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I'm replacing a old tankless with a new one. The old one is wired with 240 on two 60 amp breakers. It had two lug connects along with a ground. The new heater is 4 lugs and requires two 60 amp breakers, so i'm good there. How do i make it for 4 lugs? Do i just put 2 pigtails in junction box and then to heater?

Thanks for any help, quinnenter image description hereenter image description hereenter image description hereenter image description hereenter image description here

  • Including the model of the unit, along with a picture within your question will go a long way in getting help. – stevieb Jul 3 at 12:59
  • okay thanks, I'm heading there in a little bit and will post them up. – quinn Jul 3 at 13:12
  • Hello, and welcome to Home Improvement. We're looking forward to those pictures. And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Jul 3 at 13:26
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    @quinn, in breaker terminology, what you're calling two breakers that toggle together is more accurately known as a (one) two-pole breaker. If your new heater says it needs two 60A 240V breakers, it means you need two of those two pole breakers, along with four wires -- that may be what the four lugs are for. So you may need another set of breakers + wire, but the model/nameplate pictures of the new tankless will answer that for sure. – Nate S - Reinstate Monica Jul 3 at 16:12
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    Can you post a clearer photo of the inside of the box where the water heater joined to the house wiring at? Also, how large is your existing electrical service, and can you post a photo showing the full extent of the breakers in your panel?\ – ThreePhaseEel Jul 3 at 22:24
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It appears Circuit B powers nothing but heaters 3 and 4, so consult with the factory. It may be possible for the unit to happily run with circuit A only, at the 60A power setting.

Other than that, you will have to find 2 spaces for another 60A breaker. This appears to be a GE Qline which supports their advanced design for "double-stuff" breakers, including 2-pole double-stuffs that straddle 2 spaces (as in right above the 60A). Convert 4 spaces worth of breakers to double-stuffs and you'll have the room.

Now the bad news. The wires seem to be run in 1/2" EMT conduit, with individual THHN wires, presumably 6 AWG. They didn't need a ground wire, but they ran one, so the wire count would be 3 instead of 2 - it's a conduit fill rules thing. Regardless, this 1/2" conduit cannot hold four #6 wires. For that, you'll need 3/4" conduit, and will just fit with that one #10 ground. So you will have to re-run all this conduit.

When you buy wire, use two black and two red. The blacks are circuit 1, and the reds are circuit 2. For each circuit, the two hots are interchangable - no value in phasing them - but you certainly do need to tell the circuits apart!

Now if you run 1" or 1-1/4" conduit, you can run #4 aluminum wire. No idea if that's any kind of savings for you. Whether the tankless can accept #4 or aluminum is a factor; otherwise you'd have to pigtail with expensive Polaris connectors.

Given that, you might as well rethink the location of the heater. Very often, these on-demand heaters are slapped down exactly where the tanked heater had been. That location wasn't optimal at all. It was put there because tanked heaters are huge and ugly, and often because a gas vent is possible there. It's usually not the ideal location for a small tankless. You want that as close as possible to the most important point(s) of use, e.g. the place you least want to wait, wait, wait for hot water. For me, that's the shower.

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