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  1. #21
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    Default Re: Water temperature requirement for hot water baseboard?

    hvhehcca,
    Thank you for the quick response. I read through the study rather quickly, and will give it more time this evening. I don't doubt that a condensing boiler can be used to save energy on existing systems designed for 180*F. water, although the savings will be somewhat reduced and the payback time will be greater. What I do have a problem with is supplying sufficient heat to keep the room comfortable.

    From some parts of the study I found these statements. I may be taking them out of context, and will give them further thought when I have more time:

    Conventional baseboard hydronic distribution
    systems are most common and these are designed for water temperatures in the 180 F range, well above the saturation temperature. I agree.

    The heating system as tested combines space heating and domestic hot water loads using an indirect, 40 gallon tank with an internal heat exchanger. Tests conducted during the summer months showed that the return water temperature from the domestic hot water tank heat exchanger is always below a temperature which will provide condensing operation of the boiler. I feel the use of the domestic water tank skews the test somewhat in favor of the condensing boiler.

    The results included in Figure 26 and 27 show that the condensing boiler yields higher efficiency than the non-condensing boiler in actual use. However, the increase in efficiency achieved with the condening boiler during the heating season is smaller than might have been expected.It comes as no surprise that the condensing boiler has higer eff, but most of the savings in this study seem to be in low demand situations and operating this unit in the summer for domestic hot water is not a fair comparison in my opinion.

    The primary conclusion of this work is that condensing boilers can achieve energy efficiency benefits, even when used in homes with common baseboard radiators by incorporating a reset control which modulates the water temperature supplied to the baseboards with outdoor temperature......This of course depends upon the oversizing of the baseboard convectors relative to the design load of the home and the excess air level on the burner.The report seems to indicate in several places that adding baseboard or convectors will be necessary to provide adequate heat. The study was to determine what percent of the year that savings can be obtained, not if an existing system will function without adding additional heating units.

    One must keep in mind the number one primary purpose of a heating system. It is to keep the occupants comfortable. Energy savings can be a very important factor, but if you install a system that can not keep the owners comfortable, they may use any money they saved on utilites to hire a good attorney to come back and sue you.
    Last edited by ZZZ; 01-02-2011 at 03:46 PM.
    "Lead by Example"

  2. #22
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    Jun 2010
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    Default Re: Water temperature requirement for hot water baseboard?

    There is also another point that this study did not take into consideration as it was more based on oil not gas. The rate of modulation of a condensing boiler. The rate of modulation combined with return water temps even above the dew point can produce efficiencies in the 90% range. See the attached chart. Although it is based on a particular manufacturers product the theory in process applies to all brands.

    I totally agree with you concerning comfort. My point to the entire arguement is that you can achieve increased fuel savings in investing in a condensing boiler with baseboard. This achievment can only be done with a proper room to room heat loss and measurement of the existing emitters capable output with the water temp you design around.

    When people post the question as the orinial poster did you cannot tell them it cannot be done or there is no benifit. You want to direct them that in order for them to make a decision as to what is best for them they need to have a complete heat loss and emitter comparison done. Once this is accomplished they can then take the information and decide what they want to do.

    With a condensing boiler you have the benifit of increasing or decreasing your heating curve. I never said to not choose a boiler that can't overcome the homes heat loss. Finding a heating curve that rides the heating season is a process. You cannot just set it once and forget it. You have to go through an entire heating season tweaking it. That's what we do. We don't leave after the installation we work and tweak through an entire heating season to provide the customer the comfort they want. Each and every person has a different comfort level and that is not for me to decide but for me to give.

    Speaking for Viessmann Vitodens as this is my boiler of choice I can limit the boilers rate of modulation to match my heat loss if I desire. A reason you may do this is that ever boiler in some way is oversized. They don't make boilers that fit each and every heat loss. There are also other things to consider. How about pump. That little green flat headed curve pump tends to over pump in alot of applications so your delta-t doesn't get much wider than 9 to 12 degrees. We are being to use more and more Grundfoss Alphas or similar pumps to get our delta's closer to our design parameters.
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  3. #23
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    Default Re: Water temperature requirement for hot water baseboard?

