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electric boilers?

Grallert
Grallert Member Posts: 523
I've been asked to help with design and installation of a complete Hydronic system for a friend. In the past I've installed conventional fuel boilers with panel radiators and cast iron radiators. On a previous job I did for him we used a Viessmann mod con I forget the model now. This time he asked about electric boilers. I have no experience with these but I do think that perhaps electric is the wave of the future. At the moment he has no plans for installing solar but it's not out of the question in the future. This building will be very tight with new windows and doors foam insulation etc. We are in the hills of western mass. Do any of you have experience with these and can give a little input about their effectiveness? I figured this is a good place to start. Thanks guys.
M

Comments

  • Robert_25
    Robert_25 Member Posts: 326
    Electric boilers are very simple, and are common in areas with cheap hydro power.  Assuming you have an adequate electric service and the price per kwH is favorable (in most areas it is not), an electric boiler can work out fine.
  • Zman
    Zman Member Posts: 6,714
    A fully modulating or multi stage model will help reduce demand spikes and maintain a constant temp. On-board outdoor reset would also be a nice feature. Be sure your customer understands the energy cost side of this. In most areas, electricity is the most expensive option, time-of-day metering makes it even more expensive.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Paul Pollets
  • Paul Pollets
    Paul Pollets Member Posts: 3,415
    edited September 13
    Electric boilers are somewhat common in the NW, as hydro power is lower in costs, especially east of the Cascades. They use 30-50 amps so powering them with solar PV is not really practical. The models with elements staged by OD, use less power. They're also not very efficient to make DHW, so an electric hot water heater is often used.
  • psb75
    psb75 Member Posts: 423
    I can't believe that W. Mass. power rates would be very favorable. I've only ever heard of electric boilers being used in eastern Canada due to HydroQuebec. Stick w/ Viessmann mod/con gas boiler.
  • Grallert
    Grallert Member Posts: 523
    This is all great information to start with. The bit about domestic hot water is important. As this property will be used as a rental or air B&B the water will be a real issue.
    The simplicity of electric is appealing but the operating cost will likely be the final factor.
  • Jamie Hall
    Jamie Hall Member Posts: 16,344
    Electric boilers have a number of advantages -- not the least of which is they are very easy to control and modulate (although there are real variations in how this is done -- some of which are much more robust than others). They themselves are also, relatively speaking, inexpensive.

    They also have two major disadvantages, which are closely related: they use a lot of power, and that power isn't always either cheap or green.

    The power demand is easy enough to calculate. We are all familiar with figuring boilers on the basis of BTUh -- a measure of power. BTUh converts directly to Kilowatts: 1 KW is the same as 3,400 BTUh. If you prefer to think in terms of amperes, most residential applications will have single phase 240 volt power, so that would be 4.2 amperes per kilowatt.

    As @Paul Pollets noted, then, most residential applications will require 30 to 50 amperes at 240 volts, single phase. If there is to be an electric boiler, there will also need to be an electric domestic water heater -- another 20 amperes or so, typically, and very likely an electric kitchen stove, which is another 20 amperes. At this point you are up to a peak demand around 100 amperes -- which is a common value for many residence main switchboards.

    Turning on a light will blow your main circuit breaker. So... you need at least a 200 ampere service entrance even for a modestly sized residence.

    That minor detail aside... electricity does cost money, and in many areas -- such as New England -- it's the most expensive (sometimes by a wide margin) of all power sources.

    Then there is the little question of grid reliability. The power companies really do a marvelous job of that, but... the power is most likely to go out when you really would like to stay warm. While it is perfectly possible to have a backup generator capable of running a residential electric boiler, such a critter isn't what most folks will have or want to have 50 KW generators are not exactly a Home Depot item...

