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Mini Boiler for indirect water heating?

MV10 Member Posts: 4
<span>I have the mini boiler shown below for radiant floor heat use as a supplement to forced air heat. As I need a new water heater in the near future, I've been pondering the use of the mini boiler to support an indirect water heater.

Electro Electric Mini-Boiler EMB-W-9

<ol><li>240 Volt</li><li>9 KW</li><li>31,000 Btu</li><li>3 zones totaling 400 sq ft in Minnesota.</li></ol>

Would this mini boiler with radiant floor output temps be able to maintain the indirect water heater demands? I'm under the impression a normal boiler would have a much higher temp output that would be required.

Of course your expert opinions would be of great value.





  • Gordan
    Gordan Member Posts: 891
    That's too small

    Besides, what advantage would you expect from an indirect water heater, compared to just an electric tank heater? Typically, an indirect is much more expensive, and it would not be one whit more efficient in this case than a simple tank heater - less so, if anything.
  • MV10
    MV10 Member Posts: 4

    I was thinking it would be too small as well but want an experts opinion.

    My rational for an indirect is multi-fold; I'm also replacing my furnace with a high efficiency unit to vent horizontally, if I do an indirect water heater I can also remove that vent allowing for future remodel on the main floor. An indirect from my research has a longer life expectancy than a normal gas or electric model. I could go to a direct vent gas water heater, but the venting will potentially create an issue with a patio depending on how I run it.  As I had the mini boiler already it seemed to be a handy potential fix for my issues above.

  • zacmobile
    zacmobile Member Posts: 211

    I have installed 10 KW electric boilers with indirect water heaters before in smaller homes and they have worked fine, the boiler is fully capable of ramping up to a higher temperature to supply the indirect as long as you have the appropriate control telling it what to do. Like this one for instance: http://www.tekmarcontrols.com/literature/acrobat/d260.pdf A typical electric water heater only has 3.5 KW and now you would basically have one that is 9KW, almost 3 times the power. It wouldn't necessarily be more efficient at all but recovery would be faster and like you say would have a longer tank life. 
  • MV10
    MV10 Member Posts: 4
    Follow up

    So if I went the indirect heater route, it likely wouldn't be as efficient as a normal gas water heater, maybe as efficient as an electric water heater. How about if I put the mini boiler on the electric company's peak shut off program to mitigate some electric cost? Would that be possible with an indirect? Or, am I thinking with only half a brain as they can cut off the boiler for parts of the day during the summer peak times?

    I'll look into a normal gas power vent WH and see my venting options as well to be able to remove my vertical venting.

  • EricAune
    EricAune Member Posts: 432
    edited February 2011
    It would work...

    If you add a mixing valve to drop temperature to the radiant because the boiler, with its set-point control, will need to be set at a higher temperature.  The easiest way to control it would be to add a Taco (or other mfg) zone valve control or switching relay (pumps) to gain priority for the domestic water heating call.

    The added cost of the (required by code) double wall heat exchanger and piping change, along with the addition of another circulator and possibly zone valves and a priority control will soon rise above the cost of installing a tank (or tankless) water heater. 

    I would not consider going with any type of off peak program unless you are okay with not having hot domestic water at any given time.  Price break or not, none of my customers would be happy if they had to shower in cold water. 

    Where are you located?  I am just north of the cities, have you had anyone out to look at the project?
    "If you don't like change, your going to like irrelevance even less"
  • MV10
    MV10 Member Posts: 4
    Follow up

    I've had a couple discussions with my plumber and supplier and they know my house configuration. I'm hoping to do a furnace and water heater at the same time to have some efficiency on my labor.

    My main point is to vent horizontal (or not have a vent with an indirect) to have some remodel options in the future. Everything is pointing to a power vent water heater at this point as cost would get out of control with the complexity of using my mini boiler for double duty. I'm simply looking for all the options available.

    I'm down in Burnsville.
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