OK, finally figured this out. Since I do not have a dedicated recirculation line (most homes don't), they installed a Instant Hot Water Recirculating System Sensor Valve Kit. That hot water inlet (Navien fluff pic) is for the dedicated recirculation line. Since the Navien has a built-in recirculation pump, the valve kits work perfectly. So, my longest runs (master bath and kids bath) had the kits installed. Since now I know what it is, I might install another at the kitchen sink. It's the longest wait time of 15s.
Originally Posted by ImpliedConsent
I noticed on the Watts site that they state those valve kits are not supposed to be used with tankless. That was my reading of it anyway, though I guess if it works, it works. There's something I'd like to understand about these valves and recirc systems:
If they essentially use your cold supply line as the return recirculation line for the hot until it reaches 98* don't you now have essentially 98* water in your cold line? So don't I end up negating the "savings" by having to run the cold at the tap for ~10 seconds in order to get a nice brisk rinse after shaving?
Unless you have a dedicated return line, you will heat up the cold line as well.
Yea, I'm gonna have to take a picture of what they installed. It's not exactly what I found on the Watts site. I do know that it works. When I wake up in the morning to shave, that hot water is there immediately and it's the furthest run from the WH. I usually had to wait. I know that I do NOT have a dedicated recirc line.
Originally Posted by shugs
OK, this is what they installed on the 2 long runs. This one is in the kids bathroom. Apparently there is a thermal valve in there somewhere, which, when it gets to a certain temp, it opens/closes. Any clue?
I'm going to add to this topic again. when they first hit our local central california coast market, I liked them but the problem of low flow cut out became a problem and changing boards became a regular task for us. What did become a problem was the issue remained after the 1 year labor ran out and Navien would not honor replacement of known problems with these by paying to have these replaced.
Considering the near non response of the sales distributor and the full mailbox of tech support on weekends, I wouldn't recommend this line for any reason. The recirculation pump feature in the A models can not be set up with a remote on demand feature and the pump has limited head capability. I challenged the sales rep how 98% efficiency is achieved with temps at 120 or lower at low flows, he couldn't answer that and has quite touting this at trainings.
We've been installing tankless for over 30 years and have seen our share of what works and what does not. Navien has failed to realize service makes or breaks a company and in my book they lay near at the bottom with Bosch.
98% efficiency is much less a function of the flow rate & output temp than of the incoming water temp. The output temp is only a 3rd order factor, but at low flow low-fire the lower turbulence on both the fire & water sides of the heat exchanger can start to create insulating laminar flows that'll knock a few points off the raw combustion efficiency. Whether it's actually 95% vs. 98% at minimum fire is hardly as relevant as what it is at 20-40% of full fire from a total fuel use point of view. But whether the output is 100F or 130F makes less than 0.01% difference. But if the INCOMING water temp is much over 90F you won't be making 98% thermal effciency at any output temp.
Sorry to hear that their customer support is so abyssmal though.
Tankless testing (all brands) follow a standard testing procedure for determination of combustion efficiency and EF.
10 Code of Federal Regulations Section 430.23.
In a nutshell its a series of draws at different flow rates and gallons.
So if Navien is misstating efficiency so is all others.
I wont argue about what it takes to get to it, yes it involves cooler inlet water, but so do the 80%ers to achieve 82-84%.
Whats the big deal with changing a part, make it part of the charged annual service
When did the EF test change from 6 equal draws are made during the first 6 hours of at 24 hours test perior for a total of 64.3 gallons, (at an unspecified draw rate?) They've been talking about changing it for years, but SFAIK the DOE spec hasn't changed yet. If there's a new procedure, don't give me the nutshell, point me to the document please- I'd LOVE to see what they've cooked up!
Originally Posted by zl700
All tankless units have traditionally overstated actual as-used efficiency, since real-world use isn't 6 10gallon+ draws per day. The fractional losses of short-cycles for the quick rinse or hand washing add up. Every ignition cycle & flue purge throws away some fuel or heat, and real-world use is more than 6 draws/day. The steady-state efficiency of a hot water heater isn't nearly as important as it's ignition & flue-purge losses x draws per day, and the average draw size. A low-mass fin-tube or condensing boiler only settles into the steady-state efficiency somewhere between 3-5 minutes into a firing, so the steady-state number is only relevant for showers & tub fills (which are granted, the largest VOLUME of water draw.) The 15-100 second draws can and do affect the average efficiency adversely.
The 6-draw 64.3 gallon EF number is a better comparison between different tank heaters than different tankless units (or comparing a tanks to tankless). But that too is fraught with as-used error, since the volume of use effects it's average efficiency. Steady-state most tanks will run right around 80%, but their EF numbers are much lower. But those who use less than the 64.3 gallons/day number will average efficiencies lower than the EF number, and real hot-water pigs can hit well OVER that rating.
Unless it's on a recirculator most people will see temps well below 90F for incoming water, and condensing efficiencies of condensing tankless units will still be quite high, but the real world average will be closer to 90% with a condensing tankless than a 98% steady-state or 0.98EF number might imply. See: http://old.aceee.org/conf/08whforum/presentations/1a_davis.pdf
Jan 2011....I have a Navien tankless hot water heater....and I would never buy another one...I just got off the phone with the tech dept....and when I said that you don't have any qualified techs he said we aren't required to...that if anyone wants to be trained they have the classes...well a lot of good that does for me the consumer ...it is a little late ..but I am so savy now...if one more thing goes wrong >>>I will find another company who will back up their product and I get rid of this ...can you imagine buying something and them telling you it isn't up to them to have the qualified techs....see them in court....
