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Hybrid Boiler System

Brycewvu
Brycewvu Member Posts: 38
in Strictly Steam

I'm not sure about you, but any time I hear my boiler running I just think about how much its costing to get that big hunk of metal and water from cold up to actually creating steam. I feel like there has to be a way to create an electric/oil hybid but I'm not sure how it would actually be executed.

Heres my idea; typical electric water heaters produce water temps of 140 degrees. Instead of the boiler having to heat the water from 65 degrees all the way up to 215, would there be a way to ""preheat" the water in the system so that there is a smaller temperature gap? I currently have a WM SGO-7 and based off the specs, it holds approx. 18 gallons of water. If my math is right, it required approx. 23k BTUs to take that much water from 65 to 215 but it only takes about half that, 11k BTUs to heat the water from 140 to 215. If I could use the oiler burner to heat the water the remaining 75 degrees after the electric heater, that would cut my oil costs in half (obviously electric would go up though). My immediate thought was a small 25 gallon electric water heater some how piped into the boiler maybe via the return piping with a recirculating pump to keep temps consistent that would turn off once the oil burner fires.

I know there would be some things I need to take into account like low water cuttoff and condensate levels, but I'd love to hear your thoughts on this. Has anyone seen something like this? Do you think it would work? What obvious issues have I not taken into account?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 25,262

    It certainty is feasible. There are some interesting control issues involved, and perhaps a pump (perhaps not, too — gravity might be adequate).

    The real question is whether there would be a return on the investment. You note — correctly — that while your oil bill would go down (slightly… you estimate, for instance, saving 11,000 BTU by preheating this way — which is about 30 cents worth of oil around where I am located) but the electric bill would go up (by, in fact, the same number of BTUs. Which around here would be around a dollar's worth of electricity). So for me your idea would triple the cost involved… which really doesn't seem worth it…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Intplm.
  • KarlW
    KarlW Member Posts: 175

    My boiler makeup is actually connected to my domestic hot water heater so I could start doing this already I suppose.

  • dopey27177
    dopey27177 Member Posts: 914

    Why do you a need a hybrid system to heat water to 140 degrees,

    when your oil fired heater will will only heat water one time from 65 degrees.

    During thee heating season the boiler water temperatures will always be above 140 degrees.

    Using the electric boiler to heat water seems to me to be a waste of energy to heat water to for the steam boiler.

    jake

    Steam: The Perfect Fluid for Heating and Some of the Problems
    by Jacob (Jake) Myron
    Mad Dog_2clammy
  • Brycewvu
    Brycewvu Member Posts: 38

    @Jamie Hall Good point. Thinking through the numbers, the electrical bill definitely would be a consideration. I beleive my electric is roughly 12 cents per kWh. I definitly agree that the initial heating would be higher, but since the water heater is good at keeping the water at that 140 in the long term, would the heating cost rapidly drop once it gets water to temp and is just keeping it at a steady temp?

    @KarlW If I understand correctly, you can hook the boiler up to the hot water system for household use, but I don't know if this is a closed loop heating system or not. I can imagine that if it was all the same water, your hot water in the shower would be gross like boiler sludge.

    @dopey27177 I don't beleive my boiler fires enough to keep the water 140. I may be wrong, but it seems like the boiler has to run for a while in order for me to feel heat on the header.

  • KarlW
    KarlW Member Posts: 175

    My hot water feed has a vacuum breaker to prevent back-feeding into the domestic system.

    Brycewvu
  • Jamie Hall
    Jamie Hall Member Posts: 25,262
    https://forum.heatinghelp.com/discussion/comment/1829015#Comment_1829015

    I hope it's more than a vacuum breaker… a proper backflow preventer is required.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • KarlW
    KarlW Member Posts: 175

    https://forum.heatinghelp.com/discussion/comment/1829043#Comment_1829043

    I've given thought to it, but then comes the whole regulation thing (I used to work for my local water utility). What I should do is put in a properly sized air gap.

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