    I am not familiar with the Viessmann, I have never seen one around here. I am sure some brands are much better designed than others and usually you have to pay extra for that. If someone was installing a new system where the piping and radiators could be accurately matched to the load, I could see the savings would be much better.
    The problem I see with existing systems, is that if they were accurately sized for 180 F. water, and you don't supply it, you will have complaints. Likewise, if you convince a customer to pay thousands extra for efficiency, and more for additional convectors, and they don't also have domestic hot water from the boiler(none of my customers do anymore) the savings might not materialize, and that is not a good situation. I would like to see a better study, without the domestic water heater, before I would try very hard to convince people to spend the extra money.
    Well by now, the OP is probably sorry he ever asked the question, and has most likely gone out and bought an outdoor wood furnace.
    "Lead by Example"

  4. #24
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    Jun 2010
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    93

    Default Re: Water temperature requirement for hot water baseboard?

    ZZZ,

    Being in the Northeast I believe we see much more hydronics then the rest of the country. Back in the day most installers did not do heat losses so in most homes the outside walls are wrapped in board. You also have to keep in mind that since these older systems were installed home have been updated. Newer windows, blown in insulation and possibly even vynial siding with added insulation on via a house wrap or some type insulation.

    These updates reduce the original homes heat loss. Condensing boilers have the ability to produce the 180 degree water that may be needed if circumstances call for it. You also have to keep in mind that the 180 degree water is only needed on the coldest day of the year. You don't want to cram btu's that are not needed. This tends to cause short cycling in boilers. At a minimum you want a 6-10 minute burner cycle. This allows the boiler to reach steady state efficiency.

    When I do my heat losses I run them in different outdoor design temps. I track the changing heat loss of the home at the different outdoor temps to graph a heating curve. Baseboard no matter the water temp will provide btu's. I would rather coast to setpoint meaning a slow 1 degree rise to maintain steady state of my boiler.

    There are also other contributing factors such as solar gain, appliances and thermostat placement that I also take into consideration at the design stand point.

    I never go to a home and try to compare the last job to the new job. Every job is different.

    On average we are seeing a 30-35% in fuel usage savings. I never talk dollars only therms. With the ever changing price of gas you cannot compare dollars you must compare therms.

    There is a standard rule for savings utilizing water temp. For every 3 degrees I can run a heating system below 180 degree water I save 1% of fuel.

    I also would like to thank you for taking the time to read the study and bringing some outside insight to the post instead of just throwing around an arrow.

    You should join the Taco Flo Pro Team at www.taco-hvac.com. Its only open to tradesman and a great resource to the every changing industry we belong to.

  5. #25
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    Aug 2007
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    612

    Default Re: Water temperature requirement for hot water baseboard?

    Quote Originally Posted by ZZZ View Post
    Well by now, the OP is probably sorry he ever asked the question, and has most likely gone out and bought an outdoor wood furnace.
    If the OP is in the NE I would advise them to look at a dual fuel coal stoker boiler if they are interested in saving serious money over the long term.

  6. #26
    Join Date
    Feb 2008
    Posts
    175

    Default Re: Water temperature requirement for hot water baseboard?

    Hey, hvhehcca:

    Somewhere along the way you've forgotten the truism that the central purpose of doing a "study" (by Brookhaven, or anyone else) is to reinforce, validate and "prove" the author's half-baked, half-truth contentions on the topic.

    Most of these studies have big corporate heating money behind them to make sure the study always draws the right conclusions to keep the corporate profits flowing.

    You know this,right??? Wake up and smell the coffee as they say.

    You've gotten so lost and wrapped up in all this "steady state efficiency", "condensing point", "design parameters","delta T" bullcrap jargon that you've become estranged from your homeowner customers, who hire you to provide them with pertinent info, prompt, comfortable heat and reliable equipment at a reasonable cost.

    This is known as client-centered service.

    God, I hope you're not spouting any of that jargon you put in your posts here in front of the customers--they haven't the foggiest of what any of it means, and could care less---the homeowner is freezing his balls off with a heating problem, is wearing 3 blankets, there's no heat in the house, and he expects you to solve his heating problem yesterday!

