# Tankless Water Heater



## CallMeVilla (Apr 12, 2014)

In a tight situation ... The owner wants to put a tankless water heater on the exterior wall.  The windows are within 3 feet of the unit, although the exhaust conduit will carry any off gasses above the roof line.

Advice on the best orientation?


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## Wuzzat? (Apr 12, 2014)

CallMeVilla said:


> Advice on the best orientation?


"Depending on the orientation that is right for your home, your tankless water heater can either vent horizontally through an exterior wall or vertically through your roof. It is very important you realize that you will not be able to use your existing venting with your new tankless system. You will need to use venting approved by the manufacturer.

You also want someone who knows all of the national and local codes that apply."

So I guess you should post a link to the make/model that you are using, and code excerpts.  Each of us may get something different from this info.


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## CallMeVilla (Apr 12, 2014)

Don't know the details yet ... just anticipating the location issues.  Most exterior tankless models do not even have vertical venting.  They just dump the gasses horizontally in the front of the unit.  My concern is clearance requirements between the face of the unit and the nearby window. (see attached picture)

What I was looking for was anyone who had dealt with that problem when installing a tankless.


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## Wuzzat? (Apr 12, 2014)

See page 8, second row in the table
http://www.noritz.com/commercial/files/manuals/Installation_Manual-_NC380-SV-ASME.pdf
Also pg. 9., plus I've seen 5' or 6' numbers.  With all the caveats in this manual many customers may opt out of installing these things.

Probably bigger input BTU/hr units need more space.  

You might try pulling up another manual picked at random from the Web.  If the numbers are close you're in good shape.  If not, if the numbers are all over the map then maybe U.L. has the final word on this.

Hope this helps.


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## havasu (Apr 13, 2014)

Here is how I installed my TWH. This was done by code and passed all inspections.


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## Wuzzat? (Apr 13, 2014)

havasu said:


> Here is how I installed my TWH. This was done by code and passed all inspections.


Any openable windows nearby?

If you can post a link to your manual we all can see what differences there are between the link I posted and yours.  These things may have a range of 50,000 to 500,000 BTUh so there may be other differences besides the size of the gas supply lines.

I'd think even the hot water line would need protection against freezing in some places if there is a long time between the demands for hot water but my link only mentioned cold water line protection.


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## CallMeVilla (Apr 13, 2014)

Hope to have the unit specs next week.  There is an operable window nearby ... but it can be secured to comply with inoperable requirements.  Will take pics of the actual site and share as we get to that part of the total remodel.  

Since this is Southern CA (Neal, that would mean "California") we don't have freezing problems.  I anticipate vent piping to divert off gasses away from the wall and the small overhang (only 3").

THANKS for all the really excellent input from Wuzzat and Havasu


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## nealtw (Apr 13, 2014)

How did I get into this, I just thought CA was short for ca ca.


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## havasu (Apr 13, 2014)

The Navien TWH has a built in freeze protection, where it will begin to cycle when the temperature dips to just above and at freezing temps. 

Attached below is the PDF spec. sheet for the Navien NR-240 TWH. 


http://www.navienamerica.com/__DATA/Tech/2013/2/21/NR Series Spec Sheet (compressed).pdf


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## Wuzzat? (Apr 13, 2014)

Thanks.  Pg. 35 has some clearances.
http://scudhomestore.com/wp-content/uploads/2012/01/NavienNR-NP-Installation-Manual-20101210.pdf
these suckers are heavy. . .

Regarding "the time to burn a child" table on pg. 66, I've heard that 42C will never burn an adult with normal blood circulation so if you don't have kids you can crank up the temp a bit.  

At 11 GPM and 200,000 BTUH you only get a 37 F water temp rise but with a bathtub filling at 6 GPM you'd get a 67 F rise.  I guess this is enough.

I don't have one of these but the numbers are telling me that as the temperature of the incoming water gets colder in winter you'll need to fill the bathtub more slowly if you want the same bath temp.


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## slownsteady (Apr 14, 2014)

I'm really surprised to see these units on the outside. Must be ok in CA but n/a in OK.

(sorry, just got a little carried away) Can these be installed indoors in areas where the temps get chilly?


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## CallMeVilla (Apr 15, 2014)

There are interior and exterior models so the off-gasses get vented accordingly.  Many places, they are put in the basement.  California does not have basements typically ... you are fortunate to get a crawlspace.

While the units sold in cold country have anti-freeze technology, I would choose to mount them on the interior to reduce risk and wear-and-tear.


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## havasu (Apr 15, 2014)

I agree. The unit would probably last longer mounted on an interior wall, however when I completed my garage make over, there was just no interior wall available with easy access to the natural gas and plumbing, along with the third recirculating water line.


