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Question: I'm looking for wisdom, tips and tricks regarding installation of a "boiler reset", a device that reduces water temperature in a central heating system on moderately cold days. These have been around a long time, I think the concept predates the internet. I'd love to hear the voice of experience, and also if there are better more modern approaches. Are these effective at either increasing comfort on moderately cold days or at saving money or both?

Situation: I have gas hot water heating in two zones (upstairs/downstairs), a regular (not high efficiency, Weil Mclain PFG-6) boiler about 10 years old, cast iron radiators, located near NYC in a fairly lossy 1896 house. It is insulated and most windows are modern, but the house is not at modern new-house insulation standards. I'm considering device like a Tekmar 256 or Taco PC700. I am not asking for product-selection advice, this info is just in case it helps. Heating runs mid-September to early May, sub-freezing outside temps are mainly in January and February.

Other background:

  • Smart Boiler Reset: The device I'm looking at has its own sensors and no online connectivity. The same company makes more "modern" versions, with multiple room sensors and apps, but they cost ten times the price and seem more geared for landlords and control of larger systems with many independent heating zones. I have two zones on one single-stage boiler, and this device seems to do one thing well.
  • Smart Thermostats: Modern smart thermostats like the Nest use outside temps and forecasts and learn system hysteresis to advance or delay temperature set changes, but they do not control boiler water temperature. You will still have 160 degree radiators even if the inside temperature is two degrees below set point and outside is not that cold. The idea of the boiler reset device is to reduce temperature gradations within rooms, temperature fluctuations and overshoots, thus increasing comfort. Supposedly it also saves money.
  • Thermostat compatibility: My not-smart thermostats supposedly also monitor and learn system hysteresis so I wonder if boiler reset will confuse the thermostats, and I need to disable that?
  • Here is a recent related question from someone just wanting to identify one of these.
  • Here is the installation and operation manual for the device I'm looking at. I'm not asking for advice on product selection, but this manual contains a lot of good background info and theory for those who want to better understand it.
  • Terminology: "Boiler Reset" seems to be the industry term for modulating water temperature according to outside temperature. It doesn't reset anything. Don't get hung up on the name.

Clarifications in light of comments:

  • Setback is reducing set temperature according to time of day or occupancy. I have setback thermostats and I use that function. Reset is reducing system water temperature according to outside temperature. It is the latter I am asking about, though their interaction is interesting too.
  • Modulating Boilers achieve a similar function by directly reducing heat output at the flame. They are always high efficiency condensing boilers. My boiler is not modulating or condensing. When the flame is on, it's at 100%. The "reset" device works by intercepting Call-For-Heat from the thermostat and cutting it off when water temperature is high enough for the conditions inside and outside the house.
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  • What boiler do you have? It's going to matter more with a low-efficiency boiler than with a high-efficiency one.
    – KMJ
    Oct 25, 2023 at 15:26
  • I've heard this called "set back" rather than "reset". It can indeed improve efficiency when installed with a boiler that supports it. It may be hard to retrofit into existing boilers I'd they weren't designed to have a lower-heat burn mode.
    – keshlam
    Oct 25, 2023 at 15:26
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    @keshlam I edited my responses to your comment into the question. Setback vs Reset, and Modulating vs Reset.
    – jay613
    Oct 25, 2023 at 17:16
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    pssst add the make/model to the question
    – FreeMan
    Oct 25, 2023 at 17:32
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    @manassehkatz-Moving2Codidact I don't think you could implement that logic on a single-stage boiler with a two-stage thermostat without jailbreaking it. The boiler doesn't have controllable water temps. There's a temp sensor on the supply pipe monitored buy the controller, it just removes call for heat when the water temp is what it wants. A Nest or similar has terminals for sensors, including outside temp, but not including system water temp, and it wouldn't have that kind of logic in it. Also the Tekmar/Taco logic is pretty sophisticated ... see the manual. Not Google's terrain IMO.
    – jay613
    Oct 25, 2023 at 19:16

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