Circulator Question

[Eric Johnson]

I get the hot water from my barn into my basement with a Grundfos 26-96F circulator. Lately I've noticed that it will stop and start intermittently when the water is hot, which seems counterintuitive. I'm thinking I'm running my water too hot at 190, and that the pump must have a protection mechanism of some sort that shuts it off in extreme heat situations. That's just a guess.

Here's a few details: The pump is controlled by an aquastat at the boiler return that kicks it on when the return temp hits 160. I also have a Taco 007 that continuously circulates water from the supply into the return for thermal shock protection, instead of a mixing valve. The Grundfos is located in the basement and is on the return line.

I'm going to run the water temp down to 175 to see if that makes a difference, but if anyone has any ideas, I'd like to hear them.

 

[huffdawg]

From what I read on that pump,it is rated up to 230f and the new design up to 288f

https://ca.grundfos.com/content/dam/GPU/pump-troubleshooting.pdf

 

[Bob Rohr]

I get the hot water from my barn into my basement with a Grundfos 26-96F circulator. Lately I've noticed that it will stop and start intermittently when the water is hot, which seems counterintuitive. I'm thinking I'm running my water too hot at 190, and that the pump must have a protection mechanism of some sort that shuts it off in extreme heat situations. That's just a guess.

Here's a few details: The pump is controlled by an aquastat at the boiler return that kicks it on when the return temp hits 160. I also have a Taco 007 that continuously circulates water from the supply into the return for thermal shock protection, instead of a mixing valve. The Grundfos is located in the basement and is on the return line.

I'm going to run the water temp down to 175 to see if that makes a difference, but if anyone has any ideas, I'd like to hear them.

Put a meter or test light on it, determine if it is losing supply power. I've never heard of a lock out on temperature, most are rated 225°F continuous.

That aquastat, what type? Does it have a high limit function?

I like to drill and install small neon pilot lights on all my circ pumps. It tells you at a glance if the power is on or off to the pump.

Is it a multi-speed circ? sometimes those speed selector switches go bad. clicking to another speed would tell if that is the case.

 

[Eric Johnson]

I like your suggestion about the stat, Bob. I'll have to check that out. I may have put a dual-function one in there. That would explain it.