    You mention photovoltaics in the future. While again it is perfectly feasible to contemplate a photovoltaic system to go with an electric boiler, you are faced with a slightly different problem: not just power output, but storing that power as energy for use when it's cloudy or at night. Generating the power isn't so bad, though it's not cheap: at present day efficiencies, a photovoltaic array with an area of around 150 square meters or around 1500 square feet, in full sun and oriented directly to the sun, will do very nicely (with, of course, a 50 amp 240 volt inverter to go with it) for the size application we are playing with. The sun, however, does not always shine, so unless one is going to depend on the grid for your backup power, one has to store that power. A commonly accepted figure for New England is that, on average, one can get 3 hours of usable sunshine per day, and one will have on occasion as many as three days in a row without usable sunshine. So... we need to have a storage capacity of 30 KW times 72 hours, and an array capable of charging that capacity in 3 hours. That is a much bigger array, to begin with -- around 36,000 square feet, or 3/4 of an acre. Then you need the batteries... an 8D battery has around a 2.4 KW-hour storage capacity. We are trying to store around 2,000 KW-hours, so you're going to need a submarine size battery bank.

    It all sounds so wonderful... until you start putting numbers into it. As I've said before, physics is a b***h..
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Paul Pollets
  • Rich_49
    Rich_49 Member Posts: 2,579
    Could it be possible he may want or means he would like a heat pump capable of doing both heating and cooling ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Hot_water_fan
    Hot_water_fan Member Posts: 118
    edited September 13
    This is all great information to start with. The bit about domestic hot water is important. As this property will be used as a rental or air B&B the water will be a real issue.
    The simplicity of electric is appealing but the operating cost will likely be the final factor


    Frankly, I don't see why you'd install a boiler at all in this situation. That's a lot of expense, you could go with a furnace and/or heat pump for cheaper and get AC as well for this customer. I can't imagine someone renting a B&B cares much about radiators, but probably will want to rent out the place during the summer. Both furnace and heat pump will be cheaper to operate than a electric boiler.

    If you want simple, electric baseboard beats any hydronic set up and comes with zoning/redundancy.

    Don’t worry about battery storage now for solar, go grid tied.
  • Grallert
    Grallert Member Posts: 523
    edited September 13
    He would most likely not want to store any electricity via solar the consideration would be only to offset the cost of the service. The original plan was simply a boiler for three heating zones plus domestic. I did bring up heat pumps as an alternative and that went over like a lead balloon. We're lucky so far here in my area in that there is rarely any call for AC. Maybe a day or two. The reason for a boiler is comfort. And there's a good chance he will at some point occupy the building as it will be an easier place to manage than the home he's in how as he gets older. I don't know.
  • Hot_water_fan
    Hot_water_fan Member Posts: 118
    @Grallert I just can’t see a single advantage of an electric boiler vs electric baseboards/panels. An electric boiler has:
    1. Same conversion efficiency, worse distribution efficiency. 
    2. More expensive parts due to the hydronic distribution
    3. worse/more expensive zoning
    4. less reliable since it’s one system vs several independent systems. 
    5. More expensive/complicated installation
    6. Same comfort vs. electric panels/baseboard. 
    7. An indirect tank adds complexity and gains nothing. 

    The air to water heat pump option would have lower operating costs, but probably higher installation costs vs electric boiler. They’re also rare in the US. I just can’t see the point in a hydronic system in a house that’s not owner occupied, and that’s especially true for an electric fueled version. 


    Larry Weingarten
  • Jamie Hall
    Jamie Hall Member Posts: 16,344
    Oddly, I agree with @Hot_water_fan on this one. If the person is set on using electricity as his heating power source (I can't imagine why, but that's me) then he's much better off using direct electric heat. Baseboards, radiant floors, radiant ceilings, radiant panels... whatever.

    He won't like either it or the electric bill much, but that's not our problem...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • sunlight33
    sunlight33 Member Posts: 345
    Yes, and won't worry about pipes freezing because there aren't any with electric baseboards.
  • Grallert
    Grallert Member Posts: 523
    He is not set on an electric boiler at all. He simply asked me to have a look and get some input. Having no experience with them I knew I could get an opinion or two here. Again Heat pumps are a nonstarter for him I already went there. He's been a friend for twenty years so I know him quite well at this point. I have my answer. Thank you gentlemen.
    Rich_49
  • jumper
    jumper Member Posts: 1,668
    Radiant electric panels can heat relatively quickly (380°) so one can economize by underheating unoccupied rooms. Even if one goes with heat pump I'd still think about panels for cold days.

    Theoretical possible advantage of electric hot water heating is thermal storage. So if utility can promise extra low rates at certain times of day....... I do not recommend that route. Needs multiple large high temperature tanks.