Finding Your Pump’s HP and Voltage Is Easier Than You Think
If you’re considering our Reservoir Tank System for Low-Producing Wells, you’ll notice we ask for your existing well pump’s voltage and HP rating. But what if you don’t have that information? It takes a little detective work — but getting a reliable estimate is easier than you’d think.
Step 1: Determine Your Pump’s Voltage
Go to your main electrical panel and find the breaker for your well pump:
- Two slots in the panel — 230V pump
- One slot in the panel — 115V pump
Note: 99% of well pumps are 230V. 115V well pumps are rare.
If you’re not comfortable identifying breakers, or can’t tell which one powers the well, use a multimeter to read the incoming voltage at your pressure switch. This short video shows how a pressure switch is wired.
Step 2: Determine Your Pump’s Horsepower
There’s no guaranteed way to know HP without pulling the pump, but here are three reliable methods:
Method A: Check for a control box
- No control box — your pump is almost certainly under 1.5HP. These are called “2-wire pumps.” You can safely select the under-1.5HP option on our product page.
- Control box present — look for a sticker on the front labeled “Control Box.” It should list the motor’s HP rating. These are called “3-wire pumps.”
Method B: Use your breaker size as a guide
This isn’t foolproof (not all installers follow standard sizing), but it gives a good approximation. For standard 2-wire pumps:
| Voltage / HP | Breaker Size |
|---|---|
| 115V, 1/2HP | 30A single pole |
| 230V, 1/2HP | 15A double pole |
| 230V, 3/4HP | 20A double pole |
| 230V, 1HP | 25A double pole |
| 230V, 1.5HP | 30A double pole |
For standard 3-wire pumps (with external control box, HP not labeled):
| Voltage / HP | Breaker Size |
|---|---|
| 115V, 1/2HP | 30A single pole |
| 230V, 1/2HP | 15A single pole |
| 230V, 3/4HP | 20A double pole |
| 230V, 1HP | 25A double pole |
| 230V, 1.5HP | 30A double pole |
| 230V, 2HP | 30A double pole |
| 230V, 3HP | 40A double pole |
| 230V, 5HP | 60A double pole |
Method C: Measure amp draw with a clamp meter
For the most accurate result, use a clamp meter to measure the amp draw on one of your pump’s hot leads while it’s running. Then cross-reference that reading with Franklin Electric’s AIM Manual (page 52) to get a solid HP approximation based on load amperage.
