Forced Hot Water: Pipe is hot then goes cold

Hi,
I'm a new home owner and I have forced hotwater heat. The pipe for the downstair baseboards is fine, but the pipe leading upstairs has a problem. The pipe leading upstairs starts off hot from the boiler/burner (it's a Burnam, incidentally) but then maybe 10 ft away from the boiler, it goes cold. Anything I can do or does anyone have any idea what this may be?

It sounds like you're feeling the return pipe. It's hot near the boiler due to thermosiphoning/convection currents. Once the circulator starts, the pipe turns cold because cold water from your zone is now flowing towards the boiler, cooling the pipe. Find out which way the water is flowing and see if it turns cold as it flows out of the boiler.

heat

Sounds like that zone is air bound and needs to be vented (if there are screwdriver vents on the radiation) or purged (if your boiler is set up with gate valves on each zone and boiler drains between.)

The return line should get hot within seconds.

Possible causes:

-Air lock
-Boiler pressure
-Separated impellor on circulator.
-Very rare{Partially plugged line}