Swaping out indirect for electric tankless WH

[senorFrog]

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...

(broken link removed)

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

 

[thephotohound]

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?

 

[titan]

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?

 

[senorFrog]

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.

 

[velvetfoot]

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

 

[Highbeam]

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.

 

[Eric Johnson]

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.

 

[velvetfoot]

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.

 

[senorFrog]

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.

 

[velvetfoot]

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.

 

[senorFrog]

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.

 

[Bill]

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.

 

[jjbaer]

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.

 

[Eric Johnson]

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?

 

[WarmGuy]

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.

 

[jjbaer]

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.

 

[drizler]

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.

 

[KeithO]

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.

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.

 

[keyman512us]

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...

(broken link removed)

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:

 

[jjbaer]

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......

 

[cbrodsky]

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

 

[jjbaer]

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.

 

[backpack09]

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.

 

[cbrodsky]

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

 

[Bill]

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.