# Swaping out indirect for electric tankless WH



## senorFrog (Sep 24, 2007)

I have a ~ 15 year old indirect hot water heater off my oil fired boiler.  It seems to kick the boiler on more frequently than the heating system does in the winter.  In the summer we hardly hear from it.  I made a number of improvements last year to reduce my oil usage: insulate attic with R-30, insulate crawl space under kitchen and breakfast nook with R-30, vapor barrier in crawl space and the addition of my wood stove.    I was considering swapping the WH out for one of these...

http://www.plumbersurplus.com/Search.aspx?search=Stiebel+Eltron+Tempra

They seem to be reasonably priced.  Anyone know anything about these?  BTW, no gas, only electric here.


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## thephotohound (Sep 24, 2007)

I will be eagerly watching the responses to this thread, as I have the same setup and am considering a similar change. Could anyone also comment on going to an electric tank? Also, if I get an electric tank system, can this be hooked up to solar panels down the road?


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## titan (Sep 24, 2007)

I've only seen these tankless heaters installed in apartments and small condos.They likely serve their purpose in such a setting but would they meet the hot h2o demands of a family or my wife and her wasteful,oversized jet-tub?


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## senorFrog (Sep 24, 2007)

They're made in germany and a respectable brand and supposedly the larger models 29 & 36 will service a whole house.  

http://www.stiebel-eltron-usa.com/

I'd still like to get more info.  The lower price makes it easier to swallow than a Rinnai.


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## velvetfoot (Sep 24, 2007)

If you hardly hear from it during the summer, what good would switching it out do?


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## Highbeam (Sep 24, 2007)

The power supply for these things must be huge. The wire to carry the huge load can be 3$ a foot at the HD. It takes a lot of energy to heat water on an as-needed basis. My guess is 40 amps of 220 power, say 10,000 watts. What do the manuals say.


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## Eric Johnson (Sep 24, 2007)

You might want to check out this forum and see what the pros say. My guess is they'll recommend sticking with the indirect, but who knows?

http://forums.invision.net/index.cfm?CFApp=2l.


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## velvetfoot (Sep 24, 2007)

That's a nice site, Eric.
I just read one topic on using a snow melt system for a deck.
They didn't seem to go for it too much, but I could see a real application for a circulating loop to loosen up the ice on my back deck, 'cause the ice freezes in big heavy lumps after it slides off the roof.

Sorry for the thread hijack.  Back on topic.


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## senorFrog (Sep 24, 2007)

I called them up earlier today.  They're based in good ol MASS.  You need 200A service for al models with the exception of the 36 which is the largest and requires 300A service.  I'll have to replace my hot water heater soon anyways as it's getting near end of life.  A new indirect not installed will be about $1200 for an Amtrol boilermate.



> If you hardly hear from it during the summer, what good would switching it out do?



Well, because it seems like it's kicking the boiler on every couple hours in the winter.  Which means lot's of oil being burned for naught.  There is more to the story, the basement is small and short as the house is approx 200 years old.  The current WH is underneath the basement staircase and inaccessible for maintenance.  A unit like this would be nice because it's very small and I could locate it practically anywhere.  On their website they say like 15-20% more efficient than an electric heater.  About half the cost of a indirect WH.  Still, I'd feel better if I could find some real world feedback from an end user located in New England, or other cold climate.


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## velvetfoot (Sep 24, 2007)

But doesn't winter use put the heating system into the mix, whereas in summer its all hot water?
What are the symptoms of your current system being at the end of its life?
How do you know it's the hot water zone that's driving the boiler activity in winter?  
I'd look at your fuel oil use during the summer and see what that looks like.
This is all pretty subjective.


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## senorFrog (Sep 24, 2007)

In the winter, even when I have my heating system turned off because I'm using the woodstove, the boiler will still kick on frequently to heat up the hot water heater.  The WH is on a separate zone.  The WH is at the end of life because I can see some leakage.


