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Do electric boilers benefit from outdoor reset controllers ?

Maxl Member Posts: 6
edited September 2017 in Thermostats and Controls
From what I understand the efficiency gained from outdoor reset controllers is due to the increase of efficiency of the heat transfer from the heat source to the return flow to the boiler, i.e. the cooler the return flow, the greater the difference between the heat source and the return water, the more efficient is the heat transfer. I would think that electric boilers are pretty efficient, since the heat from the heating element has nowhere else to go since the are surounded with water. Is it the case that the efficiency of electric boilers is such that outdoor reset provides little gain, if any ?


  • hot_rod
    hot_rod Member Posts: 22,120
    the reset control on an electric boiler will attempt to match the output temperature to the load. So it basicly modulates the output and prevents from temperature overshoot, so some energy saved.

    Also it helps eliminate on/ off cycling that extends component life
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Canuckerdelta T
  • Maxl
    Maxl Member Posts: 6
    @hot rod is short cycling even a problem for an electric boiler ? I can see how temperature overshoot can lead to reduced efficiency even for electric boilers, but from what I read the main efficencies gained from an outdoor reset controller is due to an improved heat transfer betweeen the heat source and the water. *If* an electric immersion heater is close to 100% efficiency, then the temperature difference between returne water and the element won't make a difference right ? I don't know how efficient an electric immersed element is in %, but the higher the efficiency, the lower the gain from an outdoor reset controller.
  • Gordy
    Gordy Member Posts: 9,546
    Excessive Cycling causes higher rates of component wear.

    ODR efficiency gains are through using lower water temps. Ideally water temps just high enough to match the load.
    JUGHNE Member Posts: 11,060
    A simpler method of control is outdoor thermostats. These limit the number of elements that could operate. This could give you longer cycle times and reduce overheating and the short cycling that accompanies it.
    These were used for electric furnaces to limit the number of elements that could turn on. Forced air electric furnaces had a fixed amount of air flow.....as an electric boiler may have a fixed GPM flow rate. This helped alleviate the problem of burned out elements or cycling on high limits. FWIW