# Tankless HW heater



## Hippie (May 12, 2011)

I have an electric tankless water heater to hook up, it requires 3 separate 40 amp feeds. How do you guys do disconnects for these things? 3 breaker locks? I'm planning on running my 3 circuits in carflex across the crawlspace back to the panel, and I'm not sure what to do with it. Set a box and 3 disconnects? I've only done the gas ones before, 3 feeds seems weird to me


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## mbednarik (Oct 10, 2011)

6 space panel within sight of the water heater. That's how i would go about it.


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## Going_Commando (Oct 1, 2011)

3 40 amp feeds for a tankless? That seems just crazy! How are hose things the least bit cost effective in that configuration? Why not use a couple smaller tankless heaters instead?


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## BBQ (Nov 16, 2010)

Hippie said:


> I have an electric tankless water heater to hook up, it requires 3 separate 40 amp feeds. How do you guys do disconnects for these things? 3 breaker locks? I'm planning on running my 3 circuits in carflex across the crawlspace back to the panel, and I'm not sure what to do with it. Set a box and 3 disconnects? I've only done the gas ones before, 3 feeds seems weird to me


Don't forget that you will have to derate if you run it all in one carflex.


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## BBQ (Nov 16, 2010)

Going_Commando said:


> 3 40 amp feeds for a tankless? That seems just crazy! How are hose things the least bit cost effective in that configuration? Why not use a couple smaller tankless heaters instead?


They would never equal the capacity of the large unit.


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## bobelectric (Feb 24, 2007)

And they save money?


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## BBQ (Nov 16, 2010)

bobelectric said:


> And they save money?


They can becuse they only draw current when water is flowing.

They also regulate how much current based on how much flow. If you are only using a little hot water only some of the elements are energized.


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## Hippie (May 12, 2011)

mbednarik said:


> 6 space panel within sight of the water heater. That's how i would go about it.


I didn't consider that.. I'm not sure how much it actually draws at maximum but what would you feed the panel at? Would 100A be enough? All seems ridiculous for a water heater the size of a shoe box.


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## chicken steve (Mar 22, 2011)

Hippie said:


> I have an electric tankless water heater to hook up, it requires 3 separate 40 amp feeds. How do you guys do disconnects for these things? 3 breaker locks? I'm planning on running my 3 circuits in carflex across the crawlspace back to the panel, and I'm not sure what to do with it. Set a box and 3 disconnects? I've only done the gas ones before, 3 feeds seems weird to me


I just happen to be finishing up a 35KW Emax for a 9 unit joint in town


http://www.eemax.com/

we provided it's own 200A commercial serv drop from the street, all HD, down to a 200A MLO w/ 8 spaces, 4-50A 2pole brkrs, and of course a #8 bond from the unit to plummage.

you need a disco to comply w/422.30,424.72....but it can assume may different forms

~CS~


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## BBQ (Nov 16, 2010)

Hippie said:


> Would 100A be enough? All seems ridiculous for a water heater the size of a shoe box.


I seriously doubt it, but you just need the total heater KW times 1.25 to figure it out.

Keep in mind that if you do this the feeder to the panel will have to be a full sized one selected from the ampacity tables not the reduced sizes for services and main power feeders in dwelling units.


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## chicken steve (Mar 22, 2011)

The poco here is swapping the 15KW can for a 50KW

There are rates for spikes too

Maybe i just can't do the math, but i can't see these units saving much $$$ in a situation that would be near constant usuage.....

~CS~


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## BBQ (Nov 16, 2010)

chicken steve said:


> Maybe i just can't do the math, but i can't see these units saving much $$$ in a situation that would be near constant usuage.....


I would guess you are right, with continuous usage or close to it, it seems like a minimal if any savings.


In my own home I think it could save money as there are many hours of the day no one is home or are sleeping.


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## chicken steve (Mar 22, 2011)

I'm told these are more prevalent in _'energy sensitive'_ countries BBQ, for perhaps the very usage scenario you've made 

But the manufacturer, who i've spoken to, insists it's a cost savings in any situation

go figure....

~CS~


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## xlink (Mar 12, 2012)

chicken steve said:


> The poco here is swapping the 15KW can for a 50KW
> 
> There are rates for spikes too
> 
> ...


