If they fit the outdoor reset curve reasonably, even a 180F design day temp requirement it can run at condensing temps much of the season. With better load modeling it could run lower temp MOST of the season (but that level of sophistication isn't likely to be used in a residential app, and the setup costs would be ridiculous.) Design day temps represent less than 3% of the hours in heating season, and a small fraction of the actual fuel burned. But even on the afternoon of design day it's not unusual to have a heat load that's less than 15% of what it was in the bitter pre-dawn hours. The modulating factor alone (even when not condensing) produces very real fuel savings, just not nearly what it does when in the condensing zone. Anybody who runs baseboard at fixed 180F temp with a mod-con is throwing away money (double-digit percentages of the total heating bill.) Since they all come with outdoor reset built in, I can't imagine why anybody WOULD run 'em at 180F??
Originally Posted by zl700
Still, it's not always worth it to go mod-con. If you get the total heat load low enough it's hard to rationalize the expense even WITH low-temp radiation. I never need more than 130F heating water at my place but:
A: "right sized" mod con for my actual design day heat load doesn't exist, and
B: The smallest mod-cons might still do OK for heating, but would be marginal for my peak DHW loads without a large indirect.
C: A mod-con would save me at most ~100 therms/year over running the whole shebang combi-mode with the $500 tankless (or was it only $400? I forget- but it was cheap) plumbed as a boiler, and a reverse indirect, with burner to spare on the DHW front. The fact that a tankless modulates and is very low mass makes it easy to design a system that maintains near-maximum operating efficiency on the tankless, especially when combined with the thermal mass of the reverse-indirect plumbed as a heating buffer (not a heating zone.)
Since I need to maintain an indirect at ~125-130F for DHW anyway, I'm already suffering that standby, and the financial benefits of going with lower radiation temps are marginal, it was easy to head toward the buffered combi solution, if not the mod-con. Until/unless NG gets a WHOLE lot more expensive I'm not likely to swap in a mod-con. But if/when it does, the system as-is runs in the condensing zone for majority of the burn time, and well into condensing on heavy DHW draws, but still over 100F. With a mod-con it would realistically get 90-92% efficiency as-is, and I could reconfigure it slightly and probably squeak another percent or two out of it in heating mode but again, the difference in annual cost even at 4x the current fuel price wouldn't necessarily make it worth the effort to make those changes.
But that's my situation- YMMV.
Still most homes in the US have design-day heat loads well under that of a tankless, and peak DHW loads well OVER what a perfectly sized boiler for heating will deliver. The answer to making them both maximally efficient is usually mass, and combining the thermal mass for both DHW and heating buffering is something that SHOULD be done more often that it is. Modulation has it's limits- the most you get out of residential sized mod-cons is about a 5/1 turn down ratio, (most are around 4/1). The real difference in LOAD is more than 5/1 on every day of the heating season, but with sufficient mass cycling losses can be minimized even with fairly oversized boilers.
Back to the original question. With many of these in place now, I feel they warrant the slightly higher cost than the others if recirculation and the stainless steel heat exchangers are the consideration. The leak detection is a great feature. They are how ever more complex than the others.
Originally Posted by willl
The problem Navien and any other manufacture's have to over come except Rinnai (who has done a great job) is service and has is to create a national service program.
When CEC imported and distributed Bosch, you couldn't ask for better technical support. When Bosch acquired CEC, they seemed to completely down play service, maybe not understanding the north american market. the fast development of new products, lack of parts and support killed them in their tracks, for now. the B series is bullet proof and no one has anything like Bosch's H1600. The 2400 and 2700 series are a mile stone and all Bosch has to do now is build confidence back because these are both superior units. Bosch's C800 condensing is also a worthy contender. Rheem's ECO line holds its own.
What matters at the end of the day is service and not just calling customer support but someone local who knows the product, has the experience and can take care of the problem and you just can't do this over the phone. When the customer has no hot water and you have to wait for parts to arrive, the customers experience with a tankless goes south in a heart beat.
If auto manufactures treated repair and service the way most tankless treat service, we'd be riding horses.
Who has the greatest influence on a purchase in my experience, the plumber, for better of worse. All manufactures need to increase training of installers and service personnel. If we were trained as plumbers the way manufactures train installers, we'd still be in the 18th century. I've sat in on too many late afternoon installation classes where the trainers have flown through the material and lost most after 5 minutes. Training should be a day long affair, not an hour or even two and include live fire, practice an installation and at least some limited trouble shooting to understand problems due to short sided installations.
Tankless is clearly hear to stay and the old excuse for using tanks is in the history books. Does anyone still install galvanized water piping, no! Are homes built with cast iron waste except in the second story, not many.
