One heating zone does not get hot?

Question

I have an oil fired hot water system. There are 2 seperate circulators. Both circulators are working. One zone gets nice and warm, the other doesn't. With the ciculator running the radiators only feel slightly warm and the house remains cold. The thermostat seems to be working properly. This just started recently. Any suggestions?

The system has 2 seperate thermostats. I have bled the system at the circulator and get a steady stream of water.

I tried everything, but still not enough heat. I even bypassed the thermostat to keep the circulator running. The pipes at both circulators are about the same temperature when you touch them. I have bled the radioators. They are still only slightly warm and not enough to warm the house. There are no electic zone valves on the system. Any other ideas?

Answer 1

The output side of both circulators should be hot and about the same temperature at the furnace end. If one is hot and the other is cold or just warm, then the colder one is not working properly since both are pumping hot water from the boiler. If they are both hot then the problem is downstream from the boiler. Check the circulation valves and the temperature of the input and output pipe at each rad.

Answer 2

Oops...I see you said you bled it "at the circulator"...did you bleed it at the radiators?

Ok...you should look for a zone valve on the line that isn't getting hot, and open it manually. There is usually a lever on it that lets you do that. Also, check the t-stat to that zone, and if you suspect that t-stat, you might try trading it for the other one and see if that fixes it.
The solenoids on zone valves is usually what goes on them and they are not too hard to replace.

If both pumps are running, and there are no zone valves (electric valves in the lines that open/close according to the thermostat) and you only have one stat....look for a valve that got closed, or the most common reason...air in the radiators.
Bleed the radiators until you get a steady stream of water out.
If that doesn't fix it, or you don't get water out...post again and we can dig deeper.
But it's usually a simple thing, like air in the radiators.