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Old 03-09-2010, 10:17 PM   #16
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Tankless water heater Navien cr-210 ?


Yes that's a very interesting study. I've seen statements made like that before by people, could very well have come from that very article. They are right when they say that tankless units are only 22% more efficient than there tank counterparts. The efficiency rating is a measurement of how much of the energy, measured in BTU's, is used for the task being done. They measure that based on the number of BTU's into the unit and the amount that comes out as waste fumes.
This is a good basis for comparing apples to apples. In this thread we are comparing tankless, (apples) and tanked, (oranges). The proper way to tell the energy savings of one over the other is to compare the total energy each one uses over the course of a year. Or as you suggested a before and after test.

I have had the opportunity of doing just that with customers. They showed a savings of nearly 50% in there gas bill. I have a tankless unit in my home and that is the only gas appliance i have. My gas bill is $13 a month and $5 of that is as service fee! The Center for Energy posts yearly operating costs of most appliances, much like the gas mileage posted on new cars.
Not everyone will get the same savings. A family that is home all day and is using water on and off all day will not get as much savings out of the tankless as someone that uses it only in the morning and evening.
Again the main reason we save money with tankless units is not just the efficiency rating, but the fact that it only runs when you need it. It's suggested that 30-40% of the operating costs of water heaters are not in making cold water hot but keeping hot water hot.
But as was said before, and i would agree, it's just nice to have never ending hot water!

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Old 03-09-2010, 10:53 PM   #17
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Tankless water heater Navien cr-210 ?


I made the switch and I'll never go back. In my house I have a Takagi which has been excellent for three years so far. It does have its compromises.

Gas fired tankless heaters can cover only about a 10x range of heat. If they are rated at 7 gpm, they will be excellent for up to that ... BUT

That also means that they don't work at below 0.7 gpm, which is still a large flow. If you want a trickle of warm water while brushing your teeth, be prepared for it to go cold as soon as the water stored in the pipes runs out.

My solution to this was to put a 2.5 gallon Bosch tank heater in line with the tankless. I've used them in single sink installations with good success. It buffers the tankless heater and my wife has only managed to defeat the system a couple of times.

Unfortunately, the Bosch developed a leak after two years. I will have to put up with complaints from the wife until I get a replacement in place.

My next installation will use a smaller tankless water heater with a lower low flow cut-off. If too many people try to shower at a time, the water will be only warm (but not cold as you get when your tank runs out).

I am more driven by performance than costs, but the cost advantage comes because you don't keep a large tank hot, whether you use water or not. The numbers on payback may be right, but I expect the tankless to last a lot longer than the tank.

Rick
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Old 03-10-2010, 07:58 PM   #18
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Tankless water heater Navien cr-210 ?


Quote:
Originally Posted by frozenfoodguy View Post
Had this system install approx 1 year ago. Do not know if i got a lemon but this thing sucks. Which is good if it was a vacuum but it's not. At first it was just a problem with the unit keeping up to demand. This model is supposed to allow up to 2 users or uses at once.Example someone showering and the washing mashine goin or so forth. My unit was not able to keep up with the promise of the demand. The company that installed it did several software upgrades and the problem still persisted. Finally a rep from the company flew out and checked the unit himself. He installed a brand new software app and it was finally doing what it was supposed to do.I thought great problem fixxed. WRONG! Since then it has been shutting down with an error code 22. Something about a limit switch. Now my unit is 6 weeks past 1 year warrenty with the people who installed it and i am having the same problems. The service tech told me the r models have been replaced with the new n model. He said that they had way too many problems with the r model and the company maded the new n unit.I can not say i would recomend this brand to anyone, after 1 year the installers now started to charge for service calls.Hate to think what will happen down the road when everything is off warrenty. Have sent e-mails to navien to switch my unit for an "n" model.No response yet but will post when i here. Anybody else having problems?
then the heater was not installed correct!
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Old 04-11-2010, 11:11 AM   #19
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Tankless water heater Navien cr-210 ?


coolluke01
I have a question regarding the use of the 'autocirc' valve, did you use the internal circ pump?
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Old 04-11-2010, 12:16 PM   #20
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Tankless water heater Navien cr-210 ?


My gas usage compared to peers - Bosch tankless, I like.

SoCal - 1800 Sq feet - 2 adults - built in 84' - gas heat and hot water
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Tankless water heater Navien cr-210 ?-gas-usage-comparison-bell-curve.jpg   Tankless water heater Navien cr-210 ?-gas-bill.jpg  

Last edited by vsheetz; 04-11-2010 at 12:22 PM.
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Old 04-11-2010, 10:45 PM   #21
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Tankless water heater Navien cr-210 ?


I think it's best to get the A unit because it has both the pump and the tank. The pump can be run through an existing recirc line or bypassed inside. In either case the pump can be set to run at times you set on the controler. I am installing a NR 210A in my home soon and I'll be installing a recirc line to the upstairs bathroom.
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Old 04-12-2010, 07:23 PM   #22
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Tankless water heater Navien cr-210 ?


Dude,
I have a CR240A, my old system with the hot water tank was equipped with the Laing Autocirc. I was going to install the pump/timer into the line with the Navien, but.......will the integral recirc pump perform the task? And have you run this format
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Old 04-12-2010, 09:59 PM   #23
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Tankless water heater Navien cr-210 ?


The CR unit has a different config than the NR units that I use. I have seen the config of both units and I believe that it should work. There is a 3 way valve in the unit. This will have to be set to the proper position for the intended use.
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Old 04-13-2010, 11:09 AM   #24
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Tankless water heater Navien cr-210 ?


I think I can clarify some confusion here. I'm an engineer and spec systems like this sometimes.

