| Monoflow systems typically have higher head requirements than other piping schemes. The B&G 100 is a low-head circulator, so there's not enough 'oomph' to get the water into the emitter loops.
As I recall, the Raypak is also a fairly high-head boiler. So you are working against both the high-head boiler and the high-head piping.
I'll also guess that you are not pumping away from the expansion tank (e.g., circulator is on the return, expansion tank is on the supply hanging from the spirovent). That doesn't help, either.
First thing I'd do is figure out what circulator is actually required. Figuring head loss in an old monoflow system isn't ridiculously hard, but not as simple as a series loop or other piping scheme. You also need to consult the Raypak manual and see what the flow requirements are so you don't kill the boiler by underpumping, and take account of the head loss in figuring the right circulator for the job. Second thing I'd do is repipe to pumping away.
On the first point, in a small system, you might be able to just throw a Grundfos 15-58 or a Taco 00-R 3-speed circulator in there, and see which speed works best. But I'd absolutely do the pumping away change too.  |