Electrical Boiler

Discussion in 'Electrical Forum discussion & Blog' started by technogirl74, Jan 19, 2012.

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  1. technogirl74

    technogirl74 New Member

    Messages:
    17
    Location:
    ny
    We are in upstate NY where electricity is cheap.
    We are planning to change out the boiler in our bungalo and have choosen to go with an electric boiler.
    This way we can remove the dilapitated chimney and simplify installation.

    The boiler we are leaning to is a Slant Fin Monitron EH24M2 which is listed at 100amps at full load. It is also 82,000btu on single phase.
    My husband wants to go with #2 Romex wire on a 100amp breaker for the installation.
    Since we only want to do this once, I thought I'd get the opinion of the folks on this site.
  2. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    Is the current boiler gas? oil? What do you pay per kwh of electricity vs. how much per therm of gas or gallon of oil?

    On the heat strips for my heat pump (on 100A breaker), I used #2 THHN copper (I could have used #3, but the place that I got it from only had #4 and #2 by the foot). Having individual conductors in conduit was easier than trying to fight with larger SE cable (often aluminum). I would probably use THHN or similar, but cable might be cheaper.

    Before you go down this road, there are a few things to check:
    1. cost of operation. How does electric compare to other sources? How might the price of electricity change in the future compared to other fuels?

    2. Can your current electrical service handle an additional 100A load? If it wasn't installed with the assumption that an electric furnance/boiler would be installed, it is probably undersized for the load. You would then need a service upgrade to handle the additional load.

    3. There are many types of boilers and you may find something that will ease the chimney issue and installation and not require going to electric

    4. This is a good time to look at the size of boiler that is really needed. There are some calculations that can estimate the need, but the more accurate method is to look at how much fuel you used during a heating season along with your location to see what the real heat load is. Your old boiler may have been greatly oversized (often the case) and you may be able to go much smaller (save on initial costs as well as operating costs).
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    My father used to live in Fairport, where the elecric rates were quite inexpensive (Niagra Falls generates a lot of electricity cheaply). He ended up with a heatpump system. While it got cold there, it didn't need to run the resistance heater that often. This may end up a better deal for you than an electric boiler...a heat pump gives you more heat than straight reistance heaters do plus, it would give you a/c for the hot, sticky days in summer when you want it. If you don't have ductwork, there are ductless systems that work quite well with at least some room layouts, or high velocity ducts that care fairly easy to retrofit.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    As has been pointed out be sure that your service will carry the load.
  5. technogirl74

    technogirl74 New Member

    Messages:
    17
    Location:
    ny
    We had the service redone after the tropical stroms that ripped through.
    200 amp service.

    We are going with the electric boiler as we can get one for a really really good price.

    JW Electric, were not asking how to do it but do you forsee any problems with going with #2 romex / SER cable
    and putting it on a 100 amp breaker?
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    2 copper NM-B or 2 SE-R copper is good for 95 amps. As long as the boiler ampacity is below 76 amps then installing it using #2 with a 100 amp breaker will be fine.
    If the heating elements are rated at more than 48 amps and the boiler does not have an ASME stamp on it then the maximum ampacity cannot exceed 60 amps. If the boiler does not have an ASME stamp and the elements are rated more than 48 amperes the load has to be divided into loads that does not exceed 60 amps. This can be done inside the control panel of the boiler by having fuses or breakers that subdivide the loads.

    Once again please do a service load calculation to be sure that it will handle the new load. Remember that the boiler is to be figured at 125% of its ampacity.
  7. technogirl74

    technogirl74 New Member

    Messages:
    17
    Location:
    ny
    JW,

    Not exactly following you on your post.
    This much I know.
    The 200 amp service to the house is for a future home we plan to build.
    Right now the bungalo has 2 bedrooms, a kitchen/bath and small open room.
    Stove is on propane.
    Only lights and a small fridge.
    Hot water is from a 30 gal electric heater.

    According to the installation instructions the boiler has "heater ampres @240 is 100"
    I spoke with technical assistance and they said that it has three elements and at full load it will be about 92amps.


    http://www.slantfin.com/index.php/products/boilers-residential/monitron-eh
  8. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    What are your electric rates?
  9. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    988
    Location:
    NY State, USA
    #2NM is not nearly enough. This unit is a 100A DRAW.
    You need 1/0cu at least.

    IMO, unless you electricity is almost free you'd be nuts to go with an electric unit this big.
  10. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Hereabouts all the inspectors allow #2 cu for 100 amps

    But I can save her a ton of money with a few water heater in series [unless they are making steam] I heat my house with 2 water heaters with 4500 and 5500 watt elements set up to run both together. Been running fine for 10 years. If she is comparing against propane, cheap electric wins hands down. If against practially free nat gas, then thats the way to go.

