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Thread: Electrical Boiler

  1. #31
    DIY Junior Member technogirl74's Avatar
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    Thanks for all the answers guys.

    Spent the better part of yeaterday talking to some contractors to instal as well as Slant Fin technical assistance.
    The boiler fully running draws 93amps with the circulator included.
    The elements are modulated to come on as needed. The boiler has an outdoor reset built in to it.

    Originally we were going to try and do alot of this work ourselves but we really liked one of the contractors.

    He's proposing to run 2/0 copper SER out of the panel. (On a 100 amp breaker) to the boiler.
    When he pipes in the boiler, he''s gonna make it so that we can valve off the electric boiler and switch to the propane boiler and vice versa.

    JW. Speedy Petey, DO YOU GUYS SEE ANY ISSUE/PROBLEM WITH USING 2/0 SER ON A 100 AMP BREAKER? (not shouting)
    Could we get away with 1/0?

  2. #32
    Electrical Contractor/Instructor jwelectric's Avatar
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    You could use 1/0 copper SE type cable and a 125 amp breaker. This is something that your electrician should know and if he don’t you might want to consider another electrician.

    For reference have him/her look at 424.72 of the NEC and the sections that it references

  3. #33
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by technogirl74 View Post
    Thanks for all the answers guys.

    Spent the better part of yeaterday talking to some contractors to instal as well as Slant Fin technical assistance.
    The boiler fully running draws 93amps with the circulator included.
    The elements are modulated to come on as needed. The boiler has an outdoor reset built in to it.

    Originally we were going to try and do alot of this work ourselves but we really liked one of the contractors.

    He's proposing to run 2/0 copper SER out of the panel. (On a 100 amp breaker) to the boiler.
    When he pipes in the boiler, he''s gonna make it so that we can valve off the electric boiler and switch to the propane boiler and vice versa.

    JW. Speedy Petey, DO YOU GUYS SEE ANY ISSUE/PROBLEM WITH USING 2/0 SER ON A 100 AMP BREAKER? (not shouting)
    Could we get away with 1/0?

    It all has to do with Duty Cycle. Go for it. The worst than can happen is the breaker will Need reset often. But not likely if the controller is properly setup.
    Last edited by DonL; 01-24-2012 at 07:52 AM. Reason: English
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  4. #34
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by jwelectric View Post
    The link you posted on the cover of the manual is calls it a boiler
    Perhaps its a canadian thing. When you read deeper, it certainly does not make any mention of steam production, but only as use for hydronic heating. Boiling water in Pex would be rather a problem. Maybe the OP will clarify.

  5. #35
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by ballvalve View Post
    Perhaps its a canadian thing. When you read deeper, it certainly does not make any mention of steam production, but only as use for hydronic heating. Boiling water in Pex would be rather a problem. Maybe the OP will clarify.
    It does not have to produce steam in order to be a boiler. Most water heaters are ASME rated as a boiler

  6. #36
    DIY Junior Member technogirl74's Avatar
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    JW,

    Its actually an HVAC contractor that will be doing the install. Here he is allowed to do the electrical as well.
    We discussed permits and I talked to the town and they said that I do not need one. (Yippee)

    I priced 2/0 as opposed to 1/0 and for a few additional dollars I will be going with the 2/0.
    You mentioned SE cable, the boiler directions call for two hots, a neutral and a ground. Wouldn't that be 4 wires. I was told SE cable is only 3.


    Also, do you any issue with the breaker being a 100 amp.
    I called and they do not make a 125 amp breaker for my panel.

    thanks again.

  7. #37
    Electrical Contractor/Instructor jwelectric's Avatar
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    Maybe I should have said SE-R which is a 4 conductor cable. In the trade most will know that SE sometimes means SE-R

    It is up to you as to what you use. What I have posted is what the NEC requires

  8. #38
    In the trades Dana's Avatar
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    Quote Originally Posted by ballvalve View Post
    Perhaps its a canadian thing. When you read deeper, it certainly does not make any mention of steam production, but only as use for hydronic heating. Boiling water in Pex would be rather a problem. Maybe the OP will clarify.
    It's not a Canadian thing, it's a hydronic thing (steam also fall under the "hydronic" heading, BTW), and they are indeed boilers, not mere water heaters despite the lack of steam output.