They can keep up with the demand if the use is constant. Your teenagers can stay in the shower all day and you still get a hot a hot shower at night. Good for commercial kitchens, too. 

They cost more to operate if you have teenagers who only get out of the shower when the hot water is gone.


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## Roger123 (Sep 23, 2007)

Is there any code language with reference to the tankless units?


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## BBQ (Nov 16, 2010)

chicken steve said:


> But the manufacturer, who i've spoken to, insists it's a cost savings in any situation
> 
> go figure....


Your whites will be brighter and your chickens will lay more eggs. :jester:


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## backstay (Feb 3, 2011)

Hippie said:


> I didn't consider that.. I'm not sure how much it actually draws at maximum but what would you feed the panel at? Would 100A be enough? All seems ridiculous for a water heater the size of a shoe box.


I did one (3-40 amp) and I think it was 20kw. You'll need a 125 amp panel. Also, the HOs weren't happy with it. They turned the temp higher than normal, then they would turn the hot and cold on in a ratio that drops the heater off for low flow(very little hot). That call back cost them.


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## Vintage Sounds (Oct 23, 2009)

chicken steve said:


> I'm told these are more prevalent in 'energy sensitive' countries BBQ, for perhaps the very usage scenario you've made
> 
> But the manufacturer, who i've spoken to, insists it's a cost savings in any situation
> 
> ...


With a tank style heater there are standby losses incurred while the tank full of hot water is just "sitting there". The element has to periodically turn on just to maintain the set point even if there is no immediate usage occurring. 

A tankless will only turn on when usage occurs.


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## BBQ (Nov 16, 2010)

Vintage Sounds said:


> A tankless will only turn on when usage occurs.


Right, but as Steve was pointing out if it is used often, as in a commercial setting there really is little storage time and the high cost of the units combined with the high cost of the instillation really make a bite into and savings under those conditions.

I believe they also have a problem with scale building up and reducing the efficiency greatly.


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## toolaholic (Aug 13, 2010)

*Want the real info on going tankless ??????*



chicken steve said:


> I'm told these are more prevalent in _'energy sensitive'_ countries BBQ, for perhaps the very usage scenario you've made
> 
> But the manufacturer, who i've spoken to, insists it's a cost savings in any situation
> 
> ...


 I'm a regular on www.ridgidforum.com See what Plumber Rick has written about tankless [gas]. Power outage NO HOT WATER! Can't run down to the supply house for parts. sounds like a jet engine on the side of Your house for Your neighbors. Have to do regular flushing on unit. Chances are Gas line has to be enlarged for mucho BTUS ,or unit will starve for gas. He put one in His own home to track $$ savings. Not worth it !!!!!!


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## Hippie (May 12, 2011)

BBQ said:


> I seriously doubt it, but you just need the total heater KW times 1.25 to figure it out.
> 
> Keep in mind that if you do this the feeder to the panel will have to be a full sized one selected from the ampacity tables not the reduced sizes for services and main power feeders in dwelling units.


This is a 27kw unit, /240 gives 112a x 1.25 ends up being a 150 amp panel... That seems weird to me.

I'm just running 3 circuits from the panel, 6 #8s are still good for 44 amps.. putting a box on the wall and 3 pullouts out of it I think cheaper and easier than a panel and all the breakers and wire. Also my supply house doesn't have 150 amp panels as a normal item. I just paid 100$ more for a 150a 3r homeline than I get the 200 amp ones for :l


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## chicken steve (Mar 22, 2011)

my install was 35Kw/240=145A, x 1.25=180 odd A

I'm told the units have multiple elements that are sequenced, and the plumber intends on a holding tank as a buffer

but i'm curious of it because it may get worked hard when 9 units hit peak H2O time

145A on an _across the line _ analog meter would be something to watch imho...

too bad it's all smart meters now, i used to like to watch the old wheel units and give ball parks on the draw, just for fun...~CS~


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## chicken steve (Mar 22, 2011)

Hippie said:


> This is a 27kw unit, /240 gives 112a x 1.25 ends up being a 150 amp panel... That seems weird to me.



so go 200A Hippie, the cost dif is minimal.......~CS~


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## BBQ (Nov 16, 2010)

Thinking on this more I may have screwed up, I don't think you have to go 125% as this is not a storage water heater.


