Combining Multiple Electrical Wires of Different Gauge (AWG)

Can you combine drop wires of different gauge?

Yes! You may combine, 2 or more, different gauged (AWG) wire for installing your deep well pump.  Use the formula below to ensure that National Electrical Code (NEC) requirements are met.

Formula:
(Wire1 Length ÷ Max Allowed) + (Wire2 Length ÷ Max Allowed) + ... ≤ 1.00

Where maximum allowed (maximum run) is the maximum length permitted for that specific gauge of wire. See our drop wire selection table for maximum run information.

Example:

You have 375 feet of #6 wire buried between the service entrance and the wellhead. A new 3HP 230V single phase pump will be installed to replace a smaller pump. The new pump will be set at 200 feet below the wellhead.

What wire gauge is suitable?
 
From the drop wire selection table, #6 can be use for up to 750 feet and #10 for up to 300 feet, (375 ÷ 750) + (200 ÷ 300) = 1.167 which is greater than 1, so #10 can’t be used;  #8 wire can be used for up to 470 feet. Using the same formula, (375 ÷ 750) + (200 ÷ 470) = 0.9255, this is less than 1 and will meet NEC standards.

Continuing the above example…

In the same installation, you also have 110 feet #10 submersible wire from your existing well. Can you add 90 feet wire to achieve 200 feet? What wire gauge?

The answer is yes, and you can use 90 feet #6 wire.

(375 ÷ 750) + (110 ÷ 300) + (90÷750) = 0.9866

Now the decision is whether to buy a brand new 200 feet of #8, or 90 feet of #6.  Check the prices for each wire to make a smart decision.

Check out our dropwire selection and splice kits to get the job done!