Tankless hot water heaters

[icerube]

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Thats a great idea!!!!! The marathon would have to run a little because you would get a shot of cold water into it every time you called for hot water. I have a tankless heater, problems I have with them is that they waste alot of water. The wait time for hot water is alot longer and the temp yo-yo's a little befor you can get in the shower The other problem I have with it is on hot summer days I can't take a cool shower, when I turn the hot water down to a nice cool temp, the water flow is to low and the burner shuts off and bam ice cold I regret going tankless

[MARINERMAGNUM]

Quote:

Thats a great idea!!!!! The marathon would have to run a little because you would get a shot of cold water into it every time you called for hot water. I have a tankless heater, problems I have with them is that they waste alot of water. The wait time for hot water is alot longer and the temp yo-yo's a little befor you can get in the shower The other problem I have with it is on hot summer days I can't take a cool shower, when I turn the hot water down to a nice cool temp, the water flow is to low and the burner shuts off and bam ice cold I regret going tankless

[icerube]

I have a bosch unit, capable of supplying two showers, $1000 unit, not cheap!!! Thought these were good units

( I thought wrong!) There customer service is a joke!!!

[echo2010]

Exactly. The place I used to live had everything softened except for one line that went to a small faucet in my kitchen sink area.. The water was good and hard there but my laundry was great and my toilets never got a ring...

Right now in my house we drink bottled water but would go back to tap water if I ever got the faucet installed

[MARINERMAGNUM]

I have a bosch unit, capable of supplying two showers, $1000 unit, not cheap!!! Thought these were good units

( I thought wrong!) There customer service is a joke!!!

I'm not familiar with that brand. When I saw the Rheem/Paloma on sale for 1/2 price I read all the reviews I could on them,paying special attention to what certified plumbers had to say about them-which was about all positive.

A couple of things most people overlook that leads to poor performance:

1. Sizing. A properly sized unit for a house in Florida would be too small if that house was in the midwest.

2. Gas supply. These units need their own seperate 3/4" line as close to the gas source as possible so you have between 10"-14" water column. Otherwise,your 200,000 btu unit may only put out 120,000 btu and make you think it's a bad unit.

3. Location. Many folks don't want to pony up the extra money for longer exhaust vents,so they mount it to an exterior wall of their foundation where freezing could be possible in extreme cold. Better to mount to a stub wall in the basement or if you have no other basement walls,drop some 2x4's down from your floor joists and build a little wall for it-they only weigh 50lbs.

4. Installation. Some folks try to install these themselves and they really aren't qualified. You really need some experience in plumbing to do it right so it will last and offer all the performance it can deliver. If you don't know a street elbow from a close nipple-don't even attempt it.

5. Supply. These units require good,softened water free from lime,scale and rust. After digging deeper on some of the gripes online,most of those jokers admitted to running their rusty,hard water right out of the well to it-a big no no. That will ruin it in short order.

[BobT]

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Correct,but in case you didn't know,most elect. water heaters have dual 4500 watt elements one at the top and one at the bottom-thats 9000 watts churning if you run it out completely,thus you need the heavier breaker when they both kick in. So Bob,if your marathon has 2 4500w elements and it's on a 30 amp breaker,you should have your's looked at. grin Mine is wired with #6awg copper.

Take another look at the rating of your water heater. I would bet it is rated at 4500w. I have never heard of any residential water heaters designed to operate both elements at the same time. When your top element has priority. If it's thermostat is calling for heat, the bottom element is disabled while the top element heats for rapid recovery. I have never heard of anyone wiring a residential water heater using 6awg. wire but if yours is, then you're probably okay.

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BobT,the common denominator you are forgetting is the cost of a KW hour vs the cost of a gallon of propane.

Not forgetting anything. At full price you would be correct that it costs more to heat water using electricity than LP gas however, if you read my earlier posts I also stated that taking advantage of off-peak electric hot water programs in most cases will be less costly than LP gas. This can be calculated if you know the efficiency of your gas water heater and do a little math.

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"Heating water using electric heat is 100% efficient."

I would say this depends on the wiring,a longer run and undersized wire will create more draw thus killing efficiency.

A long run with undersized wire will likely result in an electrical fire and system efficiency would be the least of your problems. In terms of efficiency you're talking about nearly immeasurable difference so I guess if you want to include those calculations you can use 99.9% instead of 100%.

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I would argue this point but the more important aspect of it is,if you use alot of hot water and your tank is not too big-you're gonna run out of hot water pretty darn fast!

Obviously when selecting an appropriate tank, the size is an important consideration. It needs to be sized adequate to meet the needs of the household but too large is adding cost unnecessarily.

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"The only savings between the two comes from not having to pay for the heat loss during storage.

This is not quite accurate. You're not considering the savings of using propane over electric when the rates favor propane.

Again, refer to my comments regarding off-peak electric.

I have said this in many threads. Electricity is one of the most expensive ways to generate heat if not THE most expensive when talking about using the full electric rate. Use off-peak and dual-fuel program rates and it suddenly becomes one of the least costly if not THE least costly method.

