04:53PM | 07/23/07
Member Since: 07/22/07
4 lifetime posts
I am looking to replace my Electric Water Heater (broke) with an Electric Tankless Heater. The existing Water Heater uses 2 30-amp breakers. The Tankless I am looking at requres 3 60-amp. I can't seem to get an electrician to return my call so I need your help, please. Before I purchase the tankless, how can I tell if the Breaker Box can handle 3 60-amps? Sorry not real knowledgeable about the Breaker Box. Thanks!


05:46PM | 07/23/07
Member Since: 04/25/05
1915 lifetime posts
The problem is not the panel. If there is not enough spaces it is easy to add a sub-panel.

However, what you need to verify is the size of the electrical service.

Under current codes the minimum size a service is 100 amps. However, many have 200 amp services. and a few larger homes have 400 amp services.

Look at the handle on the main breaker. It will be marked with the amperage. And do you have more than one panel?

" The existing Water Heater uses 2 30-amp breakers."

If you have a convention storage tank WH then it should have ONE breaker, but it will be 2 pole and twice the size of the others.

Two pole breakers are used for 240 volt loads.

"The Tankless I am looking at requres 3 60-amp. These would also be 2 pole breakers.

That would be a 180 amps and very, very few home could supply that without major upgrades.

However, that is based on circuit load and note the real load. Also the largest one that I have heard of uses 3 40 amp circuits.

So it would help if you could post a link to the spec sheet on this or at least the brand and model number.


08:32PM | 07/23/07
Member Since: 07/22/07
4 lifetime posts
Thanks for the reply BillHart. The main breaker says 200 amp 240 VAC. Sounds to me like if I need 180 for this unit then no way will it work.

There is no direct link to the tech specs but if you click here and then click Technical Data in blue halfway down it will show. Thanks again for the help!


05:12AM | 07/24/07
Member Since: 03/31/05
265 lifetime posts
You are correct in your assessment that it will not work. The electric tankless will come close to pulling all 180A when demand is maximized as when it uses all three heating elements. The only way to go tankless is with gas.


05:22AM | 07/24/07
Member Since: 04/25/05
1915 lifetime posts
The actual load is 150 amps.

That website is TERRIBLE. There certific is out of date, dead link, etc. I would not deal with them on principle.

The problem is on of physics. All brands are going to have the same problem if you need to heat that much water with that much rise in tempature.

But if you don't then there are smaller models from this brand and others.

This link shows all the models of that series. And a chart shows the flow rate and tempatrue rise.


05:25AM | 07/24/07
Member Since: 04/25/05
1915 lifetime posts
Here is how you size the electrical requirement for your house.


07:02AM | 07/24/07
Member Since: 07/22/07
4 lifetime posts
Thank you very much househelper and Billhart! It looks like I will be using a tank wh. For my own education, what would be involved in say upgrading my 200 amp panel to 400 amp? Thanks again!


07:22AM | 07/24/07
Member Since: 04/25/05
1915 lifetime posts
There are two ways of doing a 320/400 amp service. One uses a 409 amp panel and they are VERY EXPENSIVE.

However code allows upto 6 switches in one location for disconnecting power to a building. That is due to an old sytle of panel (split bus) that is no longer used.

But by the same rule you have more than one "main" panel installed side by side.

So a 400 amp upgrade will be a new meter and a additional panel.

If there are no complications it should cost no more and possiblyless then upgrading an old service to 200 amps.

But there are lots of variations such how finished the area is, if there is legal space for the 2nd panel, if underground feed is the conduit big enough, etc.


07:48AM | 07/24/07
Member Since: 07/22/07
4 lifetime posts
Well that definitely explains why the local homecenters don't stock the electric tankless WH :) Thank you all again very much for your expertise!


12:00AM | 11/07/07
Member Since: 11/06/07
1 lifetime posts
The Stiebel Eltron Tempra 36 should be strong enough to run 3-4 bathroom at the same time. Typically that unit could be used to replace 2 standard water heaters. How many bathrooms does your house have? Are you in a northern state or Canada? Most homes can use a TEMPRA-24 and that should be fine for a typical 2 bathroom home. The requirements are only 2 60 AMP double pole breakers. I am in south Florida and installed a Tempra 12 in my home and it only required 1 60 AMP breaker.
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