Water Heaters

[turbodog]

water fountains use the same device

If I was doing new construction, I'd consider have point of service heaters using preheated water with a heat recovery device like this one:

http://oikos.com/esb/49/gfx.html

-john

 

[ledlurker]

A passive solar water heater can be built for very little money. An old burned out water heater can be used. You strip off the outer shell, paint the tank a fllat black, plumb it in a insulated box that is painted black and place black painted rocks in the bottom and cover the top of the open box with glass. The cold water inlet goes into the solar tank, the hot water outlet goes to your hot water heater inlet. The most expensive piece of hardware for safety concerns would be a temperature control valve on the hot water heater out let to mix cold water with the hot water to bring the temp down to a safer temp. People I know can produce water up to 150 F in the summertime to where their water heater never runs. The built the whole system for under $200 (scrap hardware and lumber) with the mixing valve taking up the majority of the cost.

 

[Brock]

Bill already looked in to the GFX water heat recovery. I have one and swear by it, but you have to have access to you main drain water line and hopefully it is near your hot water heater.

You can see the stub outs on for my old inline electric. It takes our well water from 52F to 75F and you can take endless showers with our 40 gallon 30,000BTU gas heater.

 

[BB]

Brock,

The other suggestion (I thought this came from you--but it is possible that I miss-invented this myself :lolsign: ) is to place this in your shower drain and connect to the cold water input to the shower (if the drain is not near your hot water heater).

It isn't perfect, but if you run your hot water around ~125 F (Hot, as opposed to just barely warm), you will preheat the cold water mixed with your shower (and therefore use less hot water).

-Bill

 

[evan9162]

Also called a gravity feed heat exchanger. Quite honestly, I can't believe that every house with an upstairs shower doesn't already have one. It costs almost nothing relative to the energy it will save.

 

[yuandrew]

Well, I'm having my water heater replaced tomorrow. My mother decided to still go with a 50 gallon tank since the on demand (tankless) types are still very expensive and require some special venting and larger (at least 3/4" gas pipe; mine is only 1/2" to the water heater location)

I did help one of my neighbors 8 houses up install a Rinnai Model 85i Tankless water heater. It took us pretty much the whole day and countless trips to Lowes since we had to re-route the plumbing comming out of the ceiling to get it down the wall and into the bottom of the unit and run a new 3/4" gas pipe directly from the meter which, fortunately, was only on the other side of the wall and a few feet away. We rigged it to vent through the original water heater chimney but then I later found out tankless units require a stainless steel vent so that had to be upgraded as well.
We also ran some new wireing for power (electronic ignition and forced draft) plus some thermostat cable to the laundry and kitchen areas for the remote thermostats.


Recently, I've read about a new water heater that uses microwaves to heat water. The magnetrons are activated on-demand similar to a Tankless. It's being introduced in Canada.

 

[John N]

Interesting. I wonder if an on-demand induction based heater would make sense. The coil would basically become the heating element. Probably safer than microwaves, and it has been stated (not just this source) that induction can boil water about twice as fast as gas with about 40% more efficiency. Not sure how it compares to microwave tho.

-john

Edit: Hmm. At least somebody is thinking about induction hot water heaters.

 

[James S]

the microwave company is at:

http://www.pulsar-at.com/

and more interesting info and some pictures of potential insides are at:

http://www.mahiconsultant.com/

That site seems more interested in using it for smaller applications like hot drink machines and such. That would make your big barrista coffe maker a lot cheaper if it had a microwave heater inside instead of all the complicated heaters and boilers and such... I've seen the guys that service those things...

There was even a slashdot article about it here:

http://science.slashdot.org/article.pl?sid=05/11/25/0413215&from=rss

And as a poster pointed out, there is no more efficient method of turning electricity into heat than your standard cal rod. 100% of the energy used gets turned into heat. Anything that adds complexity, be it a magnetron or a complex magnetic heating system like the induction one will reduce the efficiency not increase it.

Why aren't we doing research into super insulated tanks for traditional heaters? Why can't I get a thermos bottle tank? (hard to lug up the stairs I suppose without breaking it...) There are already insulating attachments to keep the heat from radiating up the pipes and other such things.

