Navien CC210 natural gas.

moussa

Hello all, doing a little research on the cc210, has anyone installed one? thoughts on the product? Im in the market and my local store has one for about 1k. I know that the units produced in 2008 have a recall.



Do these have an outdoor reset like the newer models?



Any advice would be appreciated.

HDE

Outdoor reset?

Its a tankless water heater not designed for heating only and it doesnt have heating only boiler certification

Based on your question of does it have outdoor reset, sounds like you in the market for a boiler, and you should be looking for a boiler.

moussa

Thanks HDE

Im actually in the market for both a hot water heater and a boiler so this combi is of great interest.



Any experiances with this unit? pros cons?

HDE

I'd pass on the CC model

If you like Navien, consider their CH model combi boiler.

You should never install a tankless as a combi with radiant floor without a plate heat exchanger. And for all the added cost, just buy a true combi boiler.

JohnHenry_2

I've had a ch-210 for about a year now.

And so far I've been really happy with it. There's quite a bit of technology for the money.



The AFUE rating on it is a bit deceiving in that the rating is a combination of heat and hot water. For heat it's just as efficient as any other mod/con for given conditions.



If I had to complain about something it would be the way they've set up their outdoor reset logic. If you use the outdoor reset, you have to use their controller and can't use a thermostat. Their controller isn't exactly a precision thermostat but it works well enough as a high limit room temp controller. So you set your "K" value (reset curve) to where you think the unit will keep your house at whatever temp you want (this does take some fiddling). The logic I'm not particularly fond of is that if you do reach your high limit room temp, the unit will wait until the room has cooled down 5*F before it'll fire up again. There is probably a little more nuance to the logic that I haven't discovered yet.



I run a small electric HWH to mitigate the 30 sec. lag time in DHW flow.



HTH

gennady

thermostat with outdoor reset?

why in the world would you use outdoor reset with the indoor thermostat? outdoor reset is not a high limit, it is a method of space temperature control.

HDE

To keep people happy

As ideal as it sounds, you can never set the curve exact to the indoor preference. Mama gets cold she better be able to raise the indoor temp no matter what the temp is outdoors. Most will add a 5-10 degree buffer to allow indoor temp to exceed outdoor design temp.

So outdoor reset is a limit at a specific outdoor temp with the thermostat as a final control.



Give people what they want comfort just a touch away, while maintain optimum efficiency.

HDE

Not quite

"If you use the outdoor reset, you have to use their controller and can't use a thermostat"



Not true, flip dip switch 3 of 8 up and connect a input or stat to R&W

Remote is no longer a wall stat but still controls curve.

gennady

Outdoor reset

I stopped installing thermostats few years ago. Had no complaints. As a matter of fact, if you combine outdoor reset with thermostat you cannot raise temperature with thermostat . Outdoor reset becomes a limit.

SWEI

high limit control

Assuming there's no indoor sensor and associated controls logic, an indoor tstat is still useful as a high limit control  Set it a couple degrees higher than the desired indoor temp and it will prevent the boiler from firing when there is heat gain from some other source (wood stove, solar gain, cooking heat, etc.)

gennady

outdoor reset

Neither outdoor reset , not thermostat address room by room temperature changes due infiltration, heat gains and so on.

In case of thermostat temperature changes can be addresses only in the place where thermostat is located.

Regarding indoor sensor, boiler knows when to change firing rate not only because of outdoor temperature, but also return water temperature.

If house gets hotter, temperature difference between radiator surface median temperature and room gets smaller, heat rejection decreases, return water temperature increases, and boiler has to down-fire to keep supply water temperature in line with outdoor reset settings.

It is very easy to calculate curve when heat loss calculations done via heatloss software.

I have customers insisting on keeping thermostat. I of cause comply, but with the one condition: thermostat will be disconnected from the boiler, and if they want me to connect it later, i will comply. Then I get a phone call, with question: How did you do it? Thermostat becomes just a thermometer and it is dead on temperature I set up with outdoor curve no matter what.

Jean-David Beyer

I have outdoor reset and indoor thermostats.

I have outdoor reset and indoor thermostats. Since there is only one of me living in this house, I have set the indoor thermostats to the temperature I want. I spent two years setting the reset curves to be so close to the heat loss that much (most?) of the time, the reset rules. On warmer days, when the boiler will not modulate down far enough, the thermostats remove their call for heat.



I have an upstairs baseboard zone and a downstairs radiant (slab at grade) zone but my boiler has a separate reset curve for each zone. I have these reset curves set ever so slightly higher than what is needed, so the the thermostats do shut off every day for a while. I did that because, while my house is quite well insulated, there are still small drafts when the winds are very heavy. Some years that happens. And on such days, the thermostats can call for heat the entire day and night. I think that happened once in the three years I have had this system. The thermostats are set at 69F and the temperature wanders around between 68F and 70F if it is cold enough out. Otherwise it goes up to whatever it is outside. Usually it does not go down to 68F.