    In a pumped liquid hydronic boiler micro-boil bubbles are constantly forming and collapsing along the heat exchanger surfaces, and it's the designed such that the turbulence on the water side sufficiently high to keep the micro-boil bubbles from collecting and become an insulating film. But taht creation and subsequent collapse of the water vapor bubblets is an important part of the heat exchange process- it's designed-for. When there isn't sufficient system pressure (or slow flow) that micro-boil can become large enough to sizzle audibly, and when the bubbles are allowed to get that big the stack temps go up, combustion efficiency falls. (This is an issue with gas-fired tankless HW heaters at low water pressure too. A tankless HW heater is actually a boiler too, and referred to as such in some countries.)

    Even on fossil-fired condensing boilers where the flue temps are well below the boiling temp of water, micro-boil is occurring a the end of the HX nearer the flame front, but ceases in the condensing end of the HX.

    With modulating electric boilers there may be operating temperature ranges on the low end where they don't actually get the micro boil, but that depends also on flow rate and the modulation power. While related in some ways to their technologically similar on-demand electric HW heaters, they're designed to tolerate a much higher temperature range and flows more relevant to hydronic heating applications. They are uses ALL THE TIME in radiant heating apps in conjunction with PEX tubing, but have to be output temp limited to stay within the operating range of the PEX (most often specified at 180F by the manufacturers, but they're actually good for at least 20F more at typical heating system pressures), and are widely available from a number of manufacturers and internet vendors, eg: http://www.pexsupply.com/pex/control/search?SEARCH_STRING=electric+boilers

  9. #39
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by jwelectric View Post
    It does not have to produce steam in order to be a boiler. Most water heaters are ASME rated as a boiler
    Thats a bit redundant. You answered your own original question. Or was it a test?

    They are uses ALL THE TIME in radiant heating apps in conjunction with PEX tubing, but have to be output temp limited to stay within the operating range of the PEX (most often specified at 180F by the manufacturers, but they're actually good for at least 20F more at typical heating system pressures), and are widely available from a number of manufacturers and internet vendors, eg: http://www.pexsupply.com/pex/control...ectric+boilers
    I have 3000 feet of pex in my slab, and I certainly would stay well UNDER the temp and pressure at all times. Not a good place for a "test" of specifications. In fact, that unit scares me, as if it ever ran away on temperature, you would be calling the HVAC guys in.
    Last edited by ballvalve; 01-25-2012 at 10:53 AM.

  10. #40
    In the trades Dana's Avatar
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    How is an electric boiler's runaway risk different from a gas-fired boiler? Either could runaway in temperature (hell even a hot water heater can) but only if multiple controls have failed. The SlantFins even come with outdoor reset control, if you want it for a higher comfort constant flow setup. If the internal controls scare you, inserting a high-limit aquastat on the output piping to interrupt it may be cheap insurance, but not necessary. They come with the usual 3rd party test ratings for hydronic boilers, including ASME (which isn't often the case for hot-water heaters.)

    I'd never design ANY heating system for 180F water, but Wirsbo has a test setup that's been running a length of PEX for over 25 years at elevated temp and pressure beyond the rated spec. An excursion to 200F isn't going to be a disaster with anybody's PEX, but 220F might if the pressure relief fails. Wirsbo rates theirs at 200F @ 80psi, an insane temp & pressure for radiant floor applications. "Brand X" PEX is often only rated at 180F nominal operating temp, but it can take much more at typical heating system pressures.