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## nealtw (Apr 15, 2014)

havasu said:


> I agree. The unit would probably last longer mounted on an interior wall, however when I completed my garage make over, there was just no interior wall available with easy access to the natural gas and plumbing, along with the third recirculating water line.



This system is a lot cheaper to run than recirculating pump and there is one that works with motion detector so by the time you take a pee the water is hot.
http://www.conservastore.com/productdetail.php?p=53


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## Wuzzat? (Apr 15, 2014)

nealtw said:


> http://www.conservastore.com/productdetail.php?p=53



"saves the average family of four up to 17,000 gallons of water annually."
The family may be average but, with low flow or high flow faucets I doubt the average savings is anywhere near this high.  
The water wasted is that in ~50' of half-inch ID pipe, about a half gallon.  The family will be using about 100,000 gals/yr.

"Puffery as a legal term refers to promotional statements and claims that express subjective rather than objective views, which no "reasonable person" would take literally.[1] Puffery serves to "puff up" an exaggerated image of what is being described and is especially featured in testimonials."

I guess the "up to" is the operative term in the pitch and using a number gives this pitch an objective veneer.


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## nealtw (Apr 15, 2014)

Wuzzat? said:


> "saves the average family of four up to 17,000 gallons of water annually."
> The family may be average but, with low flow or high flow faucets I doubt the average savings is anywhere near this high.
> The water wasted is that in ~50' of half-inch ID pipe, about a half gallon.  The family will be using about 100,000 gals/yr.
> 
> ...


The numbers aren't mine but if it takes two gallons of water to get to hot, even with low flow it will still take  the same two gallons just slower. They sell  all systems with the idea of saving water which I like but the cost of continuesly heating that water can be expencive. The system I posted returns the cold water to the cold water line and shuts itself off and the other system which I haven't found yet works with a motion detector or a switch there by saving water and fuel. Plug in your own numbers, it works.


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## nealtw (Apr 15, 2014)

http://www.gothotwater.com/plumbing-installation/plumbing-layouts


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## havasu (Apr 15, 2014)

I do know that I watched my natural gas bill for the year prior to the installation and a year after the installation and saved an average of $20 a month after the install. That is $240 a year. Since the unit is now nearly 5 years old, it has nearly paid for itself, not to mention the $1500 tax credit in the initial tax year. I also use the recirc timer to turn on at 6 AM for morning showers, and again at 10 PM for nightly face washing, washing dishes, and occasional showers. Not a drop of water is wasted because the water just circulates within itself.


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## slownsteady (Apr 16, 2014)

> "Puffery as a legal term refers to promotional statements and claims that express subjective rather than objective views,



In other words, "Bullsh*t"


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## slownsteady (Apr 16, 2014)

havasu said:


> I do know that I watched my natural gas bill for the year prior to the installation and a year after the installation and saved an average of $20 a month after the install. That is $240 a year. Since the unit is now nearly 5 years old, it has nearly paid for itself, not to mention the $1500 tax credit in the initial tax year. I also use the recirc timer to turn on at 6 AM for morning showers, and again at 10 PM for nightly face washing, washing dishes, and occasional showers. Not a drop of water is wasted because the water just circulates within itself.



Why should it circulate at all? I thought the savings were achieved by instantly heating the water when needed. When you do your calculations on savings, you have to take the power to recirc into account.


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## Wuzzat? (Apr 16, 2014)

havasu said:


> I do know that I watched my natural gas bill for the year prior to the installation and a year after the installation and saved an average of $20 a month after the install. That is $240 a year. Since the unit is now nearly 5 years old, it has nearly paid for itself, not to mention the $1500 tax credit in the initial tax year. I also use the recirc timer to turn on at 6 AM for morning showers, and again at 10 PM for nightly face washing, washing dishes, and occasional showers. Not a drop of water is wasted because the water just circulates within itself.


My electric tank WH lost 250 BTU/hr (75w) through the insulated jacket.  At $1 per 100,000 BTU for NG I didn't think a tankless would ever pay for itself.


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## havasu (Apr 16, 2014)

slownsteady said:


> Why should it circulate at all? I thought the savings were achieved by instantly heating the water when needed. When you do your calculations on savings, you have to take the power to recirc into account.



Those little pumps, similar to the small Grunfos pumps, are so small, that there was no noticeable increase in power consumption. I have both of my bathrooms about 70' away, so without initial circulation, those 1/2" copper lines must first get warm and eliminate the cold water before achieving the warm water, unless the pump was first activated where the water would come out instant hot.


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