    I am lucky to have an OLD grandfatherd in seasonal rate schedule of 6 to 8 cents per KW.
  11. technogirl74

    technogirl74 New Member

    Messages:
    17
    Location:
    ny
    Thanks for the replies guys.
    The boiler is to replace a propane fangled mess we have right now.
    We need something to get us through the year and something that will be able to handle the "new" home we plan to build in the future.
    In that home we are going to go with a new propane boiler but have the piping done so that we can switch between the electric boiler and propane boiler.
  12. technogirl74

    technogirl74 New Member

    Messages:
    17
    Location:
    ny
    Ballvalve,

    Can you send me a diagram of what you have.
    I've heard about using electric water heaters but read that the recovery rate is not so good.
  13. Dana

    Dana In the trades

    Messages:
    2,790
    Location:
    01609
    At ANY per kwh rate with the seasonal heating required anywhere in NY state heat pump technology would pay for itself. If you're already committed to the electric boiler concept, size the boiler to minimum of what you need now, and when you graft on the new dream house do the financial analysis on what a variable-speed air source heat pump (ductless or ducted), or a ground source (geothermal) system would deliver. But doing that financial analysis NOW may make even more sense.

    You may be able to cut your heating costs by maybe a third to half by going to electricity, but why stop there? Propane is currently the most expensive heating fuel possible where electric rates are cheap (at about the national average or higher pricing on electricity your electric boiler might be more expensive), and heating with a heat pump in cheap-electricity-land will be something like 1/4 the cost of heating with propane, maybe even less. Even with the prospect of a future lower price on propane locally as the Marcellus & Utica shale gas fields are developed, it's doubtful that it'll ever approach heat-pump technology on a BTU/$ basis, even if the price of electricity doubles.

    And with heat pumps you also get air-conditioning to take the sticky edge off the hazy heat of July.

    With any heating system it's important to get a good handle on the size needed, and you may not need anything like 62000BTU to keep a 1500-2000 square foot bungalow warm (even at -25F outdoor temps you might see in Saranac or other higher-cooler place.) If you've gone through at least a heating season or two on propane and know your annual fuel use it's possible to get a fairly good handle sizing based on fuel use, heating degree-day data for your zip code, and the nameplate efficiency on the propane boiler. (My at -25F the heat load on my ~2200' bungalow w/1500' of semi-conditioned insulated basement is still well under 50,000BTU/hr.) If you don't have that information, "manual-J" type heat loss calculation would get you there.

    Even a single 1.5-2 ton ductless mini-split heat pump would likely handle the shoulder season heating loads, at an operational cost a third that of an electric boiler, and it's contribution to the mid-winter heating would be at ~half-cost relative to the electric boiler. Geo would even be a bit better, but would usually be a much higher up-front cost unless subsidiesed. (A 2-ton mini split is ~$5KUSD, installed, in my neighborhood, but 2-ton geo runs ~$15-20K, often more.)
  14. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    988
    Location:
    NY State, USA
    For electric heat with a 100A draw? I don't think so.
  15. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Obviously it depends on the distance. And the wire and its temperature rating of insulation. It goes as high as 130 amps.


    http://www.thelenchannel.com/1amps.php

    As to water heaters, you can buy 30 gallon rigs for $195, do a little rewiring and get both elements on, so you have a 9 or 11,000 watt unit. Just interconnect them until you get the BTU's you need. Or buy a commercial unit with several elements and anodes.

    Here is a USA made rig with multiple choices of current inload - gold plated elements, and 60 to 150 amp current draw;

    http://www.americanwaterheater.com/products/pdf/lchde40.pdf

    I find it very hard to believe you need a 100 AMP RIG.... Is your bungalow 4000 square feet with no insulation, built on an iceberg?
    Last edited: Jan 21, 2012
  16. DonL

    DonL Jack of all trades

    Messages:
    3,815
    Location:
    Houston, TX

    The manufacture says #2, so it can be used. NEC don't seem to care about the length, even tho it is part of the formula.
    I go by voltage drop when I install wire.
  17. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    988
    Location:
    NY State, USA
    Wow. Really?

    No, NOT really. An electric boiler with a draw of 100A simply CANNOT use wire rated for 100A.
  18. DonL

    DonL Jack of all trades

    Messages:
    3,815
    Location:
    Houston, TX
    If the wire is rated at 75-90degs C, You may could get by with it. But not using 60 deg wire. Should use 90C for good measure.
  19. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    988
    Location:
    NY State, USA
    The rating of the wire has NOTHING to do with it.
    An electric boiler like this has to be figured @ 125%. So the ampacity of the conductor must be at least 125A.

    How do you figure temp has anything to do with this? I never mentioned wire size, just ampacity.
  20. DonL

    DonL Jack of all trades

    Messages:
    3,815
    Location:
    Houston, TX
    I thought that we were talking about #2 ?

    You say Temperature does not mater ?

    That unit has bank switching and would very rarely (If Ever) require 100 amps to operate.

    You also have to add < 10 amps for the rest of the system.
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