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Inverter/Charger for Steam Boiler Ops

Dave_23 Member Posts: 190
A few topics ago, some folks mentioned that a steam boiler could be run using 12 or 24 VDC to 115 VAC inverter/charger. I have a WM EG35. What size would be recommended to carry my WM boiler for three days or so in the event of a power outage?

I suppose another method would be to use a computer-style UPS system in series with the 115 VAC supply to the boiler. (Such as those manufactured by APC).



  • Larry C_13
    Larry C_13 Member Posts: 94
    Usual answer.

    It depends.

    Home owner here.

    Have an electrician measure how much power the unit consumes, the peak current when it runs, and how long it runs in a 24 hour period at the expected temperature. Make sure you measure the current for EVERYTHING associated with the heating system including condensate pumps and heater tape for the fuel piping/tank.

    From the data collected, you should be able to size the UPS and battery pack(s). If the furnace is hardwired versus a corded plugin unit, you will probable need an electrician to modify the furnace wiring so that you can plug the furnance into the UPS.

    If the furnance controls are computerized, you may have an issue with the furnance running off of an UPS or generator.

    Remember I am not a heating professional nor a Licensed electrician. I do not know what safety, fuel, electrical or building codes are affected or need to be consulted.

    Good Luck.

    Larry C
  • Jon Held_2
    Jon Held_2 Member Posts: 21

    Typically, UPS units used for computer back up power will get very unhappy running motors. If you have a gas fired steam system, then that would absolutely work. An oil fired hot water unit would give the UPS a bellyache.
  • Jamie Hall
    Jamie Hall Member Posts: 23,635
    Jon's right.

    If -- and only if -- you have a gas fired steam system you might be able to get away with a UPS, provided that the gas burner system has no blowers or fans.

    Otherwise, I have to presume that you have a very good reason indeed to not use a standby generator. This is not to say that it is not possible to run, to take the most power hungry option possible, an hydronic system with several circulators off batteries. Of course it is. However, you will need a good-sized battery bank, plus a really good, powerful (motor starting rated) inverter suited to both the motors involved and the system electronics. Plus a charger with float capabilities and monitors for those big batteries. These things are available. These things also aren't cheap, and they will need to be professionaly wired.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • tim smith
    tim smith Member Posts: 2,774
    There are battery backup power supplies for larger current useag

    e, they usually are a small closet size with lots of 6 volt golf cart batteries and yes they can handle motor and gas valve loads as long as sized to watt useage. You could also use a Laing dc circulator to decrease power requirement on inverter and just use 120vac to 12vdc converter. Good luck, Tim
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