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## Hippie (May 12, 2011)

I might end up getting a service upgrade out of this job as well, I was there today and they have electric heat also, only has 200 amp service... I could see them taking a shower while running the dryer or something and someone turns on a light and trips the main lol


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## Shockdoc (Mar 4, 2010)

I don't see where they fall into efficient, If I run a 50 gallon tank at 17 amps for about three hours I have 50 gallons of hot water made , now cycle about a half hour every couple of hours to stay hot. I just can't see how a unit that draws 130+ amps for a long shower, to fill a tub and run WM and DWs is more efficient.


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## Hippie (May 12, 2011)

I just can't get over the massive amount of power they need.. normal 200 amp services are not really designed for an extra 100 plus amp load even if it is intermittent.. If you're trying to save energy with the water heater why not just put a timer on the tank type so it doesn't run when no ones home?


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## donselec (May 7, 2011)

#8??? for a 200a service. should be a #4 shouldn't it


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## backstay (Feb 3, 2011)

donselec said:


> #8??? for a 200a service. should be a #4 shouldn't it


8's are for the feed to the heater off a 40 amp breaker.


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## Southeast Power (Jan 18, 2009)

I have a 21kw electric tankless only because someone gave it to me.
It hasnt saved me a dime. 
No one in there right mind could ever justify buying one and expect any kind of savings.

It wanted two 40 amp circuits, It got one 80 amp circuit and some blue wirenuts. Please dont ask for details. 
We all know how many and what size conductors will fit under a blue wirenut.:whistling2:


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## Hippie (May 12, 2011)

jrannis said:


> I have a 21kw electric tankless only because someone gave it to me.
> It hasnt saved me a dime.
> No one in there right mind could ever justify buying one and expect any kind of savings.
> 
> ...


Let me guess, #6 with 2 #10 tails?

That's what it would have gotten at my house anyway


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## A Little Short (Nov 11, 2010)

BBQ said:


> Thinking on this more I may have screwed up, I don't think you have to go 125% as this is not a storage water heater.


Correct! Tankless don't require the X 1.25.

BTW, by the time you even get close to your ROI, the parts are very near the end of their life. Scale does harm them if not flushed regularly.
Also, if you have very cold ground water feeding them it takes longer for them to heat up.

There isn't a plumber in these parts that will recommend an electric tankless, with the exception of maybe a small point of use one. Gas is a different story.


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## chicken steve (Mar 22, 2011)

BBQ said:


> Thinking on this more I may have screwed up, I don't think you have to go 125% as this is not a storage water heater.


BBQ , perhaps we are in part VIII of 424, not VII, see 424.82....~CS~


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## BBQ (Nov 16, 2010)

chicken steve said:


> BBQ , perhaps we are in part VIII of 424, not VII, see 424.82....~CS~


424 does not apply to water heaters.


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## chicken steve (Mar 22, 2011)

ok, then help a brother out BBQ....

~CS~


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## BBQ (Nov 16, 2010)

chicken steve said:


> ok, then help a brother out BBQ....
> 
> ~CS~


Don't creep me out with that union brother crap. :laughing:

Best I can tell we do not have to go 125% for tankless.

In 422 there is a requirement for 125% for storage water heaters but I don't find one for tankless.

Of course nothing prevents us from adding 25% for design reasons.


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## chicken steve (Mar 22, 2011)

C'mon BBQ, you're the code jedi here, i'm getting to be old news....

while i suppose the broader 3 hr rule might dumb it down to 100%, i'd like something more specific, thought i had it, maybe not?

~CS~


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## Dennis Alwon (May 9, 2009)

Look at 422.13


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## chicken steve (Mar 22, 2011)

Dennis Alwon said:


> Look at 422.13


thanks , but there's nothing _storage_ about these units Denny.....

~CS~


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## Dennis Alwon (May 9, 2009)

chicken steve said:


> thanks , but there's nothing _storage_ about these units Denny.....
> 
> ~CS~


Exactly that is why they don't need 125%. I thought that was what you were looking for. Didn't read the thread from the beginning sorry


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## chicken steve (Mar 22, 2011)

ok, what are your thoughts on 422.11(F) here?
~CS~


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## Dennis Alwon (May 9, 2009)

Not sure what you want to know but I see it as basically you cannot protect heating elements at over 60 amps. Every water heater I have seen that was a large kw had fuses inside the case of the water heater that subdivided the load.

