How noisy should circulator pump be?

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Old 01-22-12, 12:20 PM
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How noisy should circulator pump be?

About three months ago I moved into a house with a gas-fired Utica boiler. There are two heating zones in the house and a separate loop for the house hot water supply. There is no bypass line, and the hot water loop joins the heating loop between the taco pump and the boiler inlet.

The circulating pump (a Taco 007-F5) has been continuously running for who-knows-how long (longer than I've lived here), and is noisy to the point where it can usually be heard no matter where in the house you are. It didn't matter if both the heating zones were off -- it would still run and be noisy. Occasionally the pump would go quiet for a few minutes, but this was only a temporary condition. For contrast, the circulating pump in the separate hot water loop (a Grundfos 15-42F) is always very quiet.

Today I found out why the pump had been continuously running (the thermostat lines from the aquastat relay were just tied together and not connected to the zone control valves). Correcting this does make the Taco pump turn off and on like it should, and it is on average quieter than before but it is still noisier than I would like. My suspicion is that running the pump for long periods with no flow in the heating loops may have damaged the pump bearings.

My question is: since the pump has been running continuously, even when there is no demand from the heating zones for longer than I've owned the house, should I replace the circulating pump, or is there something else I should try first? I don't want to replace it unless it will reasonably make the system quieter.

Thanks!
 
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Old 01-22-12, 01:55 PM
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I can't quite visualize your system's piping - but if the Taco pump has been running with no flow, it might have overheated and be damaged. You can pull the cartridge and inspect it, particularly the plastic impeller. Removing the cartridge may require depressurizing and draining the system unless you have the necessary isolation valves.
 
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Old 01-22-12, 03:59 PM
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Mine is barely a low hum when it runs. I would change it out and because the old one works, but is noisy keep it for an ultra late night, Christmas day emergency spare.
 
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Old 01-22-12, 04:53 PM
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Having a spare pump isn't a bad idea for a DIYer. Superbowl Sunday might be almost as bad as Christmas day.

But, it might be almost as good, and less costly, to have a spare cartridge - which is the only moving part in those Taco wet-rotor pumps. Personally, I would order a replacement cartridge (which comes with a new gasket) before removing your existing cartridge. Then keep the old cartridge, even if it's damaged, as your spare. To remove the cartridge, you just remove four cap-screws and slide off the motor housing.

My guess is that the pump, operating without flow, overheated, damaging the plastic impeller (which is part of the cartridge).
 
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