Thread: Hybrid Water Heaters

I have a client who has specified Eternal hybrid: the world's first and most advanced hybrid water heating system for his new house being built. This is new terriotory for me. Does anyone have personal experience with these in the field?

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No experience with this brand but it is very similar to tankless system that one high end custom builder uses. He uses a circulator pump with a small (6 gallon) electric heater to make continuous hot water available without having the tankless continuously start-stop firing. He gets the best of both worlds, continuous and instant hot water.
If they execute the plan well, sounds like they have a winner.

Gentlemen: Thank you for your comments.

Originally Posted by A.D. Miller

Gentlemen: Thank you for your comments.

There are gentlemen in both Florida and Texas......hmmmmm

Originally Posted by Ted Menelly

There are gentlemen in both Florida and Texas......hmmmmm

TM: The politic on this side must be rubbing off on me.

The Eternal hybrid is nothing but marketing hype. They make claims of these great GPM rates over the Tankless units out there. for example they claim their largest unit will do 20.8 GPM but fail to say the temperature rise right away. If you have a look that is at a 20º temperature rise. Now lets compare it to the largest Noritz unit, Noritz says they get 13.2 GPM @ 45º rise. Their largest unit only gives 9.4 GPM @ a 45º rise. I do get many calls to install a Eternal hybrid after I explain to the people that here in Illinois our incoming water temperature is around 50º so they would need a 70º temp rise which puts their unit at 6 GPM but the Noritz at 8.9 GPM

Also the tout how they are the only one to have a buffer tank, Navain has been doing that from the start. Navain also has units with built in recirculation pumps.

So please do not fall for the marking hype that any manufacture advertises and look at their true flow rates at the needed ΔT rise.

Originally Posted by Ron Hasil

The Eternal hybrid is nothing but marketing hype. They make claims of these great GPM rates over the Tankless units out there. for example they claim their largest unit will do 20.8 GPM but fail to say the temperature rise right away. If you have a look that is at a 20º temperature rise. Now lets compare it to the largest Noritz unit, Noritz says they get 13.2 GPM @ 45º rise. Their largest unit only gives 9.4 GPM @ a 45º rise. I do get many calls to install a Eternal hybrid after I explain to the people that here in Illinois our incoming water temperature is around 50º so they would need a 70º temp rise which puts their unit at 6 GPM but the Noritz at 8.9 GPM

Also the tout how they are the only one to have a buffer tank, Navain has been doing that from the start. Navain also has units with built in recirculation pumps.

So please do not fall for the marking hype that any manufacture advertises and look at their true flow rates at the needed ΔT rise.

RH: Good information. Thanks!

one of these days i will get something like the hybrid too, as the idea seems good.

without getting into the politics and greed that drives sometimes business (including the so called supply and demand by shady sources), I was pretty surprised upon arrival to the US when I found out that many people here are using electrical water heaters to heat water for the whole house (including me .
Nothing wrong with the equipment itself because there are instances where is the best option but many systems have the units not located in a central position "because you will use the kitchen more anyway"..I almost always swear when I want to take a shower and have to wait for the hot water....

It took me a while to adapt being used to the gas tankless water heaters back in europe (by now possibly the electrical ones too) which have been offering hot water on demand for decades

go tankless heaters (so i can buy one cheaper)

Tankless water heat not so hot
TheStar.com - Recession - Tankless water heat not so hot

May 31, 2009
Ellen Roseman

You're thinking about replacing your old water heater tank. Is it time to go tankless?

There's an endless supply of hot water, suppliers claim, since you only heat water when you turn your faucet on.

You can save room in your basement with a wall-mounted tankless unit and save money on your gas bill.

Kevin Kennedy installed a tankless water heater last fall after doing an energy audit of his four-year-old house. He's not impressed so far.

"It hasn't lived up to the hype I read in the papers, nor the sales pitch from the contractor," he told me. "The only savings have been the rental fees on the tank we removed."