When I first started Plumbing in the 1970's, there were still lead closet flanges that had to be repaired, 7 gallon wall hung with 14" rough bowls were still in use. I remember working on a Rhuud water heater that was copper tank with rivets from the 20's with gas and air levers for adjustment.
I still have my roughly 60 caulking irons and asbestos Italian runners for lead work when I first trained and my gas torch and lead pot. Who would have thought of a fraction of the tools and materials now available much less micro chips on a water heater? To sit and deny what is changing is a fools death. Tankless is here and not going away and more manufactures will enter the market. How they treat plumbers and service personnel will influence who will be around at the end of the day...
Having taught plumbing and heating classes, you can't teach common sense nor, preach anymore than we can how important it is to read and follow the installation manual. If a "installation tech" comes to an advanced class we should be able to assume they understand gas piping, venting, power and controls. That's where we lose them in the first five minutes.
In my area, most that attend installation classes have never even opened a code book, read gas charts much less understand how to calculate for them. I have yet to see another plumber who owns, much less use and understand a manometer or a digital multi meter. Manufactures have a large gap to close as do plumbers too.
California does not require the individual to hold a license or training certificate but the plumbing contractor must have 4 validated years and pass a test, have a bond and insurance. I worked for the state contractors board to help re write the test in an attempt to stave off the contractor schools from selling answers. We are sadly behind many other states in this regard.
I just happen to have a background that has involved build desalination equipment world wide and have taken AC/ Dc theory, motor controls, designed and built water, waste equipment and fluid processing equipment and happen to have a degree in mechanical engineering/
I live in Colorado at 6200 feet elevation. I have a Navien Tankless hot water heater and I am extremely satisfied with it. The 12 year waranty on the entire unit is the best in the industry. They may be made in Korea, but that country is one of the coldest climates in the world (in winter) so they got it "right" in their own country before shipping it to the U.S. I don't know how tough it is to find a trained tech to do the installation in your area. You might want to check their website. But I really appreciate being able to use PVC instead of stainless for air intake and exhaust. That saved a bunch of bucks. It easily services 2 simultaneous showers.
Originally Posted by happy
:-) :-) :-) :-) :-) :-)
That's pretty funny- of the many places I've spent whole winters, I'd be hard pressed to say Korea was even in the coolest five. Seoul's heating season is only ~5000 HDD, well below most locations at 6.2K' in Colorado. See:
(If you can't read Han-gul, there are some koringlish bits toward the end. Heating degree data are presented in celcius. Multiply by 1.8 to come up with 'merican degrees. )
BTW: Were/are there any alitude adjustment tweaks made to optimize it for 6.2k' elevation? Very few populated places in Korea are that high- not sure if they thought to design it in...
I have personaly installed over 50 of these units, I have the new NR-210A in my home for testing. There are pros and cons to every brand of tankless including Navien. Bottom line Navien delivers what is promised,
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Was installed by plumber in area and It runs all night and keeps me awake. Live in big bear city 7000 ft. altitude. is there any solution?
By "runs all night" I presume you mean the blower never stops after the flue purge, in which case there's something defective on the control board or a sensor. This is one to run by a Navien trained tech, but it may be diagnosable via phone. Have you run it by the installer?
Originally Posted by Donald
We just had a Navien installed last week and what a HUGE mistake!
It took 2 guys (plumbers) almost 12 hours to install, but that would have been fine if had turned out to be everything it had been touted to be.
First of all, it takes over 2 1/2 minutes of running full blast to get hot water to my kitchen sink. When I asked the owner of the plumbing company he said, "Yea that's normal"
Then I asked him why was there this weird noise every time we turned on the hot water? A noise that shakes the whole house? (Pause while he's thinking "lady you're a nut") Then he says "never heard of that before.
Then I explained that since we live in the country and have well water, that to get any type of water pressure we had to turn both the hot and cold faucets to full when bathing. If not you would get a drip bath. He said they didn't want to turn the temp past 130 because of scalding reasons.
I've run my dishwasher twice and noticed things not getting clean like they did with our old water heater.I don't want to blame this on the tankless yet, but give me time.
Washing your hands, or washing dishes by hand is useless unless you don't mind cold water or don't mind chancing running your well dry by leaving the faucet running for 20 minutes.
How many of you professionals would have recommended a tankless water heater to someone on well water? Just curious.
This isn't a problem with the Navien- it's a problem with the installers!
2-1/2 minutes to call hot water to your sink is distinctly NOT normal- it's an indication that it isn't operating correctly. If it's "normal" in the installers' experience, it means they have no business installing a tankless!
A noise that shakes the whole house on startup is also distinctly not normal, and potentially an indication of a hazardous condition. (Improperly purged flue and a flue explosiong on igntion would be my first guess, but not having heard it I won't make that call outright. If I'm right it's a fire hazard now and may turn into a carbon monoxide hazard later if it cracks the plastic flue.)