My experience yesterday.
My friend, Kenny, has a rental that he had a Navien installed about a year ago.
After numerous calls from the renter about improper water temp variations and reading the manual and trying different solutions, Kenny called out someone to look at it.
Rocky, the service man, showed up and told us he has plenty of experience with Navien. Even the plumbing company owner has one installed in his home.
First Rocky inspected the intake and exhaust lines from the outside.
Then he went inside and looked at the unit.
He called tech support and explained the problem to them.
They questioned him on the size of the gas line feeding the unit. OK on that point.
Had him check gas pressure at the unit. Not quite what they wanted as the pressure fluctuated as the unit cycled. He replaced the 3/4" gas shutoff valve with one that has a larger ID. Gas pressure hardly fluctuated at all after the change out.
Unit still not operating correctly.
Rocky pulled the inlet and outlet water filter screens. Inlet was pretty plugged up. Cleaned that and reinstalled.
Rocky mentioned he has come across a solenoid that would act up. He removed it and found a broken o-ring. He replaced the o-ring and now the unit would not make hot water at all.
He called tech support again and was told to check the flow sensor. The remaining broken piece of o-ring found its way to the sensor. He replaced the sensor and the unit fired up.
Water temps were checked at different locations in the house and they varied no more than 5 degrees.
The renter called kenny this morning and told him that this morning's shower was the best he has had since he moved in.
Rocky's opinion is the Navien is a well built unit. He prefers them over other units he has serviced but it depends on the application.
Kenny was ready to pull this unit out and install a tank type.
even considering relatively lower federal tax rebates for 2011, i believe it's still worse it to install a tankless water heater.
I just had a Navien installed in my 6000 sf home in Pinehurst NC. I got the unit with the option of a circulating pump and controller. The plumbing co. installed in my garage. It works great. I had three water heater for the house, each with a 50 gal tank. I was keeping 150 gal. of water at 125 degrees 24/7 which was a huge waste. I travel a lot and we have other homes that we visit and the Pinehurst house sits empty for two to three weeks at a time. When I go I just touch the pad and the circulating pump shuts down and I have zero activity until I return. The plumber has a service to come by once a year and flush (clean out) the system, but that is what people are supposed to do with a regular hot water tank and they never do. I was looking at replacing my tanks as they were getting old and the cost was estimated at $3,100. My Navien system cost $3,800 with return lines installed and insulation of pipes, running the gas line, etc. I could care less if the $700 difference is not saved right away, I have a great system, water is instantly at the outlets, no problem with showers going. What's not to like? I had no preference at all, my plumber recommended Navien and I liked the fact it had a little cirulating pump included in the unit. My friend in Tennessee built a new big house and he installed two Rennai heaters and had to install external pumps to circulate the water and he put in a small 10 gal water heater as an instant reserve. I did mine with one unit and no heated reserve.
Originally Posted by willl
navien is the best I've tried thus far. no temp variation, built in recirculation and stainless steel heat exchanger. definately more reliable than the 'big 3'. and as for tank type heaters & 30% of energy usage for hot water? these people must be taking cold showers & using cold water for most everything. tank type heaters in real world operating conditions are 50 - 60% efficient on their best day unless you go with commercial. also- good warranty support on navien heaters.
There is scant evidence to support that assertion, and plenty to support a different conclusion. The DOE EF test consistently over-rates tankless units due to the unrealistically larger volume and fewer draws. Real world performance of tankless comes nowhere near the EF test numbers, but tanks do at DOE test daily volumes, and easily exceed their ratings in high volume use.
Originally Posted by drdrain1
I could no longer find it on line, but the results of PG & E sponsored testing you're both overstating the real-world efficiencies and understating the lowly tanks. See if you can't dig it up somewhere:
Testing Water Heaters with Different Draw Profiles
Robert Davis, PE
ACEEE Water Heating Forum
In real world residential apps the "98% efficient" Naviens do no better than high-80s due to short-cycling and flue-purge losses, whereas in a high-use draw profile with a crummy 40 gallon atmospheric drafted tank with standing pilot that tests at 0.59 EF in a DOE test can easily hit the high-60s. With cheap tanks it's all about volume- at low volume usage it falls off an efficiency cliff, but at steady state (the only condition in which a Navien is actually anywhere near 98% efficient), they're all around 78-82%. At ~28 gallons/day use the same 0.59EF that's pushing 70% on a high-use profile is down around 40%. Same heater, different volume.
With tankless it's all about the number & volume of individual draws and time between draws, since the flue purge is a fixed loss with each draw, but there's also some amount of standby loss from the heat abandoned in the HX between draws.
Water heating fraction of total energy use in a house is well UNDER 30% as a national average, but the national average heating/cooling load is also much higher than the CA average due to climate differences. In MN or ND even people who take long showers won't be exceeding 20% as the hot water fraction, whereas in southern FL it could be close to 50% for some people.
The DOE EF test does not include electricity use in tankless heaters too, which for Navien has both a standby and active use components.
Endless-shower folks get more bang/buck (and higher net-efficiency at a lower overall cost) out of a 0.55-060EF 40 gallon tank and a drainwater heat recovery heat exchanger than going condensing-tankless, but for the fill-a-big-spa types a condensing tankless is as good as it gets.