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

    I am converting from Oil to Gas. 2500 sq ft house with 150 linear feet of hot water baseboard new. I was looking into high efficiency 90%+ AFUE gas boiler model when one plumber suggested that I will not get the efficiency from those boiler because hot water baseboard use high temperature water. Instead, I should stick with conventional vent through chimney model. Is this true?

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

    For the most part, the plumber may be right----especially when you're talking specifically about baseboard heat, which relies almost completely on CONVECTIVE HEAT (air currents) to circulate heat around the room from its convectors, as opposed to in-floor PEX tubing or large cast iron radiators, which rely much more on lots of STORED HEAT in their concrete, wood or metal BULKY MASS to exude RADIATED HEAT WAVES (like the sun) to propagate heat around the room.

    The high efficiency condensing boilers rely on hot water that is approx. 90-120 degrees to burn a high percentage of their fuel, but to take advantage of this low-heat process, the low-heat BTUs have to be stored in a LARGE MASS RADIANT EMITTER, like the ENTIRE FLOOR, OR LARGE BLOCK OF CONCRETE over a LONG PERIOD OF TIME, like 8 to 24 hours---in effect, the entire floor of the house becomes one large radiator, heated to 120 degrees over an 8 hour period---once this occurs the floor gives up its heat to the living quarters for a very long time.

    Baseboard was designed mostly to operate as a convector with hot water at 180-200 degrees; at this temp. baseboard puts out approx 600 BTUs/hour per foot of baseboard---150 ft. of baseboard X 600 = 90,000 BTU/hr as heat output for the house; a standard HEAT LOSS CALCULATION for a 2500 sq.ft. house is 2500 X 36 BTU (per square ft. to heat the house) = 90,000 btu/hour----so the heat output from the baseboard equals the heat loss from the heat escaping thru walls, glass, roof, etc. & the house remains warm---heat response is within minutes, so the occupants are always comfortable.

    There's always the option of dramatically increasing the linear footage of the baseboard to approx 500 linear feet & run the boiler water at 120 degrees to get the same effect,------ or leave it at 150' and simply rely on a much slower response to the house heat needs & keep the baseboard running constantly during the winter months (24 hrs/day) at 120 degrees to maintain a warm house----this would mean slow response time to sharp drops in outdoor temp until the system could catch up, & most people would find this annoying and unacceptable---but it would be more efficient in long-term fuel costs, but also would burn more elec. to run the pump/circulators 24 hrs,
    Last edited by NashuaTech; 12-23-2010 at 11:10 PM.

  3. #3
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    Default Your Plumber As Well As Nashua Are Wrong

    Sorry, have to chime in on this one. Have been designing and installing low temp hydronics for 20 plus years. Both your plumber and Nashua are wrong period.

    Yes a condensing boilers efficiency in part is based on water temperature but that not alone predicates efficiency.

    In order for anyone including myself to give you a 100 percent anwser we would have to conduct a room by room heat loss. Measure existing footage of baseboard in each room/zone. We would then have to compare the baseboard capable output for a water temp based on the heat loss which tells us the water temp you need on your coldest day to heat your home. Generally and this is a fact, 95 percent of homes are over-radiated and current equipment oversized.

    As for Nashuas post concerning BTU output of baseboard he is wrong. At a 1gpm (10,000 BTU'S) flow rate and with 180 degree water fin-tube baseboard can deliver 550-560 btu's an hr depending on which brand. That same basebard at the same flow rate with 160 degree water puts out approx 480 btu's and hour.

    I wanted to list the 160 because this is a very important point as to why both your plumber and Nashua are wrong. A tradiational hydronic heating system is designed based on what we call a 20 degree delta-t. In other words, 160 degree water leaves the boiler throught the zone when it gets back to the boiler it's 140degrees.

    The dew point which in our world generally starts when we can get return water temperatures back to our condensing boiler at 134 degrees. This begins the high efficiency range of condensing boilers and gets you in the 90% AFUE.

    Now back to the baseboard. Lets take a heat loss of a room that is 20x20 or 400sqft. Has R-19 insul, good windows. After the thousands upon thousands of heat losses I have calculated I can safely use 20btu's a sqft. That room would have a heat loss of 8,000 btus which is probably high. The room has a total of 20 feet of baseboard. It is on a zone that has a total heat loss of 10,000 btu's. If I take the loss and divide it by 550 I would only need about 15 foot of board to heat the room with 180 degree water when it is the coldest day outside.

    Now take that 8,000 btu's and divide it by 480. I only need about 17 feet of baseboard. I could safely start my heating curve for this room with 160 degree water.

