Pump stopped flowing water at speed 2, but 3 is working - pump bad?

tommygags

Hi everyone. I have a Grundfos UPS15-58fc, 3 speed, 1/25 HP, 115v, which I've had no issues with my radiant heat set up for over a year until today. Noticed the return pipe wasn't that warm and looked at the floor temp setting was low. I then switched the pump from speed 2 to 3 and then noticed the return pipe was getting warmer within a few minutes.  

Does it make sense that the pump was on (felt it vibrating) but an issue with speed 2, yet speed 3 working fine?  The pump was "on" for many hours, yet the floor sensor never increased temperature and the room was Cold. Already within 20 minutes of speed 3, the floor sensor temperature increased a couple degrees. 

Should I continue to run at speed 3 or replace the year old pump?

Anything else I can do to troubleshoot?

Thanks!

Jamie Hall

Run it at speed 3 to keep yourself comfortable for the time being. The problem, however, may not be the pump itself, but something -- possibly even air -- restricting the flow and the pump just can't do it on speed 2.

tommygags

Thank you, @Jamie Hall! Would you suggest I bleed the entire system? Not sure if it matters, but I am getting 18 psi from the boiler - would air in the system cause a lower psi? Or do you think something is blocking water in the pump itself and I should take the pump off and inspect?

rick in Alaska

I have had more than one of those that just seemed to have lost one of the speeds where the pump is not running at all. I turn it to a different speed and it works fine, so I just figure it is just a bad pump winding.
Rick

Alan (California Radiant) Forbes

.............so I just figure it is just a bad pump winding.

Or a bad 3-speed switch.

Zman

If you have an amp clamp you could determine whether the issue is with the pump electrically or a system that will only allow water to flow with the pump is on speed 3. My bet is that the pump is bad...

tommygags

tommay said:

Typical for grundfos...

Glad I have 3!  Is there a brand you recommend over grundfos?

tommygags

Zman said:

If you have an amp clamp you could determine whether the issue is with the pump electrically or a system that will only allow water to flow with the pump is on speed 3. My bet is that the pump is bad...

Thanks!  Any thoughts if the savings of going to a 2 speed warrant buying a new pump vs keeping this one and keep it on 3 speed?

Le John

tommay said:

Typical for grundfos...

I just replaced two 1558's with two Alpha 2'S. Is there a more reliable pump?

hot_rod

Le John said:

tommay said:

Typical for grundfos...

I just replaced two 1558's with two Alpha 2'S. Is there a more reliable pump?

I think the first Alphas came out in 2005, over 3 million Alpha 2 have been manufactured. I've watched the Alphas being manufactured in Fresno, California.

Possibly Wilo was the first to introduce ECM residential circulators in the US, the Alphas were close behind as I recall.