48 amps is 80% of 60 which is why they chose that number


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## chicken steve (Mar 22, 2011)

I think i might have the largest unit this manufacturer sells, requiring a 50A brkrs for 4 individual 39A elements

I _still _sized the whole thing up 125%.....

~CS~


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## Roger123 (Sep 23, 2007)

BBQ said:


> Best I can tell we do not have to go 125% for tankless.
> 
> In 422 there is a requirement for 125% for storage water heaters but I don't find one for tankless.


That is why I asked in post #15. I couldn't find anything either.


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## Fredman (Dec 2, 2008)

xlink said:


> They can keep up with the demand if the use is constant. Your teenagers can stay in the shower all day and you still get a hot a hot shower at night. Good for commercial kitchens, too.
> 
> They cost more to operate if you have teenagers who only get out of the shower when the hot water is gone.


:laughing:

That's my kids. They'd wait till the elements burn.


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## bobelectric (Feb 24, 2007)

Did a single point of use sink,30 amp 120 volt. Plumber said "I have to put in a flow restrictor".There is your savings...


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## Southeast Power (Jan 18, 2009)

Hippie said:


> Let me guess, #6 with 2 #10 tails?
> 
> That's what it would have gotten at my house anyway


It kinda evolved.
I just intended to only connect one element, so just threw in a piece of #8.

The experiment ended up requiring a temporary connection of the #8 to both of the elements.
Then an 80 amp breaker appeared. 

I am still collecting data on this experiment.


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## Louieb (Mar 19, 2007)

Seems like some super dishwasher booster to me... how hot do these run? my guess is 422.11(F)(3)


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## Hippie (May 12, 2011)

So I got a call today that the water isn't getting hot enough. I told them to make sure all the breakers were on and check the temp adjustment knob.. I wasn't able to test it when I wired it because its the customers second home and the water was shut off for the winter. 

The only thing I can think is maybe I mixed up my wires coming in and landed the same phase on 2 of the elements? It's getting warm but not hot. Im 99% sure its wired right but that's the only possibility I can think of. Going to look at it Monday, is there something I might be missing here?

Install errors aside is it possible it just doesn't work good? It's 28kw that should be enough to heat water for the flow from a tap or shower in a house I would think


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## Southeast Power (Jan 18, 2009)

Hippie said:


> So I got a call today that the water isn't getting hot enough. I told them to make sure all the breakers were on and check the temp adjustment knob.. I wasn't able to test it when I wired it because its the customers second home and the water was shut off for the winter.
> 
> The only thing I can think is maybe I mixed up my wires coming in and landed the same phase on 2 of the elements? It's getting warm but not hot. Im 99% sure its wired right but that's the only possibility I can think of. Going to look at it Monday, is there something I might be missing here?
> 
> Install errors aside is it possible it just doesn't work good? It's 28kw that should be enough to heat water for the flow from a tap or shower in a house I would think


I have found that about 1/3 of them lose an element during the first three months or so of operation.
I hate them.


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## A Little Short (Nov 11, 2010)

Hippie said:


> So I got a call today that the water isn't getting hot enough. I told them to make sure all the breakers were on and check the temp adjustment knob.. I wasn't able to test it when I wired it because its the customers second home and the water was shut off for the winter.
> 
> The only thing I can think is maybe I mixed up my wires coming in and landed the same phase on 2 of the elements? It's getting warm but not hot. Im 99% sure its wired right but that's the only possibility I can think of. Going to look at it Monday, is there something I might be missing here?
> 
> Install errors aside is it possible it just doesn't work good? It's 28kw that should be enough to heat water for the flow from a tap or shower in a house I would think


Someone already mentioned it, but you probably need a flow reducer.
On some I have even read in the instructions to put in a ball valve between the unit and the faucet. It said anywhere else and it wouldn't help.









Idea is to keep the water in the unit longer so that it can heat better.

