On Demand Water Heaters?????????

[Diesel-ME]

Low flow point of use electric is good and quite manageable. House capable electric units will need at least 100A @ 220V to warm the higher flow used. They work at an escalating electronically controlled duty cycle as flow increases more and more above the amt needed to turn them on. Theyre great if you have the robust electric service where you need it.
larry

Not to get too far off topic... but just curious what you pay per kilowatt hour down there for electricity? I'll bet that there are places where the cost of electriciy has not skyrocketed as much as propane/gas/oil has, where super efficient electric stuff may be worth looking at again.

~paul

 

[Cap-n-Cray]

I am currently having a Navien tankless water heater that runs on propane installed for a client. It claims to be 98% efficient and has a buffer tank that eliminates the "cold water sandwich." It also has a recirculation option. There are a bunch of high tech things on it. It uses 3" PVC as the exhaust vent system.

I will be looking at it very closely.

Cary

 

[SPYDERLK]

Not to get too far off topic... but just curious what you pay per kilowatt hour down there for electricity? I'll bet that there are places where the cost of electriciy has not skyrocketed as much as propane/gas/oil has, where super efficient electric stuff may be worth looking at again.

~paul

After you add up all the surcharges, taxes, etc you come up with $0.10/kwhr. Just heard it is going up 18%. -- but which charges?? If all, itll be about $.12.
larry

 

[_RaT_]

The standby losses are the only actual daily financial benefit to tankless. Both systems still spend energy to heat the needed number of gallons. The tank heater is arguably more efficient at actually converting energy into hot water since the ondemand heater requires rapid heat transfer. Electric is always 100% efficient at heating and the newer tank units are of course better insulated.

If the hot water is used constantly or regularly then your stand by losses approach zero as the water heater is effectively a pipe. If your uses are very intermittent then the tank has a lot of dead time to lose heat and this is the time when a tankless gets a slight advantage.

On and off all day, get a proper tank.

Very intermittent use, consider the tankless.

The side benefits of a tankless might be very valuable to you. Endless hot water and space savings are the big ones. These tankless units cost a lot to install and maintain, and they don't work when the power goes out. In the event of an emergency you have a reservoir of drinking water as well with the tank.

Lastly, do you really want an endless supply of hot water? I would propose that this could lead to abuse of your energy supply. If you really do want it I have seen homes with two water heaters to provide enough reserve for the high demands.

Being the owner of a Rinnai tankless, I completely concur with Highbeam. The hype about tankless has some caveats. Highbeam I believe has it well figured out. I really like the space saving of the tankless but don't like the limited gpm of the tankless. If you want a super efficient water heater at a price not to much more than a tankless look at Polaris. Polaris Water Heaters - Home , you get much better efficiency as far as how much energy actually is used to heat the water, the exhaust vent is plastic. The insulation is high enough in R value to really limit the re-heat of the water and since the exhaust vent is at the bottom, you almost eliminate the heat loss through it while the heater sits idle.

My energy cost with tank versus tankless was practically imperceptible.

 

[Doc_Bob]

. If you want a super efficient water heater at a price not to much more than a tankless look at Polaris. Polaris Water Heaters - Home , you get much better efficiency as far as how much energy actually is used to heat the water, the exhaust vent is plastic. The insulation is high enough in R value to really limit the re-heat of the water and since the exhaust vent is at the bottom, you almost eliminate the heat loss through it while the heater sits idle.

Any advice on just super insulating a standard hot water heater? I have often thought I should just take 6 inches of fiberglass batt insulation and wrap my current heater (not covering up the required inlets for air, etc). Seems like this would duplicate much of the benefit?

What do folks here think of this idea?
Bob

 

[SPIKER]

Any advice on just super insulating a standard hot water heater? I have often thought I should just take 6 inches of fiberglass batt insulation and wrap my current heater (not covering up the required inlets for air, etc). Seems like this would duplicate much of the benefit?

