2 heat zone question

[Don]

I rent out a condo that is having some heat problems. I just replaced the two circulaor pumps (one was bad, figured I'd do both at once. This is a 2 story condo with two heating zones, 1st floor and second floor. I'm having a hard time getting hot water to the second floor. I have bled all the air from the lines and it appears to be free of air. There are two circulating pumps, both controlled by a separate thermostat, and no zone valves. I've got a question concerning the configuration of the circulators. The configuration is this:

boiler | water flow--------> |

[SQLit]

Are the pumps identical? I would think that the one for the upstairs would have an bigger head (higher lifting capacity) and more gallons by at least

50% I would think that there would be an back flow preventer on both of them. But I am really guessing on the drawing. If I read it correctly it seems to me that the upstairs pump is on the wrong side of the piping. Most pumps push better than they lift. That is why you usually see the pump closer to the source. Probably does not make any difference on the downstairs cause there is little vertical difference for the loop.

[Stormin Mormon]

Circulators are put in the return side, cause it's cooleer water going through.

What does come to mind is to wonder if he's got enough head to actually get the air out of the lines. Have you got a "fast fill" valve?

A new Spirovent or equivilant air eliminator is a good idea.

[Edwin Pawlowski]

It would need more head, but not more gpm. Most circulators can carry a two story house. but thee will always be an exception.

There is a valve of some sort in my system. It is also adjustable and can prevent flow. This may be part of the problem.