• 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 ContractorRadiant & HydronicsThe Glitch & The Fix

The Glitch & The Fix: One size doesn't fit all

glitch-fix-feature
April 3, 2023
✕
Image in modal.

The Glitch:

A project requires both medium temperature (140° F at design) and low temperature (105° F at design) radiant floor panels. The system will also supply domestic hot water using an indirect water heater. The installer proposes the system shown in Figure 1. Assume each zone circuit requires a flow rate of 4 gpm when operating. Since the mod/con boiler has 1-inch pipe connections, the installer decides to use a 1 inch domestic hot water tempering valve to lower the water supply temperature to the lower temperature zones. He also decides to pipe the entire system with 1-inch tubing.

Can you spot at least six design or installation details that are going to create problems?

FIGURE 1
GF-april-2023-fig-1 [click image to enlarge]

The problems

  1. If the total design flow rate is 6x4 = 24 gpm, the 1-inch header piping is grossly undersized. Its use will likely create a high pressure drop when all zone circulators are operating. The undersized piping will also create more hydraulic interference between simultaneously operating circulators;
  2. The circulator labelled (P2) is in series with the zone circulators. The mod/con boiler requires a dedicated circulator that is hydraulically separated from the zone circulators;
  3. There is no central air separating device in the system;
  4. The purging valves are installed upside down;
  5. The expansion tank is very close to the outlets of circulators (P1) and (P2);
  6. The inlets of the zone circulators are shown very close to the header. This creates turbulence at the eye of the impellers, which could induce cavitation. There should be at least 12 pipe diameters of straight pipe on the inlets side of all circulators;
  7. The 1-inch tempering valve with Cv=3.0 is grossly undersized to supply 3 zone circulators at 4 gpm each. Pushing 12 gpm through a valve with a Cv of 3.0 would require about 16 psi. That’s much higher than any residential zone circulator can manage. A mixing valve with a Cv of approximately 12 would be the proper selection;
  8. The DHW circulator lacks a check valve. Without it, there will be some reverse flow through the coil of the indirect water heater when the space heating portion of the system is operating; and
  9. A mod/con boiler serving 6 zones is likely to experience short cycling when only one zone is on.

One fix

One way to correct the short-cycling issue is to install a buffer tank as shown in Figure 2.

FIGURE 2
GF-april-2023-fig-2 [click image to enlarge]

The buffer tank temperature is regulated by the boiler’s internal controller. It could be based on a setpoint with differential, or on outdoor reset control. The latter would improve the boiler’s efficiency, and the logic for such controller is built into most modern mod/con boilers.

A higher flow capacity mixing valve is used to reduce the water temperature to the lower temperature zones.

Other details that were incorrect in Figure 1 have been corrected in Figure 2.

Another fix

Although the system in figure 2 will work, it does require two tanks, one for domestic water heating and another for buffer. Needless to say (but I’ll say it anyway…), tanks are getting pretty expensive these days, especially when you need two of them.

The system shown in Figure 3 uses a reverse indirect water heat to provide domestic hot water (through its internal coils) as well as buffer the space heating loads. This tank also provides hydraulic separation between the boiler circulator and the two load circulators.

FIGURE 3
GF-april-2023-fig-3 [click image to enlarge]

The boiler would maintain the temperature within the tank at a temperature that:

  1. Is always high enough to provide the required DHW delivery temperature; and
  2. Is always high enough to supply the higher temperature radiant panels.

At design load that temperature would be 140° F (e.g., the stated design load supply temperature for the higher temperature panels). This is also likely to be hot enough to supply a typical DHW load.

Under partial load conditions the tank temperature could likely be reduced, but not lower than needed to produce the required DHW deliver temperature.

The load side of the system does away with 6 zone circulators, replacing them with 6 zone valves and two variable-speed pressure-regulated circulators.

This approach also requires less space in a mechanical area, and reduces standby heat loss since only one tank is holding heated water.


KEYWORDS: hydronics plumbers and pipefitters radiant floor panels radiant heating troubleshooting

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...
    Plumbing News
    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

IPEX celebrates grand opening of new Florida distribution center

IPEX celebrates grand opening of new Florida distribution center

NIBCO Press Solutions

NIBCO Press Solutions

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

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

AI can boost efficiency and profitability for plumbing, HVAC contractors

AI can boost efficiency and profitability for plumbing, HVAC contractors

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

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

Using hydronics to leverage time-of-use electrical rates

Watts Nexa mobile image

Behind the Wall: Where smart plumbing gets smarter

Six tankless water heaters that feed the nutraceutical manufacturer’s operations.

How to deliver large volumes of hot water quickly and intermittently

PMCE Home-X April 29 Free Webinar: From Legacy to Leadership: Preparing Your Home Services Business for the Next Generation

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

  • The Glitch & The Fix figure 1

    One size doesn't fit all when it comes to piping sizes

    See More
  • G&F-Fig1-Jan2022

    The Glitch + The Fix: One shot after another

    See More
  • glitch-fix-feature

    The Glitch + The Fix: Swapping one “box” for another

    See More

Events

View AllSubmit An Event
  • April 10, 2014

    Workshop: Hydronics for High Efficiency Wood-fired and Pellet-fired Boilers

    Session added to April 9-11 Northeast Biomass Heating Expo.
View AllSubmit An Event
×

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!