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Does anyone have any experience with Crossover water heaters?

jberks | Posted in General Questions on

I’m looking at the HTP RGH-199, which is what they call a crossover. Basically its a modulating condensing tankless heater, but has a small 3.5 Gal tank as a buffer (they also have a floor model which has a bigger tank)

I plan to use this for both domestic hot water and minor radiant heating. Also, Comparing the cost of these to a combi boiler, I’m considering getting two of them to do a cascade install, probably not necessary but it doubles the capacity and adds redundancy. I like the buffer tank concept after reading articles and conversations on here regarding short cycling of boilers on radiant systems.

Anyone have any experience with this unit? Are there other brands that have units like this? any other words of wisdom?




  1. user-2890856 | | #1

    You could use it for an application with an air handler . All water passes through a high head heat exchanger and the amount of pumping power you'd need is almost certainly too high for a radiant application . HTP would never honor their warranty used this way . Using the Crossover floor would work however . Mass is your friend and you'd get better performance using less BTUs . Crossover floor now available or soon available in a 40 gallon unit also . Remember that you must separate the DHW from the central heat with a brazed plate or other secondary heat exchanger .

  2. GBA Editor
    Martin Holladay | | #2

    Richard McGrath has a lot of experience with hydronic systems, so I would pay attention to his advice if I were you. You may also wish to read this article: Using a Tankless Water Heater for Space Heat.

  3. Expert Member
    Dana Dorsett | | #3

    The thing doesn't have a tank, it has a high volume heat exchanger. It's one of several products designed by Kiturami for the export market, some sold by Laars, or Noritz. The high volume finned heat exchanger is similar in concept to (but not identical with) the fire-tube heat exchangers in their hydronic boilers (which would be more appropriate here), which have a comparable amount of internal mass, and the same 10:1 turn down ratio.

    Like most low-mass combis these things are a poor fit for houses with low to moderate heating loads.and moderate hot water loads. The 199K version has enough burner for the average house, but the ~19K output at mininimum fire is well over half the whole house load for a typical 2500 square foot IRC 2015 code minimum house, and WAY above the output of a typical zone radiation if multi-zoned.

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