Checking a circulator pump

Low-cost testing device for heating pumps

Submitted by: Armin Köhn, Mutterstadt, Germany

Online since: 27/12/2018,

The inexpensive test devices shown here will help you determine whether a heating pump is currently running. They can also show whether the pump is operating at low or high speed, and in which direction it is rotating. This information is useful for identifying a faulty pump and for checking whether the heating control system is working as programmed.

The basic version of this testing device is quick to build, as shown in the first picture. Most households have non-magnetic pin-shaped items on hand, such as wall plugs, brass clips, brass screws or knitting needles. By sliding one of these through a ring magnet and holding it near the circulator pump, you can test whether an electric motor is turning. Incidentally, this method works with many types of electric motors.

Those who want to build something for permanent use will need:

Plastic cap from a PET bottle or similar
2–3 mm brass screw with nut
Ring magnet type R-06-02-02-G
Sharp knife
Screwdriver
Soldering iron
Adhesive and toothpick

1. Cut the plastic cap down to a height of approx. 10 mm and, if necessary, remove any sealing parts inside the cap. This last step is optional, but I wanted to make sure that the ring magnet would not be slowed down by the rubbery seal.

2. Screw the brass screw in from the outside until it stops.

3. Heat the screw thread with a soldering iron and simultaneously press the screw head or cap against a hard surface. This will push the head flush into the cap top. If the screw becomes crooked during this process, straighten it vertically and allow everything to cool.

4. Draw two lines on the ring magnet with a felt-tip pen so that its rotational movements are easier to see.

5. Place the ring magnet on the screw and tighten the nut until it is almost touching the magnet. This is best done with a non-magnetic tool such as a toothpick. Then secure the screw by applying a small amount of adhesive with the toothpick.

Now you can hold the plastic cap up to the circulator and immediately see if and in which direction the magnet is rotating.

Since the device is very small and you could accidentally touch the screw when handling it, I made a storage box out of an old film canister. I filled it with foam rubber so that the assembled tester just reaches the top edge. The snap-on lid then secures it in place when closed.