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Thread: Navien Tankless Water Heater Comments and questions

  1. #76
    Plumber @ Mechanical Contractor MechGuy's Avatar
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    Default Balderdash

    Quote Originally Posted by nhmaster View Post
    What other reasons? This is a crap statement. I like to spend more money for very little return because what? Give me a break. And don't go telling me they are environmentally friendly because that's crap also. They are manufactured in a factory spewing carbon into the air. They burn gas spewing carbon into the air. So what are the "other reasons" Your house is so cramped you cant take up another 6 cubic feet of space? face it. You got talked into it, bought it and now have to find a way to justify it. So where is the advantage? Oh I know. It doesn't run all day long when I'm not home (that one from Trethewey) News for you guys a newer tank type heater doesn't run either due to the very high level of insulation. In fact last winter I shut off my boiler. Went to Florida for a week. Came home and the tank was still hot (Buderus indirect) You all have been sold a load of crap just like Hybrid cars, wind mills and all that other junk that costs 3 times more than it will EVER pay back and has zero environmental impact. If this junk did what it was supposed to do, why would the government have to subsidise it?

    Don't forget to watch the biggest scam of all on Tuesday.
    Gosh it's nice to know people who know everything. Plumbers love tanks because, especially in emergencies, no one questions your charges or cost or efficiency they just want it fixed. You draw down the old heater, snap 2 water connections off/on, 1 single wall or "B" vent exhaust and the cash is in your pocket.
    You can make a ton of money a week just doing tanks but in my area the tankers are known as the N*****s of the plumbing fraternity.
    Insulation didn't beef up in tanks until the FVIR system came along with it. Wholesalers bought literally a million extra tanks the year before FVIR came in just to avoid it as long as possible.
    NH you're familiar with tankless if you're using the Buderus GB142 with a Priority circuit for DHW so don't shame tankless.
    Show me a tank capable of producing 250 gals per hour?
    And you Combi criers.....radiant despite it's real efficiency and comfort will always be backseat to FA till people give up CA/C. Paying for Ducts and tubes isn't rational in a less than luxury house.
    And as to Market penetration it comes with Marketing. Tankless had it so easy coming ashore in CA they have no idea how to market to the rest of America. I deal daily with Noritz, Takagi, Rinnai, Navien, Eternal, Rheem/ECO, Bosch and most of their RSM's and Mfrs Reps are clueless.
    I reinstall 100's of units a year installed by DIYers, handyman and, yes, fellow licensed Master Journeyman Plumbers who miss or screw up important installation requirements.
    New rules or ideas have never been welcomed into plumbing; FVIR omg no, indoor plumbing, Mr Rudd's Water Heater,
    When you started installing tanks there were no 7 head human car washes flowing 17.5-22 GPM. New Technology.......I was installing tankless Burkay coil units in 1979 in conjunction with 300 gal storage to produce huge gph.
    Cold water sandwiches can be overcome by about 3-4 methods every plumber should know or have been taught (I know them and there ain't no big red "S" on my chest).
    In Japan in new building the water heater is universally piped and actually moves with the homeowner from residence to residence as they buy/sell their units. Except for the initial piping, plumbers are cut out of the loop there after in dealing with moving or replacement of water heater.
    Jist is get familiar with the future. Feedback improvements to Mfrs and maybe, just maybe you'll stay in Plumbing or Fittings and not lose your way preaching the old tyme religion.
    Yesterday ain't tomorrow and it sure as heck ain't next week.

  2. #77
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by MechGuy View Post
    Show me a tank capable of producing 250 gals per hour?
    Many of the indirects can produce that and more. Mine is rated at over 266 gallons, it's actually more since the boiler fires up a bit hotter than the 180 and less than the higher value. And, it does it at mid-90% efficiency all day long, which a tankless won't do. I do have a nice wall-hung Buderus unit. Can fill my 6' air tub while doing dishes, washing clothes at the same time without worring about flow issues or running out of hot water.
    http://www.htproducts.com/literature/lp-81.pdf
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #78
    In the trades Dana's Avatar
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    Quote Originally Posted by jadnashua View Post
    Many of the indirects can produce that and more. Mine is rated at over 266 gallons, it's actually more since the boiler fires up a bit hotter than the 180 and less than the higher value. And, it does it at mid-90% efficiency all day long, which a tankless won't do. I do have a nice wall-hung Buderus unit. Can fill my 6' air tub while doing dishes, washing clothes at the same time without worring about flow issues or running out of hot water.
    http://www.htproducts.com/literature/lp-81.pdf
    An indirect is only as "big" from a first-hour rating point of view as it's volume and the boiler behind it. In MANY instances you'd have to oversize the boiler for the heating load in order to deliver anything like 250gallons/hr.

