I have a hot water recirculation system with a Rinai tankless water heater and a 10 gallon electric buffer heater. About 18 months after all this was installed, the recirculation pump failed. It was a smaller Grundfos model the plumber thought that it had been undersized for the system. He installed a much larger Grundfos pump (model UP26-96BF). I thought that this pump was quite noisy, you could hear it in the upstairs master bath (the pump is in the basement), whereas the older, smaller pump was nearly silent. It started looking at the specs for this pump on the Grundfos website and saw that there were control electronics in the plastic box on the side. Being the curious troublemaker I am, I opened the plastic box to find that there was nothing in there. In other words, this pump has no controller circuit and is simply running full bore! My question is: is this a problem? Is it OK for this fairly large recirc pump to be running a full speed like this? Any help is appreciated.