I replaced a 30 amp double breaker (one unit with two switches tied together) with a 40 amp of the same kind to install a tankless unit. Immediately my A/C kept trying but wouldn’t start up and another appliance on another circuit started flashing so I went back to original set up with a new 30 amp breaker (one unit like the first. I even replaced a new 100 amp breaker for the A/C. I have it wired the same as before. My A/C repairman just told me now I have 240 coming in from the utilities but only 120 going out to all the breakers. What could I have done wrong?
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330A is enough for a standard tank heater (30 or 40 or 50 gallons). But 40A is enough for only a tiny tankless. What model of tankless? Do you really think it can (when everything is working properly) actually provide enough hot water?– manassehkatz-Moving 2 CodidactCommented Sep 11 at 18:00
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OK, did you verify that the 40A breaker is good? That when set to 'on' there is continuity from input to output? That there isn't a resistive short in it or that you didn't introduce one when you installed it? It could be a faulty breaker.– JeffCommented Sep 12 at 19:52
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1 Answer
One of your two hot lines is open or broken somewhere upstream.
It's possible that one pole of the main breaker tripped (or didn't reset) but not the other. Try switching it off and back on. If that is unsuccessful, you'll likely need an electrician or the lines company to investigate further.
Note that the wire on a 30A breaker is likely not thick enough to be safely connected to a 40A breaker. Did you verify the wire size was suitable first?
answered Sep 11 at 17:41
