• 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!
Columns

Transitions, Part 2

By John Siegenthaler, P.E.
November 1, 2011
How to extract more heat from a storage tank.

Figure 1


Last month we looked at the basic piping and controls needed to connect a wood gasification boiler to a low-temperature hydronic distribution system. The piping layout we discussed is shown in Figure 1.

The wood gasification boiler is fired at a high rate of combustion and transfers its heat to a large, well-insulated storage tank.

Upon a demand for space heating from any heating zone, an outdoor reset controller is powered on to measure the temperature at the top of the storage tank and compare it to its “target” supply water temperature. If the tank is deemed sufficiently warm to supply the zones, circulator (P2) is turned on to deliver heated water to the closely spaced tees that hydraulically separate the distribution system from the heat sources.

If the storage temperature is too low to supply the load, the auxiliary boiler is turned on along with circulator (P1). Again, heated water is delivered to the closely spaced tees.

Figure 2

Milk It For More

One limitation of this basic control scheme is that there is no operating mode where both the storage tank and auxiliary boiler can supply heat to the load. Consider the situation where the temperature at the top of the storage tank is slightly lower than the lower limit established by the outdoor reset controller, but still warmer than the return temperature of the distribution system. Under these conditions, the tank can still contribute some heat to the space-heating load. The remaining heat would be supplied by the auxiliary boiler.

The addition of a differential temperature controller (∆T controller), such as those used to control solar thermal systems, allows the storage tank to be utilized at a lower temperature. Figure 2 shows where the sensors for the ∆T controller would be located. Figure 3 shows a ladder diagram containing the hard-wired logic for the overall system.

If the outdoor reset controller determines the tank is too cool to supply the load, its normally open contact closes to power up the ∆T controller as well as a relay that enables the boiler to operate. The control of circulator (P2) is solely at the discretion of the ∆T controller.

The ∆T controller measures the temperature difference between water at the top of the buffer tank and that returning from the distribution system. If the top of the tank is at least 2 degrees F above the return temperature, the normally open contact in the ∆T controller closes to keep circulator (P2) operating.

The boiler and circulator (P1) also are operating at this time. The boiler is monitoring the temperature downstream of the closely spaced tees. Ideally it modulates to add just enough heat to maintain this temperature close to the target temperature required by the distribution system, based on the settings of its internal reset controller.

The mixing valve, operating under its own outdoor reset controller and with the same settings as the boiler reset controller, should be at or very close to its fully open position.

Figure 3

If the temperature difference between the top of the buffer tank and the return side of the distribution system drops to less than 1 degree F, very little heat is extracted from the tank. Under this condition, the ∆T controller turns off circulator (P2) to prevent heat supplied by the auxiliary boiler from being added to the buffer tank. The auxiliary boiler and circulator (P1) remain on to supply the space-heating load as required.

When the buffer tank temperature again rises to where the temperature differential between the top of the tank and the return side of the distribution system reaches 2 degrees F or more, circulator (P2) is turned back on to again extract available heat from the tank.

This strategy makes sense when a large storage tank is used in the system. I suggest it only be used when the storage tank contains at least 500 gallons. The ability to lower 500 gallons of water by an additional 10 degrees F implies a release of almost 42,000 additional Btus from the tank. Smaller tanks would contribute proportionally smaller amounts of heat and provide less justification for the additional controls.

If you implement this strategy, be sure the temperature sensors for the ∆T controller are mounted in identical, or nearly identical, manners. Ideally, both sensors would be mounted in identical sensor wells, immersed in the system water and with ample coatings of thermal grease. If mounted to the surface of copper tubing, be sure the sensor surface makes good contact, is well secured and is fully wrapped with insulation.

Remember, you’re asking the ∆T controller to detect differences in temperature as low as 1 degree F. That’s about one-third the temperature difference you can detect with you own fingers.

This approach to extracting more heat from storage also is applicable to large storage tanks charged by other heat sources such as solar collectors, heat pumps and electric heating elements running on off-peak electrical power. It’s another example of how to “tweak” some standard control technology to amplify the benefits of hydronic heating.

Links

  • Follow PM on Twitter!

Share This Story

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

Siegenthaler

John Siegenthaler, P.E., is a consulting engineer and principal of Appropriate Designs in Holland Patent, New York. In partnership with HeatSpring, he has developed several online courses that provide in-depth, design-level training in modern hydronics systems, air-to-water heat pumps and biomass boiler systems. Additional information and resources for hydronic system design are available on Siegenthaler’s website,  www.hydronicpros.com.

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
close

1 COMPLIMENTARY ARTICLE(S) LEFT

Unlock the future of plumbing trends with Plumbing & Mechanical.

REGISTER TODAY

Already a Registered User? Sign in now.

Subscribe For Free!
  • eNewsletters
  • Online Registration
  • Subscription Customer Service
  • eMagazine
  • Manage My Preferences

NIBCO Press Solutions

NIBCO Press Solutions

AI can boost efficiency and profitability for plumbing, HVAC contractors

AI can boost efficiency and profitability for plumbing, HVAC contractors

IPEX celebrates grand opening of new Florida distribution center

IPEX celebrates grand opening of new Florida distribution center

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

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

  • Transitions, Part 1

    See More
  • Smart Balancing - Part 2

    See More
  • Beware of bottlenecks, Part 2

    See More

Related Products

See More Products
  • ACCA Tech Guide_EPA 608_COVER_small (1).jpg

    Technician's Guide & Workbook for EPA 608 Test

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

    Pumping Away and other really cool piping options for hydronic systems

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!