Tankless units are running just fine with well water all over the world. Water hardness can be a longer term maintenance issue (annual de-liming/descaling), but other than that, the fact that it's on a well isn't an issue.
If it's taking 2-1/2 minutes to get water to the sink, your diswasher is never getting hot water- EVER. If yours is a particularly low-water use dishwasher it may short-cycle the tankless resulting in lower efficiency draws, but unless it fills in 10 second bursts the tankless should be able to serve it.
Thank you thank you thank you
Originally Posted by Dana
And it really IS 2 1/2 minutes to get hot water. I timed it.
The plumber acted like I was crazy and everyone knew 2 1/2 minutes was normal and that I was hearing things as well. How long SHOULD it take to get hot water to a fixture?
He was supposed to come to check things out today, but didn't show up or call. My husband called him at 7 pm and he was short with him because he was at his accountant's office.
The noise is a rumbling, vibrating noise that vibrates the whole house, not an explosion noise. Should I still be worried about fire and CO2 hazards?
So I wasn't dreaming that my dishwasher wasn't cleaning?? what do you know. So speeding up the 2 1/2 minute heat time will fix that?
How about my HE frontloader washer? Is it getting hot water if the water takes 2 1/2 minutes to heat?
A normal startup sequence on a modern tankless takes no more than 2-6 seconds:
seconds 0-1: Flow is detected.
seconds 1-2: the blower starts purging the flue of any potential unburnt fuel
seconds 2-3: The gas & igniters come on
seconds 3-6: flame it detected and the gas & combustion air flow are modulated to produce the programmed output temperature.
The exact timing varies with model and manufacturer, but I've never seen it take longer than 6 seconds (which seems interminably long compared to faster units.)
The time to get the hot water to your sink is a function of pipe diameter and flow, but it should take no more than 6 seconds longer for the hot water to reach the tap than when a tank type heater was installed in the same location. If it's taking 150 seconds where it used to take 10 with a tank heater, it's having SERIOUS startup problems. The rumble & vibe may in fact be a series if micro-explosions as it's trying to ignite a too-lean mixture or flucutating mixture due to gas pressure/regulation issues. The operational gas pressure, combustion mixture & combustion efficiency is something a competent boiler-tech would verify with manometers & combustion analysers before calling the installation complete.
Gas pressure & too narrow gas line pipe diameter issues are possible culprits, but I'm not a certifiied tech, haven't seen the installation, and don't feel it's safe or sane to web-diagnose this one. I can say with a high degree of certainty base on your info that these installers are not competent to diagnose or fix this problem, and that something is terribly wrong with either the unit (less likely, since it's new) or the installation (highly likely, since the installers deemed these eggregious symptoms "normal".)
Many HE front loaders fill with short bursts of hot water, but as long as the bursts of flow are long enough to establish ignition on the tankless some hot water should be reaching the washer. If it's taking several 10s of seconds to establish ignition you're probably not getting much (if any) hot water to the washer. As a short term fix many HE washers have high-heat "sterilize" or "steam" cycle which super-heats the water electrically in the washer. But you really need to have the tankless problems properly diagnosed, and the entire installation inspected by a competent party. Document what has transpired so far, including the where/when/what of the conversations you've had with the installers- you may need to go after them legally to recoup the cost of fixing their likely-botched job.
Call Navien America, see if they can't find a certified installer in your area to come deal with this. Don't wait. The Illinois sales reps might be able to help you find a factory certified installer (and need to know about the screwup installers):
Tel : 815-886-9200
Fax : 815-866-6277
Download their diagnostic manual and familiarize yourself with as much of it as you can absorb so you can get more out of the conversation with the techs.
I am new to this forum. I have a question regarding tankless efficiency. Dana posted a chart on 12-09-10 regarding condensing efficiency. It showed that if the return water temp was too high heater efficiency was greatly reduced. I realize the actual transfer of heat through the heat exchanger is decreased because of the smaller delta t. If concentric venting were used wouldn't the exhaust temp approach the air intake temp? Would the overall efficiency be higher? Thanks
Originally Posted by Gary Swart
Rinnai R85V2532 Tankless heater
I am one of those people that do not care about numbers; I just wanted endless hot water. After some searching around, I decided on the above hot water heater. It delivers endless hot water just like they said it would. I installed it myself (No harder than a regular hot water heater) it took me about a day and a half.
It was delivered to my door for about $1100. On 09-06-06 with all the parts, vent pipe system, isolator flushing valves. It has been running all these years, with the only maintenance consisting of pumping 5 gallons of vinegar through it for an hour, once a year. The only time the cover was off it, was when I installed it. I just took a look at what was there.
My original tank hot water heater is still piped into the line, if this ever stopped working I can just close two valves and open two more and its back on line. So far it has never been needed. I have no financial interest in Rinnai.