    My indirect is rated for 907 first-hour 140F gallons, but it takes a 500KBTU/H burner to deliver that. It'll deliver 267 first hour gallons with a 200K burner behind it, but my design day heat load is under 30K, and a 200K burner would make absolutely NO sense, even a 100K burner is 3x oversized, and would only deliver ~150 first-hours gallons.

    But using a tankless as a boiler, and the indirect as a buffer, the tankless will modulate to match the load for the DHW, and it's average output under heating loads is less than 1.5x oversized, with decent minimum-burn times to keep the efficiency from falling off a cliff. I won't be filling a 100 gallon spa with 115F water with this system in the dead of winter, but with the extra kick from drainwater heat recovery I can run showers continuously, even under more-severe-than-design-day heat loads and never run cold.

  4. #79
    Plumber @ Mechanical Contractor MechGuy's Avatar
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    Default You forgot

    Quote Originally Posted by chris8796 View Post
    If you have the right physical layout, this would be the ideal situation for drain heat recovery units (lots of showers, high fuel cost). Preheat the incoming cold water with warm drain water. It is easy to get a 20 degree rise in incoming water temp (45 to 65) and has an actual payback.

    2.2 gal/min x 6 showers x 20 degree F x 8.8 lbs/gal = 2323 btu/min

    Propane is 91600 btu/gal x 80% water heater efficacy / $3 gal= 24400 btu/$


    2323 btu/min / 24400 btu/$ = 9.5 cents/min, (When all 6 showers running)

    200 campers/6 showers x 6 min/shower =200 minutes of showering

    200 mins x 9.5 c/min = $19.00 a showering cycle.

    I would assume $1500 in capital costs w/free labor. Thats about 79 shower cycles for full payback, so it depends on how often the camp is used. You also get the benefit of increased capacity and no maintenance issues.
    Basically unless you designed it from the start any shower waste water would have to be lifted to flow through your Waste Water Heater Recovery System.
    This adds a cost you're ignoring. Also a BTU return loss in your recovery calculation.
    These system are most efficient when gravity designed.
    Manly men plumbers hate them as they constantly whine that graywater will eventually contaminate freshwater in these systems while these systems are U/L and UPC listed.
    Just as out friend nashua is so opposed to tankless 50+ year ago he would have raged against copper vs. galvanized pipe.
    Tankless isn't perfect but improved and lowered in cost and designed in from the beginning it will eventually replace tanks.
    Ever visited a flooded basement to see a tanks damage? And nash, admit it 2nd line recircs are beautiful but they waste energy magnificently. The real basis of tankless problems for Mfrs coming is ashore is the Americans who want 4-6-8-17 GPM hot water flow rates. NO WHERE IN THE WORLD BUT AMERICA DO YOU SEE THIS HIGH A FLOW DEMAND.
    Do people really need the 5-7 head human carwashes?
    And your 50gal gas tank it's more or less standard first hour delivery is 83 GPH. Flow more than 2 heads at 2.5GPM and you don't have much shower time. I love you folks with your 6 min shower.......ever had a teenager or two?

  5. #80
    Plumber @ Mechanical Contractor MechGuy's Avatar
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    Default Sorry but...

