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Pump capacitor fitment

Grundfos MQ3-45 Capacitor

The Grundfos MQ3-45 is a 0.85 kW single-phase pressure booster pump commonly found in well & domestic pumps setups. Here's the capacitor it most likely takes and how to confirm the exact value.

Pump type
pressure booster pump
Motor
0.85 kW · single-phase
Run capacitor
40µF · 450V · CBB60
Tolerance
±5%
Terminal
flying-lead
Application
Well & domestic pumps
Also sold as
MQ3-45, MQ3-35, MQ Series, MQ3
Customer-reported40µF · 450V

A Grundfos MQ3-45 pressure booster pump typically takes a motor-run capacitor of around 40µF 450V (about 36–44µF) — treat that as a starting point, not a spec. Capacitor values vary even between identical-looking pumps, so read the rating printed on your existing capacitor (or the motor nameplate) and match the µF before ordering. Unsure, or the print worn off? Send us a photo and we'll confirm it.

The capacitor that matches that spec

One listing covers every terminal style — open it and choose your terminal (lug, flying lead, or stud) from the dropdown to match how your old capacitor's wires come out. Not sure? Any works electrically; the terminal is just the connection.

How to be sure you get the right one

  • µF must match — the MQ3-45 needs 40µF (about 36–44µF), within roughly ±5–10%. Too low and the motor won't start; too high and it runs hot.
  • Voltage can go up, never down — a 450V (or higher) cap is correct here; a 450V part safely replaces a 370V or 440V one. Don't fit below 450V.
  • Check the terminal + size — make sure the new cap physically fits the housing and the connections match (the MQ3-45 typically uses a flying-lead terminal).
  • When in doubt, read your old cap — the printed µF and voltage on the part you're replacing is the final word.

Other Grundfos pump capacitors

Replacing the capacitor on a different Grundfos? These models have a confirmed or documented fitment too:

Use the find-my-part wizardBrowse all well & domestic pumps capsPump capacitor guide

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