    In many cases the equipment should include non-condensing boilers in situations where a condensing unit is not indicated.

    Fuel usage has dropped dramatically with these "traditional" boilers while efficiency has greatly improved, or haven't you noticed in that technocratic haze you're staggering around in???

    Read the latest posts just written by ZZZ, and learn from him.

    His views on customer comfort, skepticism toward studies, and most of all, making sure the customer is completely satisfied with his heating system, even if it isn't fitted with the latest bells and whistles, is a pleasure to behold.
    Last edited by Dobbs; 01-02-2011 at 11:25 PM.

  7. #27
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    Aug 2008
    Location
    Midwest
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    Default Re: Water temperature requirement for hot water baseboard?

    Quote Originally Posted by bp21901 View Post
    If the OP is in the NE I would advise them to look at a dual fuel coal stoker boiler if they are interested in saving serious money over the long term.
    What is the price per ton for coal, and what type of efficiency is typical? We aren't allowed to burn coal here by local ordinances.
    Outdoor wood boilers are common here, and at $85/cord/24,000,000 btu's for seasoned oak they save money. Even with a 60% eff. wood boiler operating costs are about half the cost of natural gas at $.90 per therm at 80%eff. They are popular around here, but they do create smoke. For unknown reasons, we have no ordinances regulating them. Did I mention they really smoke?

    http://www.hearth.com/econtent/index...on_calculator/
    Last edited by ZZZ; 01-02-2011 at 11:01 PM.
    "Lead by Example"

  8. #28
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    Aug 2007
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    612

    Default Re: Water temperature requirement for hot water baseboard?

    Quote Originally Posted by ZZZ View Post
    What is the price per ton for coal, and what type of efficiency is typical? We aren't allowed to burn coal here by local ordinances.
    Outdoor wood boilers are common here, and at $85/cord/24,000,000 btu's for seasoned oak they save money. Even with a 60% eff. wood boiler operating costs are about half the cost of natural gas at $.90 per therm at 80%eff. They are popular around here, but they do create smoke. For unknown reasons, we have no ordinances regulating them. Did I mention they really smoke?

    http://www.hearth.com/econtent/index...on_calculator/
    $160 per ton for anthracite, efficiency of between 70 to 85% depending on the mfg & model. Not even close to the smoke generated by the wood boilers you're used to seeing. The ban is probably based upon bituminous coal, not anthracite. My neighbors can't tell when mine is firing and when it isn't. There is a reason I used the NE location note in my post. Your cost per cord is about 1/2 ours and maybe even better than that - lucky for you. Is that a face cord or full cord? A 2500 sqft house, not "super insulated", might burn in the neighborhood of 5 ton per year and include DHW. We personally burn about 3.5 and I know of some others in older farmhouses that are draftier than ours that burn about 6. Depending on the OP location, the strength of his desire to save long term money and his willingness to be hands on I'd advise looking at anthracite, but it isn't for everyone.

  9. #29
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    Midwest
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    Default Re: Water temperature requirement for hot water baseboard?

    That's $90 a full cord, if you go outside of town about 20 miles and purchase green oak, its about $65 a cord. We have lots of oak around here. I will check into the coal ordinance to see if it specifies a type.
    "Lead by Example"

  10. #30
    Join Date
    Jun 2010
    Posts
    93

    Default Re: Water temperature requirement for hot water baseboard?

    You've gotten so lost and wrapped up in all this "steady state efficiency", "condensing point", "design parameters","delta T" bullcrap jargon that you've become estranged from your homeowner customers, who hire you to provide them with pertinent info, prompt, comfortable heat and reliable equipment at a reasonable cost.

    How do I provide the prompt, comfortable heat and reliable equipment without properly sizing? I know. I just read the label off your old boiler because it did the job. Heck with sizing it properly, just give me heat.

    I wouldn't be doing my job if I didn't offer you options. How are you going to feel when you end up with a gas or oil hog to replace the gas or oil hog you have now.

    What is reasonable? The cheapiest? The average? Define it.

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