Prosecution Insights
Last updated: April 19, 2026
Application No. 18/827,439

WATER HEATER HAVING HIGHLY EFFICIENT AND COMPACT HEAT EXCHANGER

Non-Final OA §102§103
Filed
Sep 06, 2024
Examiner
DOERRLER, WILLIAM CHARLES
Art Unit
3993
Tech Center
3900
Assignee
A. O. Smith Corporation
OA Round
1 (Non-Final)
78%
Grant Probability
Favorable
1-2
OA Rounds
2y 10m
To Grant
91%
With Interview

Examiner Intelligence

Grants 78% — above average
78%
Career Allow Rate
312 granted / 398 resolved
+18.4% vs TC avg
Moderate +13% lift
Without
With
+12.8%
Interview Lift
resolved cases with interview
Typical timeline
2y 10m
Avg Prosecution
24 currently pending
Career history
422
Total Applications
across all art units

Statute-Specific Performance

§101
0.7%
-39.3% vs TC avg
§103
36.5%
-3.5% vs TC avg
§102
17.7%
-22.3% vs TC avg
§112
22.3%
-17.7% vs TC avg
Black line = Tech Center average estimate • Based on career data from 398 resolved cases

Office Action

§102 §103
DETAILED ACTION Notice of Pre-AIA or AIA Status The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA . Reissue Applications For reissue applications filed before September 16, 2012, all references to 35 U.S.C. 251 and 37 CFR 1.172, 1.175, and 3.73 are to the law and rules in effect on September 15, 2012. Where specifically designated, these are “pre-AIA ” provisions. For reissue applications filed on or after September 16, 2012, all references to 35 U.S.C. 251 and 37 CFR 1.172, 1.175, and 3.73 are to the current provisions. Applicant must submit the second page of the patent in response to this Office action. The first page which has been submitted fails to provide all of the references that were cited during the original prosecution or provide the full abstract. Claim Rejections - 35 USC § 102 In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status. The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form the basis for the rejections under this section made in this Office action: A person shall be entitled to a patent unless – (a)(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention. Claim(s) 21-29 is/are rejected under 35 U.S.C. 102(a)(1) as being anticipated by WO 84/02387 to Gerstmann et al (hereinafter “Gerstmann”). Gerstmann discloses a heat exchanger with a flue gas path between a burner and an exhaust assembly, a water circuit extending between a cold water inlet and a hot water outlet and a recirculation system in fluid communication with the hot water outlet and configured to recirculate a portion of water from the hot water outlet to the water circuit at a location along the water circuit between the cold water inlet and the hot water outlet. See the below annotated Figure 2. PNG media_image1.png 602 920 media_image1.png Greyscale In regard to claim 22, the recirculation pipe and recirculation pump are shown above. In regard to claims 23 and 24, the first and second sections of the flue gas path are shown above. Shown is the flow gas flowing along the second section of the flue gas path not in heat transfer relationship with the recirculated portion of water. The flue gas flows over the second coil section before passing over the first coil section. In regard to claims 25 and 26, the burner is along the central axis and the flue gas passes perpendicularly over the second coil section and then passes parallel to the axis over the first coil section, countercurrent to the flow of water through the first coil section. In regard to claim 27, the claimed components are shown in the above annotated figure. The second paragraph of page 8 states, “A further advantage of recirculating water through the primary heat exchanger is that it increases water flow rate and thus establishes high water-side heat transfer coefficients. This minimizes liming of the main heat exchanger coil.” In regard to claim 28, the flow of water in the first water coil section passes upward while the flue gases are traveling down. In regard to claim 29, the figure shows the recirculation pump. Claim Rejections - 35 USC § 103 The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action: A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made. This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention. Claim(s) 30 and 31 is/are rejected under 35 U.S.C. 103 as being unpatentable over Gerstmann in view of WO 2006/105605 to Baker (hereinafter “Baker”). As discussed above, Gerstmann discloses the fired water heater heat exchanger of claim 29. Claim 30 depends from claim 29 and claims a plurality of water heater circuits delivering water in parallel and receiving heated water in parallel. Baker discloses a heat exchanger with helical flow paths for a fluid to be heat exchanged. The last paragraph states, “a plurality of such units would allow for a multiple fluid streams of different fluids to be heated and cooled to differing temperatures and cooled simultaneously”. It would have been obvious to one of ordinary skill in the art at the time of filing to modify the heat exchange system of Gerstmann by using a plurality of heat exchange units in parallel to permit the heat exchange with multiple fluids and to allow the heat transfer with a larger volume of liquid. In regard to claim 31, Gerstmann shows thermostat 36 to control a burner in response to the sensed water temperature. Allowable Subject Matter Claims 1-20 are allowed. Claims 32 and 33 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims. The following is a statement of reasons for the indication of allowable subject matter: Claim 1 requires “an insulation layer positioned over a last one of the plurality of inner coil turns of the inner coil and a last one of the plurality of outer coil turns of the outer coil.” This is not taught by Gerstmann, and there is no motivation to add such an insulation layer found in the prior art. The same is true of “an end member positioned over a last one of the plurality of inner coil turns of the inner coil and a last one of the plurality of outer coil turns of the outer coil” of claim 8 and “an insulation layer positioned over a last one of the plurality of inner coil turns of the inner coil and a last one of the plurality of outer coil turns of the outer coil” of claim 17. The greatly reduced heat input rate associated with the lower flow rate and associated thermal efficiency for such a heat exchanger of claim 32 is not taught by the prior art. Conclusion Any inquiry concerning this communication or earlier communications from the examiner should be directed to WILLIAM C DOERRLER whose telephone number is (571)272-4807. The examiner can normally be reached M-F, 7-5. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Eileen Lillis can be reached at (571) 272-6928. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000. /WILLIAM C DOERRLER/Reexamination Specialist, Art Unit 3993 Conferees: /WILLIAM E DONDERO/ Reexamination Specialist, Art Unit 3993 /EILEEN D LILLIS/SPRS, Art Unit 3993
Read full office action

Prosecution Timeline

Sep 06, 2024
Application Filed
Sep 06, 2024
Response after Non-Final Action
Mar 13, 2026
Non-Final Rejection — §102, §103 (current)

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Study what changed to get past this examiner. Based on 5 most recent grants.

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Prosecution Projections

1-2
Expected OA Rounds
78%
Grant Probability
91%
With Interview (+12.8%)
2y 10m
Median Time to Grant
Low
PTA Risk
Based on 398 resolved cases by this examiner. Grant probability derived from career allow rate.

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