Tankless water heater: Love 'em? Hate 'em? Let's go to the phones!

Automatic Washer - The world's coolest Washing Machines, Dryers and Dishwashers

Help Support :

Hi Veg. I am having tankless put in. The vent pipe had to be changed. Also, an air intake pipe was installed on the roof.
The gas supply line had to be changed to a 1 inch line. That had to be run over the roof from the central a/c/furnace.
Almost ready to fire up the new water heater.

Ross
 
I just bought a brand new house that has a tankless,gas water heater mounted outside.I love it and I have 4.5 bathrooms , a huge kitchen w/island,a laundryroom,a jacuzzy and a heated pool that are all connected to the unit for hot water.I have it set for 165F,and never run out of hot water.I highly recomend this to all who are tired of the old tank type units that can leak and seam to be problematic.
 
My tankless hot water heater was just installed. It works fine. And with the extra space, there will be more washing machines.

Ross
 
Wow, 165°F is very high! You'd probably get a considerably lower gas bill by cranking it down closer to usage temperature. You don't have any trouble with temperature fluctuations when showering, for example? Unless you're tolerant of unusually high temperatures, the hot water flow must be cut down quite a lot to get shower temps, which may sometimes drop lower than the activation GPM and cause the unit to shut off.
 
he's right, you really don't need to set it that high for showering or hand-dishwashing. High hot-water temperatures like that are a hold-over from tanked hot water days. In order to extend the amount of avaliable hot water, most people would crank up the temperature of the tank, and then compensate by mixing cold water in at the faucet until the desired temperature is reached. The result is less hot water flowing.

In a tankless however, this is not needed since it will never run out. You can set the water heater thermostat to the acual desired temperature, and the water heater will regulate the amount of heat to achieve that temperature...non eed to add cold water! This is also the way to do it if you have more than one shower running at a time. Now, when you need hotter water to do dishes in the DW or run the washing machine, you can turn the 'stat back up to the desired wash temperature. I'm not thinking you need anything over 130F for that however
 
My "normal" temp setting is 103°F for showering. I raise it appropriately for washing clothes, and to 110°F-112°F when filling the whirlpool bath (which doesn't happen often). I don't raise it for dishes, the dishwasher takes care of that, heating its 0.8 gal fills to the specific temp it wants for the selected cycle's main wash and final rinse.

Being that Chuck's unit is installed outside the house, adjusting the temperature per usage is likely not convenient unless it has remote controls at strategic locations inside the house. Mine doesn't have a remote control, but is installed in a broom closet inside my utility room so is easily accessible.
 
going tankless....

To really have a adequate tankless supply, you need something that will deliver at least 4 gpm at 120* or hotter. This requires a lot of gas input, and the units with the electric gas guns (power burners) are going to be the best at this. In addition to the venting, you really need to look at your GAS supply line as its size & length is likely going to determine the maximum gas input you have available before you have to make major mods.

Assuming no losses, it will take about 115,200 BTU of heat to raise 4 GPM with a 60* rise. In reality, most non-condensing gas appliances will have a max efficiency of about 80% which will dictate an actual required gas input of approx. 144,000 BTUH minimum. If you factor in losses in the plumbing itself, especially for longer, underground and/or uninsulated runs, you will need even more. Based on the forgoing, I would recommend a minimum 150K+ BTUH of usable input capacity unless your usage is minimal and/or you don't use a shower.
 
When I do my tyle floors,I like to use the hottest water available,Otherwise,it doesn't cut the grease or sanitize.I used to have to boil pots of water to be able to do that.
 
Good point about design failures.

Was just visiting my aunt. They built an entirely custom house (stark modern contemporary that is reallly beautiful) a couple years ago. (Pity her husband died about 6 months after it was finished).

We were talking about the building of it...which was a several year task. She bought the kitchen (model at a kitchen shop...Snaidero cabinetry in Corvette yellow (!), Gaggenau appliances, etc etc. and had the kitchen built around it. That kind of place.

ONe thing she mentioned which was a success...the architect insisted on 8 foot ceilings upstairs, which are precisely perfect...the downstairs is 10' and is airy and light, but airy/light upstairs would have been overkill...paradoxically, in the living/sleeping areas you need a little more coziness for comfort than the more "public" gallery/entry areas

Two failures...they thought that there was going to be exterior lighting (this house is all surface and planes...think geodesic dome) so there were electricity drops (with 110v) all around the house which are nothing more now than trip hazards in the yard.