    Quote Originally Posted by jadnashua View Post
    Many of the indirects can produce that and more. Mine is rated at over 266 gallons, it's actually more since the boiler fires up a bit hotter than the 180 and less than the higher value. And, it does it at mid-90% efficiency all day long, which a tankless won't do. I do have a nice wall-hung Buderus unit. Can fill my 6' air tub while doing dishes, washing clothes at the same time without worring about flow issues or running out of hot water.
    http://www.htproducts.com/literature/lp-81.pdf
    You guys just don't get it....A Buderus and a indirect isn't a normal tank. It's really a tankless with an alternate heat source.
    No 100-125 gal or less residential tank will produce 240-268 GPH. Don't muddy the waters comparing apples to pomegranates.
    Also you're going to have to temper that production at anything above 125F as you can't legally deliver residential hot water over that temp.
    And fess up on that Buderus if it's a GB142 or such that's a $4000 equipment cost you seem to overlook although the indirect does help wring cost out of the whole set up.

  6. #81
    DIY Senior Member zl700's Avatar
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    A indirect can never be confused with a tankless as being the same.
    Get the meaning of the word tankless? It means less tank.
    An indirect water heater is a storage vessel with an indirect means such as a coil or tank-in-tank that heats the water indirectly from an external source, such as a boiler.

    Tankless holds no appreciable measurable stored water and have their own burners, heating as used.

    Certainly as indirect tanks dump their water and depending on the BTU input of the indirect heat source, it can approach near instananious heating of DHW based on flow and input, but still not entirely the same.

    No confusing the 2

  7. #82
    Plumber @ Mechanical Contractor MechGuy's Avatar
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    Default Why not

    Quote Originally Posted by Bring on the heat View Post
    Love the way "NHmaster" layed into the whole environmental solar, windfarm, hybrid, et al & etc. things and ALL the other useless crap good money is being wasted on - to control what? - carbon emissions! To save a polar bear? Crapola!

    Don't buy it! If we continue to allow the powers-that-be to regulate US (and I mean all the USA) for carbon emissions, we grant them the power to legislate US all out of existence. We're all made of carbon and exhale it all day long. If it were not for us, the trees would all die and we wouldn't even have a "geen" planet to worry about.

    I WAS considering a tankless WH, but it sure don't make $ense to me. Maybe in 10-15 years when I need a WH again, I'll look into it again. That is, if we haven't destroyed the plannet and I am still here TO look into. Don't get me wrong, I am not damming the innovative spirit. I just prefer to spend MY money on something that has proven its self, rather that gamble on something that may not be better and may be less reliable.

    Maybe 10 or 15 years from now, will see that Hybrids and windfarms were the answer. However, I suspect they will go away quietly and we'll not hear from them for much longer.

    Nice to chat with you guys!
    just burn your house down to heat water?
    You all keep sticking your heads up your arse and relying on cheap NG and Petroleum prices (under $12 for propane) and by the time you realize what hit you you'll be Arab Camel dung.
    And by God , thank God, in America we have the right to be just as stupid as we like.

  8. #83
    In the trades Dana's Avatar
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    Quote Originally Posted by MechGuy View Post
    You guys just don't get it....A Buderus and a indirect isn't a normal tank. It's really a tankless with an alternate heat source.
    No 100-125 gal or less residential tank will produce 240-268 GPH. Don't muddy the waters comparing apples to pomegranates.
    Also you're going to have to temper that production at anything above 125F as you can't legally deliver residential hot water over that temp.
    And fess up on that Buderus if it's a GB142 or such that's a $4000 equipment cost you seem to overlook although the indirect does help wring cost out of the whole set up.
    Methinks it's YOU that just doesn't get it- a Buderus & indirect isn't very much like a tankless AT ALL! (How do you figure? Just because it's low mass & wall hung?) It's far more similar to a standalone tank, just one with (typically but not always) more burner behind it (and lower standby loss on the tank itself.) And so what if it needs a tempering valve? (In MA where I live tempering valves are required for standalone tanks too.) With enough heat exchanger in the indirect you need not maintain the indirect storage above 125F anyway (although there may be valid efficiency reasons to let it run higher to get longer burns out of the boiler.

    Boiler + indirect vs. standalone tanks is more like apples vs. pears. If there's a pomegranate in the mix of choices it's the tankless, not the indirect. The near-zero thermal mass & inherent short cycling of the tankless make it distinct from the others.

    But you correctly state the obvious when you assert that no conventional standalone tank delivers 250 first-hour gallons (which takes ~150kbtus of storage + burner-output to pull off.) IIRC there's at least one condensing tank that can deliver it though (at a price.)

