Any suggestions on an electric tankless water heater. Need a a whole house unit. Two baths.
I have heard these might not be all they are cracked up to be do to the huge amp draw on the electrical system. (I have a 200 amp service).
Thanks,
Keith
Any suggestions on an electric tankless water heater. Need a a whole house unit. Two baths.
I have heard these might not be all they are cracked up to be do to the huge amp draw on the electrical system. (I have a 200 amp service).
Thanks,
Keith
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Replies
I don't think the electrical ones are practical, unless you have very special circumstances. Certainly not the most efficient option.
Agree that Marathon are a good choice--we are installing one now--but I have a client with an electric tankless and it works fine for him. Single guy, often not home, able to locate the heater ~4 feet from the panel, already had extra space for (4) 2-pole breakers, no good place for a tank, etc. etc. I'm not sure there's any loss of efficiency at all....?
"Certainly not the most efficient option."You want to try that again..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
OK: "Certainly not the most efficient option."
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
Electric water heaters are almost 100% efficient. Specially tankless that don't have standby losses..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
In any scenario except a weekend cabin a Marathon tank will be more efficient than the equivalent electric tankless.
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
Electric HW heaters are NOT 100% efficient from a global point of view.Admittedly, they are nearly 100% efficient at your home. However, globally, the total energy used to extract and transport the fuel that is burned to generate electricity (mostly oil, ng and coal) and the energy lost on transmitting the electricity to you home makes electric HW heaters probably no more effeicient than gas or even oil burning ones.
Agreed, but normally don't look at global inefficiencies in any fuel. Put a gallon of gas in your car and how many miles can you drive ... you don't count the inefficiencies of drilling for and refining the oil and transporting that gas to the pump to alter your gas mileage. Why should we do that w/ electricity.
Your point is well taken ... we need to think more globally when acting locally. If you are going to do it for one commodity, you should do it with all.
When we pay for a commodity, we pay for all of the associated costs and inefficiencies it takes to deliver the commodity. Our high cost of electricity allready accounts for the 30% efficiency of producing it.
While your point is valid, we, as individuals have no easy way of accounting for the other efficiencies. We just have a KWH or Therm to use ... and we can determine the relative efficiencies within our little systems (at the point of the meter).
FYI, electric is the most efficient ... maybe not the most economical to run (a Btu worth of electricity is often much more than a Btu of gas).
Problem is, they draw so much current that you lose 10-20% in the wiring, unless you rewire specifically for the unit.
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
That's where my technology is a little rusty; not my expertise/knowledge .... electrical wire efficiency of moving current. So what do you mean you lose 10-20% in the wiring? 10-20% of the overall energy being delivered doesn't reach the device because of the resistance of the wire? The amp draw is 10-20% different at the breaker than at the device? I'm obviously electrically challenged. I always thought that in the little world of wiring in a building that 'line loss' was not significant and all amps/volts were converted to thermal Btus at the device. I understand some basic inefficiencies of e.g. wiring and connections, but thought that over short distances (from the electric meter) that they would be small.
The unit draws so much current that, if you don't upgrade the house wiring, breaker panel, et al, you're apt to see several volts of voltage drop reaching the unit. Eg, if you have 240V at the meter but only 230V at the heater, only 92% of the energy is making it to the heater -- the other 8% is lost to the wiring. If the voltage drops to 220V only 84% of the power makes it to the heater. How much voltage drop you get depends on a number of factors, but primarily on the amp size of your service and the distances involved.That's assuming you even have enough spare capacity for the unit in the first place.A regular tank-type electric water heater draws much less current, and so the voltage drop is less and the efficiency is better. (Even there, though, it might make sense to oversize the wire feeding the unit.)
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
"That's assuming you even have enough spare capacity for the unit in the first place."If you have the capacity then you won't have a problem with high voltage drops..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
If you have plenty of capacity (eg, you already have electric heat) then you won't have much trouble. If you try to squeeze by on a smallish service then you will.
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
PS: Check out the Marathon tank units.
Good sized electric tankless water heaters can require 150 amps or more all by themselves to operate, so they may not be practical to install. You need to look at the manufacturer's specs and figure out what capacity you need first.
Thats what I was thinking. Severe amp requirements. The gas ones arent getting rave reviews, cant imagine how the electrics show.
My electrician friend put one in after we we installed a shower in his 1945 home. It would only run a kitchen sink on an 80 amp circuit. He went back to a regular electric water heater. Its going to take more amps than you have to run an instant on heater. You can do the math and it just doesnt figure out to work in most instances.