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Like I said earlier,it all boils down to how much continuous demand you have for hot water and what your utility rates are for gas vs electric. If you have an older couple who don't do much laundry,no kids,and only shower every couple days,forget it,it won't make a difference. That 105 gallon marathon would run out on us almost daily-then you have to wait.

There is a reason behind why tankless has been used in Europe for 40-50 years.

You must use a tremendous amount of hot water. Looking back at the sample monthly electric cost says this. We have a family of four (2 teenage girls), live on a farm, electric range, electric dryer, off-peak electric water heater, dual-fuel electric heat, dishwasher, and livestock that add demand to the well. We reduced that demand by putting in a Richie Waterer so at least we aren't paying $.08/kwh to run tank heaters.

I can tell you that during the summer when we aren't using the electric heat our off-peak monthly cost was about $11.00 per month. That's what we pay to heat our water. I did a quick search and priced some Rheem tankless. Seems they run right around $1,000.00. Let's do some math.

If my Marathon was only 50% efficient at the rate we use hot water, half my cost would be lost, or about $5.50/month. For argument's sake, let's say the tankless is 100% efficient, which it isn't but let's suppose. So, using these numbers if I switched my hypothetical system to a tankless system I would save $5.50/month.

I did a quick search and priced some Rheem tankless systems. They seem to run about $1,000.00 give or take depending on the flow rates.

$1,000.00 / $5.50 per month = 182 months. Even if I could realize that huge savings percentage we're talking 15 years before I'd pay for the tankless. Now let's go to more realistic numbers. Marathon water heaters are rated between 91% and 94% depending on the model. Using 92.5% I can calculate that approximately $.82 per month is heat loss

$11.00 * .075 = $.82

That works out to 101 years to pay for a $1,000.00 tankless. That's more than my expected lifetime even if I started at my birth much less starting the calendar now. Heck, the 15 years I calcuated at 50% eff. might be more than my lifetime.

[MARINERMAGNUM]

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$.08/kwh

Lol,you could have just posted what I quoted and saved alot of typing-you're rate is waaay cheaper than ours,and we aren't offered any "off peak" or similar deals from our company,so all that's irrelevent to my situation.

Again,like others you are assuming everyone has the same deal as you do,when in fact,most are miles apart.

There's no way you can figure how much it costs to heat your water alone unless you have a seperate meter for it-which is unlikely.

And yes,we use alot of hot water. If you're assuming it only costs you $11.00 per month to run an electric water heater and all 4 of you bathe regularly,you're fooling yourself-or your power company is fooling you,or you don't use much hot water at all.

The only math that needs done is when I see my electric bill drop by 45%-there is no argument for that.

What does the meter on your water heater register for a month's use in kw/hrs? And what does your flow meter register for a month of water usage in gallons?

[swamptiger]

One thing I'd like to point out is that many of the tankless type gas water heaters are in the low to mid 80% range in terms of heating efficency, so they are no more efficient than a standard vented gas appliance in terms of heating efficiency. If you go to a sealed combustion, modulating, condensing type, the heating efficiency goes up - (along with the cost of the unit).

Also, sometimes if there is a long plumbing run from the unit to the point of use, installers will add a circulating pump and a loop to the point of use, so efficiency will be reduced even further.

So there are a lot of factors that can come into play on these units, which explains why some people seem to love em, and others hate em....

[MARINERMAGNUM]

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So there are a lot of factors that can come into play on these units, which explains why some people seem to love em, and others hate em....

Words of wisdom.

For us,it really made a substancial difference and after having it a short time I can honestly say I'll never have another tank system in my lifetime. No way.

[Redlantern]

Swamp, how can you run a circ line on a tankless heater and not have the heater running all the time? I've only installed a few of them so I'm no expert (and it's been a few years) but I don't see how it would work.

[swamptiger]

There are some pumps on the market now designed specifically for tankless systems that have a built-in thermostat to maintain water temperature to the point of use. Don't know exactly how they work, but it sounds counterproductive, IMOP...

[MARINERMAGNUM]

Must be for the folks who can't spare the extra 5 seconds for the hot water to arrive!

[backlash 1]

Eric

We plumb in a 6 gal elec water heater before the tankless. Using a check valve, the 6 gal provides the heat to maintain the circ line. The only time the tankless runs is when you draw hot water.

[BobT]

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There's no way you can figure how much it costs to heat your water alone unless you have a seperate meter for it-which is unlikely.

Yes there is a way to figure out how much it costs to heat our hot water. Because of our off-peak system our elecric heat and hot water are separately metered. During the summer months when I have the electric heat turned off there's only one appliance left operating on the system...our water heater. The off-peak bill ranges between $10.00 and $12.00 per month during the summer months.

I also estimated our hot water heating cost at about $35.00 per month before I installed the off-peak system for hot water and based on the drop in our electric bill after it was installed I learned that my estimate was pretty accurate.

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If you're assuming it only costs you $11.00 per month to run an electric water heater and all 4 of you bathe regularly,you're fooling yourself-or your power company is fooling you,or you don't use much hot water at all.

Now who's making assumptions? The results don't lie.

