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Indirect Fired Hot Water Heaters vs Stand Alone Systems


I am considering replacing my old steam boiler with a new one also of steam. I currently do not have a hot water heater. It seems that most people think that an indirect hot water heater is the way to go. However, one contractor suggested that I get a Toyotomi OM148 stand alone oil-fired water heater instead. It appears that I could just shut off my boiler when the heating season is over and just run this for my hot water. Does shutting off a boiler like this cause any problems?




  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Steam indirect

    Using an indirect DHW Tank with a steam boiler requires skillset. This website details how to take a HW zone from beneath the water line of steam boilers. The Viessmann V300 tank is rated for steam, as well as HW. I've converted several steam boilers to make DHW using the Viessmann indirects. If you follow the instructions...it works well. If you don't, than it won't.

    The efficiency of using the boiler to make DHW with an indirect, will be better than a stand-alone tank. However, if you can't find a Pro who has done it before, you may be in for trouble. BTW, I've timed the recovery of the Viessmann tank on a HW loop from the steam boiler...it takes an average of 7-8min. to recover 53g of water from 55 to 120 degrees.

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  • bigugh_4
    bigugh_4 Member Posts: 406
    boilers, computers, airplanes

    all seem to be better left "on". even though not being used to capacity. In the air force the aircraft in commission stayed in commission longer if flown regulary. A computer will act better if not turned "off" excessively. and a boiler with is attending subsystems will be more apt to go into big time heating, if left "on" to heat DHW during the summer. People are the same way, most have to wake up a bit before going full blast. Me I'd leave well enough alone. Besides, the fast recovery and efficency of the boiler vs. the stand alone water heater is very nice.
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