Replies

1. 
   TLRice | Oct 18, 2002 04:23pm | #1

   Jack,

   "I've got electric baseboard heat in my condo, someone suggested that I can switch to electric hydronic baseboard and it will be cheaper and more efficient."

   This is incorrect. Electric resistance heating is as efficient and costs the same no matter how it is pckaged. You pay the same for every kilowatt-hour and you get the same heating effect from every kwh.

2. 
   Piffin | Oct 19, 2002 02:52pm | #2

   Seems like a problem with termionology here.

   Hydronic heat uses water or intrifreeze to supply heat from the boiler. An electric boiler?

   There are electric heaters that heat a reservoir of oil which then gives off a slower radiant for some time after current flowed through the resistant heating material. For some people enjoying radiant heat over space heat, it can feel slightly warmer, allowing thermostats to be set slightly lower, and saving a buck or two.

   I wouldn't waste my time with it.

   .

   Excellence is its own reward!

1. 
   CloudHidden | Oct 19, 2002 03:40pm | #3

   Always break heating into its two parts: how you make it and how you spread it around the house. With electric baseboard, you make it and distribute it at the same place. Not efficient to make, but cheap to install. With hydronic baseboard, you make the water hot somewhere else and distribute it to each room via the water in the tubes through the baseboard unit. If you use electric resistance to heat the water, you haven't gained any efficiency. Heat pump (air or ground source) and gas boilers are each more efficient than elec resistance for creating hot water. And hydronic radiators don't seem to improve the distribution of the heat over what you already have. Now hydronic floor loops are fantastic and worth the extra cost/effort imho, but they are totally different experience from baseboard.

1. 
   TLRice | Oct 21, 2002 03:28pm | #4

   Cloud,

   "Heat pump (air or ground source) and gas boilers are each more efficient than elec resistance for creating hot water."

   This is wrong.

   Electric resistence heat, whether it be used to heat air, water or oil is practically 100% efficient. Due to the cost of electricity in most of this country, it is almost always less expensive to heat in other ways than electric resistance, but not more efficient.

   Edited 10/21/2002 8:35:27 AM ET by Tim

1. 
   CloudHidden | Oct 21, 2002 03:43pm | #5

   I've been told many times, and can find the references when I have a minute, that for one unit of elec *in* elec baseboard will give 1 unit of heat *out*, while a heat pump will give ~2.5 units of heat out and GSHP will give ~4 units of heat out. What is the proper way to word that if "efficiency" is not--I'll be happy to change the terminology to be as accurate as possible.

   From one source:

   "Heat Pump cooling performance is defined by an index called EER (Energy Efficiency Ratio).This is the cooling affect produced by the unit (in Btu/hr) divided by the electrical input (in watts) resulting in units of Btu/watt*hr. Electrical input includes compressor, fans and “pumping” allowance (for the groundwater or ground loop).

   Heating performance is defined by the index called COP (Coefficient Of Performance). This is the heating affect produced by the unit (in Btu/hr) divided by the energy equivalent of the electrical input (in Btu/hr) resulting in a dimensionless (no units) value."

   This is what yielded the 1, ~2.5, and ~4 numbers that I refer to as efficiency.

   Edited 10/21/2002 11:45:14 AM ET by Cloud Hidden

1. 
   UncleDunc | Oct 22, 2002 12:35am | #7

   Efficiency is an important factor in choosing an HVAC system, but you need to define exactly what resource you're trying to make efficient use of. Efficiency is a fraction. Everybody seems to agree that heat delivered to the room is the numerator, but what should the denominator be?

   If the denominator is electricity used, then the ground source heat pump does look a lot more efficient. But all that extra heat has to come from somewhere, and for a strictly technical energy efficiency calculation, you'd have to include the ground heat along with the electricity in the denominator. If the denominator is initial capital cost, the resistance heater suddenly looks a lot better, especially as you move farther north and have to install a larger ground loop to get enough heat out of it for a longer, colder winter. If the denominator is present value of anticipated lifetime cost, you have to anticipate system durability, future interest rates, future energy prices, future income, etc., and it's no longer obvious (to me, at least) what the right answer is.

