Which way to pump

americanpacemaker

I am installing a hot water boiler with a primary / secondary plumbing system. The boiler is plumbed as a secondary into the primary pipe. Should I install the pump for the boiler pumping into the return on the boiler or on the supply pipe into the primary pipe ?

hot_rod

pump into the boiler, away from the expansion tank connection. This assures the boiler sees the additional pump head when it starts.