    May I ask how many days it is zero? That's the only day I need 160 degree water. What water temp do you think I might need when it's 23 degrees out? (I used 23 because that was the average temp last year in Dec/Jan/Feb here in my climate). About 130 degree supply water.

    I have hundreds of condensing boilers running on fin-tube baseboard systems and they all are running with low water temps. The key is design and heat loss. Problem with most contractors is they are wrench turners and good at it. Most couldn't tell you the forumla for figuring flow rate never mind doing a heat loss.

    So when your plumber or anyone else tells you that you cannot get efficiencies out of condensing boilers with fin-tube baseboard they are talking out their back side.

    I have a study that was conducted by Brookhaven Lab's. The study was conducted in Long Island. The study revelead that you can clearly get the high 90% efficiencies out of a condensing boiler with fin-tube baseboard 90% of the heating season. The other 10% your getting 88-90%. Whats more efficiency that 80 or 83% gas hog all year round or a condensing boiler?

    Stay tuned for Class 2 - How the rate of modulation plays a key role in obtaining high efficiencies in condensing boilers using water temps above the dew point? Yes I can get 90% efficiencies with 140 degree return water.....

    I'm not being sarcastic or trying to make anyone feel bad but you have the right to the correct information based on fact not based on myth.

  4. #4
    Join Date
    Feb 2008
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    Default Re: Your Plumber As Well As Nashua Are Wrong

    [QUOTE=hvhehcca;232395]Sorry, have to chime in on this one. Have been designing and installing low temp hydronics for 20 plus years. Both your plumber and Nashua are wrong period.

    Yes a condensing boilers efficiency in part is based on water temperature but that not alone predicates efficiency.

    In order for anyone including myself to give you a 100 percent anwser we would have to conduct a room by room heat loss. Measure existing footage of baseboard in each room/zone. We would then have to compare the baseboard capable output for a water temp based on the heat loss which tells us the water temp you need on your coldest day to heat your home. Generally and this is a fact, 95 percent of homes are over-radiated and current equipment oversized.

    As for Nashuas post concerning BTU output of baseboard he is wrong. At a 1gpm (10,000 BTU'S) flow rate and with 180 degree water fin-tube baseboard can deliver 550-560 btu's an hr depending on which brand. That same basebard at the same flow rate with 160 degree water puts out approx 480 btu's and hour.

    I wanted to list the 160 because this is a very important point as to why both your plumber and Nashua are wrong. A tradiational hydronic heating system is designed based on what we call a 20 degree delta-t. In other words, 160 degree water leaves the boiler throught the zone when it gets back to the boiler it's 140degrees.

    The dew point which in our world generally starts when we can get return water temperatures back to our condensing boiler at 134 degrees. This begins the high efficiency range of condensing boilers and gets you in the 90% AFUE.

    Now back to the baseboard. Lets take a heat loss of a room that is 20x20 or 400sqft. Has R-19 insul, good windows. After the thousands upon thousands of heat losses I have calculated I can safely use 20btu's a sqft. That room would have a heat loss of 8,000 btus which is probably high. The room has a total of 20 feet of baseboard. It is on a zone that has a total heat loss of 10,000 btu's. If I take the loss and divide it by 550 I would only need about 15 foot of board to heat the room with 180 degree water when it is the coldest day outside.

    Now take that 8,000 btu's and divide it by 480. I only need about 17 feet of baseboard. I could safely start my heating curve for this room with 160 degree water.

    May I ask how many days it is zero? That's the only day I need 160 degree water. What water temp do you think I might need when it's 23 degrees out? (I used 23 because that was the average temp last year in Dec/Jan/Feb here in my climate). About 130 degree supply water.

    I have hundreds of condensing boilers running on fin-tube baseboard systems and they all are running with low water temps. The key is design and heat loss. Problem with most contractors is they are wrench turners and good at it. Most couldn't tell you the forumla for figuring flow rate never mind doing a heat loss.

    So when your plumber or anyone else tells you that you cannot get efficiencies out of condensing boilers with fin-tube baseboard they are talking out their back side.

    I have a study that was conducted by Brookhaven Lab's. The study was conducted in Long Island. The study revelead that you can clearly get the high 90% efficiencies out of a condensing boiler with fin-tube baseboard 90% of the heating season. The other 10% your getting 88-90%. Whats more efficiency that 80 or 83% gas hog all year round or a condensing boiler?

    Stay tuned for Class 2 - How the rate of modulation plays a key role in obtaining high efficiencies in condensing boilers using water temps above the dew point? Yes I can get 90% efficiencies with 140 degree return water.....