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## Bill (Sep 25, 2007)

I have the Bosch on demand water heater, natural gas. By the way you can vent them through basement walls. It dropped my gas bill by $15.00 per month. It can blow steam out of the pipes and my wife has a whirlpool tub, you never run out of water. The big savings is from only heating water when you need it. They have used these water heaters in Italy for many years. Another advantage is they take up very little room. But they are not cheap.


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## jjbaer (Sep 25, 2007)

Cheapest way to get hot water (if you use electric) is to get, say, a 30 gal elec HW heater and hook it to a timer or manually activate it. You know when you're going to need hot water so about 45 min before you need it, you turn on the current and bring the 60F water up to about 110F. This costs a whopping 42 cents or about $13/month. It gives you 30 gallons of 110F water, enough to take a quick shower and do some dishes and other stuff but it only works well if you don't demand hot water all the time.

Even cheaper: if you have a power vent Nat Gas HW heater. These will only run if the logic circuit senses that the blower fan has been turned on and these fans run on 120v so they're a good candidate to plug into a cheap, electronic timer. You program the timer to come on at a set time, run for about 30 min and then power off. This gives you a full tank of hot water and you've used NG (which around me is cheaper than electric). The same 30 gal tank will cost about 20 cents or $6/month to run! I have such a power vent model and put a timer on it and then when my wife tried to shower at a different time I got a call at work asking "why is the water warm" (now you see why it works best with guys...........LOL.....) but, electronic timers allow multiple settings so one could program it to come on twice during the day and still only pay $12/month.

Bottom line:  some of what we pay for hot water goes to waste.  The two culprits (most important first) are: 1) just keeping the water hot even when you're not using hot water (this is about 30-60% of your bill) and 2) running water at a remote faucet until hot water flows.


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## Eric Johnson (Sep 25, 2007)

If I didn't heat my hot water with wood, cast, I'd be all over this. As usual, good advice when it comes to things electrical.

I understand #2, but are you saying that it's more efficient to heat cold water on demand rather than keeping hot water hot? True with all fuel sources? And if so, is there a practical amount of insulation on the tank that could balance out the equation?


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## WarmGuy (Sep 25, 2007)

We've had a tankless propane water heater for two years, and I highly recommend it.  It's dropped our propane usage enough that we only need to buy propane once/year, in the summer when prices are low.  $1700 installed, and with propane prices at $2.42/gal, expect full payback in another year or two.

I was worried that it wouldn't keep up when, say, two people are using hot water at the same time, but that has never been a problem.

But, here's the main disadvantage: with a tank water heater, hot water diffuses into the pipes, so when you turn on the tap, it's not long before you get hot water.  With the tankless, you've got cold until the water travels the full distance.  For some of our faucets, this means a two minute wait.  That's annoying if you just want to wash your hands, or if you pay a lot for water.


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## jjbaer (Sep 25, 2007)

Eric Johnson said:
			
		

> If I didn't heat my hot water with wood, cast, I'd be all over this. As usual, good advice when it comes to things electrical.
> 
> I understand #2, but are you saying that it's more efficient to heat cold water on demand rather than keeping hot water hot? True with all fuel sources? And if so, is there a practical amount of insulation on the tank that could balance out the equation?



No, all I'm saying is that before I'd spend beaucoup $ on one of those "on demand" tanks that could cost several hundred dollars, I'd use "operational tactics" on my existing heater that cost nothing to implement and actually saves you $.  My hot water heater is 50 gallons.  If I fire it up from cold (60F) up to about 110F, it costs me about 34 cents/day for hot water or $10/month:

50 gal x 8 lb/gal x 50F rise x 1BTU/lb/deg F x $1.20/100,000 BTU gas x 1/.7 efficiency = 34 cents/day = $ 10/month

This assumes only about 2 quick showers and whatever is left can be used for laundry or do cold washes and, if you wanted REAL luxuary, you could do two tankfuls (100 gal of hot water) at 68 cents/day for a whopping NG bill of $20/month for 100 gallons.  This only works on a power vent model where you can prevent the fan from coming on (until you need it) and therefore no NG is used until you need it.  Harder to do if you have a pilot because then you'd have to do it manually by dialing down the thermostat or re-liting the pilot which could be a PITA.  For electric at 13c/KW-hr, one 50 gal tank of hot water costs 76 cents/day or $23/month but with elec you'd have to either put a timer on it (hard to do) or use the breaker as a switch (not what it's intended for) or dial down the thermostat after you achieve a hot tank.