2. 
   CloudHidden | Oct 22, 2002 12:53am | #8

   Not addressing cost at all. Just amt of heating/cooling.

   I referenced "EER (Energy Efficiency Ratio).This is the affect produced by the unit (in Btu/hr) divided by the electrical input (in watts) resulting in units of Btu/watt*hr." Is there a reason this is not good?

   My elec water heater draws 19 amps and produces 12000 btu/h of heat. My GSHP draws 13.9 amps and produces 54000 btu/h. I'd be inclined to say that one produces heat more efficiently than the other. What would be better wording?

   A document from the Aussie govt uses efficiency in it's description:

   "The star rating for air conditioners is determined differently to other appliances. For air conditioners, the measure of energy efficiency is the Energy Efficiency Ratio (EER) for cooling and the Coefficient of Performance (COP) for heating. The EER and COP are defined as the capacity output divided by the power input. Typically, the EER and COP are in the range 2.0 to 3.5 (meaning that the cooling or heating output is 2 to 3.5 times as great as the power input, or an efficiency of 200% to 350%). This is achieved by the use of a refrigeration heat pump which collects internal heat and moves it outside when in cooling mode, or collects ambient heat from outside and moves it inside when in heating mode. The apparent efficiency of heat pumps is high as they can move much more low grade energy in the form of heat than they require as electrical power input."

3. 
   UncleDunc | Oct 22, 2002 01:12am | #9

   Nothing at all wrong with your wording. Your message did exactly what I was suggesting, specifying exactly what units you used to calculate efficiency. I should probably have replied to ALL rather than directly to you.

   The point of my message was that if the units are not specified, people will make differing assumptions and end up arguing with each other needlessly.

4. 
   TLRice | Oct 22, 2002 03:52pm | #12

   Cloud and Uncle Dunc,

   There is much confusion in the terminology. Whether that is intentional or not, I don't know. For refrigeration equipment, (chillers, air conditioner, heat pumps, etc.) there is not a direct in/out connection because you are dealing with "effects" vs energy. A heat pump, by the way, does not produce heat, it transfers it from one place to another.

   Pure and simple, efficiency is work out/energy in. In terms of heating, it is heat out/heat in.

   You have to keep the units the same of the comparison is merely a coefficient. COP and EER are useful only in comparison to other devices rated in the same way at the same condition.

   A law of thermodynamics is that energy can neither be created or destroyed. There is no such device that creates more energy than it consumes. Period. An efficiency of over 100% is only refered to by idiots and sales people.

   If you corrupt the term efficiency, and modify it to mean;

   "what you get"/"what you pay for". This is where SEER, EER and COP come in.

   You heat pump would transfer more heat to your house if the ground temperature was 65 instead of 55. Using only a little more energy in the process. Every step in the refrigeration circuit has plenty of losses and it is not 100% efficient, probably more along the lines of 30% efficient.

5. 
   CloudHidden | Oct 22, 2002 05:32pm | #13

   How to best reduce any confusion, then? What are the better terms to use?

   If I pedal a bicycle to generate current and convert it to the proper form, and use that current to power elec baseboard, air-sourced heat pump, and GSHP, would they each yield the same btu/h (all else being equal)? If not, and if you'd prefer we don't say that one is therefore more "efficient" than the other, then what word would be more acceptable?

6. 
   TLRice | Oct 22, 2002 07:23pm | #14

   "How to best reduce any confusion, then?" First of all, ignore anything related to energy or HVAC posted by Uncle Dunc.

   Second, compare apples to apples.

   For instance, when you tell me that you water heater draws 19 amps and produces 12,000 btu of heat, you are leaving out important information. 19 amps at 120 volts, single phase power is 2280 watts and is the equivalent of 7780 btu/hr.

   The point is that ratings, whether they be for a water heater or heat pump or an air conditioner, at given at specific conditions. SEER ratings mean absolutely nothing, unless compared to another SEER rating at the same conditions.