What about a set-up where you have a solar hot water system pre-heating the water and only need the electric tankless as a booster in the cold months?
I've thought about the electric tankless units because I'm not sure how much longer natural gas is going to be around at a reasonable price.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Good point. If you use pre heated h2o the delta t (change in temp) will be less. My thinking is you will need a couple of units in parallel configuration. I am not an expert, only telling you what my friend found out when he tried it. He was also pleased that he purchased it with his American Express card that ensured his satisfaction. Its all energy in -BTUs out. What I am thinking is... Which is going to be more regulated.. Electricty or gas?
Yea two electric tankless units one for the radiant heating and one for the DHW. My solar guy says that we can provide all the DHW needs from late spring to early fall but to try to size the SHW system to provide the bulk of my winter heating would just be stupid. The radiant heating is being set up for a max temp of 100 deg F which should maximize the usability of the solar pre-heated water in the winter.
I'm told that decent gas boilers will last a loooong time so no sense in buying one now only to have to switch to electric when the nat gas runs out.
My plan is to hopefully be able to put enough solar panels on the roof that even with the electric heating I still cover most of my use with them. I've read in a lot of places that by 2010 the price of solar panels should be substantially cheaper than they are now.
As far as which one is more regulated? Electricity or Nat gas? I'm not sure what you mean. I think that nat gas costs will rise much faster in the coming years than the price of electricity.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
What is your cost for electricity and natural gas. Dont have gas available where I live in central Wa. and my place on the Oregon coast..Its always a few miles away and not getting any closer. Same thing with high speed internet. Half mile away and not coming any closer.Elect. is $.0587+ $15.00 for the Ore. place. Little less in Wa. Your system sounds good.
Keith,
I have a 24 kw unit. It runs a shower just fine. Problem is, don't turn on any other faucets, or you get a cold or cool shower till the heater catches back up after the faucet is turned off.
The family is getting pretty good at not using hot water while someone is in the shower.
With that said, I am going to install a 12 kw unit ahead of the 24 to preheat the incoming water. I will set it to bring the temp of the water up partway, and then have the larger unit finsh heating the water.
Both units together will pull about 150 amps. I have a 200 amp service. The electric company recently upgraded our electric service along the street by splitting the approx 12 houses into two transformers and upgrading the wire between the poles. That helped immensely.
If needed, they will upsize the wire from their line to my meter if my voltage drop is too much.
So, long story short, if you can do all the installation yourself and don't count your time, it might be a viable option. I spent about $600 to purchase and install the unit. If you are going to pay for the install, maybe not. If you need the space like we did in our small house, maybe ok.
Will I do one for our second bath? I haven't decided yet. If both heaters were on at the same time, the draw would be way over what my system could handle. So, that decision remains to be made.
Hope this helps. I like the idea of not having a tankful of hot water sitting there idle. Just don't know if it was the best way to go.
Bryan
"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio - just south of the Glass City
The system my friend took out was an 18KW unit. It would run the kitchen sink but anything more it went totally cold. He got a new circuit board from the mfg. and it was the same. Ammeter showed current but it wasnt getting hot wierd. He also taught electrical at the local trade school. Glad your system works.
atrident,
His system was probably working fine. If the flow is too great, the water will not be heated.
I can attest to that. When taking a shower, if someone turns on a faucet, the shower turns cool or cold. It then takes time for the heater to recover and begin heating the water to the temp setting again.
Some other factors that can affect this are:
Not enough current being supplied to the home. For example, in our situation, the power company's delivery system to our home had not been upgraded in years. Several houses had been built in the meantime, with ours being total electric. The voltage would drop to around 217 volts. While this is sufficient voltage for the heater to work, since it is rated at 208/240, it meant that the heater was only working at 75% capacity. Since the wiring/transformers have been upgraded, we now have more capacity.
Another variable is the incoming water temp. The heaters will only heat the water so many degrees in rise. The lower the incoming temp., the cooler the water will be upon being heated. 75 - 80 degree water feels cool, especially if you are trying to take a shower.
Did your friend use a thermometer to check the water temp. to see if there was any rise, or did he just stick his hand under the water and say: "Hmmmm, it's not working."?
I thought I did enough research on our situation before ordering the heater. It does sufficiently heat the water. You just can't use more than one appliance at a time.
Bryan"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio - just south of the Glass City
Got a lot of juice?
This baby sucks up 36 KW
View Image
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.†—Albert Einstein
Am I missing something? Or is the plumbing in the unit run in such a way that we can't see it in the picture?
edit: After enlarging the picture, the piping must be at the bottom of the unit behind the front flange?
