[Doublej]

Gas fired hot water baseboard system. One furnace, two zones; one for the second floor and one for the third floor. The heat output to the second floor is much less than to the third floor. When I put my hands on the circulator pumps one is much hotter than the other.

Someone suggested that I need a new circulator pump for the second floor zone.

[JLM]

Not furnace, water heater (or boiler is rating is greater than 200,000 BTU/hr).
 
Yes the hot one is probably trying to turn against a worn bearing, thus running slower.  So yeah sounds like you need a new pump.


100 years ago folks knew how to design a home hot water heating system without circulating pumps. 

[thunderbrick]

Gas fired hot water baseboard system. One furnace, two zones; one for the second floor and one for the third floor. The heat output to the second floor is much less than to the third floor. When I put my hands on the circulator pumps one is much hotter than the other.

Someone suggested that I need a new circulator pump for the second floor zone.

Until recently I had such a system, but it used just one pump for both zones.  The last 2 or 3 years the basement zone wouldn't heat up, and I suspected an air block of some type. Before I get serious about fixing it I went to a two-stage heart pump for A/C and heat and never looked back.

[Peter J]

A couple of things to check.

1. Are you certain that the pumps serve individual zones? Could be both in one universal loop with a valves controlling zones.

2. Do you have a way to check temperature of  water into each zone? Like an infrared thermometer. Could be a faulty control valve or even zone thermostat.

3. Do you have a way to check for voltage at pumps both when there's zone demand for heat and also no demand so you could compare? This would determine if problem is in the control system.

FWIW, the system I have in shop runs 2 primary zones off one loop and the pump closest to boiler is always hotter because it's at the front end of loop. Zone valves open and close according to demand.

JLM, that's the first I've heard of BTU determining whether a boiler or water heater. Munchkin terms their 80,000 btu a boiler, but of course it never gets to the temps of old systems, which were actually producing steam, so in that sense it's not a boiler. Most modern condensing "boilers" run temps south of 150°.

[thunderbrick]

My "boiler" was the size of a small end table, and I think the output temp was 160 degrees.