Question: again wiring my new construction home. My septic has a pump that must have 220v. It only pulls 7a max. My septic man said to run the 220 circuit on a 20a breaker with a 12/2 conductor. The septic pump is approximately 75' from my service panel. I have never seen 12/2 wire on a or a 20a breaker on a 220v circuit. I'm not trying to sav money here. I thought it should be 10 wire and a 30a breaker. Any advice? Thank you.
Jim in Tennessee

 

Your Septic Man is correct.
I suggest you run it in 3/4" or 1" PVC conduit and use 12/2 type UF.
Did he also talk about a Septic Alarm?
Let me know and then I have suggestions about the final connections at the tank.

 

That would be 240 volt, not 220. This is an aeration pump? Will there be a timer at the panel?

 

Why would you run UF thru conduit ?

Run 3/4" PVC and pull three #12 THWN wires.

 

Depending on the terminations at the tank, UF may be a better choice.

 

Is this a Sand Mound type of septic tank?

 

Thanks to all who read my question and responded. If I got your answer right it is correct to only put a 20a breaker on a 240 circuit. That is news to me. And regardless of the conductor I will use conduit because I don't want the future risk of hitting The wire with an implement during landscaping. Now for your other questions. This is a modified low pressure system. The pump actually pumps waste liquid into the field lines. It is a pretty complicated system on a 10,000 sq ft field. I'm in TN and that design was the only system the county would approve for my build site. Back to my original question; is there any benefit to putting it o need a 30a breaker and 10 wire?
And lastly yes it does have an alarm on a separate circuit. I was going to put the alarm on a common house circuit so if it ever tripped a breaker I would know. Thanks for your help

 

No need for a 30 amp breaker and number 10 would only be needed if the one way distance is more than 200 feet. It would probably work okay even on a 15a breaker and #14 wire but #12 gives you future proofing for a larger pump.

 

You can run 10/2 if you want but it would still be on a 2 pole 20 amp breaker. 10/2 is overkill.
Talk to your electrical inspector and make sure he'll accept 12/2 UF in 3/4 PVC conduit. An alternative is 3/4 PVC conduit with three THHN wires.
UF should not be in conduit but some inspectors will approve it for septics.

The Alarm is low voltage and can not be in the same conduit, so you'll be running two separate conduits. The alarm can use 14/2 UF or larger. Again the alternative is 3/4 PVC conduit with three THHN wires.

The way most of these systems work is:
1. there's a float in the tank that acts as a switch for the pump motor. When the fluid gets high enough, the float turns upside down and the pump runs. When the fluid is low enough, the float hangs straight down and shuts off.
2. a second float activates the alarm. It hangs higher than the first float and if the pump fails the fluid will eventually turn it upside down and the alarm sounds.

Some people install a plug and receptacle inside the tank for the pump and a second unit for the alarm. This environment is highly corrosive and the receptacle fails after a few years.

A better connection is heat shrink. You can purchase an underground splice kit for #12 wire than comes with everything you need except the heat. The difference between normal heat shrink and underground heat shrink is there is an epoxy that oozes out of the unground type creating a better seal.

Either way, make sure you leave plenty of extra wire inside the tank. Heat shrink has to be cut off for future repairs.

The power for the pump will go directly to the breaker panel.
The wire for the alarm will connect to two screws on the alarm and is low voltage. The alarm plugs into a standard 120V receptacle.

Again, I would ask your electrical inspector about all of this before you install it. Some may want the receptacle or a means of disconnect at the tank. Most accept heat shrink and agree it's a better method.

 

Thinking this over, you may be able to mount a weather proof box and in-use cover outside the tank and bring the pump and float wires to it. The pump float looks like this:



The plug is both male and female also know as a "piggyback"
The plug on the float goes into the 240V receptacle. The pump then plugs into the female of float plug. One leg of the power flows to the switch in the float and back to the female, similar to a switch loop.

If you splice this with heat shrink, you must wire the float like a switch loop.
You one shown in the image is 120V, yours will be 240V.
Your septic man may be using different float and controls but the theory is the same.

 

Talk to your septic man, he may handle the connections at the tank.

 

Thank you folks for all your points. Your advice and explanations are very helpful.
Jim