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

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.

 

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?

 

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

 

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.

 

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

 

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

 

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

 

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.

 

That all depends on how your fuel is transported. But seriously, I'm not trying to nit pick. In general your point is correct, especially with the way most power plants work today. What I am trying to do is make people think about power costs and distribution. Electricity is a *lot* better than what most people think.

Tom

 

Transport costs for fuel (natural gas) to your house will nearly always be higher than transport costs to a power plant.

 

It might also be wise to remember that there are economic "costs" for any given transaction, and then there are "true/environmental" costs. Economically cheap energy has often (and continues to) come at a huge (unpaid) environmental cost.

So just because one form of energy cost your $X/mbtu net/net, doesn't mean it is "cheaper" than one that cost $X plus Y to pay for the environmental costs.

Icarus

 

That puts only electric resistance heaters behind the best gas units.

Electric heat pump water heaters should be over 200% efficient at the wire terminals, so even after generation and transmissions losses, they should beat gas.

For cooling-dominated climates, the heat pump versions ought to be win-win. For heating dominated climates with the water heater inside the conditioned space, more analysis is needed.

 

In fact, it IS resistance heating.

What a great thread. I'm coming up on year 12 of our tank water heater, and KNOW I want to do something different and better when the time comes. I do think that a demand unit coupled with solar will be the best long-term situation.

 

We have a simple home made flat plate solar system, feeding into a Takagi TkJr propane demand. This simple system cost under ~$1000 (not including the Takagi which was already in use). In the grey Pacific NW it produces ~75% of the water heat for two of us on an annual basis. (150% in the summer, ~50% in the winter).

As has been suggested, it is the best solution except for hot climates where heat recovering from heat pump is likely to be more efficient (If you use A/C.

Icarus

 

The key is to use the waste heat created during electrical generation. We don't do a good job with this in our country, but places that do vastly increase the efficiency. As for natural gas, the original point was for propane. Propane transportation costs are much higher than natural gas.

I suppose we would have to know what most people think. I can only guess about that, since most of the masses are clueless. As an electrical engineer, I have been pleasantly surprised by the efficiency of modern electrical generation. Given the inherent thermodynamic losses, I'm surprised it's as good as it is.

Tom