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Flow Concerns and Remote Thermostat Control

Hello everyone, first post here! Two part question, part 1. I am to the point in my closed-loop radiant heat design where I am researching on-demand water heaters. I installed a Takagi T-H3S for potable water years ago in my primary residence and have been extremely happy with it, so I will likely use Takagi again unless there is a good reason not to. The crux of my question/concern is, how do you keep the circulation pumps and the water heater itself from "fighting" over flow? When the whole system is up to temp, I don't foresee a problem. But, during startup when there may be a 70-80 degree delta initially, the water heater may only be able to heat at 3-4 gpm. Would the pumps be trying to push water through the heater faster than that, and how would they react to flow restriction from the water heater? Part 2. I would like to be able to monitor and control the thermostat remotely so as to "pre-heat" the structure prior to arrival etc. Does anyone have recommendations on a vendor/platform/technology to accomplish this? I am familiar with Nest thermostats, for example, on my gas furnace in my primary residence, not sure on compatibility with radiant heat controls. Thank You!


  • eheinkel
    eheinkel Member Posts: 4
    Here are some details on the design so far if anyone is interested or if it helps with my questions.
  • Jamie Hall
    Jamie Hall Member Posts: 23,655
    You will be much happier if you use a boiler made for heating -- which is a low head loss relatively high flow but low delta T design -- than a water heater like the Takagi -- which is a high head loss low flow high delta T design. Use the right tool for the job. Not, for example, that I can't pound in nails with my pipe wrench, but a hammer works better.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England