Tankless water heaters?

leezarrd

What is your opinion of Marathon water heaters? I have read that they are the best... no corrosion cause they are plastic and they are heavily insulated.

1K2GO

I am thinking of installing a tankless NG. I want to put it in the mech room in the basement, however the basement walls are completely underground. Could i possibly run the vent pipe horizontally underground and under the garage slab, simultaneously, to the exterior garage wall/daylight? I am thinking i would sleeve the vent pipe in 6" pvc or something to protect it. Any ideas are appreciated.

Thanks

moneymgmt

Unless I'm mistaken, they don't make tankless heaters.

1K2GO: You must be working on a new build? You would have to check with the manufacturer, but I have two initial thoughts: first, that will be a huge expense as you have to use special vent pipe that's a few dollars per foot. Second, I believe the exhaust has to slope down after the initial direction change out of the unit so water vapor does not condense and drain back into the unit. If you ran the vent out of the unit, across under the slab, then UP, I think you'd have drain issues. But, like I said, those are my initial thoughts, you'd have to check with manufacturers to be sure.

leezarrd

I have pretty much given up on the tankless water idea and was asking about the Marathon electric water heaters... you know, the ones with a tank.

missyz17

This thread was very helpful. My husband and I are in the process of building a new home and the builder is pushing the tankless idea. We will have well water and originally going with gas water heater. I think we'll now stay that route after reading the through the thread. If someone really has a strong feeling for going tankless, please let me know. Thanks.

LawnGuyLandSparky

If you gas is (or was) municipal natural gas, and now you think you're paying less for electric hot water, I can tall you you're mistaken. Unless your old gas water heater was extremely inefficient, there's no way any electric water heater could cost less to provide hot water than gas. Now, if your gas was via propane, and you're paying top dollar for propane, maybe there's less of a difference.

It takes X amount of BTUs to heat X amount of water X number of degrees. There is no way of getting around that. Btu/hour x 0.293 = watts.

LawnGuyLandSparky

Builders push tankless, as well as things like heatpumps, because their overall cost is LESS. With a gas water heater - you need a flue. A standard gas water heater requires no electricity to operate. During th Northeast grid failure, I had the working shower. Gas water heaters are typical, standard, and regardless of marketing hype, are all pretty much in line as far as energy use.

Tankless gas still needs a flue, but requires electricity to operate. Not a bad idea overall but the units are not typical, common, there aren't 25 different competing manufacturers vyying for your business, they each contain manufacturer-specific parts so the overall initial costs are higher, which eats away the payback from using something that a tiny bit more efficient.

Electric tankless are simple, smaller, use a ton of power (WILL cause lights to dim when it kicks on,) often require upsizing an electric service, but cannot fill a bathtub at full blast.

missyz17

Thank you - thank you! You have been so helpful!

moneymgmt

Interesting, but again give me proof and I'll buy in. I'd love to have everyone over to my house so I can show you that most of the negative garbage people spew about tankless heaters is not direct knowledge. Its hearsay or made-up; and I bought into it all..... until I did the research for myself. We're so used to the comfort and our direct knowledge of tanks that we don't want to understand something different.

If it were a new build I'd say that more often than not I'd recommend a tankless unit. Who cares what the builder pays for the unit, get around the idea of being "sold" and actually look into pros and cons. As i've said before, there are many factors that weigh into the decision; not just "which is cheaper?" There are dozens of manufacturers. No it does not dim the lights when I turn on my electric unit. And regarding my gas to electric cost difference, nowhere did I say that I was making the change to save money. I said I made the change to save space during a remodel, and am delighted with the difference between what people who don't have one TOLD me I would pay vs what my ACTUAL bills are.

If my electricity went out for an extended time frame, I think the last thing I'd be stressing about was when I'd take a shower. Taking a shower in the dark would be an adventure though.

LawnGuyLandSparky

Generally, people are "sold" on the tankless Idea with the impression they're going to save boo-koo bucks in energy. Again, the payback period for a tankless electric over a traditional electric with a tank is a very long time, if at all.

Now I have to ask since you've probably experienced this - how hot is your water when you're running a shower and the kitchen sink simultaniously? Can you fill a tub while using another faucet?

It wasn't dark. The power failed on a Thursday afternoon on one of the hottest muggiest days of the year, and off until the following Saturday morning. Without a/c, people sweat.

moneymgmt

Right now I only have one bathroom and installed one unit. Part of my remodel is adding an additional bathroom and have already plumbed in a place to run a parallel tankless unit right next to the current one. Individually each unit gives roughly 2.5gpm at about 70% ability. If I cranked this one to 100%, I can use two outlets but what you're getting at is correct, probably not at full blast. For instance I wouldn't try to run a load of laundry on "hot" while taking a shower. 70% is plenty hot enough for a shower so that's what we preset it to. The really nice units have remote temp. controls for showers and sinks so you can easily change the temp depending on the application. Once the second unit is connected we should have no issues running 3 usages concurrently in the unlikelyhood that ever happened; 5gpm is a lot of hot water and that's not at full capacity. I can't say I've tried doing my dishes while in the bathtub though....

scorrpio

It really all depends. Tankless efficiency stems from the fact that you don't have a tank of water bleeding all that heat. There are also a couple other factors. When tankless operates, water is constantly moving through the exchanger for maximum transfer, whereas tanks rely on convection.