    And the boiler + indirect is usually the net efficiency winner, since tankless units never actually meet their EF numbers in residential apps (due to the effects of short cycling on low volume draws). High mass boilers may have lower-than tankless summertime HW heating efficiency, but during the heating season it's right up there, and increases the AFUE of the boiler by a significant amount if properly designed & controlled. Low mass boilers (and tankless units configured as boilers) will beat standalone tankless units on efficiency for just DHW when coupled with an indirect, in most residential apps since they can't short-cycle, and have extremely low standby losses compared to standalone tanks.

    Since you seem concerned about the equipment cost factores, calculate this: Using a cheap ~82-84% efficiency Takagi instead of a Buderus as a boiler, with a ~$1000 reverse-indirect acting as a heating system buffer & hotwater heater it'll meet-or-beat condensing tankless real-world efficiency(!) at hot-water heating for less than the in-the-crate cost of a condensing tankless (or a Buderus without the indirect).

    BTW: Who the hell really NEEDS 250 first-hour gallons in a residence, anyway? Lessee, the teenager is taking an endless shower while mi esposa is fillin' the soaking tub, and I want to clean up... I s'pose it's theoretically possible. But 250gallons/hr is like having two full showers going for that full hour. I might be able to pull that off with my system AND heat the house at the same time due to the drainwater heat recovery returns, but probably not in tub filling without tweaking the primary loop flow in the system, and even then it'd be marginal- at highest modulation you only get ~150KBTU/hr out of a Takagi T-KD20. But with the kickback from drainwater heat recovery, at full flow in a dual shower condition it's apparent-output would be over 200K.

    Also, you don't need expensive radiant for radiation to pull off an efficient combi design- coils in air handlers are easily up to the task. (Indeed that's my "hail mary" second stage heat for extended design-day heat load periods &/or setback recovery on my staple-up.) There are many ways to slice the combi-apple without spittin' pomegranate seeds.

  9. #84
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by MechGuy View Post
    Also you're going to have to temper that production at anything above 125F as you can't legally deliver residential hot water over that temp.
    Bullshit. I keep seeing this claim but it isn't true.

  10. #85
    Retired Defense Industry Engineer jadnashua's Avatar
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    Where I live, you are required to have a tempering valve on the output of the WH. Now, that doesn't say where you have to have it adjusted, just that you must have one. Unless changed, they normally come set at 119-120 degrees. I run my tank at 140, but have the boiler set to allow it to cool off more before it rewarms it. Often, with no use, it may not need to fire for a day. Adds to the efficency, especially in the summertime.

    Now, I started a whole bunch of comments when I threw in an indirect. I know it isn't a tankless. But, I was responding to a comment that said you can't get a tank to provide 250 gallons the first hour. To that comment, BS! There are lots of tanks that can do that. Now, is it reasonable or economical, that's another story altogether. But, with a decent sized indirect tank (mine's 60-gallons) vs a typical tankless, you can get UNRESTRICTED FLOW at all locations at full output temperature that would take a VERY large tankless system, especially where I live in the winter. I can be filling the tub, washing clothes, running the dishwasher, and have someone washing hands, etc. all at the same time and have full use of the hot water. I've measured my inlet water at 33-degrees in the deep of winter. So, depending on your circumstances, there are good reasons to avoid a tankless. Now, again, lifestyle comes into play here, and I'm not going to comment on that and about how spoiled we are. Also note one of the comments on tank verses tankless are the standby losses. The tank I have is rated at less than 1/2-degree per hour of loss. So, if the power was off for a day, it still may not trigger the boiler to come on, if it could. If you were quick, you could probably get a few days worth or hot showers out of it without power. Try that with your tankless! A normal gas-fired tank would lose a lot more, but it's still not horrible. Fired by a mod-con, my system is rated at 94%. Since it modulates, and it is sized to be able to provide about 1/3 the normal design day needs at low end, it can run at barely 'idle', but ramp up to what's needed on a cold day, or to reheat the tank. Not all mod-cons have as large a modulation range. The tank is SS, and should outlive me. Expect the boiler will need replacing before the tank, but the guts are SS on it, too.