What do folks here think of this idea?
Bob

this is actually a very good idea if you have a WH in the basement where it may be 50 degrees ambient in winter. or even in the house where a/an air flow can drag heat away. while even in a closet where no real airflow can pull heat away it probably would still reduce cycling of the W.H.... I have used the foil radiant type bubble insulation on several units now and have been loving it. used to always have a WARM to touch heater, I buy 2 rolls of the 24" wide stuff available @ HomeDepot/Lowes and use tape & wrap it around the W.H. tape close the seams using good foil tape. there is enough left over to make tops and bottoms but remember to leave enough room if using gas fired W.H. as it is flammable. other great benefit is to buy pipe insulation and use it on the hot water side and one or two feet up the cold side as well as it will draw heat out through cold side when setting...

there are also hotwater heater KITS at some places made to do jut this using regular fiberglass and a plastic outer jacket with tape and every thing needed. kits are getting harder to find, (haven't looked in a long time just got the foil bubble stuff insulation last 2 I did)

Mark M

 

[Charlesaf3]

I generally agree with Highbeam with one caveat, which may be my misunderstanding of what he is saying.

Heating with electricity, although more "efficient" almost always costs MUCH more than heating with oil or propane.

I run a sidestore off my oil burner. Properly sized, this costs me around 5-10 gallons of oil a month. If and when I get around to playing with the furnace so it isn't constant temp, but rather on demand, this will go down.

Oil or propane will deliver hot water much faster. Practically speaking, electric tankless is no way to go anywhere north of south carolina, at a guess.

Natl. Gas tankless can be quite useful in the right implementation.

If you really want to save money, insulate and put in solar hot water. A lot of solar is hype, but passive solar and solar hot water is the real deal.

 

[Doc_Bob]

I have used the foil radiant type bubble insulation on several units now and have been loving it. used to always have a WARM to touch heater, I buy 2 rolls of the 24" wide stuff available @ HomeDepot/Lowes and use tape & wrap it around the W.H. tape close the seams using good foil tape. there is enough left over to make tops and bottoms but remember to leave enough room

Mark M

Yes, good to hear that you agree. I plan on 6 inches fiberglass surrounded by the bubble (for the looks!!!!) and then good foil tape for seams. The GW heater is in the basement.
Bob

 

[SPIKER]

Doc Bob:

check to see if you're local Home Hardware place carries the pre-made HW insulation jacket. this may be a better option than making it up BUT also compare price/cost of home made vs the store made.

Last one I did I had a left over roll (~7' x 24" foil bubble reflective) and ended up needing a bit more so I got a 16" roll x whatever length store had to finish the job. from what my hands tell me the single layer of foil bubble bubble foil I used on this job was more than enough no extra fiberglass was used. but this unit was/is inside the living space so it is in warm air. last unit I did I put 2 layers of the radiant "foil-bubble-bubble-foil" stuff on and it was in basement. it was ambient air temp to touch after that. SO maybe you don't need the fiberglass ???

though I admit more is better when insulation is done but returns dimish exponentially..

Mark M

 

[Doc_Bob]

Doc Bob:

though I admit more is better when insulation is done but returns dimish exponentially..

Mark M

I have a lot of left over 6inch fiberglass bat, so I can use it for something.
Bob

 

[Highbeam]

Efficieny and cost to operate are two very different things. It takes a certain amount of energy to heat water nomatter what fuel you use. We are smart enough to get most of the btus made from burning a petroleum fuel into the water but a lot goes up the chimney. The electric tank has no chimney. Every single btu of energy that you send to it (and pay for) gets added to the water. Making the electric water heater the most efficient choice.

Of course the petroleum is(was) cheap so wasting some of it is no big deal. So the efficiency doesn't really matter unless you are the type of guy that wants to do the math. You will find that LPG has so many btus per gallon and that a KwH of electric is equivalent to so many btus. You then attach cost per btu to the fuels based on local rates. You then MUST attach efficiency of the water heaters to arrive at actual cost to heat that water.

Electricity is becoming cheaper and cheaper every day compared to the other energy sources. Those on demand electric heaters might just become the smart choice someday.

