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