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I have this tankless electric water heater. It’s 18kW; at 240V, I am running two 8/2 Romex cables which connect to two 40 amp double pole breakers in the panel.

Since the breaker is out of sight, I require a disconnect for this appliance, but the disconnects I am finding are only for two poles. My system has four due to the amperage. I cannot seem to find a disconnect (non fused is fine) to handle this scenario. I can easily get two $15 disconnects, but the water heater only has a spot for one cable whip connection.

What’s the normal way of going about having a disconnect for two wires?

Other details

  • I am a DIY-er in California with the appropriate permits pulled as the property owner.
  • I am confident in doing this work myself, I just feel like there’s a knowledge gap here somewhere.
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    What make and model are the breakers feeding this circuit? Using breaker lockoffs might be a better bet than spending the $$$ on a 4-pole switch (they exist but are very expensive) or trying to use two disconnects (which sounds a bit error prone unless you do something funky)
    – ThreePhaseEel
    Commented Jul 22 at 1:26
  • @ThreePhaseEel Would two disconnects side-by-side be any different from two breakers with lockoffs side-by-side? Only way I can see a way to make the breakers "better" than the disconnects is if you could handle-tie the two double-breakers together, which I suppose may be possible for some brands.
    – manassehkatz-Moving 2 Codidact
    Commented Jul 22 at 2:20
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    You don't have an 80 amp circuit. You have two 40A circuits, and if you can see both disconnects from the unit, one disconnect for each circuit is safe, legal and easy to buy.
    – Ecnerwal
    Commented Jul 22 at 3:01
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    @manassehkatz-Moving2Codidact -- I was thinking of handle-tie shenanigans, yeah
    – ThreePhaseEel
    Commented Jul 22 at 3:11
  • @ThreePhaseEel I am using these. You're right that the 4 pole switch is too expensive!
    – C Fairweather
    Commented Jul 22 at 15:28

1 Answer 1

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There are a bunch of ways to solve it. One possibility:

  • Cable whip to a junction box
  • In junction box connect wires to two pairs of 8 AWG wire.
  • On each side of the junction box, use a nipple to connect to a disconnect.
  • Run one pair of 8 AWG wires through to each disconnect.
  • Run 8/2 cable (or 8 AWG wires in conduit) from each disconnect to a breaker.

The disconnects are each for 40A, because each circuit is only 40A. Which means a typical inexpensive HVAC disconnect rated up to 60A will work just fine.

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  • Excellent advice. This definitely puts the picture together for me. Step 2 seems unnecessary to me, as I still need four wires going to the water heater, so I will run four wires to the junction box and then route two each into the disconnects. Thanks so much!
    – C Fairweather
    Commented Jul 22 at 15:32
  • Typically an included whip has wires that are only a few inches longer than the metal casing - i.e., not enough wire to extend through a junction box to the disconnects. If there is enough wire then there is no need to attach the pigtails.
    – manassehkatz-Moving 2 Codidact
    Commented Jul 22 at 18:55
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    I am noticing that. I have plenty of extra cable length to replace the wires in the whip, or I'll find some without them.
    – C Fairweather
    Commented Jul 22 at 21:59

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