   As I said before, heat pumps do not produce heat. They transfer heat from one place to another. The only "output" you get from a heat pump is an "effect". Efficiency does not apply, not in terms of electricity used vs heat added to the space. That is why no reputable manufacturer rates their heat pumps in terms of efficiency.

   You said, at 13.9 amps (I'll assume at 240V), your HP provides 54 mbh of heat to the space. The heat pump takes the equivalent of 11,386 btu/h of energy input and delivers 54,000 btu/h to the space. So is it 474% efficient? No.

   It would be the equivalent, if an automobile's milage was stated in btu/hr. It just doesn't apply.

   If you want to determine which is the most cost effective, you have to account for energy cost.

   "...and use that current to power elec baseboard, air-sourced heat pump, and GSHP, would they each yield the same btu/h (all else being qual)? If not, and if you'd prefer we don't say that one is therefore more "efficient" than the other, then what word would be more acceptable?"

   It would be incorrect apply "efficiency" to these different processes, my preference has nothing to do with it. It is a matter of technical accuracy. The energy conversion processes will always produce the same output/input regardless of conditions. The heat transfer processes effect/input will always vary with conditions. This is the reason that they only have "ratings", or "ratios" or "coefficients".

   Clear as mud, right?

   For really simple people, ignore everything above and apply "efficiency" to everything.

7. 
   CloudHidden | Oct 22, 2002 08:04pm | #15

   >It would be incorrect apply "efficiency" to these different processes

   I accept that. I really, really do, Tim. I swear I do. And I appreciate your quest for technical accuracy here. There are areas where I have a similar interest (I identify those by when DW calls me "anal"--just kidding). So, the demonstrable fact that for a given electrical input, different devices are capable of yielding (I'm not saying "produce") different amounts of heat should go by what term instead of "efficiency"? Is there a single, acceptable word?

8. 
   TLRice | Oct 22, 2002 08:43pm | #17

   DW? Is that "dear wife"? (I've seen this before, but just don't recall)

   "Is there a single, acceptable word?"

   Not as far as I know. Not that is purely, technically correct. (I believe the COPs, EERs and SEERs were invented from a discussion not unlike this one.)

   But, the splitting of technical hairs aside, I would have to go with something like "energy effectiveness"?.

   BTW, I understand and agree with your point, and you are correct. The GSHP is certainly more "energy effective" than electric resistence heating.

   The rubber really meets the road in a $/"net heat effect" comparison. In my part of the world, your GSHP would cost me (at 13.9A, 240V, $0.08/kwh) $0.27/hour for 54,000 btu of heat added to my house, vs $0.06/hour for my LP-fired 92% efficienct furnace (LP at $0.85/gal, for the same net heating effect, 54,000 btu.

9. 
   UncleDunc | Oct 22, 2002 08:17pm | #16

   >> ... ignore anything related to energy or HVAC posted by Uncle Dunc.

   That seems unnecessarily personal, especially since I agree with nearly everything else in your message. Could you take some time to point out where I went astray?

10. 
    TLRice | Oct 22, 2002 08:45pm | #18

    Uncle Dunc,

    Sorry about that. I didn't mean that quite as directly, personal as it came out.

    What I meant, to Cloud Hidden in the context of the efficiency-as-applied-to-an-"energy in/heat out"-device-vs-an-"energy in/heat moved"-device discussion, was that what you said was more distracting from the point at hand, than it was clarifying.

    You said:

    "Everybody seems to agree that heat delivered to the room is the numerator, but what should the denominator be?",

    I do not agree with that statement.

    Now, this gets back into splitting hairs, but in terms of efficiency, a heat pump does "work". So you cannot accurately say that "heat out" is the "work" the system performs. It does not "produce" heat from the energy supplied to it. It does work in the form of a refrigeration cycle, compressing and expanding the refrigerant, absorbing and rejecting heat to/from the refrigerant. In the process, it does not produce heat, not exactly (it does, but only due to the inefficiencies of the compressor). It moves it from one place to another. The heat delivered to the space is a byproduct of the "work" that the system performs. In terms of work, the heat pump is fairly inefficient. So it is not an accurate comparison to say "heat effect out" is the numerator for comparing the efficiency of one device to another.