The only problem will be if I die and the new owner wants it warmer and just raises the thermostats. It might get a little warmer, but it would have all the symptoms of an undersized boiler (even though it is about twice the size the house needs). I hope they get a wise contractor who figures out to raise the reset curves a little bit. But I doubt it. I have John Siegenthaler's Hydronic Heating book and the W-M instalaltion manual on my bookshelf, but would anyone read it? I was  going to write up how to run the system, but it got too long and no one would even read that.



The major problem they will have, though is that radiant slab zone. I have a fancy thermostat that I like. It has fancy setback features so that I can have 4 different temperatures each day, so I could set 28 different temperatures each week. As a practical matter, I use setback only when I go on a vacation longer than a few days. But they will try to use setback on that slab that takes about 24 hours to deal with recovery from setback. That will drive them crazy. The people I know cannot even set a thermostat for a one-zone forced hot air system. 8-(

Jean-David Beyer

It is very easy to calculate curve when heat loss calculations done via heatloss software.

"It is very easy to calculate curve when heat loss calculations done via heatloss software."



Maybe it is when you have a new building and you could watch what was going on before they poured the concrete (if radiant slab at grade), and knew what was inside the walls, and so on before they put in the interior walls.



My house was about 60 years old and I knew nothing about what was inside the walls (I knew there was urea formaldehyde foam in the walls, but do not know about cavities, how corners were constructed, etc.). I did not know the amount of copper tubing in the slab or its spacing. I do not know what insulation was under and around the slab (I suspect there is none). And so on.



So I did calculate the heat loss of my house to determine the size boiler I needed. It was accurate enough to size a boiler, but not enough to do the reset curves.  I got the smallest in the product line, but it is really too big. It was not to difficult to calculate the reset curve I needed for each zone, but that resulted in the curve being much hotter than actually needed. And with the wrong slope besides. So I fixed it by trial and error and that took a lot of time because I could not adjust the outside temperature (of course). If I could, I could probably have set the curves in a week or so instead of two years.

gennady

outdoor reset

All what counts is heat loss. you have to deliver amount of heat to area heated equal to amount of heat that got lost. so in simple words keep heat balance of the space. Means of heat delivery can vary.

loss=gain

I see a lot of issues with balancing of the system, either seam or hot water. Balancing is the key to comfort in my opinion. And this is most neglected area in heating systems.

Also, if there places with different obstacles, then ODR is needed for each are separately, in addition to boiler ODR. Lets say sun room with baseboards has completely different requirements then basement with radiant floor, and i would do them on each own ODR.

But id house has similar characteristics troughout, then boiler ODR is good enough.

JohnHenry_2

I've tried flipping 3 of 8 up

and had issues. I called Navien and they said "don't do that. If you want to run ODR, you can't use an indoor thermostat, period". I've had 3 different tech support staff tell me the same thing. I called multiple times as it seems strange to not be able to just have the supply water temperature set by the reset curve independent of other control.

JohnHenry_2

What happens when

for example, heat loss at outdoor temp X* and desired indoor temp Y* is 25K BTU/hr but the granularity of the reset control combined with the emitter characteristics allows situations where you can get 24K BTU/hr or 26K BTU/hr into the house? In my situation, I can get 72* indoor temp with a "K" value of 1.5. The next click up, 1.6, gives me 74*. I want 73*. Am i being too nit-picky about my indoor temp, expecting too fine of control?

HDE

Interesting

Something's missing because if you had multiple zones you would need to switch to external input, not using remote as room control, but still for reset curve.



I have seen it done many times.

JohnHenry_2

I'm trying

to figure out what's missing. I've called Navien tech support several times about this. On the first call I was told that there may be a software glitch in that the control can get unstable using an external thermostat along with outdoor reset. On every call the support tech said "you can't run an external thermostat with outdoor reset".



There also seems to be some sort of minimum sensed temperature threshold the controller needs to see to re-fire the burner if it stops for any reason such as upper limit being reached or the burner can't modulate low enough to keep the supply temp from exceeding the curve value. This threshold seems like it changes with "K" value and outdoor temperature. Lower "K" values and higher outdoor temperatures seem to make the minimum sensed temperature threshold go lower. The lowest minimum sensed temperature threshold seems to be 68*F.



I'd love to be able to use the old timey thermostat that was put into my house when the boiler was converted from coal to oil in 1941. And I'd like to be able to have a separate zone for my basement.



If you have any suggestions or ideas, I'm all ears.