    If you have a boiler and aren't using an indirect, I don't think you're being very efficient. If you live where the incoming water doesn't get really cold, a tankless has some benefit. If you don't want to put up with variable water temperatures, no hot on a low flow use, or need a high flow rate, then avoid a tankless. It can be set up to overcome that, but it gets more complicated, and a boiler may be a better choice. Ganging tankless units to get high flow is quite expensive in both the infrastructure (large gas lines) and available combustion air and flues. In some places, your no-use gas charge is based on possible demand, so you're paying more for gas, even when you aren't using any.

    So, pick your poison, understand the benefits and limitations of the choices and make an informed decision. My energy use compared to my neighbors is about 1/3 less, and is without compromises they have. People can shower one-after-the-other all day.

    A boiler is going to require less service than a tankless system since it is using less 'fresh', mineral laden water, so there'd be little scale. An indirect doesn't see high enough temperatures at the heat exchanger to precipitate out any amount of mineral deposits, so efficiency should stay reasonably constant. On a tankless, the goal is to heat the potable water very fast, and you'll get the mineral deposits (unless you also have a softener).

    No one system is 'best' for everyone. Pick the best for your circumstances. To exclaim only one choice is viable is not taking into the whole account of use patterns, volumes required, existing equipment, tolerance for restrictions, and amount of money you wish to spend. Energy costs here may approach many other country's, but only if the tax rates go up. It costs the Europeans about the same for gas as here, but their taxes are MUCH more. There should be a move to make things more efficient. This is a good thing, but you have to weigh the costs/benefits. We could all drive mopeds and get 70mpg, but it just wouldn't be the same...not one answer is best for all.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #86
    DIY Senior Member zl700's Avatar
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    Wow did this take a derailment off course of the title post (Navien)

  12. #87

    Default

    Quote Originally Posted by Runs with bison View Post
    Bullshit. I keep seeing this claim but it isn't true.


    It depends on where you live.

    "The standards apply to every owner-occupied or rented dwelling, dwelling unit, mobile dwelling unit or rooming house unit in Massachusetts which is used for living, sleeping, cooking and eating. Dwelling unit shall also mean a condominium unit. These regulations have the force of law. Local boards of health have the primary responsibility for their enforcement."

    and

    "Hot Water Facilities

    Facilities for the heating of water must be provided (i.e. supplied and paid for) and kept in good working order by the owner. The owner must supply hot water in sufficient quantity and pressure to satisfy the normal use of all plumbing fixtures which generally require hot water to function properly. The temperature of the hot water is not to exceed 130 Fahrenheit (54 Celsius) nor fall below 110 Fahrenheit (43 Celsius). Under certain leases, an occupant may be required to provide the fuel for the heating of the water. [410.190]"



    http://www.sec.state.ma.us/cis/cissfsn/sfsnidx.htm



    .
    Last edited by Ladiesman271; 12-09-2009 at 10:18 AM.
    Samuel James Witwicky

  13. #88

    Default

    Quote Originally Posted by jadnashua View Post
    Where I live, you are required to have a tempering valve on the output of the WH. Now, that doesn't say where you have to have it adjusted, just that you must have one. Unless changed, they normally come set at 119-120 degrees. I run my tank at 140, but have the boiler set to allow it to cool off more before it rewarms it. Often, with no use, it may not need to fire for a day. Adds to the efficency, especially in the summertime.

    Now, I started a whole bunch of comments when I threw in an indirect. I know it isn't a tankless. But, I was responding to a comment that said you can't get a tank to provide 250 gallons the first hour. To that comment, BS! There are lots of tanks that can do that. Now, is it reasonable or economical, that's another story altogether. But, with a decent sized indirect tank (mine's 60-gallons) vs a typical tankless, you can get UNRESTRICTED FLOW at all locations at full output temperature that would take a VERY large tankless system, especially where I live in the winter. I can be filling the tub, washing clothes, running the dishwasher, and have someone washing hands, etc. all at the same time and have full use of the hot water. I've measured my inlet water at 33-degrees in the deep of winter. So, depending on your circumstances, there are good reasons to avoid a tankless. Now, again, lifestyle comes into play here, and I'm not going to comment on that and about how spoiled we are. Also note one of the comments on tank verses tankless are the standby losses. The tank I have is rated at less than 1/2-degree per hour of loss. So, if the power was off for a day, it still may not trigger the boiler to come on, if it could. If you were quick, you could probably get a few days worth or hot showers out of it without power. Try that with your tankless! A normal gas-fired tank would lose a lot more, but it's still not horrible. Fired by a mod-con, my system is rated at 94%. Since it modulates, and it is sized to be able to provide about 1/3 the normal design day needs at low end, it can run at barely 'idle', but ramp up to what's needed on a cold day, or to reheat the tank. Not all mod-cons have as large a modulation range. The tank is SS, and should outlive me. Expect the boiler will need replacing before the tank, but the guts are SS on it, too.