    Most everything else you said, don't dissagree with.

    As a practical matter, heat delivered where it is needed IS the "paid for" product. How much do you get for each $ is the bottom line and the only reason we talk about these things, right?

    Edited 10/22/2002 2:26:45 PM ET by Tim

11. 
    UncleDunc | Oct 22, 2002 10:17pm | #19

    I see your point, but I think you're defining the word too narrowly. The word efficiency appeared in English long before we figured out the technicalities of energy and work. I would argue that it is perfectly acceptable to speak of a ratio of some resource input to some desired output as efficiency and to compare the relative efficiency of different products and processes in terms of that ratio. (I should have said ratio instead of fraction in my first message, but I don't know the technical terms for the first and second terms of the ratio, and I knew everybody would understand what I meant by numerator and denominator.)

    I do agree with you that it doesn't make sense to state the efficiency as a percentage unless the input and output are measurable in convertible units. BTU out as a percentage of KWH in makes sense. BTU out as a percentage of dollars in doesn't make sense.

    It may make sense to speak of relative efficiencies in terms of percentages. For instance, if you established the physical efficiency of resistive electrical heating as the benchmark, then it's not simply nonsense to speak of GSHP being 380 or whatever percent efficient, as long as everyone in the discussion knows that we're talking about efficiency relative to the benchmark. It's like radio antenna efficiency being specified in dB of gain. It's pretty clear that there's no gain going on in an antenna, so the real measure is how much signal we're getting out of this antenna relative to some reference antenna, but nobody ever specifies the reference antenna. They just talk about an <N> dB antenna and everybody is presumed to know about the comparison to the reference antenna.

    You want to restrict the meaning of efficiency to include only the physics definition. That's a perfectly reasonable desire, since it would make communication easier if everybody used it that way. But to assert that the existence of a strict technical physics definition of efficiency invalidates all the other definitions is simply wrong. That's not how English works.

12. 
    TLRice | Oct 23, 2002 03:44pm | #23

    UD,

    I am a Mechanical Engineer by training and by profession. It is a frequent problem in discussing technical matters that definitions are not precise. As to whether or not the word "efficiency" predates a physical science based definition, I cannot speak to that. I was born after both came about, and never really looked into it.

    But that is beside the point. We are talking about mechanical, physical energy transfering processes.

    "BTU out as a percentage of KWH in makes sense. BTU out as a percentage of dollars in doesn't make sense."

    I don't think that mixing units makes sense. I think in evaluating a heating or cooling system, from an end user's perspective, a comparison of cost vs desired effect makes the most sense. Not as a percentage, though.

    "if you established the physical efficiency of resistive electrical heating as the benchmark, then it's not simply nonsense to speak of GSHP being 380 or whatever percent efficient, as long as everyone in the discussion knows that we're talking about efficiency relative to the benchmark."

    You qualified this a lot, and with all your qualification accepted, I agree. However, qualifications aside, efficiencies over 100% are physically impossible, and as they are usually stated without all the qualifications, are nonsense.

    "But to assert that the existence of a strict technical physics definition of efficiency invalidates all the other definitions is simply wrong. That's not how English works."

    English, as it is commonly used and understood, is inadquate for technical accuracy. This is why terms are strictly defined; to exclude the ambiguity of common language.

    You tell me a device is 250% efficient, I will assume that you have very limited technical comprehension. You tell me in comparison to another predefined bechmark, that a device "appears" to be 250% efficient in the delivered effect, I would buy it.

13. 
    HammerHarry | Oct 24, 2002 04:32am | #24

    But what if we all give 110% effort?  Wouldn't that count?  I heard that it helps. <G>

14. 
    CloudHidden | Oct 24, 2002 05:29am | #25

    Boy, Cairo, that was an efficient response! :)

15. 
    booch | Oct 23, 2002 12:29am | #20

    There is a Carnot (Lazare Nicolas Marguérite Carnot) equation that describes the loss that occurs in changing one form of energy to another. Heat of fuel to mechanical to electrical generation, or back again from there.