The problem of course is that you can't run enough of them to get the heat into the water fast enough to do a tankless without some more exotic methods. But if you could reduce losses from the tank which you certainly can then...

 

[CandleLite]

Have had a Bosch natural gas tankless water heater for a little over 3 years and am very pleased with it. I decided on it after my 40 Gal. tank tanked after 6 years and 3 months. Of course it had a 6 year warranty.

The Bosch has a 20 year warranty and every piece of it is available for replacement if ever necessary. It is solidly made of copper, steel and brass and takes up about 20 % of the space that the tank did because it is wall mounted.

Apart from it's expected longevity it has saved us a significant amount of money because it is quite efficient. You are not keeping 40 gallons of water hot 24/7. A regular tank keeps water hot always, even when you are gone for 12 or 24 hours or even days unless you shut it off and then have to wait many hours to heat up the water when you return. A water tank is almost like keeping the motor in your car at a constant idle waiting for when you may decide to take a drive.

On the downside, although the tankless heater will produce enough water for two taps or appliances it takes a few moments to modulate the heat to produce the hot water for the new demand. This is not a big problem unless one of the users happens to be in the shower. A sudden cool surprise until the heater ramps up and heats the water to your chosen temperature. On the other hand, you and your family and all your neighbors, if you wish, can take endless showers.

A great idea and one that you will see more of with our diminishing resources. I understand that in Europe and Asia something like 70% of the homes use tankless water heaters. Perhaps some of the European CPFers can comment on this.

 

[yuandrew]

Why aren't we doing research into super insulated tanks for traditional heaters? Why can't I get a thermos bottle tank? (hard to lug up the stairs I suppose without breaking it...) There are already insulating attachments to keep the heat from radiating up the pipes and other such things

A regular tank keeps water hot always, even when you are gone for 12 or 24 hours or even days unless you shut it off and then have to wait many hours to heat up the water when you return. A water tank is almost like keeping the motor in your car at a constant idle waiting for when you may decide to take a drive.

James, my old water heater actually had some thick insulation between the tank and the outter jacket; there's a tag on it that says it's insulated to an R-16.7 value. I almost never hear the burner come on unless I run the hot water faucet for at least two or three minutes but it does keep going for about 15 to 20 mins after someone takes a shower to bring the cold water which entered back up to temp. Most of the time throughout the day, it just sits there, full of hot water, pilot on only, ready to be used. I did shut the gas off to my old heater the night before but there was still enough hot water for me to wash up this morning. I was discussing this with my friend's dad (who's also a plumber and installed the new tank) this morning as he was checking to see if an R-16 insulated model would fit. Most common, cheaper water heaters, he told me, are R-8 insulated.

The new water heater is also insulated to the same value. I didn't time it exactly but I think it took a little over an hour from the time we started it up to the time it reached the set temperature. I checked it out a few more times but I didn't hear the burner running until after I took a shower towards the evening.

Maybe in a colder area, it may lose heat faster to have the main burner come on a few times during the day or if we go on vacation for more than a day or two days, it may also have to reheat the water that cooled inside the tank.

 

[CandleLite]

Hot water tanks are a passing technology. People double their tanks and super insulate their tanks but there is a limit to what can be done whith this old concept.

Tanks heat and reheat the same water and tries to maintain it at 130 or 140 degrees. When you want to use it you have to cool it by mixing it with cold water. A bit of a waste don't you think? And if you take a shower or two you can still run out of hot water. Of course if you maintain a huge amount of heated water you may not run out but you are just increasing the scale of the inefficiency.

Tanks run at 80% efficiency when new, then constantly decreases with age. After several years you are wasting a great amount of energy and hoping that you are home when your tank finally gives up the ghost and floods hot water through the house. Only anecdotal, but I have known 2 people in my lifetime that this has happened to. Tankless heaters run at a constant 98% efficiency throughout their 20 year or more lifetime.

A feature that I like is that you are always heating up fresh water that can be used in cooking. Tank water has been sitting for days or weeks in a stew of hot impurities that collect in the bottom of your tank unless you flush it every year or more often as recommended.