A tankless water heater needs extra maintenance, he found. It has to be serviced once a year with a vinegar solution to keep it clean and functioning properly.

"Estimated cost is $100 a year – more than the gas savings."

He had to remove his water-saving shower heads, since there wasn't a strong enough flow to keep the water heater on.

"I now waste more water waiting for the hot water to arrive. It takes 10 to 15 seconds every time you turn on the tap for the hot water to get up to temperature – and up to a minute with the tap on full for the hot water to arrive on the second floor."

Reliance Home Comfort (formerly owned by Union Gas) tests tankless systems in its labs to simulate the water use of a typical family.

It finds you can save about 15 per cent of the energy previously consumed by the hot water tank.

A family of four with a 50-gallon tank spends $30 a month to heat water, says John Krill, director of operations support.

A 15 per cent gas saving means an extra $4.50 a month, or $54 a year.

That's not a big deal – and Krill agrees with Kennedy that the gas saving is often eaten up by the cost of extra water use.

"Many households take longer showers. From 10 minutes, they go to 12 minutes, knowing they won't run out of water. So, what happens to the savings? Zero."

You save energy only when you keep your hot water use the same as before, he emphasizes.

You may be disappointed with what you get when you need a trickle of water – say, to clean a razor blade while shaving. The cold water has to flow through the tankless unit and kick on a heating mechanism. This can take a while.

"Tankless systems won't give you the same hot water in a low-flow scenario as what you get from a storage tank," Krill says.

Second, there's the peak flow scenario when you want an endless flow of hot water. Again, you may be disappointed. A hot water tank uses about 40,000 BTUs of energy (British thermal units) but a tankless unit uses five times that, or 200,000 BTUs. "It fires up the burners and pounds the cold water to raise the temperature to 120 degrees Fahrenheit," he says.

The municipal water temperature is about 70F in summer, but can drop as low as 40F in winter.

The tankless unit has to work harder to heat water from 40F to 120F. This means your endless supply can run out in the cooler months.

So, scale back your expectations in winter. Instead of two showers and doing dishes at the same time, do the dishes later.

Next week we'll look closely at the cost of buying/renting a tankless water heater system.

Raymond Wand thank you for that post. There is a few things that they say are a bit wrong, or a misunderstanding on the article writers part.

First of all yes a Tankless system must be maintained, so does a tanked water heater (which almost no one does). If you fail to maintain a tank heater you lose efficiency and eventually will cause it to over fire and shorten the life of the tank. Now where a tankless is not maintained it will adversely effect the flow rate. But the tankless unit will tell you with an error code that it needs maintenance. Also a gallon of vinegar does not cost $100.

The 10 to 15 seconds of cold water you get when you turn on the hot water is the same amount of time you have to wait with a tank heater. The problem is not how fast a tankless unit can make the hot water, it is the hot water pipes after the water heaters cooling down. So what he is noticing is the time it takes to purge the water that was sitting in the pipes. Same issue with how long it takes to get hot water up to the second floor. There is a fix for this with a tank type and tankless water heater. It is an on demand recirculation pump that can be added easily to the farthest fixture. When you need hot water there is a button you press and the pump will recirculate the water from the hot pipe back into the cold piping (no wasted water) until it gets up to temperature.

About the flow rate to turn on these units. It does take .5 gallons a minute to trigger them. A bathroom faucet has an aerator that restricts the flow to 2.0 GPM. You can run the faucet full hot at a slow flow to turn it on. I never had a single complaint about this issue. Also all tankless units today are modulating burners. Meaning depending on the flow rate it may only use 11,000 BTU to provide you your hot water need up to 199,900 BTU for a full flow condition.

Speaking of the 199,900 BTU tankless units, apparently he does not have one. When he talks about incoming water temperature and output flow rates, he is showing he has an undersized unit. Noritz makes a unit that will run Max 199K BTU to 11K min BTU and at a 70º incoming water temperature it can provide enough hot water flow for 4 showers with the 45º water temperature it does go down to 2.5 showers. Sizing the unit to the home is very important, an undersized unit will always run at full BTU's and need maintenance more often, as well as make the home owners very unhappy with how many fixtures they can run.

