Additional Breakers


Old 03-21-19, 05:44 AM
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Additional Breakers


I am looking to have a tankless water heater installed, replacing my standard water heater. I need to add either 2 each 50A breakers, or 3 each 40A breakers, depending on the unit I buy. I currently have a 200A elec service, and adding up all the existing breakers in the panel comes to 595A. Can I safely add either of these additional breakers, or is there more I need to consider? I'm not an electrician but when I call one out to install the additional breakers, and possibly new wiring, I want to be comfortable that he knows what he's doing.
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Old 03-21-19, 05:49 AM
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Adding the the total of the breakers is not really going to tell you much.

You will need to do a load calculation to see what your present power requirements are.

You don't add the breakers up to do this as you normally don't run everything at one time at full power so this method is misleading for that reason.
Old 03-21-19, 06:16 AM
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Search for "demand load calculation" to find some online resources to assist in the calculation to get an accurate answer.

For a gut feeling answer, you probably do not have enough electrical capacity to add a tankless heater of that size. Usually when I have encountered this situation it requires upgrade to 400A electrical service -- one 200A panel for the house, one 200A panel for the tankless. You also need to notify the power company of the substantial increase in load, and they may need to make some upgrades or changes on their side.
Old 03-21-19, 09:30 AM
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I have thought of going from standard electric water heater to an electric tankless, but the more I read the less I feel it's worth it. I just don't get great fuzzy feelings about electric tankless. Now gas tankless, that's another whole story, but I don't have gas.
Old 03-21-19, 01:16 PM
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Agree. Electric tankless from all I have read is not worth it. Tankless is only effective if you have gas.
Old 03-21-19, 02:09 PM
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That's certainly true up here in the north anyway. But even with gas units you might need to upgrade the gas service or lines which can get pretty expensive too. My estimation is that energy savings is unlikely to ever payback the installation costs in many cases.
Old 03-21-19, 03:08 PM
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Electric tankless just don't have enough btu to heat cold water. It works fine down south and during summer even in northern region.
If you use full hot, (meaning you don't mix cold water) it might be hot enough. However, some shower valves don't even allow full hot.

Most gas tankless units require 3/4" gas line and sometimes even gas service upgrade.
There are some gas tankless units that uses 1/2" gas line and does not require gas service upgrade in most cases.
Gas tankless is worth it if you install one yourself. However, if you have to have a plumber come and install, chances are they will charge you an arm and a leg.

Price of the gas tankless water heater itself is not much more than a power vent water heater.
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