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## drizler (Sep 25, 2007)

Just how cheap is the electricity in your area???   Where we are it's more expensive than Germany, literally.     I have the same basic rig you do with a Weil Mclain storage tank about that old.   I just leave it set at its lowest setting and in the summer months we just turn it on once a day to heat up the 40 gallons.     One thing I did to make it easier to do this was ad a remote thermometer.   All it is amounts to a  $10 Lowes  indoor outdoor thermometer with some 22 gauge wire soldered on to make the lead 40' long instead of 6'.   I just opened up the top of the insulation capsuel on the tank and slid  the probe down and pressed it onto the top of the tank and covered it all up again.    Precision HVAC it aint but it tells me if I have 110F water  which is enough for a shower.   The wimmin think differently  but anyways it works for us.     This season for the winter I am going to super insulate the tank by wrapping it with insulation and setting the tank up on a piece of 2" styrafoam insulation rather than its cinder blocks.       
    For me its hard to believe how any electric rig could save you anything.     As for your tank being shot have you considered changing your boiler back over by installing the heating coil so it works more or less like an on demand unit?  That should be pretty cheap and not require much changing over.    Then you can just fire it off as you need water hot water.      I plan on doing that when mine goes kaput as my Kraut wife says.    BTW you don't find many Germans using electricity to heat their hot water.   Unless its a tiny studio apartment they use the boiler just like you do.   Its metered by each tenants usage and billed accordingly.     In this of course I am no plumber or hvac guy, just someone who has had a similar setup a long time.   In any event there just has to be a more efficient system for you than the dreaded electricity monster.


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## KeithO (Sep 26, 2007)

The right way to use the tankless systems is to have them installed in the bathroom.  No waiting for the water to get hot and no pouring water down the drain.  In Europe, many have combusters that can be modulated to cover a wide range in heat demand.   The main unit in the house is typically tied to the central hot water heating system.  Nobody likes a cold bathroom in winter and with the unit running more frequently in winter it is a nice way to keep the bathroom and towels dry and warm.

See this site for a lot of info on these modulating NG / Propane tankless heaters: http://www.aimradiantheating.com/store/boilers.html  Modern units are really small and easy to fit in modern homes.  There is something screwy with their prices for the "boiler in the box" systems (over $1Bn ?).  Just give them a call or email.



			
				WarmGuy said:
			
		

> We've had a tankless propane water heater for two years, and I highly recommend it.  It's dropped our propane usage enough that we only need to buy propane once/year, in the summer when prices are low.  $1700 installed, and with propane prices at $2.42/gal, expect full payback in another year or two.
> 
> I was worried that it wouldn't keep up when, say, two people are using hot water at the same time, but that has never been a problem.
> 
> But, here's the main disadvantage: with a tank water heater, hot water diffuses into the pipes, so when you turn on the tap, it's not long before you get hot water.  With the tankless, you've got cold until the water travels the full distance.  For some of our faucets, this means a two minute wait.  That's annoying if you just want to wash your hands, or if you pay a lot for water.


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## keyman512us (Sep 26, 2007)

senorFrog said:
			
		

> I have a ~ 15 year old indirect hot water heater off my oil fired boiler.  It seems to kick the boiler on more frequently than the heating system does in the winter.  In the summer we hardly hear from it.  I made a number of improvements last year to reduce my oil usage: insulate attic with R-30, insulate crawl space under kitchen and breakfast nook with R-30, vapor barrier in crawl space and the addition of my wood stove.    I was considering swapping the WH out for one of these...
> 
> http://www.plumbersurplus.com/Search.aspx?search=Stiebel+Eltron+Tempra
> 
> They seem to be reasonably priced.  Anyone know anything about these?  BTW, no gas, only electric here.