I also warned you in an earlier post about the electric units....not good!:no:


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## Hippie (May 12, 2011)

Yeah and I have heard bad things about them from other people.. Wasn't really expecting problems with it though. All I did was wire it I didn't size it or choose the unit. It's made by Bosch if that makes a difference. The house has city water not sure what the flow is like since it wasn't on when I was there. I have a hard time believing I wired it wrong but it is possible.

Voltage in the panel was good, 125/250 its maybe 50 feet of #8 copper per element so I can't see that being the problem


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## woodchuck2 (Sep 18, 2009)

I have never wired one for electric and i have talked people out of it before. I always push for a propane on demand unit. They are getting to be used more and more around here. In fact my brother in law yanked out the oil burning heating system in his parents house several yrs ago. He replaced it with a propane on demand unit that heats the domestic hot water and 3 other heat zones for the house. His parents installed a 500 gallon propane tank and joined an energy CO OP for cheaper propane. They claim they went from costing anywhere from $3k-$4k a yr for heat oil down to about $600 a yr in propane. The unit is very small and mounts on the wall so they were able to get rid of the fuel barrel and boiler giving them more room on the basement.


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## A Little Short (Nov 11, 2010)

Hippie said:


> Yeah and I have heard bad things about them from other people.. Wasn't really expecting problems with it though. All I did was wire it I didn't size it or choose the unit. It's made by Bosch if that makes a difference. The house has city water not sure what the flow is like since it wasn't on when I was there. I have a hard time believing I wired it wrong but it is possible.
> 
> Voltage in the panel was good, 125/250 its maybe 50 feet of #8 copper per element so I can't see that being the problem


I don't think you wired it wrong either, but it would be easy to check.

As I said earlier, have the plumber install the valve I posted.:thumbsup:


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## BBQ (Nov 16, 2010)

Little-Lectric said:


> As I said earlier, have the plumber install the valve I posted.:thumbsup:


Why not just use a flow control valve, they sell them at HD for less than $10.00. I use them on my tankless at home.


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## Hippie (May 12, 2011)

Well it turned out to be a bad unit or else they damaged it somehow when installing or turning it on. 

When I went out I found 2 sets of elements weren't getting power. Reset one of the thermal cutouts and went to check water, it was steaming hot at full flow. Let it run 10 minutes and figured it was good, I go back downstairs to put the cover back on and it was tripped out again. I reset it, tripped again. Found it was trying to run one of the elements with no water flowing causing overheating.. spent an hour + on the phone with very rude foreign tech support guy who did nothing more than get me to ohm out the elements and then proclaimed it a lemon. They're supposed to send a new one and a return shipping label.


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## chicken steve (Mar 22, 2011)

So over a year later , with hot h20 bills from an exclusive 200A serv drop averaging $600 mo., and multiple tenants screaming '_no  hot h2o_' , we're being asked to meet with the plumber to discuss options. 

I swear, no good energy retro goes unpunished....:no:~CS~:whistling2:


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## nrp3 (Jan 24, 2009)

Good deal, you can get paid to do it again.


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## macmikeman (Jan 23, 2007)

Gas.


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## chicken steve (Mar 22, 2011)

When one resides in a state as green as mine, one is subject to all manner of predatory energy gurus. 

They do a fine job of selling what they have based on an _expected ROI_, but all long gone dust cleared when _'reality ROI'_ rears it's ugly head

~CS~


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## MTW (Aug 28, 2013)

BBQ said:


> Why not just use a flow control valve, they sell them at HD for less than $10.00. I use them on my tankless at home.


Good idea BBQ. :whistling2::laughing:


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## McClary’s Electrical (Feb 21, 2009)

MTW said:


> Good idea BBQ. :whistling2::laughing:


I miss that dude. ....


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## five.five-six (Apr 9, 2013)

toolaholic said:


> I'm a regular on www.ridgidforum.com See what Plumber Rick has written about tankless [gas]. Power outage NO HOT WATER! Can't run down to the supply house for parts. sounds like a jet engine on the side of Your house for Your neighbors. Have to do regular flushing on unit. *Chances are Gas line has to be enlarged for mucho BTUS* ,or unit will starve for gas. He put one in His own home to track $$ savings. Not worth it !!!!!!


YES. I put one in my last house and as a result, I learned how to do isometric drawings of a gas system.