Now for energy savings. It is true that a household may only save any where from $60 to $180 a year in fuel costs. Which can be lost when people take a longer shower due to the fact they have an endless supply of hot water (which does make this more a luxury item). But in commercial applications like in Hotels that run five 500,000 BTU boilers to handle the demand of 150 rooms, laundry, and the kitchen. Many have switched to eight 300,000 BTU tankless water heaters and have seen a savings of $1200 a month in fuel costs. If you think about it a hotel uses very little hot water in off peak hours. But every time one of them 180 gallon boilers cooled down a little they fire up their full 500K BTU to reheat the water. Same goes for restaurants.

Here is an added benefit that he failed to talk about. When you tank water heater breaks(leaks) what do you do just replace the tank and keep the burner controls and the jacket the tank is wrapped up in? No you end up replacing the whole water heater. When a tankless water heater breaks or leaks you no longer need to replace the whole water heater, you just replace the defective part. Heat exchanger leaks, you remove it and put in a new one. Burner goes bad You remove it and install a new burner. The unit is very modular inside to make for easy repairs to a properly trained installer.

I have to tell you I was originally in the same boat as the person that wrote that review. But that was due to tankless units like Bosch being sold at Home Depot, and the unknowledgeable sales people. Many people think the $450 Bosch will give them endless hot water. It will but at a cost of poor performance. It goes back to a properly sized unit for the house's needs. One thing that all the manufactures tell us contractors do not size the tankless system to how many people currently living there but size it to the house. I do get people say to me "Ron why do we need such a large unit its just me and my wife?" I explain to them what if something happens and a child or a relative needs to move in, or if you sell your home to a larger family and they will be using all three showers at once. If they still will not listen to what unit I sized for their home, I will apologize to them that I can not do their work then.

all that good info is fine and dandy and greatly appreciated..

No matter what I still keep my golden memories of turning the hot water back in portugal and have hot water running in the shower in seconds..not minutes

I am aware that here would take a little longer because I have a well and the water pressure is lower than public.

My time is also valuable...if I want to take a quick shower here in my house in the US I end up swearing in portuguese about the cold water (so my kids don't understand what i am saying ..
back in PT a quick shower was turning the water on, undress,and getting into a warm shower...

I would not be surprised if the tankless water heaters here are also different and less efficient....Like cars...
glad Schwarzenegger contaminated Obama with his mighty power about emissions but that is for another time and might not be allowed here..

Well one other thing is when a contractor installs a tankless water heater he likes to move it to an outside wall for ease of venting. In other words to save a buck on the install in venting pipe. But when they do this they move the water heater further away from the whole plumbing system, in some cases adding 40 feet of pipe between the tankless unit and where the original tank was. I prefer to put the tankless unit in the same location as where the original tank heater was, then the time to get hot water is the same no matter what. Yes that means more vent piping, and redoing the gas piping in many cases, which translates to a happy home owner when all is said and done.

Originally Posted by Joao Vieira

all that good info is fine and dandy and greatly appreciated..

No matter what I still keep my golden memories of turning the hot water back in portugal and have hot water running in the shower in seconds..not minutes

I am aware that here would take a little longer because I have a well and the water pressure is lower than public.

My time is also valuable...if I want to take a quick shower here in my house in the US I end up swearing in portuguese about the cold water (so my kids don't understand what i am saying ..
back in PT a quick shower was turning the water on, undress,and getting into a warm shower...

I would not be surprised if the tankless water heaters here are also different and less efficient....Like cars...
glad Schwarzenegger contaminated Obama with his mighty power about emissions but that is for another time and might not be allowed here..

Don't forget modern shower heads in the US are required to be low flow and thus will take longer to drain the cold water parked in the pipes.
Sounds like you would be a good canidate for a circulator pump to deliver instant hot water.