    This is one of those calculus things that describes in a predictable manner what happens to energy. If you use electricity to generate heat the "efficiency" is great. Almost no loss is incurred. This is due to the fact that the heat is generated by purely electrical activity. (resistance or radiance) The rub is how did you get the electricity?

    Burn coal, make steam, turn the turbine, capture the disrupted electrons from the windings and there you have electricity. From my college days (1979)the best you could hope for from in pure electrical generation from heat was about 45% +or- 5%. If you take the waste heat (used steam) and use it to heat the buildings in the community you can up the energy utilization to about 60 percent. You get about 5% loss to power lines to your home. So burn gas/coal/methane/ or whatever and you only get 1/2 of the energy available.

    For that reason I shake my head at the electric cars and electric heat options. If you want to save the environment or $ then use the energy source closest to the function you need.

    http://www.phy.ntnu.edu.tw/java/carnot/carnot.html is the longhand version of what I said above.

    In a really short synopsis: Use gas or wood or coal to heat. Use electricity to run computers, or tablesaws. It is cheaper and no matter what some marketing person tells you, in the global scope, electricity is a waste of energy for heating.

    (how's that for an easy pitch?)

    The only reasoning I can find for the heating with electricity is localized control (tile warming) or heating an otherwise difficult place to pipe the heat.

16. 
    HammerHarry | Oct 23, 2002 04:35am | #21

    I agree with your basic philosophy: if you want heat, use heat (ie, burn something).  You can't beat it.  But that is based on the assumption that the point of use type of heat (wood, coal,  or gas fire, for example) is efficient enough to be comparable to a properly run electricity generating station. Which it CAN BE, but isn't necessarily so.  And, though this has nothing to do with efficiency, that there is some sort of emission control on the thing.  I still think that burning garbage with proper emissions control, is so obvious and logical that you have to wonder.  The areas that generate huge amounts of waste are also the areas that demand huge amounts of energy.  Hmmmmmmmmmmm.

    Heat pumps.  You are taking heat (ground, ground water, or air) near the point of demand, and merely using the electricity to transfer that heat into the place you want it.  That's pretty obvious too, isn't it?  But the economics and practicalities are the sticking point for many installations.

17. 
    booch | Oct 23, 2002 05:32am | #22

    If you have a real heat source you can rob of its energy, then a heat pump may make sense by concentrating the energy. If you are pulling the heat out of 30 degree air outside your house then pick a new method.

2. 
   HammerHarry | Oct 22, 2002 12:30am | #6

   I think you need to define "efficient".  No form of heat is more efficient than electric, if you go by the technical meaning of efficiency, and take the source of energy as the wires into the house.  If you take the generation of electricity at its source into account, you will find that with a properly efficient boiler, hot water heat with a gas or oil fired boiler is more efficient, depending on the method of generating electricity.  However, you might be meaning cost effective, which is a whole different ball of wax.  Efficiency purely means, how many kW of heat do you get out, vs how many kW of energy put in.  Electric baseboard has NO moving parts; no friction loss, etc.  The only loss is the resistance in the wires to the baseboard, which is pretty close to 0.

2. 
   jackstraw9 | Oct 22, 2002 03:08am | #10

   I think you hit it on the head. What was suggested to me was a baseboard unit,filled with some type of oil, that would replace the existing electric baseboard in the house. From what I could gather it would be powered up by the same feed wires as the existing units. Maybe I've got the terminology wrong in my previous post, but unless it's made of wood I can be pretty ignorrant about things. I'm not even sure where I can buy this stuff if it is worth using, I was just looking for some input from people who either have had experience with,or knowledge of this type of system. Thanks.

1. 
   Piffin | Oct 22, 2002 03:44am | #11

   Those units are quite a bit more expensive than what they replace for modestly less cost, driven by percieved, steadier, heat and reduced use.

   Personally, I think the biggest claims for increased efficiency and reduced bills come from those who have invested heavily in the changeover and their egos won't let them admit that they made a questionable choice. That's just an opinion tho'.

   Excellence is its own reward!