    But I s'pose with an idiot system designer it's possible to defeat about any safety or temperature limit spec. :-)

    Electric boilers are relatively simple-minded & rugged beasts, and they're cheap. But even in nickel a kilowatt-hour land, in an upstate NY climate the total seasonal energy requirements it won't be ultra-cheap to operate. The boiler in question is likely to be more than 2x oversized for the load too, which is never a good idea for comfort and equipment longevity. Money spent on it is better spent elsewhere:

    A 1.5-2.5 ton inverter-drive ductless air source heat pump (mini-split) appropriately sized for the heating load would pay for itself in under 5 heating seasons even with nickel electricity (and that's at the full installed price of the heat pump not some delta between an electric boiler installation and a mini-split.) Going with an electric boiler and NOT a mini-split would only make sense if you were willing to pay for the extra comfort-cush of a radiant floor or something. A heat pump with some cheap resistance electric backup for the sub-zero peak loads makes more sense otherwise. It would have have half (or less) the operating cost of an electric boiler during mid-winter, and less than 1/3 the operating cost during the spring & fall. In a ~7000 heating degree day climate those are significant savings.

  11. #41
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by Dana View Post
    A 1.5-2.5 ton inverter-drive ductless air source heat pump (mini-split) appropriately sized for the heating load would pay for itself in under 5 heating seasons even with nickel electricity (and that's at the full installed price of the heat pump not some delta between an electric boiler installation and a mini-split.) Going with an electric boiler and NOT a mini-split would only make sense if you were willing to pay for the extra comfort-cush of a radiant floor or something. A heat pump with some cheap resistance electric backup for the sub-zero peak loads makes more sense otherwise. It would have have half (or less) the operating cost of an electric boiler during mid-winter, and less than 1/3 the operating cost during the spring & fall. In a ~7000 heating degree day climate those are significant savings.
    What I suggested back on page one...the advantage is not only cost, but for those few occasions (maybe more?) when the humidity levels get to you, you'd have a/c available, too.
    Jim DeBruycker
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  12. #42
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by jadnashua View Post
    What I suggested back on page one...the advantage is not only cost, but for those few occasions (maybe more?) when the humidity levels get to you, you'd have a/c available, too.
    That would make sense.

    Lets not be too sensible...

    You will take all the fun out of the forum. lol
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  13. #43
    General Engineering Contractor ballvalve's Avatar
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    Going with an electric boiler and NOT a mini-split would only make sense if you were willing to pay for the extra comfort-cush of a radiant floor or something
    I cannot imagine life in cold, or any climate for that matter, without hot floors. Boot driers everywhere, dog warmers in all spots, all objects warmed in the rooms, and warm pants to put on in the morning by laying them on the floor. Lowered temps from that word radiant, and no dust devils made up of cat hair, cheetos, and the kid peeing into the floor vents, growing the next super-virus / allergen in the leaky duct work.

    My uncle the HVAC guy, got cut everyday for 50 years. Then one day a cut from some projection inside an old mouldy duct gave him gaseous gangrene, and his arm looked like a telephone pole. They were just ready to get out the skil-saw when the old army doctor cut the arm open lengthwise, and pumped him full of Penicillin and sulfa drugs. Never went in an old duct again.

    As to boilers, Having grown up in a dry cleaning and tailor shop, a BOILER was a big nasty scary beast that made STEAM. Next to it was a little thing called a water heater, and though it may have had micro steam bubbles forming at the heat source, it had better never BOIL the water. Semantics.
    Last edited by ballvalve; 01-26-2012 at 12:13 PM.

  14. #44
    DIY Junior Member technogirl74's Avatar
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    Quote Originally Posted by jadnashua View Post
    What I suggested back on page one...the advantage is not only cost, but for those few occasions (maybe more?) when the humidity levels get to you, you'd have a/c available, too.
    Actually in the new house we plan on using radiant for the flooring.

    Sometimes you gotta know the whole story, but there isnt eough space to write the whole story.


    thanks JW and Speedy petey for the help.
    We're gonna go with HVAC contractor and use the 2/0 and 125 amp breaker.

  15. #45
    General Engineering Contractor ballvalve's Avatar
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    I would thank dana and I for telling you your boiler "water heater" is about 2x oversized.

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