Harold Kestenholz
The present Armstrong Astro line starts with higher model numbers. Someone might have the old catalog. The present models are cartridge types like TACO 007. I have heard many plumbers describe this noise problem with 007’s. I have heard this transmitted noise through my own home system from my TACO 007 when The non-electric zone valves are open to provide little resistance.
There were older Armstong circulators that used a magnetic drive and that impeller made noise when it was running under light load. Armstrong and TACO are very long-lasting circulators, it is not lack of quality. The circulators require a steady back pressure on the impeller to run quietly. Put a balancing valve at least 10 pipe diameters away from the circulator outlet. Adjust the balancing valve until there is a 20 degree temperature difference from supply to return after running the burner and system until the return water gets to 120 F (when the weather gets cooler.)
Other suggestions from Sylvan to provide even comfort levels are worthwhile when investment permits.