TonyS

Most of my jobs are multi zone

The water temp for degree day is never the same in both zones. I have no choice but to set my curve for the highest temp zone. If I didn't use stats I would overheat the other zones.

How do you get around this problem with no stats?

gennady

zones with ODR

zone with 3 or 2 way valve and outdoor sensor and ODR, with curve set for zone served. If common system pump is used, then pump better be deltaP VFD,

gennady

granularity?

these are limitations of low priced boilers. Weil mclain, Viessmann Vitodense 200, and other boilers allow for very precise settings of the ODR curve. Also, sensors for supply and return water temperatures must be located on the system loop, before and after hydrolic separator or close spaced tees, not on inlet and outlet of the boiler. These should read system water temperatures.I do not know why Navien installed them where they are.

TonyS

Are you saying

run a separate motorized valve on its own reset or using a manual 3 way valve and mixing to the lower temp zone?

That would be possible and expensive, maybe in some large building I could see it.

A normal situation for me would be a three story gravity conversion and a second zone on a modern kitchen renovation with baseboard. After doing a heat load and then an edr count on the rads I may find I need 160 in the board on a design day and maybe 145 in the radiators...Im going to start my curve at 160 and use 2 stats. What possible value would I be giving my customer by eliminating stats(not to mention control of their own heat in their own house). Besides remixing from the return does nothing to improve efficiency because the boiler has to run at the higher temp anyway.

Not giving my customers some type of control over their new boiler wouldn't go so well.

I know my own wife would flip and just start turning on bathroom heat lamps and hair dryers to make up the difference. Funny but true

Truth is before I would do that I would add TRVS to every radiator. Now we could control the temp of every room and use ODR.

gennady

thermostat with navien

You actually can use external thermostat with navien. On manual page 51 setting dip switch 3 on is allows external thermostat.

But when you are using external thermostat, you have to set up a number of dip switches.

gennady

taco ivalve

I would use taco Ivalve

http://www.taco-hvac.com/uploads/FileLibrary/100-19.pdf

I would pipe lower temperature zone after high temperature zone with close spaced tees, so water returning from the system will be coolest. It means using closed spaced tees and locating high temperature zones first on the flow of water and lower temperature zones further down the flow. We want cool water return to condensing boiler, don't we?

The benefit will be better condensing, and minimizing short cycling, getting much better efficiency and comfort.

gennady

TRV

Could not agree more on TRV

TonyS

Well there you have it

A TRV is a thermostat. 

HDE

Not quite

Give your self a little room operating water temp a little above required outdoor reset and above WWSD and you can avoid those "I'm cold heats not working callbacks"

HDE

Limited outdoor reset

John,

The outdoor reset operation is limited since you can't adjust WWSD, max high temp, min start temp etc. But that's what you get for $35 I guess. You could always upgrade to a Tekmar 260 and have complete control , I suppose.

What K factor setting (.05-6) are you running and is it set for supply or return water temp operation?

SWEI

TRV is

actually a proportional, modulating thermostat.

JohnHenry_2

"K" factors

It's set for supply temperature and I keep the limit at 73*F. K=1.5 keeps my house at 72*F, k=1.6 keeps it at 74*F. That is until the boiler can't modulate low enough and it shuts down and won't fire up again until the controller has seen 68*F...



It also seems that with a K value of 2.0 or above, the heat comes back on when the temp gets down to 72.



As soon as daily high temps drop to a bit under 50* it becomes a moot point as the house is shedding at least 20K BTU/hr all the time.



I've been thinking about using something else for control. Or I could just set the K factor to 2.0 during the shoulder seasons and 1.5 during the winter.

Jean-David Beyer

All what counts is heat loss.

I completely agree. My problem was that my heat loss calculation, that I did with the Slant/Fin program, was not accurate enough to use to set the reset curve(s). No fault of the Slant/Fin program. It was a G.I.G.O. problem. The data I fed the program were not accurate enough to get accurate enough answers. And that was mainly because I did not know, and could not find out, the needed data in enough detail to do it. It did give me enough accuracy so that I could insist that the contractor install the smallest boiler in the product line, rather than the next larger size. (80,000 BTU/hour instead of 105,000 BTU/hour; the house needs only around 30,000 BTU/hour, and that only when it is 0F outside -- 14F below design temperature.)

gennady

TRV

I thought TRV stands for thermostatic radiator valve. Thermostat is the box on the wall stopping and starting zone pump or zone valve for the zone upon air temperature changes at the thermostat location. TRV modulates water flow rate to the radiator based on temperature near thermostatic actuator or remote sensor. If this is thermostat, then in this case I'm for thermostats when they named TRV.

TonyS

Thats correct ,thats what it stands for

But lets stay focused here. What function does it serve? It stops the flow of water to the radiator when its thermostatic head says it reached its setpoint. When I install remote TRV,s my customers ask what numbers do I set the THERMOSTAT to.