Err Umm...If you do install that gizzmo...let me know...

I would like to buy the old indirect...lol  :ahhh:


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## jjbaer (Sep 26, 2007)

Driz said:
			
		

> Just how cheap is the electricity in your area???   Where we are it's more expensive than Germany, literally.     I have the same basic rig you do with a Weil Mclain storage tank about that old.   I just leave it set at its lowest setting and in the summer months we just turn it on once a day to heat up the 40 gallons......For me its hard to believe how any electric rig could save you anything.



I know this wasn't asked of me but if you only use energy to heat one, 40 gallon tank of water and you only do it once a day, even electricity is cheap.  Here's the calculation to raise 40 gallons of water from 60F to 115F using electricity.  Don't know what your electric rates are but this link

http://www.nyseg.com/SuppliersAndPartners/2007EstFixedElecSupplyPrices/residential.html

says they are about 10cents/KW-HR.....is that wrong since you said your rates are higher than in GE????  Anyway, assume a high value of 15 cents/KW-HR

40 gal x 8.3 lb/gal x 50F rise x 1BTU/lb/deg F x KW-HR/3,412 BTU x $0.15/KW-HR =  73 cents/day  = $22/month which is minimial to say the least....

if your rates are more like the 10 cents/KW-hr that the link suggests, then your cost is about 50 cents/day or $15/month......


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## cbrodsky (Sep 27, 2007)

Personally, I think electric "on-demand" water is a terrible thing for the power grid - and as time-of-day metering comes into common practice, the value proposition for these devices will go down the tubes.  It's coming... the market is going to drive it.  With gas/propane, you could argue that it's not quite as bad assuming you aren't overloading the distribution network - which is probably less likely w/local propane storage.

For the money people are spending on some of these tankless systems, they'd be well on their way towards a solar HW system which could be coupled to an oil heater for winter backup, or a single electric element inside the highly insulated solar tank.  It's remarkable how well it holds the heat compared to a typical $250 hot water heater.

These electric demand heaters are far from "green" IMHO, and a well-insulated tank (solar or elec powered) running with a timer for night-only charging using readily available and underuitilized power is a much better solution for the grid and your long-term cost of ownership.

-Colin


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## jjbaer (Sep 28, 2007)

Here's more "food for thought".  Let's say you'll spend $1,000 getting one of these tankless units installed.  If you put that same $1,000 in the bank instead and get, say, 4.5% after taxes, thats $45/year you've saved.  If you do the "30 gallon one-tank of hot water once per day" thing I spoke about, this $45 covers almost 5 months of free hot water.........6 months if you use natural gas......

Side note:  these tankless heaters have been in use in Europe for well over 25 years so the technology has been perfected on them long ago.


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## backpack09 (Sep 28, 2007)

On my last trip to the HD I took a look at my options in heaters.  Up on the wall they had a savings chart.  To use the tankless electric rather than my 80 gal tanked electric heater, it would actually cost me more than currently.  

The only way you can save with the tankless is to use propane or gas more BTUs per buck than electric. Unfortunately gas heat is a big ole  :gulp: in my $$book.


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## cbrodsky (Sep 28, 2007)

castiron said:
			
		

> Here's more "food for thought".  Let's say you'll spend $1,000 getting one of these tankless units installed.  If you put that same $1,000 in the bank instead and get, say, 4.5% after taxes, thats $45/year you've saved.  If you do the "30 gallon one-tank of hot water once per day" thing I spoke about, this $45 covers almost 5 months of free hot water.........6 months if you use natural gas......
> 
> Side note:  these tankless heaters have been in use in Europe for well over 25 years so the technology has been perfected on them long ago.



You're right and a lot of people think too much about payback in years, versus payback as a ROI compared to their alternatives.  To be strictly correct, you'd also need to account for energy price inflation as you project out your avoided costs in future years with an energy savings device (or deflation depending on your belief...) and account for this over the life of the improvement.  An assumption of 5% inflation starts to impact the numbers as you go into this calculation for a few years.

