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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21536
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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Re: Grundfos UP 26-64 pump Pump was shut-off

Customer Question

Re: Grundfos UP 26-64 pump Pump was shut-off for several months while away from home and when turned on, no longer would circulate hot water when pump is is turned on and audibly running. What should be done to find problem?
On cap where specs are printed, is a slot for screwdriver. What is it's purpose?
Submitted: 2 years ago.
Category: HVAC
Expert:  Rick replied 2 years ago.
You must have a really old pump since they did away with that screwdriver plug over 25 years ago. The idea behind the plug was that you removed it once the system was purged of air so you could let a little water out ensuring the impeller (which is water cooled) wasn't air bound. They have since figured out that it's unnecessary. But it is useful because you can remove it to see if the impeller really is turning. If you can hear the pump spinning then unscrew the plug to confirm that it is indeed turning. Only a very small amount of water will leak out. If the pump is turning and this pump is dedicated to the indirect hot water tank then you could have air in the line and it will need to be purged out. I assume you have a hot water boiler making the hot water to circulate through the coil in the tank. If so is the boiler hot? is the burner firing if it isn't