 

[Charlesaf3]

ok, I agree with all of that of course - thought you meant operating cost, but wasn't sure.

Probably right about electricity eventually, especially if we get more nukes built.

 

[fluffyone]

Does anyone have any knowledge of these hot water heaters? Cost to run vs tank type etc.? What brands are the best? TIA, Jim

i have had one for over 14 years. My is an aqua star. we love it and it is inexpensive to operate. i know they have improved them over the years and when our home sells and we build another one we will have one.

BTW any one looking for a 3200 sq foot log home on 23 acres in NW al, let me know

love this site

 

[WayneB]

We have two Aquastar units one the FX-125 at our summer home which really works great for us. Key reason for going tankless there was the ease to winterize the water system. Prior to this we had a 40 gallon tank to deal with. Second reason was with the on demand heater we can arrive at camp at mid-night turn on the power and immediately take a shower. Before it was wait for the hot water tank to heat enough water.

I know that it is much cheaper for us at camp having the on demand hot water heater mainly because we don't have to worry about if we shut off the hot water tank (many times it would be left on and maintain 40 gallons of hot water for a few weeks) before leaving camp!

Here at home we have the Aquastar 250SX LP model and it provides all of the hot water we can use. There is always a short delay before the hot water gets to the shower, but we have adjusted ourselves to this. One thing I do like is not hearing the furnace / boiler kick on when it is 80 degrees outdoors!

I selected the Bosch system for the camp several years ago and at that time the support group in Vermont were really great to deal with. Now Bosch has bought them out I am not sure how the service is these days.

Just my two cents.

Wayne

 

[photogman]

I read through this entire thread and found it interesting and informational as I will be building a home next spring. I like the concept of tankless because it is just the wife and myself now. Dishwasher run every couple of days, laundry once a couple times per week. (Septics are better if you space out laundry - instead of doing 6 loads of laundry on weekend space it out like 2 loads three times weeks), and finally a couple of showers or tub baths per day for each of us. Now the tough part....when the kids come to visit and eventually grandkids. This is what worries me is that we'll all be left high and dry (excuse the pun) because the tankless won't keep up with the demand on those special circumstances like holidays etc.

 

[JimR]

Any advice on just super insulating a standard hot water heater? I have often thought I should just take 6 inches of fiberglass batt insulation and wrap my current heater (not covering up the required inlets for air, etc). Seems like this would duplicate much of the benefit?

What do folks here think of this idea?
Bob

If your tank is warm to the touch then insulating it will be worthwile. Otherwise it is a waste of time and money. A downpipe on the outlet end keeps the warm water in the tank istead of climbing up the pipe when not in use.

 

[JimR]

I read through this entire thread and found it interesting and informational as I will be building a home next spring. I like the concept of tankless because it is just the wife and myself now. Dishwasher run every couple of days, laundry once a couple times per week. (Septics are better if you space out laundry - instead of doing 6 loads of laundry on weekend space it out like 2 loads three times weeks), and finally a couple of showers or tub baths per day for each of us. Now the tough part....when the kids come to visit and eventually grandkids. This is what worries me is that we'll all be left high and dry (excuse the pun) because the tankless won't keep up with the demand on those special circumstances like holidays etc.

A tankless will not leave you high and dry if you buy one big enough to meet you GPM output. I'm still searching for the one I want to buy.

 

[WayneB]

I read through this entire thread and found it interesting and informational as I will be building a home next spring. I like the concept of tankless because it is just the wife and myself now. Dishwasher run every couple of days, laundry once a couple times per week. (Septics are better if you space out laundry - instead of doing 6 loads of laundry on weekend space it out like 2 loads three times weeks), and finally a couple of showers or tub baths per day for each of us. Now the tough part....when the kids come to visit and eventually grandkids. This is what worries me is that we'll all be left high and dry (excuse the pun) because the tankless won't keep up with the demand on those special circumstances like holidays etc.

