How can I purge air from a baseboard heating system with the spigots on the wrong side?
The hand valves and spigots near the furnace are for isolating and draining the zones to servicing the radiators. To bleed the system, you would find a bleed valve at a high point, often at each radiator. You may have to remove a cover to find it, and it may require a screwdriver or small wrench to operate the valve. Make sure to have some rags handy to cleanup any water that comes out. When you're finished, check the pressure in the system and add more water from the water main input if necessary.