
    By: Nicole Krawcke
Subscribe For Free!
  • eNewsletters
  • Online Registration
  • Subscription Customer Service
  • eMagazine
  • Manage My Preferences

NIBCO Press Solutions

NIBCO Press Solutions

IPEX celebrates grand opening of new Florida distribution center

IPEX celebrates grand opening of new Florida distribution center

AI can boost efficiency and profitability for plumbing, HVAC contractors

AI can boost efficiency and profitability for plumbing, HVAC contractors

Bell & Gossett Illustrates Path to Net-zero at AHR Expo

Bell & Gossett Illustrates Path to Net-zero at AHR Expo

More Videos

Sponsored Content

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the Plumbing & Mechanical audience. All Sponsored Content is supplied by the advertising company and any opinions expressed in this article are those of the author and not necessarily reflect the views of Plumbing & Mechanical or its parent company, BNP Media. Interested in participating in our Sponsored Content section? Contact your local rep!

close
  • J.J. Keller CMV vehicles on road
    Sponsored byJ. J. Keller & Associates, Inc.

    The dash cam game-changer for small business safety

Popular Stories

The interior of a government building.

President Trump signs executive order promoting skilled trades and apprenticeships

Figure 1 is a sketch of the flow problems of the current plumbing system.

Hydronic heating glitch solved: Why adding a circulator won't fix primary loop flow issue

Underfloor heating installation with drain sewer hole in bathroom close up on water floor heating.

Using hydronics to leverage time-of-use electrical rates

PM BEMIS June 25 Free Webinar: Optimizing Plumbing Solutions for Single-Family, Multi-Family & Public Spaces

Events

November 13, 2024

Future Proofing MEP: Navigating the 2026 High Efficiency Water Heating Standards

Join our deep dive into DOE’s new standards so you can future-proof your MEP practice.

EARN: 0.1 ASPE CEU; 1 AIA LU/HSW; 0.1 IACET CEU*; 1 PDH

View All Submit An Event

Poll

Will business be up or down in 2025?

Do you anticipate business in 2025 to be up or down in comparison to 2024?
View Results Poll Archive

Products

The Water Came To A Stop

The Water Came To A Stop

See More Products

Download the FREE Water Conservation, Quality & Safety eBook: Plumbing Trends Increasing Safe Water Availability

Related Articles

  • G&F-sept-2021-figure-1.jpg

    The Glitch & The Fix: Intentions versus results

    See More
  • Glitch and Fix Figure 1

    The Glitch and Fix: Mixed mode

    See More
  • G&F Figure 1

    The Glitch and Fix: Mixed mode

    See More

Related Products

See More Products
  • what hydronics taught holohan.jpg

    What Hydronics Taught Holohan: A Memoir of Life in the Heating Industry

  • M:\General Shared\__AEC Store Katie Z\AEC Store\Images\Plumbing\new sites\classic_hydronics.gif

    Classic Hydronics - How To Get The Most From Those Older Hot-Water Heating Systems

  • 51CHeeKvw4L._SX322_BO1,204,203,200_.jpg

    Hydronic Radiant Heating: A Practical Guide for the Nonengineer Installer

See More Products
×

Keep your content unclogged with our newsletters!

Stay in the know on the latest plumbing & piping industry trends.

JOIN TODAY!
  • RESOURCES
    • Advertise
    • Contact Us
    • Directories
    • Store
    • Want More
    • Supply House Times
  • SIGN UP TODAY
    • Create Account
    • eMagazine
    • eNewsletter
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey/Respondent Access
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • Instagram
    • YouTube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing

search
cart
facebook instagram twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • CONTRACTORS
    • BATH & KITCHEN PRO
    • BUSINESS MANAGEMENT
    • HIGH EFFICIENCY HOMES
    • TECHNOLOGY
    • WATER TREATMENT
    • PMC COLUMNS
      • Dave Yates: Contractor’s Corner
      • John Siegenthaler: Hydronics Workshop
      • Kenny Chapman: The Blue Collar Coach
      • Matt Michel: Service Plumbing Pros
      • Scott Secor: Heating Perceptions
  • ENGINEERS
    • CONTINUING EDUCATION
    • DECARBONIZATION | ELECTRIFICATION
    • FIRE PROTECTION
    • GEOTHERMAL | SOLAR THERMAL
    • PIPING | PLUMBING | PVF
    • PME COLUMNS
      • Christoph Lohr: Strategic Plumbing Insights
      • David Dexter: Plumbing Talking Points
      • James Dipping: Engineer Viewpoints
      • John Seigenthaler: Renewable Heating Design
      • Lowell Manalo: Plumbing Essentials
      • Misty Guard: Guard on Compliance
  • RADIANT & HYDRONICS
    • RADIANT COMFORT REPORT
    • THE GLITCH & THE FIX
  • INSIGHTS
    • CODES
    • GREEN PLUMBING & MECHANICAL
    • PROJECT PROFILES
    • COLUMNS
      • Codes Corner
      • Natalie Forster: Editorial Opinion
      • Guest Editorial
    • SPONSOR INSIGHTS
  • MEDIA
    • PODCASTS
    • VIDEOS
    • WEBINARS
  • RESOURCES
    • INDUSTRY CALENDAR
    • DIRECTORIES
    • EBOOKS
    • PM BOOKSTORE
    • CE CENTER
    • MARKET RESEARCH
    • CLASSIFIEDS
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • CONTACT
    • ADVERTISE
    • PME EMAGAZINE ARCHIVES
  • SIGN UP!