Tankless is smaller, more efficient and lasts longer. Sounds a bit like the way incans and LEDS are going. The future is happening all around us.

 

[John N]

Tanks heat and reheat the same water and tries to maintain it at 130 or 140 degrees. When you want to use it you have to cool it by mixing it with cold water. A bit of a waste don't you think?

This is an interesting point. It seems like an additional improvement in on-demand hot water heaters would be to use a point-of-use unit/faucet that had an electronic rheostat and not the hot-cold mixing solutions.

I don't think I've seen anything like that yet.

-john

 

[TedTheLed]

Advanced Temperature Remote Controller for Takagi TKJr., TK1, TK2, and TKD20
Information display includes: gallons per minute flow rate moving through the heater, incoming water temperature (degrees F), outlet water temperature (F). Has two functions, setting temperature between 95°F and 167°F and diagnostic tool. You can run up to 100 feet of 18 GA shielded t-stat wire and put remote in some convenient place, like kitchen or bathroom.

 

[BB]

Gas Tankless water heaters should be replacing gas tanked water heaters... But for those that use electric or boiler/tanked water heaters, I am not so sure.

For gas it is the pilot and open chimney through the middle of a hot tank of water that kills efficiency. There are forced air models that get rid of most of those "heat leaks".

For electric and boiler feed tanks, since they don't have pilots or stacks for heat to escape--the tankless water heaters have much less of an efficiency leg up...

For me, the big issue for gas fired tankless water heaters is the minimum flow rate--usually between 0.5 and 0.78 gallons per minute to fire up. With all of the water conservation going on in our area, it is very easy to be rinsing dishes or having a shower on low and not get the minimum flow rate.

I would guess that one of the issues is that the gas tankless water heaters just cannot accurately (and safely?) hold the output water temperature at those low flow rates--something that a tanked water heater can do very nicely.

-Bill

 

[John N]

After doing some research and some thinking on the topic, I think the solution to the minimum flow on gas units is to put a small conventional electric hot water heater downstream of the gas unit (maybe 5 gal). This way, you get hot water on demand, but for large demand the gas unit kicks in.

Just a thought.

-john

 

[TedTheLed]

you can wash dishes and take ashower using less than .5 gpm hot water ? hold the presses at Guiness!! really though; I got a Takagi and it takes only a trickle for the unit to come on..

(I WISH I had remembered to insulate the hot water pipe!! -- it goes through an interior wall -- so it wasn't insulated -- dumb)

 

[sunspot]

Does anyone know of a brand of electric heaters that are heavily insulated? I have no gas lines in my area.

 

[BB]

The Takagi was the one listed (jr.) that listed 0.78 gpm flow rate... Out here, the new (approved) shower heads are all 2 gpm max flow rate.

My in-laws' place over seas has the standard size on/off tankless water heater. And for taking showers, I had to adjust the flow rate for the right temperature.

With the low flow shower head and standard 40-50 gallon tanked water heater, I have never ran out of hot water (even with two kids that want to live in the shower after swimming).

I am not against tankless water heaters--but they are pretty expensive and require a bunch of work to install the first one (new gas line, exhast vent, possibly intake vent and electric too). Kind of still wondering about spending that cash for a solar thermal heating system instead.

For an electric water heater, you can easily add your own insulation (you can even get water heater insulation kits--batt+some real sticky tape)... One interesting experiment would be to see if adding shinny foil insulation + regular batt insulation helps... One vendor (of shinny foil+bubble wrap insulation) says that regular bat insulation does not do a very good at preventing IR heat transfer.

-Bill

 

[sunspot]

Re; shinny foil+bubble wrap insulation. That sounds like a good idea. Anyone else want to chime in on this?

Does anyone here use a timer? My house is empty 12 hours a day during the work week.

 

[BB]

For completeness, here is the link for the site that has information about foil+bubble wrap insulation:

www.insulation4less.com

Don't know anything about the company, but I would have like to try this when I remodeled an over the garage room (used the two inch foam board only to allow ventilation).

-Bill