Water heating options...anyone tried condensing water heater?

[icarus]

Originally Posted by Shawn Clark

Brand new A.O. Smith's condensing (which are considered premium) can be had for about $1600. The Energy Star estimator I came across suggested a price under $1000, but I assume that is once initial low volume premium's disappear. I'm not familiar with the Takagi/Rinnai. I was a bit shocked/turned off by the prices I've seen on various demand water heaters and the reviews they have gotten.

Standby losses probably are not more than 8% since electric water heaters have about 92% efficiency. The A.O. Smith also has extra nozzles that can be used with recirc...or perhaps thermal solar. I like the design of the A.O. Smith with the simple helical coil. We'll get a better idea on relative efficiencies when the first set of condensing water heater energy factors are published.

Older gas water heaters suffered more from air flow up the flue (uninsulated internal wall getting a draft) and from little insulation on top and bottom of the tank as well as from the thermosiphon in the inlet/outlet lines which typically could not be insulated. (You have to go out and find some noncombustible type material to do this--which is not carried in many of the big box builder stores anymore.) Some traps can be installed to reduce the effect as well. Since they were non-condensing as well, the efficiencies for standard dimensions have been been about 58-62%.

Demand or tank I hope to go to sealed combustion/direct vent as part of my drive to tighten up the home. So I put the costs of this aspect of the install as about equivalent.

Not to beat a dead horse,, but do look into Takagi and or Rinnai. I have installed several and swear by them. They can be set up to direct vent,, drawing combustion air from under a floor or side wall,, and vent either out the top or a side wall. They can install in very little space,, and heat virtually unlimited hot water.

Icarus

I have been using demand water heaters for better than 20 years,,, I wold never go back.

[DBird]

Suprised no one has mentioned the "Munchkin Contender."
It's both tankless-on-demand and condensing.

This is from a U.S. company (Heat Transfer Products) that makes a rather diverse line of super-efficient, though zoot-capri, water heaters.

Sorry, I happen to live where relatively simple solar water heating works for most of the year. The one I'm using is called a "TCT Progressivtube."
My in-laws live where it snows, though; and they have a Munchkin boiler that heats their space (with baseboard radiators) as well as their water. Works fine, except the space-heating radiators make some popping sounds when they expand and contract. You get used to this.
Burning natural gas, propane, LPG, etc. is definitely more efficient than electric resistance for heating; it's just that it happens to emit greenhouse gas. What's your local electricity source?

[dbcassidy]

I have the Viessman Vitidens 100 installed 3 years ago. It has reduced my natural gas consumption by 30%. I also had the hot water heater replace with an indirect fire Superstore stainless hot water heater.

After having relay problems with the Viessman, the unit is running good.

Hope this helps.

dbcassidy

[nthach]

I believe AO Smith has a "hybrid" water heater using a conventional tank and condensing technology as well.

A. O. Smith Water Heaters

I was trying to talk my parents into a tankless when our 8 year old Kenmore rusted out, but Home Depot didn't carry them and I didn't feel like taking a trip to Oakland to one of the few places that will sell the layman a Takagi. I put in a Energy Star-labeled GE/Rheem instead.

[Shawn Clark]

Originally Posted by nthach

I believe AO Smith has a "hybrid" water heater using a conventional tank and condensing technology as well.

A. O. Smith Water Heaters

Looks like the 50 gallon helical condensing water heater I was talking about.

They get one heckuva high burn rate with the helical condensing coil, 100,000 Btu/hr (about 4 gpm continuous!) Puts standard 50 gallon units to shame. (Should be terrific for filling the whirlpool tub...something my standard 50 gallon unit really sucks at. Granted, I don't use the tub that frequently, but it is nice every once in awhile.)

[harperjn]

Did you ever end up getting a gas condensing water heater? I'm looking into these, especially the AO Smith Vertex like was mentioned.

[qbee42]

Originally Posted by DBird

<snip>
Burning natural gas, propane, LPG, etc. is definitely more efficient than electric resistance for heating; it's just that it happens to emit greenhouse gas. What's your local electricity source?

Electrical resistance is 100% efficient for heating. I assume your comment is looking at the entire process of generation and distribution, otherwise it doesn't make sense.

Actually it is still 100% efficient for heating when you look at the entire process, only some of the heat ends up in the wrong places.

Tom

[drees]

While electrical resistance is 100% efficient, you still have to take into account transmission and generation inefficiencies.

Given those facts, a high efficiency gas heater will be more efficient energy wise than electricity unless your electricity comes mostly from renewable or low CO2 (nuclear) sources.

[qbee42]

Originally Posted by drees

While electrical resistance is 100% efficient, you still have to take into account transmission and generation inefficiencies.

Given those facts, a high efficiency gas heater will be more efficient energy wise than electricity unless your electricity comes mostly from renewable or low CO2 (nuclear) sources.

Modern transmission is very efficient. I suspect most other fuels suffer similar or larger losses in transportation. Generation is a different issue, since you are dealing with basic physics. Cogeneration and other modern high efficiency techniques help a lot in this area, but sadly aren't widely used.

Tom

[drees]

The grid loses an average of 7.2%. So even if your generation was 100% efficient, it'd be behind the best gas water heaters.

Sure, there's distribution losses in getting gas to your house (probably also about 10%), but there are also losses in getting gas to the power plant - and the best gas power plants (with heat-recovery systems) are about 60% efficient.

So again - electricity doesn't get close to gas unless you either get most of your electricity from renewable or low carbon sources.

Solar hot water heating on the other hand easily beats all of the above.