[BoxMN]

For our duel-fuel ($0.052 /kwh) during the summer months, when like Bob's we only have the electric water heater (120 gallon A.O. Smith from the Electric Coop, for $325 delivered) on the seperate meter, the cheapest ours has been is $5 a month, and the most expensive it has been was $16 in July when we had a housefull of guests and kids most of the month. We don't live there year-round though, but it gets a workout each weekend

[PRO-V]

One thing I haven't seen anybody mention here is a tempering tank before your water heater. Some years ago I got a new water heater and stripped the jacket and insulation off the old one for a tempering tank. This way it will raise your water temp to the heater by room temp and gain you a heat rise of 15 to 20 degrees for free. Have also seen them made out of 3" or 4" pvc as a manifold before the heater and that works well too.

[swamptiger]

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This way it will raise your water temp to the heater by room temp and gain you a heat rise of 15 to 20 degrees for free.

Not really free during the heating season, because the tempering tank is taking the heat out of the air in the room, which you are paying to heat. Works in the off-heating season, though..

[BobT]

I think you can buy or build solar systems that can do this even to a higher degree.

[MNice]

One problem I see quite often in gas units is the main gas line. These units are usually pretty high demand, like 199,000 BTU or so. Many times the main gas line (even 2# systems) is not sized to handle that additional load, so a larger main for the house would be required.

Just something to consider

[krinkle]

There are tankless heaters on the market today that have built in recirculators and small tempering tanks. The one in my house has both. Most units I have seen with out some type or recirculation require .5gpm flow for the heater to fire. Navien heater require less than .1gpm to start.

With the built in recirculating pump there is a external connection for quickly adding a loop to the hot water piping if needed. There is also a control for setting when you want the pump to come on. I set mine to come on from 7am to 9am. Very efficient.

I dont know of any 2# gas system that is properly sized that can not handle 199,000 btus. Maybe if you are trying to run it on 1/4" pipe or running the length of a foot ball field.

How well does that work adding a small tank in before the heater? I would think a 6 gallon heater would only give you less than 3 minutes of tempered water. Then you are just running cold water threw it. Cant believe a small electric after a few minutes would have the recovery rate to have any effect on the tankless.

[backlash 1]

Krinkle

It works very well to use a small elec heater for recirc. After looking at my post I noticed my error. We came out of the Tankless, into the 6 gal elec and out of the 6 gal to the fixtures. Then the recirc line came back to the 6 gal using the standard circ pump,etc, and a check valve to prevent any backflow.

Now when hot water is drawn the tankless kicks on and runs right through the 6 gal. When no water is drawn, the circ pump at the 6 gal is just keeping the circ line hot with very little effort from the small elec heater.

When we did this a couple years ago, we did not have anything available with built in recirc systems, as you mentioned, now there is.

[MARINERMAGNUM]

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Because of our off-peak system our elecric heat and hot water are separately metered.

If you'll check my prior post you'll see that I inquired about a seperate meter. I also inquired about the kw/hrs the water heater racks up in 24hrs.

Obviously a tankless system would not help in your particular case-something I already addressed in a prior post-not everyone has access to off peak programs.

You obviously don't run alot of hot water,but I'd be interested in your off peak rate price. Knowing that,and the efficiency of your heater [which I know] and we know how much the cost is [$11.00/mo] we can figure how long your heater runs every month. Seems odd that it could be the exact same amount every month. Or is that how they structure it?

Example:4500w@ 1 hr=4.5kw/hrs 50 hrs time use=225 kw/hrs @5 cets per kw/hr in 30 days=$11.25 so in a 30 day span your heater runs about 1.6 hrs per day.

That same 225 kw/hrs would cost me about $30 and we averaged about 450-500 kw/hrs just on the meter on the water heater every month-that's about $60.

You get a great rate on your elec. and if we had such a rate I would have most likely just got another 105 gal marathon and ran it in series.

Also,how does the off peak system work? are you resricted to certain times of use?

[swamptiger]

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With the built in recirculating pump there is a external connection for quickly adding a loop to the hot water piping if needed. There is also a control for setting when you want the pump to come on. I set mine to come on from 7am to 9am. Very efficient.

Convenient, maybe...probably not so efficient after you add the heat loss from the recirc loop and the cost of operating the pump.

[MARINERMAGNUM]

One thing I haven't seen anybody mention here is a tempering tank before your water heater. Some years ago I got a new water heater and stripped the jacket and insulation off the old one for a tempering tank. This way it will raise your water temp to the heater by room temp and gain you a heat rise of 15 to 20 degrees for free. Have also seen them made out of 3" or 4" pvc as a manifold before the heater and that works well too.

I've also wondered about that. I have twin 85 gal pre charged pressure tanks and wondered if they have such an effect?

[Redlantern]

Swamp, that's what I was wondering, too. When you figure the cost of possibly having to increase a gasline if it's low pressure, the venting of the heater, the repiping of the water lines and the cost of having a small electric heater and circ pump, I wonder how long it would take to pay for itself. Might not be too bad on new construction but adding them after the fact is labor can be labor intensive.