You also hit a point that I think people often fail to recognize - the power of the "tax-free" ROI they get when saving energy.

If I buy a $1000 "safe" investment like a CD, then I pay income tax on the interest.  That 5% rate could drop to 3% after taxes - or $30 take-home/year.  But if I invest that $1000 into an energy improvement, and I save $50/year on my energy, that's saving $50 of my take-home after tax pay.  You have to compare your % ROI to whatever after-tax return you'd get on alternative investments when deciding if it makes sense.

Throw 5% inflation into this example, and by the end of the 10th year, you're now making ~$81 tax free in avoided energy costs out of your take-home pay, or 8.1% return for that year, while your bank is still paying you 3% on the $1000 CD.

The other way some people look at large energy investments is as an inflation hedge.  I personally think that peak electric costs could spike tremendously in the coming decade as carbon taxing, peak metering and the high cost of adding peak power capacity all conspire to end cheap power for many of our needs.  It may or may not happen, but I would like to "insure" myself against any surprises.  I could buy futures contracts to acquire power in the future at today's prices, or today's prices plus some inflation assumption.  The money that would have been spent on those options or fixed price contracts could instead be worked into my energy improvements that I find more fun than trading options - and either case may or may not pay off depending on what happens in the world.  Of course lots of people in the northeast do this indirectly by signing up to fixed price heating contracts, sometimes with float options, and along the way, options traders are skimming a nice chunk of profits on this activity.  Not every year, but like in Vegas, the house always wins in the long run 

-Colin


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## Bill (Oct 1, 2007)

As fuel prices rise energy efficient appliances become a better value, there also are tax credits for this type of appliance, to help offset the cost. Energy conservation is more than just saving money.


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## KeithO (Oct 1, 2007)

I think the primary benefit of the tankless heater of any kind is that you don't pay to keep the water hot for 95% of the time when you don't need it.   The same way that having a programmable thermostat saves on heating bills, so will having a tankless water heater.  If the holding tanks of most water heaters was simply better insulated, it would help in this regards, but anytime a temperature differential exists heat is going to flow.

I personally think that electric water heaters suck, every variety of them.   The heating elements have a relatively small surface area and are very succeptible to degradation by disolved minerals in the water.   Furthermore, having any electrical device that potentially is going to draw as much current as a welder and that is going to kick on and off every time it is used is not going to be good for the life of other electronic devices in the home.  I'll bet the lights dim when one of those beasties kicks in.  Lets also not forget that in emergency situations your "dead in the water" again with no heat, or running a "big" generator 24/7.

Another thing worthy of consideration is that when you use a storage type water heater (particularly if it has limited storage), once you start drawing hot water, it causes cold water to flow into the heater immediately.  This is one of the factors that limits "available hot water" to far less than the volume of the storage tank itself.  If you use 50% of the volume you now have only luke warm water (like filling a bathtub).


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## cbrodsky (Oct 2, 2007)

KeithO said:
			
		

> I think the primary benefit of the tankless heater of any kind is that you don't pay to keep the water hot for 95% of the time when you don't need it.   The same way that having a programmable thermostat saves on heating bills, so will having a tankless water heater.  If the holding tanks of most water heaters was simply better insulated, it would help in this regards, but anytime a temperature differential exists heat is going to flow.
> 
> I personally think that electric water heaters suck, every variety of them.   The heating elements have a relatively small surface area and are very succeptible to degradation by disolved minerals in the water.   Furthermore, having any electrical device that potentially is going to draw as much current as a welder and that is going to kick on and off every time it is used is not going to be good for the life of other electronic devices in the home.  I'll bet the lights dim when one of those beasties kicks in.  Lets also not forget that in emergency situations your "dead in the water" again with no heat, or running a "big" generator 24/7.
> 
> Another thing worthy of consideration is that when you use a storage type water heater (particularly if it has limited storage), once you start drawing hot water, it causes cold water to flow into the heater immediately.  This is one of the factors that limits "available hot water" to far less than the volume of the storage tank itself.  If you use 50% of the volume you now have only luke warm water (like filling a bathtub).



