220 Volt, Single Phase Wire Size Help Needed

[CADplans]

I was looking at a home and the heat pump.
The air handler has a resistance backup heating element in it.
The backup heat is fed by two large wires, like maybe #6,, it is stranded and at least three times the size of #10 wire.

My question is about the ground, the two wires feeding 220 volts into the air handler are large,,
but, the ground wire is only #10.

I am only used to house wiring, like outlets, and lighting circuits, where all of the wires are the same diameter.

Does a 60 amp, 220 volt, single phase circuit only need a #10 ground?? Or did someone "cheap out"??

 

[tallyho8]

Is it only 3 wire or does it have a wire for a neutral also?

 

[Topzide]

I believe that the ground can be smaller, not sure if it's 1 or 2 sizes smaller. Stranded wire can handle more amps solid.

 

[CADplans]

It is only a 3 wire connection, no "neutral" that I can find.

 

[CADplans]

The 220 Volt large wires are stranded, the #10 ground is solid.

 

[Doughknob]

Ground can be smaller if everything always works properly. If there is ever a short, you’ll be wishing you had the #6 ground size.

 

[ponytug]

This (equipment grounding conductors) gets a little complicated under the NEC, and I am not an expert. 220V, aka 240V single phase in principle runs all the current out one hot and back on the other hot. So the only time that there would be current on the ground is momentarily when there is a short to ground. How much could pass through it? Well, enough to trip a 60Amp breaker. NEC 2014 says that is a 10ga wire. (if it is copper)

More here.

Now why would someone oversize your main wires? To reduce power losses during normal use, by decreasing the resistance in the main wires. Moreover, the wires may not be oversized if the length of the circuit (power panel to heat pump) is long. There is a nice calculator over at Southwire for that. For instance a 150' run, with a 40A heat pump load requires a 6ga wire for the power wires.

Does that help?

My suspicion is that it is all according to plan.

All the best,

Peter

 

[Roadworthy]

For 220 (or 240) volt heater use there is no neutral, there are only the two hot wires and a ground wire. The number six copper wires are probably correct for the heating elements - sized for the current load. Getting into larger wires the ground wire is usually one or even two sizes smaller. You would need to refer to the NEC code book for specific wire sizing due to ampacity and insulation for the specific application.

 

[cbg8670]

Doing hvac for few years. Ground wire is usually smaller. Need to check NEC or an electrician for definitive answer. Here is a "googe" chart though

 

[cbg8670]

Google not googe...fat fingers little buttons

 

[workinonit]

Typically 2 trade sizes lower for a ground. Heat strips can run from 5 KW to 40 KW and some maybe larger but normally residential strips are 10 or 20 KW. That determines the wire size.

 

[MAX-24-Dean]

I was looking at a home and the heat pump.
The air handler has a resistance backup heating element in it.
The backup heat is fed by two large wires, like maybe #6,, it is stranded and at least three times the size of #10 wire.

My question is about the ground, the two wires feeding 220 volts into the air handler are large,,
but, the ground wire is only #10.

I am only used to house wiring, like outlets, and lighting circuits, where all of the wires are the same diameter.

Does a 60 amp, 220 volt, single phase circuit only need a #10 ground?? Or did someone "cheap out"??

Equipment Grounding Conductor (EGC) size is determined by Table 250-122 in the 2020 National Electric Code.
From the table, the EGC size is determined by the Rating of the Over Current Protection Device (OCPD = breaker) in the table. A 60 Amp breaker in the table requires a minimum size of a #10 EGC.