The label on your pump capacitor has everything you need to order the right replacement, once you know what the symbols mean. This guide walks through each marking so you can read your own capacitor with confidence and avoid the costly mistake of fitting the wrong value.
Safety first
Before you handle any capacitor to read it, remember it stores a dangerous charge even when the pump is off and unplugged.
- Isolate power at the breaker.
- Discharge the capacitor by bridging its terminals with a bleed resistor (around 10–20 kΩ, 5 W) or a proper capacitor discharge tool — a bare insulated-handle screwdriver across the terminals also drains it but sparks violently and can pit the terminals, so use that only as a last resort.
- Then it’s safe to remove and read.
In New Zealand, fixed mains wiring legally requires a licensed electrician. If your pump is hard-wired or you’re unsure, get one in.
The capacitance value: µF and MFD
The headline number is the capacitance, measured in microfarads.
- µF is the correct symbol for microfarads.
- MFD means exactly the same thing — older and American labels often print MFD instead of µF. They are interchangeable: 25 MFD = 25 µF.
- You may also see uF (a plain-text way of writing µF).
So a label reading “25 µF”, “25 MFD” and “25 uF” all describe the identical value.
This is the number that must match. Capacitance must be replaced within about ±5% of the original. Too far off in either direction stresses the motor windings and can damage them. Always read this value off your own capacitor or the motor nameplate — never assume it from a pump model number you found online.
The voltage rating
The voltage marking (e.g. 370V, 400V, 450V, sometimes shown as VAC) is the maximum voltage the capacitor is built to withstand. It is a ceiling, not a target.
- A higher voltage rating is always a safe substitute. Fitting a 450V capacitor where a 370V was is perfectly fine.
- A lower voltage rating is not safe — the capacitor can fail prematurely or dangerously.
So for voltage, think “equal or higher.” For µF, think “must match.”
Tolerance markings
Tolerance tells you how close to the printed value the capacitor actually is. Look for:
- A percentage like ±5% or ±10%.
- A letter code, commonly J = ±5% or K = ±10%.
Run capacitors (CBB60, CBB65) are usually tight-tolerance (±5%) because they’re in circuit continuously. When replacing, aim to keep within ±5% of the original value regardless of the tolerance letter.
Frequency markings
You’ll often see 50/60 Hz or just 50 Hz on the label. This is the AC mains frequency the capacitor is rated for.
- New Zealand mains runs at 50 Hz.
- A capacitor marked 50/60 Hz is fine here.
- Avoid one marked 60 Hz only.
Other markings you might spot
| Marking | Meaning | |—|—| | µF / MFD / uF | Capacitance in microfarads | | 370V / 450V VAC | Maximum voltage rating | | ±5% / J / K | Tolerance | | 50/60 Hz | Rated mains frequency | | CBB60 / CBB65 / CD60 | Body code (run film / run film / start electrolytic) | | -25/+85°C or similar | Operating temperature range | | A safety/approval mark | Compliance certification |
The body code matters too — see our guide on CBB60 vs CBB65 vs CD60 to make sure you’re matching a run cap with a run cap.
Putting it together — a worked example
Say your label reads: CBB60, 35 µF, 450VAC, ±5%, 50/60 Hz.
That tells you:
- It’s a film run capacitor (continuous duty).
- You need 35 µF, and the replacement must be within roughly 33.25–36.75 µF.
- A 450V or higher rating is fine.
- 50/60 Hz suits NZ mains.
Order a part matching that and you’re set.
Can I round the µF up or down?
No — not beyond about ±5%. The microfarad value is tuned to the motor. If your reading sits between two stocked values, match as closely as possible and check the motor nameplate to confirm the intended figure. Wondering about going higher? Read can I fit a higher µF or voltage capacitor for the full picture.
What to do next
Read the µF, voltage, tolerance and body code off your own capacitor, then match µF exactly (voltage equal or higher).
- Browse all pump capacitors.
- Use the find-your-capacitor wizard to match by value.
- Well pump? Head to the well capacitor range.
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CapacitorsNZ — find your exact capacitor with our wizard, then shop pump capacitors or the well range.
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