Second failure...she'd wanted geothermal climate control (on a 2 acre lot so would have had plenty of space). She let herself be talked out of it ($15k upcharge) because of the architect/builder's unfamiliarity with it. Now there are 3 noisy compressors for the HVAC running a lot, plus all the energy savings, AND she realized that they spent several X 15K for decorative stuff which isn't nearly as useful as earth-based would have been.
 
Menage-a trois?

Which is French for literally "Household of three!"

YAY.

Yet another new and interesting thing to see at Casa Ross.

Oh honey, no one (to date) throws a wash-in like the holy trinity of Arizona.

Nate
Roger
Ross

..in alphabetical order.
 
Is it more efficient to run the tankless at a high temp (like 140 degrees) and mix it with cold at the tap for the perfect temp (Glenn's 103), or set the tankless to a perfect temp (Glenn's 103) and just use water from the hot tap?
 
Peter,

I imagine you're looking for a response/opinion from someone else, but here's mine anyway. A properly sized tankless won't run out of hot water (or water at the desired temperature) unless the water supply or power supply runs out or the unit itself fails, so there's no need to overheat the water to get "reserve capacity" as with a tank heater. I don't know if this is a legitimate analogy, but perhaps think of it this way: Would you floorboard your car's accelerator and use the brake to hold 30 MPH? Or would you moderate the accelerator to use just enough fuel-flow to get the desired speed?

I went on a model home tour last weekend hosted by the builders' association in a nearby town. Several of the homes had tankless water heating, all gas. One (which I missed for lack of time) was touted as having three units (3700+ sq ft house). I had a brief conversation with one of the builders of a house equipped with two units. I saw one in the garage, asked him if the one unit handles the entire house. He said there are two. I asked about remote controls at strategic locations such as kitchen and master bath to facilitate adjusting the temperature per task. He said "that's a new one on me" .. meaning he wasn't aware remotes are available. I told him that I have an electric tankless and that the most efficient use of tankless for energy savings is by adjusting the output temperature for specific tasks, not overheating the water. I could tell by his reaction that he wasn't believing any of it. The only response I got was "I know electric tankless isn't as mumble, mumble ... something as gas." I outlined some details about my experience living with electric vs. some of the complaints I've read about gas, which I don't think he believed any of that either.

Here's one of the gas tankless units, compared to my electric. Gas is more bulky with the burner and heat exchanger and vent stack.

5-22-2007-19-10-10--DADoES.jpg
 
Gas & Electricity . . .

At least here in California it is very, very difficult to get any sort of electric water heater to calculate OK on the state-required Title 24 Energy Analysis. Gas tankless units or a condensing type tank unit (which has a small tank) calculate best, so they are helpful if you have a lot of glass, or need to use some single-glazed windows on a remodel. No Title 24 approval=no building permit, so I always assume a gas heater on my projects. Many of them are available with remote controls, which is especially useful if you mount one in an attic.

If you live in an area with high gas prices and cheap electricity then the electric unit might be a better choice if there are no regulatory issues. That is especially true if your electicity comes from a non-fossil fuel source like hydroelectric or nuclear power. If the electricity comes from fossil fuels, then a lot of energy is lost in turning it into electricity in the first place which kind of ruins the overall efficiency if you're concerned about CO2 emissions and such.

My energy analysis guys like those Noritz heaters (like in the pic) a lot; evidently they aren't cheap but perform very well.
 
Well, here is how I am looking at it...

If you crank your tankless to 140 then go take a shower. To get the optimum temp for bathing, you would use "a little" 140 degree hot water and more cold tap water. Therefore the flow thru the tankless is much less and it can maintain the flow temp easier and ultimately use less energy.

OTOH, if you set your tankless to 105 then go take a shower, your hot water tap would be wide open and you would use much less cold water to get the optimum temp. The flow thru the tankless is much more and the system must quickly heat the water as it flows in a much quicker rate thru the tankless.

Which is more energy efficient?
 
Toggle is right . . .

probably if a scientist with sophisticated measuring equipment was able to study this he might find a small difference due to heat radiating from the supply pipes or some other factor, but it would be so small as to be entirely inconsequential and have no impact on your bill. Basically, you're heating a certain amount of water (the water which actually exits the shower head) to a certain temperature, and that will take a certain amount of energy.
 

Latest posts

Back
Top