    I'm not being sarcastic or trying to make anyone feel bad but you have the right to the correct information based on fact not based on myth.[/QUOTE

    --------------------------------
    HVHEHCCA has apparently done WAY TOO MUCH New Year's Eve celebrating imbibing IN WAY TOO MUCH wine before he wrote his latest distorted post----it's the only explanation I can think of for his completely distorted math calculations and other calculations that predictably draw all the wrong conclusions for baseboard output.

    It's a bad thing to intentionally spread false info on heating systems, as hvhehcca has done here.

    I stand squarely behind my calculations as noted in my first post on this thread.

    At the water temps that hvhehcca is talking about, a foot of baseboard will produce 220 btu/hr, multiplied by 150' of baseboard = 33k btu/hr to heat a house that at 2500 sq.ft. will need at least 90k btu/hr to keep it warm!

    C'mon, hvhehcca, the house is getting only 1/3 of the BTUs it needs for heat---if you've installed so many such monstrosities (as you say you have) in your alleged colorful career, you must have had a hell of a lot of callbacks and angry customers who want the system pulled and their moey back!!!

    HVHEHCCA has also falsified the baseboard output tagging it with the arbitrary 20 btu/hr/ft of radiant floor heat as his narrow-minded way of thinking---for all we know such a house in question could well require 40 btu/hr/ft or even 60 btu/hr/ft, depending on location and structure integrity.

    He gives an example of a 20 X 20 room that he claims will require only 8k btu/hr for heat, when in fact such a typical room in a moderately cold climate would require 16k btu/hr.

    These ludicrous calculations he's spouting out can only lead one to conclude that HE HAS NO hydronic baseboard installation experience at all---he hasn't got a CLUE as to how such a simple element like HW baseboard works, and he can't calculate a simple heat output of a length of baseboard.

    Not only does his math distort the btu/hr heat needs of the room, and the btu/hr heat output of baseboard in such circumstances, he completely ignores the impossibly slow response time that would be required with baseboard carrying such low-temp water until the room (or house) was comfortable---he would have people shivering for days, if not weeks while the feeble baseboard was trying to catch up with the heat loss BTUs that would be flying out the windows and walls.

    ***! this guy's dangerous---I would keep him far away from my heating equipment, or that of anyone else on the planet.

    His contention of having 20 years in hydronics and "thousands of condensing system installs" has to be a flat lie if he expects us to believe his jumbled math calculations, and the impossible logistics----clearly another symptom of too much booze.

    HVHEHCCA has submitted a grand total of 19 posts over the period of a few months, to this forum, all of them contentious, insulting and condescending to the other members who have spent years and hundreds of posts involving hard work in earning respect from and service to the other members.

    We've had plenty of troublemakers like "Leslie" and hvhehcca over the years, & I put HVHEHCCA in this same category, just another dumb reincarnation of "Leslie" and just as bothersome as the moldy slices of SPAM that show up from time to time & way too often.

    Instead of trying to work in concert with the other TOH board contributors, hvhehcca has taken the arrogant position that ONLY HE has the right answers; ONLY HIS opinion has any validity---he would have us believe that all other TOH contributors are all wet---when in fact, it is HE that is all wet!

    Hey, hvhehcca, since you seem to enjoy slamming other posters so much, do us all a favor and go haunt some other forum with your false condescending rants---you won't be missed here at all!
    Last edited by NashuaTech; 01-01-2011 at 09:06 AM.

  5. #5
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    93

    Default Re: Water temperature requirement for hot water baseboard?

    My math is not wrong and I have never had a call back for a underheated home. May I ask how many heat losses and low temp designs you have done. How many installs? What are your credentials, the amount of post you have. Those are just smoke and mirrors to you credentials.

    Heat loss of an outside panel is not that complicated and can be simplified with:

    TI - TO divide by RV = btu sqft
    70 - 0 divide by 19 = 3.684 btu's sqft

    So my 20' outside walls heat loss with an 9' ceiling is 663.12 btus an hr. Now if I have a couple of 3x5 windows I would take that 30 sqft out and then do the same math for the windows.

    Unless you live in Sibera there is no way in creatation the room of that size would require 16k of heat. Yes I have to add infiltration but that loss wouldn't create a 9k btu unless the house is from the 1880's and was never updated.

    My limited amount of posts here should not be a reflection as to my experience in the industry. The forum is here to share advice but that advice should also be done on fact not myth. The formulas you keep stating are "rule of thumb". Four fingers its a 4 section boiler, 3 fingers its a 3 section.

    I don't know where you get your information on baseboard output but mine comes from Mestek the makers of just about every piece of baseboard out there. They own the majority of the baseboard companies. You also have to use the 1gpm calculation unless the heat loss throughout the zone is known. At 160 degree water with a 1gpm flow rate the output is 430 btu's a ft.

