Replacing water heater with tankless heater

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  #1  
Old 01-05-15, 11:53 AM
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Replacing water heater with tankless heater

Present water heater is 19 years old, want to replace with EcoSmart 18 tankless. Present water heater has one dp 30 amp breaker, new one calls for two dp 40 amp breakers. Breaker box is 150 amp with no empty spots, would it be okay to move the washer 20 amp single pole wire to the 20 amp single pole GFI breaker, which is for the bathrooms, and outside recep? Dishwasher is next to it, a single pole 20 amp, I have never used the dishwasher. Moving the one, eliminating one would make room for the second dp breaker. I'm single and light bill is pretty low, hopefully lower if I can hook up the tankless. Will this work without creating a problem?
 
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Old 01-05-15, 12:00 PM
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The first thing you need to do is called a demand load calculation to see if you service will support the additional load.

The washer cannot be combined with the bathroom circuit.
 
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Old 01-05-15, 12:53 PM
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me too...

Sorry if I am hijacking this thread, I am trying to do the same thing....but slightly different at the panel, so very interested in this thread. I am trying to swap the current HWT for a tankless electric, and want to swap it straight out, like plug the wires straight into the tankless and hook up the water. I am also going to install another larger tankless to run in series.

I am wondering about wire and breaker size, and how to run it effectively. I think I can do a smaller, like 3-5 kw from the same wire as the existing heater, and then run 6 gauge wire to a 60 amp breaker for the larger heater.

I need two because of the ground water temp (zone 4 or 5). We are going tankless due to 7 people in one house running on an old tank. Add up all the showers/baths/dishes/laundry, and there isn't enough hot water for the adults to get clean at the end of the day.
 
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Old 01-05-15, 01:04 PM
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Electric tankless water heaters have a huge peak draw compared to any other appliance. In a remodel situation, this almost always requires an upgrade of the service drop, meter and main panel to provide enough power for the heater. The demand load calculation pcboss mentioned will tell you if your existing service can support the load, and if not, how big new service will need to be.

Idaho, you could do a larger tank heater such as 80 or 100 gallon to support the showering demand as an alternative to going tankless which can prove to be very expensive.

I have not found tankless heaters to be cost effective in existing homes.
 
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Old 01-05-15, 01:19 PM
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Tankless heaters sound good on paper but the reality of their electric or gas demands when in use often make them unrealistic in the real world.

As in the first example, I do not think 150 amp service is going to suffice while the second person to ask did not list their service.
 
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Old 01-05-15, 01:42 PM
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The only one I had any part of required a second 200 amp service to be added just for the WH. It had 3 40 amp circuits.
 
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Old 01-06-15, 08:40 AM
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I am wondering about wire and breaker size, and how to run it effectively. I think I can do a smaller, like 3-5 kw from the same wire as the existing heater, and then run 6 gauge wire to a 60 amp breaker for the larger heater.
Present water heater has one dp 30 amp breaker, new one calls for two dp 40 amp breakers.
My biggest fear would be spending a large amount of money to upgrade my service and install the tankless heater/heaters to only find out I have warm water, not hot water, and a high maintenance nightmare. I am sure that in both of these siuations that one shower would be hot, but what if two people are showering at the same time the dishwasher is started?
 
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Old 01-06-15, 08:50 AM
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CJ, from my understanding the thankless are sized based on the number of expected users so they can accommodate that scenario. Unfortunately that is also why the electrical loads are so high.
 
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Old 01-06-15, 09:39 AM
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I think I'll be sticking to a natural gas tank type.
 
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Old 01-06-15, 09:50 AM
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Natural gas tank type is what I have and there are NO plans to change - 40 gallon capacity and I have never run out of hot water in the shower and I've never paid any attention to whether someone else is showering or washing clothes or dishes.
 
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Old 01-09-15, 10:31 AM
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no gas

Mitch, that would be great, but it seems this thread is electric probably because we don't have access to gas. Maybe a method behind the madness there.

IG
 
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Old 01-09-15, 10:38 AM
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I'm aware of that; I was just responding to Joe in post # 9.
 
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Old 01-09-15, 12:12 PM
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Is propane an option? .
 
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Old 01-09-15, 12:52 PM
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Just curious, why are you replacing the existing,because of age? The Eco 18 does require 2 40 amp circuits as you stated,Mfg. Min size service 100 Amp,Eco 18 max load 75 Amps. Single person,living in Fla.average input water temp is 72*,this could work! what type of service panel do you have?only real option is yo try and install a couple of tandem breakers to make space for the new 2 pole 40,you will also need 2 new 8/2 cables installed to the new location.
Have you figured what the pay back period will be when you are done?
Geo
 
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Old 01-10-15, 09:54 AM
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Interesting that the OP hasn't returned since the original post in this thread 5 days ago.
 
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