"Hydronic Heating System - Circulator Pump Not Pumping"

 By Ron Stultz

Summary: check electrical box on pump. Could be loose connection or starter capacitor is bad.

Background:

Fired up my system and pump humming, getting hot, but no water flow!

Tapped pump with hammer and it started pumping BUT not reliable for me.

Pump was 20+ years old.

Clogged???

Ordered new pump.

When new pump arrived, went to disconnect old pump from Honeywell controller and found below.

A black and white wire and a starter capacitor.

Black and white wires are held in place by screw down terminals BUT starter capacitor wires were simply pushed down into some sort of "teeth" connection and one wire was so loose could pull it out and put back in with no effort at all!

Starter capacitor not working because of this connection??? Could be.

Bad starter capacitor?? In home AC units a bad starter capacitor is obvious by bulging ends but this this case, capacitor would have to be tested to determine if bad or not. Many electrical shops have capacitor testers and will test for free.

Clogged pump?

Inside Circulator pump:

After new pump installed, opened old pump to see if it was clogged by anything.

As shown, pump was not clogged by anything. Did have some black sludge build up that is common in hydronic heating systems but not enough to keep pump from turning.

Although not shown, chambers in flange were not clogged with anything either.

My guess is starter capacitor was not making good contact in electrical box.