    If you have a boiler and aren't using an indirect, I don't think you're being very efficient. If you live where the incoming water doesn't get really cold, a tankless has some benefit. If you don't want to put up with variable water temperatures, no hot on a low flow use, or need a high flow rate, then avoid a tankless. It can be set up to overcome that, but it gets more complicated, and a boiler may be a better choice. Ganging tankless units to get high flow is quite expensive in both the infrastructure (large gas lines) and available combustion air and flues. In some places, your no-use gas charge is based on possible demand, so you're paying more for gas, even when you aren't using any.

    So, pick your poison, understand the benefits and limitations of the choices and make an informed decision. My energy use compared to my neighbors is about 1/3 less, and is without compromises they have. People can shower one-after-the-other all day.

    A boiler is going to require less service than a tankless system since it is using less 'fresh', mineral laden water, so there'd be little scale. An indirect doesn't see high enough temperatures at the heat exchanger to precipitate out any amount of mineral deposits, so efficiency should stay reasonably constant. On a tankless, the goal is to heat the potable water very fast, and you'll get the mineral deposits (unless you also have a softener).

    No one system is 'best' for everyone. Pick the best for your circumstances. To exclaim only one choice is viable is not taking into the whole account of use patterns, volumes required, existing equipment, tolerance for restrictions, and amount of money you wish to spend. Energy costs here may approach many other country's, but only if the tax rates go up. It costs the Europeans about the same for gas as here, but their taxes are MUCH more. There should be a move to make things more efficient. This is a good thing, but you have to weigh the costs/benefits. We could all drive mopeds and get 70mpg, but it just wouldn't be the same...not one answer is best for all.


    The majority of people have no need for a boiler installation, so what are those people supposed to so? I have a forced hot air system, so I use a furnace for heat. That leaves a tank or tankless for domestic hot water.

    You also forget to mention the installed retrofit retail cost of a modulating boiler, vent system and indirect tank. A tank type water heater is way less expensive than that setup. A tankless water heater will also be less expensive.

    Note that my tankless works fine during power outages.
    Samuel James Witwicky

  14. #89
    In the trades Dana's Avatar
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    Hey, jadnashua- I don't care WHAT your boiler is rated, it's giving you nowhere near 94% when heating the indirect:



    Indirects don't stratify enough to give you 100F return water to the boiler from the heat exchanger coil in the indirect if you're running normal DHW temps. If you're letting the indirect drop as low as 120F you might hit 90% combustion efficiency at the beginning of a burn not more. By the time it's back up to 140F it's more like ~85%. (And that's just raw combustion efficiency at the boiler's heat exchanger, where 10-15% of the energy has gone up the flue, not total thermal efficiency of the hot water heating system, which is boiler, indirect, & plumbing-insulation dependent. You WILL have other losses.)

    Condensing tankless units run higher efficiencies because the incoming water is typically well-under 70F, but they give up a lot in short-cycling. In real-world use they're similar to mod-cons with indirects kept at lower storage temps like yours.

    But the rest of the arguments you're making ring true. If you got 150K+ output at the boiler and an indirect that can use it, you can indeed get your 250 first/second/third hour gallons out of it. (For what, we'll never know! ;-) )
    Last edited by Terry; 04-28-2013 at 05:45 PM.

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    DIY Senior Member zl700's Avatar
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    Good points Dana,
    All similar for the folks that install modcons on baseboard or whatever and run the temps right up to 180 all heating season with elevated return temps.
    They could have saved money and put in a less expensive boiler and achieve near equal efficiencies.

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