    Secondly, I didn't know you meed to heat a home to its complete heat loss every day. A homes heat loss changes as the temp outside changes so the only day I need that so called 90k btu's is my design day.

    As for response time. Whats more efficient a thermostat that gets satisfied in 5 minutes or under or a thermostat that gets satisfied in 15 minutes. That's simple. A boiler that runs for longer than 5 minutes. A boiler doesn't even get to its steady state efficiency if you don't get a 5 minute burner cycle. So when you overrated and send that hotter watertemp you don't get a good burner cycle.

    The gentleman that posted should be provided the correct advice and honestly I would suggest he post the same question at
    www.heatinghelp.com. These are the industries top names and contractors in heating from across the country. Nashua you should come over and pose some of your nonsense. I also invite you to join the Taco Flo Pro Team and the neighboorhood. As a rebuttal in fact please find the link to a pdf for the study. Its too large to attach here.


    http://www.heatinghelp.com/files/pos...0Baseboard.pdf
    Last edited by hvhehcca; 01-01-2011 at 04:54 PM.

  6. #6
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    Feb 2008
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    175

    Default Re: Water temperature requirement for hot water baseboard?

    Sorry, Leslie/havicaca, or whatever name you're using this month, but your info on hot water heating is dead wrong & I completely agree with Nashua.

    MY training & first hand experience installing HW radiant and baseboard convinces me, as Nashua states, that you are clueless when it comes to this topic.

    The output formulas can be obtained in the most rudimentary book on hydronics, and you've completely confused radiant calcs with baseboard calcs.

    I have been reading posts on this forum by Nashua for the past 3 years and have learned much from him; your insulting, mocking manner is an insult to everyone on this board who seeks the truth.

    Just go away!

    The sooner the better!!
    Last edited by Dobbs; 01-01-2011 at 07:43 PM.

  7. #7
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    Default Re: Water temperature requirement for hot water baseboard?

    i agree with Dobbs, i'm on nashua's side. i've been reading his posts for 1-2 years and i have not seen anything to make me doubt his qualifications or his answers.

  8. #8
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    Default Re: Water temperature requirement for hot water baseboard?

    Dobbs the same offer holds to you. Your welcome to visit the real pros at www.heatinghelp.com or join the guys at the Taco Flo Pro Team and pose the same question.

    Hydronic calculations are the same for baseboard or radiant except for one. Infiltration factor. The loss through an outside panel stays the same. If my emitter output says I can overcome the heat loss with 160 degree water at design then I can overcome the heat loss at any other point. I replace systems not boilers and the majority of it is fixing others mistakes when it comes to low temp hydronics. Yes baseboard can be considered low temp hydronics when the application for it is appropriate.


    I don't think I'm going to leave. I'm going to pay more attention. Nashua has such great advice. He's upset beacause I've commented on posts where he mistakes truth from myth. So instead of eating his crow he would rather attack my integrity.

  9. #9
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    Aug 2008
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    69

    Default Re: Water temperature requirement for hot water baseboard?

    Nobody's attacking your integrity, it's your stupid statements and mockery that we can't stand.

    You've got a lot of nerve attacking a respected member of this forum who's been contributing tirelessly on this forum for many years.

  10. #10
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    Default Re: Water temperature requirement for hot water baseboard?

    Attacking? I didn't see anything in my original post that was attacking. Nashuas retaliated with attackes because he does not agree with me. I didn't see anything posted in his reply to my post that was based on fact. He attacked.

    Everyone is stepping to the plate in protection due to loyalty. I respect that but at the same time you must look at reality.

    Everyone is coming at me with nothing to back up their opinions except for saying I don't know what I am talking about.

    Can someone please atleast come back with some math and real world installation to back up their claims that I don't know what I am talking about. I belive in every post I used fact and known formulas to back it up. So, because I disagess with Nashua I'm automaticall wrong.

    Like I said previously, People that post deserve the correct information and not myths.

    There are alot of arrows being thrown just no bite in them. Again, my offer to re-bunk my post is open to all. Pose what you think is my wrong on sites that are visted and responsed by leading industry professionals. Most in the field of low temp hydronics.

    www.heatinghelp.com
    www.taco-hvac.com (Flo Pro Team)

    If I am speaking untruths I would be more than happy to state that but I am not.

    I'm being attacked because someone that has been posting here disagrees with my opinions. Which is fine just bring the math and real world to the table..
    Last edited by hvhehcca; 01-01-2011 at 08:50 PM.

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