Question in regards to wiring and motors

[DennisP]

Ok, so in finishing off everything in regards to equipment I ended up replacing a timer. I now have two Intermatic timers, a T171 day-skipper timmer for running the pump and a T103 DPST timer for selecting high/low mode as well as being used for fireman's-switch functionality when it comes off high mode.

In wiring them, I notice they give their 40A rating, and they have a wiring chart that shows for 120v wiring that 14ga wire is (according to them) rated for only 1/2hp. At 240v the same 14ga is rated at 2hp.

Now, the pump I have (Pentair Dynamo 2-speed 1.5hp special rated) is rated at 11amps on high, 2.9amps on low and I have a 15amp GFCI breaker on the pump line itself. It is a 14ga set of wires (THHN rated solid copper) and I know that I am well within it's rating for my usage. The run length is right around 15-16 feet total from the timers to the pump itself and there is about 4 feet of wire from the GFCI breaker to the timers. So figure a max run of about 20ft.

I am just wondering why the timer would have 14ga wiring rated so lowly for 120v?

I can understand older shaded pole motors with heavy amp draws continuously, but with PSC motors being the norm, the in-rush current isn't enough to cause the wire to heat up, so there is very little concern for overheating wire (especially with 90C THHN) and it is well within the amp-load range, even on startup.

Granted, 12-gauge would be a better option, but I am using what was already run (and I already used my 12-gauge wire set to wire up 3 20-amp duplex GFCI outlets for the outdoor kitchen/oven/equipment pad)...

If I ever needed to go to a bigger pump (or an additional pump) I could rewire everything to use a 8-gauge 50-amp feed that was originally setup for the in-ground pools electric pool heater, but I would need to install an outdoor pool power panel and all that jazz, which I am hoping to skip until I really need to do it. At that point I would probably just go with a full automation setup as well. Or, I could just wire the outlets over to the 14-gauge feed, install a 15-amp breaker on that line and get a 20-amp GFCI and move the pumps over to the 12-gauge. I just want my cake and eat it too, if I can...

I forgot to add, that if I have to go with a bigger pump, I would probably also just look at 220v pumps and bypass the whole wiring issue. That is, unless I needed more than one, and then I am at adding the extra panel.

[CarlD]

In over my head, but I thought you couldn't use 14ga wire for anything over 20a at 120v, that 12ga would be the minimum, and for 40a I'm surprised you don't HAVE to run 12ga.
For 30A 240v, I believe you must be running 10ga. but I could be wrong.

[DennisP]

I never said I was using 14ga for 40amps. I said the timer was rated for 40amps.

I am using a 15-amp GFCI breaker with the 14ga wires.

[CarlD]

Oh. OK. That makes sense.