I think a lot of these are hand-waving arguments from companies looking to see tankless heaters.

It all comes down to how well you insulate the tank, and it's much much easier to insulate an electric tank as compared to a house, thus the thermostat argument is a bit different.  A $200 special at HD will probably be junk, but a tank with $20 of extra insulation will be a great solution.  Solar storage tanks are a good example of just how well a hot water heater can hold heat for long periods right out of the box.  And of course when that overnight electric cost is 1/2 what the day cost is, you're so far ahead of the game that you can't lose - you may only run 90% overall efficiency vs. 95% in tankless, but that doesn't matter when you're using half-price surplus power readily available on the grid.  Granted, not everyone has time of day metering, but this is the future.  Peak demand power will only become more and more costly so all those "instant" electric heaters will become expensive boat anchors.  The gas powered heaters aren't such a bad idea since they're immune to these cases, but I think the electric examples are a disaster for the grid and a very poor choice for people who are interested in green solutions.  There is nothing green about throwing up new peak demand plants (unless they're on your roof) and new power transmission lines to support tankless heater surges.

As for lights dimming, that means you've got a wiring or home supply voltage problem... and having three tankless units all kick on when three people showering sure isn't going to be a pretty sight if you can't supply the hot water tank, much less baking a roast in the oven 

Finally, water tanks have phenomenal stratification capability - I can draw far more than 50% of my tank at "hot" temperatures.  In fact, having it connected to a solar hot water generation system pushes this to an extreme - it is easy to maintain 40 degree differences between the top and bottom of the tank for hours even with active heating circulation drawing off the bottom and returning to the top.

Had I not gone w/solar HW, I would have transitioned to a highly insulated 120 gal electric tank running off an overnight heating timer - this would have still put me quite a bit ahead of an oil-fired tankless coil.

-Colin

ps - from American Council for an Energy Efficient Economy:

Demand water heaters with enough capacity to meet household needs are gas- or propane-fired; electric tankless water heaters are seldom a good idea.


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## velvetfoot (Oct 2, 2007)

Not that it matters that much, but in winter, heat loss to the house might not be a totally bad thing.


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## KeithO (Oct 2, 2007)

I have about 50ft of plumbing between my hot water heater and the master bathroom.  Before I put a circulation pump on it, it would easily take 5 minutes of running the hot water in the bathroom to get to an acceptable temperature, which requies both getting the cold water out the pipes and heating all of the plumbing.   Since I have the circulation pump on (thermostatically activated), it has increased my hot water bill significantly, and of course it is useful heat in winter, but the no free lunch rule still applies.  In summer I use a timer to turn the circulation pump on and off to have hot water for showering in the mornings.   

The decider for me will be whether or not I put radiant heating in the basement.  If I do that it would pay me to get a modulating tankless heater that runs full time at the appropriate level and a second for the remote bathrooms.  It will take up less space and be quieter than the current water heater and adapt to the demand for heating better (slow steady output fits the heating load better).


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## cbrodsky (Oct 3, 2007)

KeithO said:
			
		

> I have about 50ft of plumbing between my hot water heater and the master bathroom.  Before I put a circulation pump on it, it would easily take 5 minutes of running the hot water in the bathroom to get to an acceptable temperature, which requies both getting the cold water out the pipes and heating all of the plumbing.   Since I have the circulation pump on (thermostatically activated), it has increased my hot water bill significantly, and of course it is useful heat in winter, but the no free lunch rule still applies.  In summer I use a timer to turn the circulation pump on and off to have hot water for showering in the mornings.
> 
> The decider for me will be whether or not I put radiant heating in the basement.  If I do that it would pay me to get a modulating tankless heater that runs full time at the appropriate level and a second for the remote bathrooms.  It will take up less space and be quieter than the current water heater and adapt to the demand for heating better (slow steady output fits the heating load better).



We have a similar issue going to the solar HW tank.  Interestingly, there was another thread on that subject recently where people were claiming those thermostatic recirculators save money... 