Also, I see it is three-phase. What size wire/breakers?
"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio - just south of the Glass City
Edited 4/30/2008 10:17 pm ET by BryanKlakamp
Always check with your power provider before installing an electric tankless. I am told that some providers will not allow electric tankless because the transformers/services can't handle the huge amp requirements.
I second the recommendation for the Marathon heaters.John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
The plumbing is on the bottom under each heater.
That unit is 6 Eemax 277v heaters piped in a series/paralell configuration.
I have no idea what size the breaker is back at the panel, the unit has 30 amp fuses for each heater.
One was wired wrong from the factory------ I never want to see or hear 277v to ground in a 16g wire 12" from my face ever again.
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.†—Albert Einstein
Heating water takes a LOT of energy if you want it done quickly. A natural gas tankless heater that is 85% efficient uses 120K BTU to generate about four gallons of hot water. For electricity to do the same requires about 30kW, or 136 amps on a 220 circuit. If you have a 200A panel, running the water heater, the oven, and a dryer at the same time would max out the service.
A 15-minute shower would cost about a buck, so don't forget to hang that collection box on the bathroom wall.
Heating water quickly really takes no more energy than doing it slowly ... generally speaking. The difference is in the CAPACITY of the system. It takes a lot more system CAPACITY to do it faster. And the system size will be slightly larger in the gas system than the electric system ... due to the relative combustion inefficiency of gas. 30KW equals 120,000 BTU gas system at 85% efficiency.
By the same token, you may not have the proper gas pipe size to accomodate all your loads w/out e.g. changing delivered gas pressure or your pipe size (all depending on the configuration of your piping and current equipment capacities).
Point being ... tankless requires a LOT bigger capacity system regardless of energy source and MAY require you to upgrade any system to accomodate it.
Again, I encourage evaluation of the needs and use of the best equipment for the use. A lot of hype has been going around in recent years about how great tankless is and now everyone and their brother is installing these for their general household use. High installed costs, in my book don't warrant the tankless ... if you use hot water regularly. A small tankless at a remote fixture can be great to avoid running a lot of water while waiting for it to get hot. I think maybe the best use for larger tankless is for significant uses that occur only occasionally.
You'd be much better off spending money and effort to reduce hot water consumption for: showers, dishwashing, and clothes washing. You'd save big time on your hot water energy bills and consume a lot less water ... and in some places water ain't cheap.
Just off hand, cause I often shoot from the hip and my foot is out of the way for the moment, a whole house gas fired job should run about 190,000 BTU. They often require larger gas lines etc. To do the same with electric means you're going to need another 200 amp panel just to be safe. Go gas, it's more efficient and "Greener" for the task at hand.
Ok, so I have read thru all current messages. And I think that everyone has brought up all very good points. To answer your question about electric tankless water heaters I can only speak from my experiance. So here is what I can say, take it (good or bad) at face value.
So let me first say that I do have a electric tankless water heater for domestic hot water. It is a bosch aqua star AE125 and supplies a 5 bed 2 bath house. We built our home with the intention of installing this type of unit. It only happened to be the AE125 because I got it cheap. It will provide enough hot water to run two major appliances at one time. Like a shower + wash machine, or shower and dishwasher. Have never tried both showers at once but have never had a need to.
Things to concider/overcome in deciding if this is right for you.
1. You will usually need a seperate 150 amp panel seperate from your main panel to power the heater.
2. cost of getting the proper panel situation to make the heater work correctly so it provides the hot water you want.
3. Your power co: you may need a bigger meter socket to power up everything.
4. In my case the power co needed to put a bigger transformer on our service pole to meet our needs. This meant a bigger equipment fee on our bill.
5. On the positive side we never run out of hot water.
6. Our cost of operation is less, but the extra fees form the supplier eat it up. I would say we break even on operating cost. So do the math in your case. At this point I am currently satisfied with operating cost.
7. space saved.
8. Problems: When the heater breaks (ours has currently not) but when it does, nobody stocks any parts. so be prepared to go with out hot water for a few days. Or plan in advance and have a extra part/heater on hand to solve any problems.
This I just me experiance. hope it helps.
If you use hot water regularly, tankless is probably not the way to go. A lot of attention on tankless being more energy efficient ... they are, but not substantially ... especially if you use hot water regularly. The marginal energy benefit is probably significantly outweighed by the relatively large installed cost.
I encourage people to use the right equipment for the right applications to get the best overall value.