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RETAC Product

Hydronic Heat Transfer Enhancement Additive

Active 1017_Hydro_87
Created 10/16/2017 by Christopher Kroeker
Updated 2/13/2020 by Dale Edginton
193 views • 3 comments


Liquid added to boiler loop water that increases heat transfer and improves efficiency (claims of 15% in hydronic space heating systems).

Contributing Org
NEEA (Jeff Rigotti)
Related Products
Market/Commercial Readiness
Level 3
Niche (commercially available in NW from 1 mfr through standard channels)
Product Performance
Level 3
Lab Validation (independent lab testing of features and savings)
Program Readiness
Level 1
Energy System(s)
Energy Subsystem(s)
Other HVAC systems
Building Type(s)
Cost and Savings
Unit Cost: N/A
Savings Type: GasSavingsOnly
Elec. Unit Savings: N/A
Gas Unit Savings: 0
Unit: N/A
Benefits and Regional Potential
Non-Energy Benefits:


Elec. Potential: N/A
Gas Potential: 0

This product was tested by GTI through funding from Nicor Gas. The product did not increase heat transfer in the fluid beyond measurement error. The test report can be found here:


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Comments (3)
Kenji Spielman on 10/19/17 on 11:26 AM (Pacific Time)

 The test did show a small increase in boiler efficiency, which is encouraging. There might be something there, hopefully further testing can confirm.

Rob Root on 12/08/17 on 01:39 PM (Pacific Time)
Hello Christopher and Kenji,

I am with Northstar Chemical, we are the distributors for the loop additive EndoTherm, the energy saving additive mentioned above. I am aware of 2 pilot studies in the United states to date. One was in a heating loop at the Whidbey Island Naval Station. They achieved 12.54% savings in this trial. The other is the Nicor Gas study referenced above, showing no improvement outside of the margin for error. I looked into this with the North American manufacture to find what might cause the lack-luster results in the trial. In the Nicor Gas study, the testing was done during steady state operation (confirmed on page 5). With a margin of error of 4% in the test, the savings reported in the trial are consistent with the product claims of about 5% savings in process applications. Because steady state or process systems do no cycle on and off, EndoTherm does not have the opportunity to eliminate cycling events. The energy efficiency benefit is limited to the increased area of contact with the fluid and heat transfer surface. Comfort heating and cooling are the areas where that largest savings can be achieved. 

There have been numerous successful pilot studies in Europe and Canada that show some impressive results. I have not been involved in any of them. For this reason, we are looking for a partner to work with, so that we can validate findings with a local trial, and build confidence around the technology in Washington and Oregon. If there are any other questions or if a trial is of interest to you, please let me know. Thank you.

Best regards,

Rob Root
C: 206-475-4350
Dale Edginton on 02/13/20 on 08:14 PM (Pacific Time)
I ran this program with GTI / NICOR. 

The testing was run at steady state (against advice) thus (as Rob alluded to) eliminated the principle EndoTherm benefit in HVAC comfort heating applications (reducing run times). We have run steady state testing in heating and process cooling (data centres) and achieved 4-8% so this 4% saving is no unexpected. 

The tests were run at several GPMs to stimulate different flow conditions. The lowest improvement was at the slowest GPM (0.6) which isn't truly reflective of a HVAC circuit. The highest was in excess of 8% at GPMs more realistic. The average boiler output was 7% higher with EndoTherm which also was omitted from the public report. 

A 4% improvement in boiler efficiency through the simple dosage of an hydronic additive is not to be dismissed given the ROIs. Higher savings in comfort heating applications are also achievable. Further to Robs comment we have run close to 200 pilots in North America and the NEEA team are currently reviewing an EndoTherm install (one of many utilities currently reviewing the technology). The report suggests a ROI of less than 12 months in domestic (slightly higher in commercial due to additional pipe runs).


Happy to discuss more.