Depending on the system, perhaps you can interface a wireless switch.  We installed a TACO on-demand unit that has been going for about $40 on e-bay all summer.  I don't see any at the moment, but they have been coming up regularly.  They also make a wireless switch kit so you don't have to drop a wire.  It looks like a doorbell - just push when you wake up or get ready to run some dishes and it brings the water up in a fraction of the time, only when needed.

-Colin


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## eba1225 (Oct 18, 2007)

I had looked at this too but once I saw the electric demand decided that it was not the way to go, although I do have 200A service.  It chews up alot of electric.  The gas models on the other hand look to be much more economical.  I get my hot water from a coil that is run in my furnace, and yes it goes on from time to time just to maintain.

I am considering placing my furnace on a timer during the summer months so that it does not run when not needed.

Erik


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## Nofossil (Oct 19, 2007)

People I know with propane / NG tankless heaters love them. Never running out of hot water combined with lower monthly cost is pretty attractive. Some folks justify it on the basis that they can afford it now, and if things get bad in the future, their monthly fixed costs will be lower.

My brother and I put together what may be the most complex and hair-brained tankless scheme yet. He has a 30 gallon conventional HW tank that can be heated by solar or by the wood boiler. Of course, it may also be ice cold.

There is a pushbutton/light panel next to the kitchen sink, shower, and dishwasher. We have a controller that looks at the top of the 30 gallon tank. If it's hot enough for satisfactory use, the corresponding light is lit, telling the user that there is hot enough hot water. The dishwasher needs hotter water than a shower, and the system knows this. If you want to take a shower or do dishes or whatever and the light is not lit, you press the button.

This causes a circulator pump to come on and circulate water through the tankless heater. This does three things: causes the tankless heater to come on, flushes out all the cold water between the tank and the tankless heater, and starts to heat the hot water tank. If you pressed the sink button because you wanted to wash your hands, the pump is only on for 15 seconds, and you get your hot water just a tad sooner than you would have. If you wanted to take a shower, the pump stays on until the tank is hot enough, then turns on the light. 

There's also a bypass valve which when open bypasses the tankless heater so that the house is supplied directly from the hot water tank. This valve is open if the tank is hot enough for the current use.

This gives the best of both worlds - hot water comes from wood or solar if available. If not, the tankless heats just enough water to just the necessary temperature, starting with whatever is in the hot water heater rather than ice cold well water.

I'm afraid I haven't made a page for this project on my web site yet, but I'll post a link when I get a chance to do it.


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## Vtgent49 (Jan 18, 2008)

I was told by Houseneeds.com to not use a tankless if your water is preheated by a coil in the boiler or something else. Something about their modulation method. You may be able to plumb around this problem by using a mixer valve.

Also, LP delivered to VT is now 3.87/gallon and could br 5.00 in a year or two. So, all those cost of use comparisons you see need to be adjusted before they make any sense.


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## mikeyny (Jan 18, 2008)

You all can do whatever floats your boat, but the best way to do it is the free way. That big old yellow sun up there is kind of like a big piggy bank to me. All summer long The sun heats my water for me. I don't have to do a darn thing. Build a couple home made solar panels and plumb them into any tank you have and start banking the money. My gas usage went from 80 to 100 therms down to 15 to 25 therms a month. The system paid for itself in a matter of months. Every time the gas co raises the rates I save more money. So stop dilly dallying around trying to shop for the best deal or most efficient thing to buy and build yourself a solar collector. And oh I forget to mention there are 9 of us living here taking showers and doing laundry every single day of the year. So there ya have it My rude and crude advice to all of you is just "shut up and do it". It really works.  (thats my favorite quote, not really meant to piss anyone off)
                                                                                           Mike


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## hvcompton (Jan 29, 2008)

Be sure to check out the titan. Made in use. I have a titan n120 I just got a few days ago. I will be installing it soon. 170 bucks. Its for the entire house not just smal apartment model. Bigger ones are for cold climates. 

220 60 amps.