I do not think you would have a problem with running out of hot water with a tankless on-demand water heater. We have a Bosch 125- FX and during the summer will have a bunch of people at camp and never once have we had a problem with someone complaining about a cold shower. I am sure we could run the shower all day long and the water would stay hot. Now it is a small unit and cannot handle multiple showers / useage, so we have to warn people not to run other items while someone is taking a shower. At home here we have the model 250 SX and it is possible to run two showers at the same time. Although this would not happen too often here.

At the price of oil and LP I considered going with an electrical unit, but living in the north country they recommend a larger unit and it required some pretty heavy electrical servicing which meant I would have to have a new 200 amp service put in. This might have required changing the electrical wiring out to the meter too and I just didn't want to dig up the yard to install new wiring plus the cost of the service installation would be very costly. We live in an older home and changing the service was a major challenge and would take up too much time to complete.

You might want to google tankless hot water systems and check out the different manufacturers of units. I selected Bosch mainly because it was available locally and I trusted the person selling the unit to me. During the installation of the first unit service support was great so when it came time to add a unit at our home I went with Bosch again.

I think if I was building new I might consider point-of-use heaters verses a single source unit to provide hot water for the entire house.

A few of my contractor friends talk about putting in a circulating domestic hot water loop in with the tankless system to eliminate the lag time for the hot water to arrive at the shower head. This uses a small mini hot water tank, a circulating pump with a timer / Aqustat and provide a constant loop of hot water to circulate around the entire hot water plumbing in the house. This includes all of the bathrooms, kitchen and laundry room so once there is demand for hot water it is already there and hot! Lot of high end homes have this and it is a nice feature, but you pay for the luxury for sure. Well, being semi-retired things are much slower for us and we can wait thirty seconds or so for the hot water to be there.

Wayne

 

[Diesel-ME]

A few of my contractor friends talk about putting in a circulating domestic hot water loop in with the tankless system to eliminate the lag time for the hot water to arrive at the shower head. This uses a small mini hot water tank, a circulating pump with a timer / Aqustat and provide a constant loop of hot water to circulate around the entire hot water plumbing in the house. This includes all of the bathrooms, kitchen and laundry room so once there is demand for hot water it is already there and hot! Lot of high end homes have this and it is a nice feature, but you pay for the luxury for sure. Well, being semi-retired things are much slower for us and we can wait thirty seconds or so for the hot water to be there.

Wayne

Seems like you would be defeating the purpose of "on-demand" by constantly heating water that you are not using...???....

 

[_RaT_]

Efficieny and cost to operate are two very different things. It takes a certain amount of energy to heat water nomatter what fuel you use. We are smart enough to get most of the btus made from burning a petroleum fuel into the water but a lot goes up the chimney. The electric tank has no chimney. Every single btu of energy that you send to it (and pay for) gets added to the water. Making the electric water heater the most efficient choice.

Of course the petroleum is(was) cheap so wasting some of it is no big deal. So the efficiency doesn't really matter unless you are the type of guy that wants to do the math. You will find that LPG has so many btus per gallon and that a KwH of electric is equivalent to so many btus. You then attach cost per btu to the fuels based on local rates. You then MUST attach efficiency of the water heaters to arrive at actual cost to heat that water.

Electricity is becoming cheaper and cheaper every day compared to the other energy sources. Those on demand electric heaters might just become the smart choice someday.

Wow, really, electricity is the least desireable way for most things here where I live. The cost per kilowatt, the transmission cost and the distribution cost just don't work here to use electricity for any kind of heating. When you go to Home Depot and look at the cost of operating a electric water heaters versus natural gas heaters, the gas ones are just a fraction of the cost. I suppose electricity generation methods vary throughout the country and the reason for the cost differences. Electricity in its final form may be fairly efficient, getting it to that state can be quite inefficient. Coal fired, natural gas generated or even nuclear have huge inefficiencies. On the otherhand, the huge amount of steam pouring out of a nuclear plant is produced by a very small amount of matter. It is at this point in time a great "alternative" fuel for the US (in my opinion).