However, heavy insulation on modern tanks really helps to hold that heat in. Then, usage pattern. If you have someone at home troughout the day, using the water, tank vs tankless gap closes up. If everyone leaves in the morning and does not come home till evening, tankless pulls ahead.

More on usage pattern: tankless are great for sustained output, but burst handling is weak. That is, tank means entire family can hop into separate showers and enjoy a 5-minute hot one all at the same time - where as tankless means each family member (or at most two at a time) can take a blissfully long shower, but the rest have to wait in line, and remember not to turn on washer or D/W while waiting.

A known phenomenon with tankless is 'cold water slug'. Someone just took a shower, water in pipes still hot, but the heater is now off. Someone else hops in, turns the water on. The heater detects water flowing through and starts a new ignition cycle. However, the cold water that went through it before it fired up is now headed straight for the person in the shower, delivering a sudden icy blast. This can be easily defeated with a small (5-10gal) but well insulated electric tank piped after the tankless. The cold slug dissolves in this tank. The tank can also provide a buffer should someone decide to rinse off a few dishes in the kitchen.

Far as electric vs gas tankless - the tradeoff is simple. Gas is way way way way cheaper to run. But electric has an incredible installation flexibility. Gas unit will need a pipe for gas, a vent, and combustion air. Providing all three can amout to high installation cost and limited installation choices. Electric just needs a wire, and can be installed about anywhere. For example, in a closet just outside your bathroom or under the kitchen counter.

zollander10

it depends on who you have install your tankless unit. because as stated in other reply's there is not a lot of plumbers who do service. i came across a company that warranties their machines for ten years for the gas model and that warranty can be extended up to 20 yrs. this company imperial tankless is located in northern illinois. they do service and repair work for machines they did not install.

Piedmont

Sorry I'm late contributing, I replied to this post on Friday and got an error when I clicked post and it was gone. I have a tankless oil boiler.

Electric tankless (or tanked) is almost impossible to be more efficient than fuel as Power plants convert 60% of the fuel they burn into electricity, and have a 10% loss transmitting it to your house. You're paying the power plant for 100% of the fuel they burn to get 50% of it as electricity which is less efficient than fuel types at ones house and they don't have transmission loss. Also why per btu electricity is almost always the most expensive.

Next, how much standby losses does a tank have!? An R15 tank whose water was kept at 120F, using an 80% efficent oil boiler (which means losses due to efficiency have already been accounted for)

40 Gal tank loses 7.6 gallons/year in 47F basement or 5.4/year in 68F area
60 Gal tank loses 8.7 gallons/year in 47F basement or 6.2/year in 68F area
80 Gal tank lose 11.1 gallons/year in 47F basement or 7.9/year in 68F area

I leave it to the individual if that is significant or not, with oil costing $3.899/gallon a 60 gallon tank in a 47F basement will cost $34/year for standby losses probably slightly more.

FYI tankless system never give cold showers, even if 5 people take showers with a tankless system. Tankless systems have a flow limiter, if it can only heat 3GPM then that's all that can run through it is 3GPM. If 2 people take a shower with a 3GPM tankless than each will have shower pressure reduced to 1.5GPM so the tankless can keep up with the 3GPM but neither will take a cold shower. 3 people taking showers at the same time each would have their pressure reduced to 1GPM, etc. etc. no one ever takes cold showers instead pressure is reduced.

A tankless you have to make sure all your showers, tubs, & faucets are 2 knob (seperate hot & cold knobs) OR make sure they're compatible with tankless. Todays single-handle fixtures often use water pressure to prevent mixing (that's to say, when you turn it to hot they use the pressure of the hot to hold back the cold). Tankless systems don't work with those, the hot pressure is reduced after going through the limiter, coils, mixing valve, and some valves making the hots pressure unable to stop the cold from mixing particularly when 2 people use hot at the same time. So going tankless, go with fixtures with seperate hot & colds instead of a single OR make sure your single handle fixture is tankless compatible (doesn't depend on pressure)... if it doesn't say assume it isn't.

In summary, electric is not efficient even compared to a tanked fuel system. Comparing fuel tankless to tanked I don't see any winners or losers. With a tanked system you can have more options and convenience of using fixtures with a single handle without issue. 2 people taking showers at the same time both will have full power. But, I can see it being worth saving $40+ a year for the tankless, and not having to give up space for said tank. To each their own.

Hells_Belle

When you guys are talking about tankless, is that the same thing as a combi boiler? (Looks like this, works like this?)

If so, they are extraordinarily common in Europe. In fact, they are pretty much the standard; we use ours for heat and hot water. They take up less room and use less fuel if you invest in an A rated appliance.