This website requires certain cookies to work and uses other cookies to help you have the best experience. By visiting this website, certain cookies have already been set, which you may delete and block. By closing this message or continuing to use our site, you agree to the use of cookies. Visit our updated privacy and cookie policy to learn more.
This Website Uses Cookies
By closing this message or continuing to use our site, you agree to our cookie policy. Learn More
This website requires certain cookies to work and uses other cookies to help you have the best experience. By visiting this website, certain cookies have already been set, which you may delete and block. By closing this message or continuing to use our site, you agree to the use of cookies. Visit our updated privacy and cookie policy to learn more.
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • Home
  • Products
  • News
  • Glitch & Fix
  • Hydronics
  • Radiant
    • Radiant Comfort Report
  • Blogs/Columns
    • R&H On The Road
    • John Siegenthaler
    • Dan Holohan
    • Ray Wohlfarth
    • Mark Eatherton: Radiant Know-How
  • Buyers Guide
  • Resources
    • Radiant Comfort Report Digital
    • Rep Locator
    • Industry Calendar
    • Store
    • Market Research
    • eNewsletters
  • Plumbing & Mechanical
Home » Overly Separated
The Glitch & The FixRadiant & Hydronics

Overly Separated

June 19, 2009
John Siegenthaler, P.E.
Reprints
No Comments
Eager to keep up with new technology, an installer decides to install a hydraulic separator between a boiler and distribution system.

The Glitch


The Glitch

Overview: During the last three years, a new hardware device has been showing up in more American hydronic systems. It’s called a hydraulic separator, and it’s now available in a range of sizes from several manufacturers.

Hydraulic separators provide an alternative to closely spaced tees when the task is to isolate the pressure dynamics of one hydronic circuit from those of another, connected circuit.

Eager to keep up with this new technology, an installer decides to install a hydraulic separator between a boiler and distribution system as shown in the figure below. Some of the load circuits connected to the hydraulic separator are piped “across the headers,” while others are connected with closely spaced tees.  All the load circuits are supposed to operate independently.

Exercise: When the system was turned on, there was very little warmth from the low temperature loads. What’s the problem?

The Fix

The Fix

A hydraulic separator eliminates the need to use closely spaced tees when connecting load circuits. All load circuits can be piped across the headers. Those headers should be short, and generously sized. This keeps the pressure drop along the length of the header extremely small (e.g., negligible). The slow flow rate along the vertical height of the hydraulic separator adds virtually nothing to this pressure drop. Thus, the differential pressure between the upper and lower headers is essentially zero. Each load connected across the headers is unable to detect the presence of the other load circuits.

Using closely spaced tees downstream of the hydraulic separator adds a second – and totally unnecessary – hydraulic separation between the lower circuits and the hydraulic separator itself. The lower circuits with the mixing valves will only receive heated water when those circuits connected across the header are active. At other times the water returning to the lower header will simply make a right-hand U-turn and be drawn back into the hot port of the mixing valve. The solution is simple: Just pipe all the loads across the headers as shown.

The expansion tank should also connect near the hydraulic separator as shown.

Finally, always put 10 or 12 pipe diameters of straight pipe on the inlet of any circulator to minimize turbulence into the impeller.

Links

  • Hydronic Symbol Legend
  • The Glitch & The Fix - June 2009

pm-subscribe

Recent Articles by John Siegenthaler, P.E.

Modern Hydronics Done Right Volume 5

John Siegenthaler: New in the neighborhood

The Glitch and Fix: Keep the cost down

Single coil solution

John Siegenthaler: Low temperature leverage

Siegenthaler

John Siegenthaler, P.E., is a consulting engineer and principal of Appropriate Designs in Holland Patent, N.Y. His latest textbook “Heating With Renewable Energy,” will be released in January 2016 from Cengage Publishing. It shows how to use modern hydronics technology to create systems supplied by solar thermal, heat pump and biomass heat sources. Additional information is available at www.hydronicpros.com.

Related Articles

Overly Complicated

The Glitch and Fix: Overly complex

Hydraulic Separator Connections

Hydraulic Separators Need Help

Related Products

2019 National Repair & Remodeling Estimator

2018 International Plumbing CodeĀ®

Modern Hydronic Heating: For Residential and Light Commercial Buildings, 3rd Ed.

Related Events

Free Webinar: Achieving Hydraulic Separation in Hydronic Systems

You must login or register in order to post a comment.

Report Abusive Comment

RCR logo

RCR Buyers Guide

Plumbing and Mechanical

Plumbing & Mechanical December 2019

2019 December

Check out the December 2019 edition of Plumbing & Mechanical: 2020 B.I.G. Book, John Siegenthaler on geothermal water-to-water heat pump system design and installation, maximizing efficiency on small-diameter piping projects and much more!
View More Create Account
  • Resources
    • Reprints
    • List Rental
    • Contact Us
    • AEC Store
    • Blogs
    • Radiant & Hydronics
    • Industry Links
    • Market Research
    • Custom Content & Marketing Services
    • Privacy Policy
  • Want More
    • Connect
    • Survey And Sample
  • Plumbing Group
    • PM Engineer
    • Supply House Times
  • Advertise
    • Advertise
    • Plan for 2020!

Copyright ©2019. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing