Breaker box

Breaker box instructions

I need 240VAC, single phase, 27 kW at 113 amps. Required breaker is 3 x 40 Amp

I don't have enough space for (3) 40 Amp in my panel.

Question is: can I kill 30 Amp (hot water heater) breaker and put in this place 150 Amp breaker and from this 150 Amp make sub panel? In sub panel I planning put (3) 40 Amp

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    Hello, and welcome to Stack Exchange. I'm no expert, but I don't think you can join three 40A breakers to make a single 120A breaker. – Daniel Griscom Oct 25 '18 at 1:05
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    @DanielGriscom it's for a tankless water heater. You're supposed to power it that way. The water heater has 3 circuits to allow it to run on 3-phase (NYC 208 V delta, Brazil 220 delta, 240 delta or Euro 400V wye.) – Harper - Reinstate Monica Oct 25 '18 at 1:42
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    Well since you are changing or want to change to a new electric on demand system you can eliminate the breaker to make space but be aware I live in a place that electric used to be CHEAP,,, no natural gas in many areas because of this. I have upsized several homes to provide on demand electric water heat ,in several high end homes the owners added a single unit then had to add smaller units at bathrooms to provide enough hot water for use and another that had a huge upgrade changed back to a +80 gallon electric water heater after spending thousands to try this and hated it. Do your homework. – Ed Beal Oct 25 '18 at 2:21
  • WHY do you want to go to an electric tankless water heater? There are far better options out there, even for large water loads...what's your hot water usage like in your house? – ThreePhaseEel Oct 25 '18 at 3:23
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    @harper the biggest unit I installed was larger than the op it was the largest residential unit available and the owner had me remove it a month after putting in a 400a service and went back to a large tank based water heater this person was very picky not that the unit was undersized. – Ed Beal Oct 25 '18 at 18:49

You have a special panel called a "Rule of Six" panel. The top 12 spaces in the panel are the "Rule of Six" area, and up to six breakers are allowed in that space. Collectively, these are your house's main breakers.

The breaker in the lower right of the Rule of Six area powers the breakers below, which are a "built-in subpanel" if you will.

You may notice you have 7 breakers in the Rule of Six area. That is not allowed, but your plan will correct this.

The 150A Siemens breaker, the Q2150B, is a beast. It takes up four spaces. That means you will need to eliminate or relocate two 2-pole breakers to make room for it. An amusing side-effect is this will reduce you to 6 breakers. You are still not legal because the double-double-stuff breaker in spaces 3-4 is not allowed in this panel in that space. Double-stuffs are disallowed in the top 8 rows, as the diagram and numbering show.

I would go a different way. I would fit a 150A subpanel, and then move everything in the Rule of Six area to it. Now you have 4 spaces for the 150A breaker, two spaces for the "main" breaker, and 6 spaces free. Now I'd put the three 40A breakers in those six spaces. Done!

On second thought, I would put the three 40A breakers in the new subpanel, and leave the 6 spaces empty. That gives more reasonable overcurrent protection for the service wiring since you can only draw 250A, not 370A as in my first scenario.

  • Thank you for your answer. So far everything is ok inside the panel I just have inspection last week. But I still thinking how I can install thankless water heater. Maybe I have to give up which my plan. 🤔🤔🤔 – Roman Oct 25 '18 at 4:59
  • @Roman -- how much hot water do you need your house to provide? (or even, how many bathrooms does your house have?) – ThreePhaseEel Oct 25 '18 at 11:36
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    @Roman the inspector either has never seen a Rule of Six panel, or decided to armwave the 7 breakers, or there's a local amendment, or your house has added an outside main breaker which means the Rule of Six goes away. That last situation would be nice. – Harper - Reinstate Monica Oct 25 '18 at 17:57
  • @Roman -- do you have a main breaker located somewhere else than this panel? – ThreePhaseEel Oct 25 '18 at 22:26
  • @threePhaseEel we have 1,5 bathroom but soon it will be 2 full bathrooms and we are family of 5 so we need more weather. My wife laundry inside the garage and this tank use to match space so we looking for different ideas... – Roman Oct 26 '18 at 5:04

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