Just like a electronic thermostat turns off a pump or closes an electric zone valve.

Lets just call them high limit devices.. because that is their ultimate function.

So back to your original statement. You dont use thermostats with ODR but you believe in using TRV,s. I like TRV,s too but on more modern homes with baseboard I prefer to use a zone valve and electronic stat instead of a TRV. I guess what im asking is why one but not the other when they provide the same function?

gennady

TRV and thermostat

Yes you are right, all TRVs on all radiators are the same as one thermostat for the house. Sorry, my bad.

But, TRV does not stop flow, it changes flow rate proportionally. It acts more as a balancing valve.

It does not stop the pump it has no control over the pump.

Working with ODR it has more uniform flow trough radiator or baseboard, because with temperature of the water changing with relationship to outside temperature, flow rate is not changing drastically by TRV,

When you have electric zone valve, mounted on the radiator, controlled by 24 volt trough wall mounted thermostat, you stopping and starting flow, having temperature fluctuation in the room and bringing a lot of work involved in installation and parts that can go bad with the time. It is too much. Comfort is decreased because air temperature fluctuations. I'v seen these kind of installations and they never stop to amaze me.

Much more logical to me is to install self-contained TRV with no wires and thermostats, have them hunt temperature constantly by controlling water flow and deliver ultimate comfort without jumps in the room temperature.

TonyS

NO NO NO

We are talking about zones, remember my example, the kitchen ,the baseboard,,, its right up top there if you want to read it. You wanted to remix second zone instead of stats.

That would be two stats, one for the kitchen and one for the rest of the house. So you would remix second zone and offer no stats except you would consider a TRV on the board.

Whatever you do im sure it works well for you and your customers. My customers are just funny about controlling their own heat. Matter of fact I have sold several honeywell wireless red link stats with... are ya ready for this.. a remote control that overrides the main stat. Thats right honeywell and some of my customers feel they should be able to adjust their heat from anywhere in the house. Also millions of dollars are being spent on people controlling their heat over their smart phones and internet connections from anywhere in the world. Imagine that

gennady

red link

Honeywell Red link, Taco iWorx, and others sell means of temperature control to unsuspected customers. My selling point is : you do not have to think about temperature. You have ultimate comfort. Think about other things in your life. You come home and find comfort. Not temperature, thermostat, TRV. Find COMFORT in the house.

TRV work very well with ODR. They allow to correct local spot conditions , such as solar gains, infiltrations, and other stuff, like for example house wife cooking turkey on thanksgiving.

TonyS

What about the variables

people get sick, flu, colds whatever. They dont want to hear about a perfect setup, they want 76 degrees.

Get chilled to the bone in cold rain or spend a day in the snow, you feel you want to come in and hug a steam radiator.

ODR is a great way for energy savings but I personally would never use it to limit my customers choices.

gennady

other conditions

In case of the flue I would advise medicine. Hugging steam radiator can get one 2nd degree burns.

What about all people living in the buildings. they do not have means of controlling temperature in the apartments. And they survive. This is a matter of educating customer about comfort basics.

Also, with ODR and TRV radiators are hot all the time. they almost never get cold during heating season, unlike thermostat operation. so there will be plenty of hot radiators to hug. they will not be 180F thou, most of the time 120-140. still hot enough

SWEI

(not) limiting choices

Just bump the curve up a few degrees and the TRVs will move out of full open position during normal operation.

TonyS

You really had me going there

I thought you were pullin my leg with the Zen Buddhist comfort thing LOL. but you gave it away when you suggested that people that pay for their own heat shouldnt have any more control than an apartment dweller.

One last question, in a home with existing radiation how do you find your heating curve limits?

gennady

leg

No , i did not pull the leg. I really believe that temperature has nothing to do with comfort. Think about it. In the same room people set thermostat for 75F in the winter and 65F in the summer. I think it is mental disorder. And it has to do with the way heating cooling systems set up in USA. And it has nothing to do with comfort. My biggest compliment was , when a customer told me that her biggest problem was not knowing what temperature was outside, so she always has to check weather channel to deside what to wear, after our system installation. Calculations of the ODR is to set different design temperatures in the software and get heat losses for those temperatures. Knowing installed EDR it is easy to calculate water temperatures. Lets say you set design temperature 50F and get heat loss for this temperature. ( of couse you did previously get heat loss for design temperature) then you divide this heat loss to installed EDR, get BTU per EDR and looking at radiator charts ( like page 2 of http://columbiaheating.com/page_images/Sizing%20Cast%20Iron%20Radiator%20Heating%20Capacity%20Guide.pdf )determine what median temp shoud be in the radiator. knowing delta T you know entering water temperature. having 3-4 points you get the curve.