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## five.five-six (Apr 9, 2013)

chicken steve said:


> When one resides in a state as green as mine, one is subject to all manner of predatory energy gurus.
> 
> They do a fine job of selling what they have based on an _expected ROI_, but all long gone dust cleared when _'reality ROI'_ rears it's ugly head
> 
> ~CS~


Electric water-heaters, and cars for that mater aren't "green". Not in the least. They are about 50% coal fire powered.


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## Shockdoc (Mar 4, 2010)

I'm wondering if I did a goof a while back. I encountered a HW tank having two sets of 30 amp leads. I installed a 60 amp circuit and tied it to both.


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## bobelectric (Feb 24, 2007)

The only thing I see coming with these electric tankless water heaters are the smart meters when they start doing peak demand charges. Thats when my 4.5 kw tank becomes 3.5 kw.


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## A Little Short (Nov 11, 2010)

Shockdoc said:


> I'm wondering if I did a goof a while back. I encountered a HW tank having two sets of 30 amp leads. I installed a 60 amp circuit and tied it to both.


The ones I see that are more than 40A all require two circuits.


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## xpertpc (Oct 11, 2012)

> Originally Posted by Shockdoc View Post
> I'm wondering if I did a goof a while back. I encountered a HW tank having two sets of 30 amp leads. I installed a 60 amp circuit and tied it to both.





A Little Short said:


> The ones I see that are more than 40A all require two circuits.


I think Doc was being facetious -


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## A Little Short (Nov 11, 2010)

xpertpc said:


> I think Doc was being facetious -


Naw....me or him neither one knows what that means!:jester::laughing:


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## Shockdoc (Mar 4, 2010)

xpertpc said:


> I think Doc was being facetious -


No i did that back in 06'. Original install only had one 30 amp circuit with no disconnect. I had 6/2 on board so i used it .


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## xpertpc (Oct 11, 2012)

I'll throw my 2 cents on the tank-less heaters since I've had one for about 4 years now.

My first one was a Rheem RTE 13 kw ($220), required a 240v 60amp circuit, I pulled 50 feet of 6/3 and think it cost me $150 just in wire, but needed a new subpanel there anyways.

It worked very good, the electronics caused the house lights to flicker very faintly but noticeable. Last year during a remodel I decided to see if this unit could be powered up while immersed in water - it did not pass. everything was electronic including the flow control.

I replaced it with one I got from ebay for $134, it too works well. The good side is it has no electronics just switches, the downside is it seems to take a little more water flow to turn on, spec says 0.5 gpm but is really closer to 1 gpm with no adjustments. this means no low flow streams from a faucet.

Right now my street water is at 48F and with the unit on the highest setting #5 (1-5) I get 115F water at my sink. In the summer and fall I had to keep it at #3 or it would peel your skin off.

I save between $10 to $15 a month based on my wireless amp probes that connect to my computers trending software. Most of the savings came from replacing an older water heater that only had R5 insulation.

I did buy a new R16 insulated 30 gallon water heater for my floor heating system and calculated the recovery heat loss at 115F to be about $2 a month, which should also be close if I used this tank for my domestic water system too.

I am 1 person and this heater is intended for point of use but have it as my whole house heater, I would never pay $600 for a 200 amp toaster (only have 100a anyways). My tests only uses the ideal shower temperature of 115F.

The most important factor to keep in mind is Newtons's law of cooling which simply states that the larger the temperature difference the faster the heat loss. Keeping a water tank at 140F will result in using considerably more energy than keeping at 115F.


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## Circuit Tracer (Feb 5, 2015)

Some things look good on paper... that's all. ; )


Mike


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## xpertpc (Oct 11, 2012)

Circuit Tracer said:


> Some things look good on paper... that's all. ; )
> 
> 
> Mike


Which is why I always use real world tests and equipment to trend the results over long periods of time. As I have said in other threads I have 5 different types of wattmeters, 2 of which are wireless amp clamps in my Breaker panel with one connected to my network and feeds a computer spreadsheet.

All my tests have been done over a sufficient amount of time to get real world usage over differing demand scenarios. I never trust what the manufacture say with their bloated numbers.


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## Circuit Tracer (Feb 5, 2015)

That's very interesting that you track everything. 

Mike


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