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## pdboilermaker (Jan 30, 2008)

I have a Noritz tankless lpg, love it.  It fills my wifes whirlpool tub just fine.  According to the doe website, if you use 60 gallons of hot water per day at $1.25 per gallon, you will save $34.00 per month.  Dont forget about the $300.00 tax rebate when figuring your savings.

Your tax rebate check could cover the costs.  Check out irawood.com for many brands, electric, gas, and lpg.


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## pdboilermaker (Jan 30, 2008)

https://www.hearth.com/econtent/index.php/forums/viewthread/13183/P15/ oh yes, check out this thread and there are a couple more in the DIY forum section


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## galindog (Jul 1, 2008)

Hi. I am new here and was wondering if you guys can help me with this issue. I have a 2000 sq ft house in CT w/  baseboard hot water heat.  I bought a wood stove which heats about 80% of the house nicely. It has brought down oil usage from about  1200 to 600 gallons of oil. The boiler is 3 years old with an 83% efficiency rating . It has a tankless coil for domestic hot water use and it seems to me that firing off the furnace from April to September just to heat the water is a waste. In my conversation w plumbers, 1 of them suggested installing a 50 gallon electric water heater or propane water heater and connect the pipe leaving the boiler into the cold water intake of this heater.  He explained that the water would come into the house ,get heated by the tankless coils in the boiler  , go into the electric water heater at a warmer temp and out to the faucets. By doing it this way, the water would have a much faster recovery rate since the electric water heater would heat up the water faster since the it is coming into the tank already "pre=warmed" . The oil savings would come in the warmer months when  I could turn the furnace temp from 160 to about 100. I realize that my elec bill would go up but with elec at 18 cents per kwh and heating oil around $4.5, we've reached the tipping point a while back . Thanks .

I find the idea from castiron of turning off/on the electric water heater using a timer very intruiging since most of the water is needed for 1 hour in the AM and 4 hours in the PM.


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## Vtgent49 (Jul 1, 2008)

Galindog, 

I agree that a 50 gal elec addition is good. The preheated water should just about eliminate the electric usage in the winter.

However, I'd consider getting a solar/electric tank (like a Vaughn) and adding a single solar panel and pump. That will greatly reduce your summer fuel/elec costs, and might help in the winter. A tempering valve will help also. Your goal should be to turn that boiler off for 7+ months, not just to turn it down.

You can get various state and Fed tax credits (if you add the solar) and those credits will apply to the whole job. Thus the additional costs for the solar will net out very low.

Al


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## galindog (Jul 1, 2008)

Thanks for your reply Al. My only concern about the solar setup is that I've read in various places that turning off the boiler totally would not be a good idea during the summer months because the boiler seals shrink,  parts gets rusty, etc. In addition, would the solar be for merely pre heating the water for the elec hot water heater. I live in Ct with a lot of trees. The sun hits my roof only from 9:30 to 3:30. would that be sufficient? Thanks again


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## Vtgent49 (Jul 1, 2008)

I mean that the boiler should be off, not drained, but letting the water cool to room temp, vs. keeping it standing at 160 F. So, the seals etc will still be wet. Frankly, that type of system should be outlawed. It's design criterea was "least dollars possible" for the builder, not the homeowner.

9:30-3:30 will get you 80+% of the useful sunlight. Worst case is that you have to add another 800 dollar panel to double the solar input (I have 3). If you are maximising for Summer, a lower angle is fine. Mine is on a 4:12 ratio roof, thus way flatter than the 43 degrees reccommended for year round optimization. My electric backup is set to go on at 105 F, and the breaker is off. Hopefully, the solar will suffice til it's time to fire the wood boiler, which might be late Sept. in VT. A 4-5 hour wood fire heats the 80 gal DHW to 140+, enough for 2-3 days. 4-5 hours of sun is almost as good.

For cost analyzing, I'd assume oil will be 10 bucks, sometime during the useful life of the solar add-on. That makes it easier to figure a reasonable payback, which could be 1 year with tax credits, and if you do some work yourself. (Diesel is 11/gal in London right now.)

Again, my suggestion was to do both a tank and solar at the same time, so the credits pay part of the tank as well.


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