The sandwich is this: You turn on a faucet, the water flows, the heater fires, the water gets hot as its flowing to a faucet. Ok, so hot water finally gets to ur faucet and you feel it. great.

Now you turn off the faucet, the water stops flowing, the burner stops and the burner area cools rapidly. The water you already heated and pushed down the line is still hot.

In 10 or 15 minutes you decide to shower. This shower is near or along the path to the faucet you just used. You turn on the shower, the water starts flowing again and you feel hot water there almost immediately because its already been warm in the lines from using the faucet.
You say GREAT, and jump right on in the shower.

Back at the burner, when water started flowing again (as you turned on the shower) a bit of cold water came into the burner and got past it before getting heated as the burned was firing and getting going.

So, now you're in the shower with warm water, and this "slug" of cold is now coming down the line after your warm, and in front of your hot water.

Theres the cold slug. Suddenly, surprisingly, you get hit by this blast of cold water. BAM, unhappy owner.
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Old 04-13-2010, 11:13 AM   #25
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Tankless water heater Navien cr-210 ?


I would like to add, that the ones with a small internal buffer tank fix that issue because that first bit of cold, mixes in the little buffer tank w the hot already there, and nullifies the cold blast. However, installing a 6 gallong tank in line negates more savings because you are now losing heat through all the surface area of that tank.

The ratio of tank volume to surface works against you here.
ie: a 6 gallon tank might have 300 sq inches of surface area, but a 12 gallon tank might only have 400 (not double). So, even a small tank, still has a significant surface area to lose heat through.

The little recirc systems do work. Remember you gotta use check valves because if not, depending on how your pressure drop is through your lines, you could open a cold faucet, and if its easier for water to push through your hot line than cold, then it'll come through the heater, bypass your recirc loop, and go to the sink through the cold side. GOTTA use check valve that prevent backwards flow.
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Old 04-13-2010, 11:39 AM   #26
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Tankless water heater Navien cr-210 ?


The last thing I wanted to add here, was to a poster on page one here. He seemed disappointed that the installer had told him he could run all his things and not get cold spots like, from flushing a toilet.

These tankless manufactuers size their units on a 40degree rise. So, taking water from 80 to 120. When they list a model as a 6 GPM, they mean 6 GPM at 40 degree rise. Noone I know has 80 degree entering water.

Around here, in South Carolina, our summer water temp is about 65 and our winter water temp is around 50.

So, in winter, worst case, we need to go from 50 to 120 so a 70 degree rise.

They have charts to pick a unit to do that and what fow it'll give you.

Usually, a rated 6 GPM unit, will only give ya about 4 at a "real world" temp rise.

With ALL that said, it doesn't matter what kind of heater you use. Even if you have a bull gassing into a bucket with a hose laying in it for your heat source, the toilet flush will always give you a cold shock becaue your water lines aren't sized for the correct pressure drop. Most residences aren't. They just plumb in what looks good.
When you flush a toilet, it changes your static and residual pressure ratios in your hot and cold system and since both sides aren't balanced it changes your hot to cold ratio and you'll get a cold blast.

The only way to fix that is to replumb your house, or to install a pressure balancing shower valve. They sell shower valve assemblies that monitor the flow coming to the shower head and move the internal valve position to keep your water temp the same flowing from the head.
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Old 04-26-2010, 02:17 PM   #27
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Tankless water heater Navien cr-210 ?


Another aspect to consider before purchasing Navien is their customer support attitude ... or lack thereof. The PVC elbow (water feed) inside the case of our CR-180A sprung a pinhole leak, spraying fine mist and soaking all components for weeks or more before the system board failed (puddles of rust left on bottom of case made it obvious that metal mechanical supports as well as exposed Belkin connectors had been corroding. High-resistance contacts, anyone?). Local tech could *not* get the Navien support engineer in Calif to agree to a unit return. They shipped a new board, despite my protest that all electrical components and contacts had been soaked (there was a warning in the Navien installation manual that the unit was not designed for humid environments!!). A few weeks later, the system is now failing multiple times a day. Navien tech support in Calif refuses to send the local rep anything more than a replacement transformer as their next attempt at hit-or-mis diagnostics at our expense (no hot water at all for 3 days now ... second multi-day incident of no hot water in 2 months). Dealing with these people feels like dealing with the gate keeper of some insurance company. Based on their utter lack of consideration of customer service as well as a suspect level of competence in their tech support team, I strongly recommend avoiding them.
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Old 04-27-2010, 01:54 PM   #28
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Tankless water heater Navien cr-210 ?


I have it too. I like it. You can hear it when in the garage, but not noticable in the house. Takes a while for the water to come, but the benefit of saving on gas is better than the little wait.
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Old 08-10-2010, 11:40 AM   #29
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Tankless water heater Navien cr-210 ?


After two years, my Navien "A" model quit completely due to a design flaw. The company replaced it with a new model, but I'm out of pocket on additional labor costs to the tune of a thousand bucks. Also, I had spent extra for the recirculation model, only to find out it doesn't work in big houses. Navien produces an inferior product and its service back-up stinks.
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Old 08-25-2010, 06:17 AM   #30
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I just purchased a Bosch 2700ES-NG but, I don't think I'm going to install
it. I started comparing my gas bill with what possible savings I might gain.
We have the normal 2 1/2 bath home, plus my wife has a beauty shop in the house. I've had my two grandsons staying with me all summer and they can use some hot water. With all of this, my gas bill is still only $30.00 a month.Even if this Bosch water heater cut my bill in half it would take a minimum of 15 years just to recover the cost over a standard gas heater. By then the unit may have to be replaced and you start all over again.

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