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Hydrostat settings for direct hot water in winter

dzwestwindsor
dzwestwindsor Member Posts: 1
in THE MAIN WALL

Hi all,

I’m located in Massachusetts. This past summer, I moved into a house with a direct (tankless) hot water system that uses an oil boiler (Weil-McLain gold) and a Hydrostat 3250.

In the summer months, the Hydrostat was set to 160 low and 180 high, and our domestic hot water felt nice and warm when showering.

When showering in the colder fall/winter months, I’ve noticed that our domestic hot water will start off warm (for maybe 30 seconds), but then will drop in temperature to the point where it’s uncomfortable to shower. After a couple minutes, it will warm up again, be hot for a few minutes, then the cycle repeats.

Since we are in the middle of winter now, I’ve bumped up the low setting on the Hydrostat to 170F. It has helped a bit, but the water temp will still drop to uncomfortable levels before rising again.

I’ve observed the Hydrostat temperature during the colder lulls will drop to around 145F, even though the Hydrostat low setting is set to 170F. The boiler kicks on at 160F (10F differential) but the Hydrostat temp will continue to drop to 145F before rising again. During this time, the water becomes uncomfortable when showering.

There is a mixing valve where the domestic hot water exits the boiler but I already have it turned up all the way. The boiler and hydrostat are from 2013, I believe.

My questions:
- Should I raise my low setting above 170F?
- For colder climates like New England, what are typical Hydrostat settings for direct (tankless) water systems? It seems that 160F low/180F high are typical settings, but it doesn’t seem sufficient for me in the winter months.
- Any other thoughts on this behavior and is it normal?

Thank you and happy new year!

Thanks,

David

Comments

  • HVACNUT
    HVACNUT Member Posts: 6,504

    How many thermostats? If more than one, do all the thermostat wires and circulator wires go into a separate zone panel? Is TT in the Hydrostat connected to XX in the Zone panel? If so, the wiring isn't correct for when then boiler is using a tankless coil. That would need to be removed and rewired using ZR/ZC. Wired that way it will shut off the circulators when boiler temperature drops below the low setting.

    Also check the economy setting. Lower it to off if not already.

    If you raised the low to 170°, then raise the high to 190°. Always a 20° minimum between the two.

    A thermostatic mixing valve is recommended for the domestic hot. Typical DHW temperature is 120°

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