Bad Circulator?

Old 02-25-16, 09:27 AM
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Bad Circulator?

We have a gas-fired hydronic system that provide heat for three levels in our house. Two of the levels are above the level of the boiler and the third level has the boiler and two heating units. Everything was working well until recently. The lowest level heating units [a small radiator and a piece of baseboard] stopped getting warm even though they were filled with water [bleeding proves that]. The circulator motor began running constantly about the same time.

Is it possible that circulator motor is OK but actual circulator is broken or maladjusted? Anyway to test? Could upper level radiators be warmed via gravity flow?
Old 02-25-16, 10:12 AM
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Yes, it's possible. Can you give us a picture and brand/model info on the circ?
Old 02-25-16, 05:56 PM
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An ammeter will indicate if the motor draws current.
If you have some way to restrict the flow after the pump you can check for a change in current with closing of a valve.
Not 100% conclusive, but it may a give good indication of flow.

Gravity may well be creating flow to satisfy the rads above the boiler.
Old 02-26-16, 03:59 AM
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If it's a Taco, the little plastic Impeller may have worn itself out, they're quite fragile, and become brittle with age. I replaced a cartridge last year and was surprised that it had still been working while there was hardly anything left of the Impeller . . . . all chipped to pieces.
Old 02-26-16, 04:44 AM
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Do you have a check valve on this line?
Old 02-26-16, 08:02 AM
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I would put a wye type strainer in the cold water feed to boiler. Rust another other particles can chew up the rotors and clog pumps. Older cast iron boilers often trapped the particles in the bottom of the water jacket so they did not keep circulating. New boilers often do not do it as effectively.

If you have to replace an old pump get a new high efficiency ECM (electronic commutator motor) type that uses 80% less electricity. They are available with adjustable and automatic delta T or flow rate models. Both types will be more effective and make for a comfortable multi level system.

Last edited by doughess; 02-26-16 at 09:00 AM.

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