I replaced a rusted out millivolt natural gas pool heater with a new model, but forgot to note that it needs an electrical connection as well (for vent,etc).

I have a 240V line run out there for the pump. (2x20Amp breakers).

The manufacturer doesn't recommend hooking them both up but it's a long run to a corner of my property and it would mean removing some concrete to run the conduit out to the heater location. Seems the manufacturer's main reason to have separate circuits is to prevent a problem with one interfering with the other.

The pump pulls <9A at max load. The Heater pulls VERY little, much less than 1A.

Currently, there is nothing except an outdoor switch to the pump. Other than a very costly second run to the heater, what's my next best option? A junction box after the existing switch? replace switch with junction box and two switches? Some way to separate the line in to two (tighter to spec) breakers?

I do plan on having an electrician do this work, but I want to educate myself before I sign any work orders.


There is direct-buried 12/3 wire run out the the pump. So running another line is not at all economical.

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    Is the heater 240V, or 120? Do you have neutral available at the pump now (there will be 3 wires + ground if so)? – gregmac Apr 14 '11 at 0:05
  • @greg, it's pre-wired for 240V, (and is easily convertible to 120). I'll have to checkout the contents of the current switch about what's available. – hometoast Apr 14 '11 at 12:07

I have a pump and a chlorinator on the load side of the same 240V timer, and it works fine. But both are wired for 240V, so there's no issue with lacking a neutral leg.

I gather you already have conduit to the pump/heater area for the pump. Most conduit would have room for two separate lines, so if that's the case, another option would be to pull two new NM wires through the conduit, using the existing wire to pull them through (ideally, pull fish tape through first and then connect that to two new wires and pull them through).

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  • I totally didn't think about having room in the existing conduit! I'll have to check that out. That, along with a subpanel (I'm out of slots on my current 200A service), would be the 'cleanest' way to get it done I suppose. – hometoast Apr 14 '11 at 12:08
  • Turns out there's no conduit. Just directly buried wire. I hope I didn't damage it while finding that out. either way -- it was buried like 2 inches below the surface. not good. – hometoast Apr 14 '11 at 21:31
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    You might want to kill 2 birds with 1 stone then, install conduit and run 2 lines through the conduit. 2 Inches below the soil is likely to get nicked and electrocute someone doing any minor yard work. – BMitch Apr 15 '11 at 13:06
  • Btw, there was just a recent question about running wire underground: diy.stackexchange.com/questions/5517/… – gregmac Apr 16 '11 at 5:00
  • quick update: I ended up running a whole new line out to where I needed it. I still could only safely hook up one feed. But I trenched it out, buried the wire directly, except I used conduit where it went under the sidewalk. So far, all summer, there's been no problems with either unit. – hometoast Sep 12 '11 at 14:16

I have a pool with a 220 Volt pump and a gas heater that requires 220 volts to run the electronics. They both run from the same 220 Volt switched line from the house. They have been running this way for 4 years now with no problems at all.

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  • Thanks for the anecdote. I'm definitely stuck running both from the same line now anyway. Are they both on the same switch? -- so when you backwash your pump, you're switching off and on the heater too? – hometoast Apr 15 '11 at 10:59
  • If you do run them on the same line, you should at least put a switch for each locally. Eg, have the line come into a 2-gang junction box, then use one double-pole switch for each. That way you can still control the power to the pump and heater independently. – gregmac Apr 16 '11 at 5:02

Assuming the heater wants the same voltage as the pump, you could go for a power conditioner that would prevent motor noise from the pump from getting back to the heater.

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  • If I can't go the subpanel+two-new-drops route as richardtallent described, this sounds like it'll mitigate some potential problems. Thanks! – hometoast Apr 14 '11 at 12:14

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