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Not enough DHW in winter from boiler coil

My DHW is from a coil in the steam boiler. All summer, there is plenty of hot water, but as soon as the weather gets chilly, there's only hot water for a limited time. If you wait it out in the shower, it heats up again. Is this something that might be fixable, or just the nature of the system? Need to decide whether to try and fix the problem, or install a separate DHW heater.


  • Leon82Leon82 Member Posts: 655
    How old is it?
    Does the boiler shut off at all during the shower?
  • NippernaperNippernaper Member Posts: 7
    Not sure of exact age, it's a Utica model sfh4150st. Hard to tell if it cuts off, shower on second floor, boiler in basement, but I don't think so. Next time someone else takes a shower, I'll listen.
  • NippernaperNippernaper Member Posts: 7
    After monitoring the boiler during a shower, looks like the problem is that it doesn't fire up soon enough. By the time it comes on, the water temperature has dropped, and it takes a bit for it to come back up. Hmmmm.
  • Leon82Leon82 Member Posts: 655
    You can adjust the temp it starts but it may burn more fuel as it will run more often to keep the coil warm. The colder incoming water needs a bigger temp rise .

    Or you can use a small water heater as a buffer tank to absorb the water sandwich.
  • NippernaperNippernaper Member Posts: 7
    That's an interesting idea, maybe a small electric point-of-use water heater to preheat the incoming water a bit?
  • Leon82Leon82 Member Posts: 655
    > @Nippernaper said:
    > That's an interesting idea, maybe a small electric point-of-use water heater to preheat the incoming water a bit?

    You put it after so it absorbs the colder water while the boiler warms up again.
    That's how I run my tankless water heater. It's a 4-gallon Ariston Electric
  • Leon82Leon82 Member Posts: 655
    Or if you put a mixing valve at the end of the coil and send it to 120 degrees. Then you can make it so the boiler kicks on at 140. It may be enough time to get up to temperature without dropping the temperature inside the coil
  • Leon82Leon82 Member Posts: 655
    edited November 2017
    A third option would be to use your tankless coil with a storage tank and a stainless-steel circulation pump.
  • j a_2j a_2 Member Posts: 1,796
    Do u use water saving fixtures ? I would take a real good look at the G E hybrid heat pump water heater,to supply your domestic
  • NippernaperNippernaper Member Posts: 7
    Thanks for all the suggestions, lots to think about now. Looks like there's a couple of ways to skin this cat. Really appreciate the good ideas.
  • BobCBobC Member Posts: 5,101
    @j a A buddy of mine installed of those up in NH a few years ago and and has been very happy with it. He noticed a big difference in his bill.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
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