The whole second floor of my house is frigid. I have a oil based boiler (replaced new in late 2004), and the system is water based (hot water flows into the radiators in the house). It has two zones, the first floor and the second floor, controlled by separate thermostats.
Problems started a few weeks ago. Temperature was erratic upstairs. Sometimes we'd set the thermostat to off and upstairs would be boiling. Other times the thermostat would be high and heat would be non-existant. Most of the time it worked fine. We still had the thermostats from the older boiler (20 y/o at least) and after tinkering w/ the temperature one day the front plate fell out (w/ the thermometer coil) and heating stopped on the 2nd floor altoghether. I replaced the thermostat w/ a nice new digital one (24V compatible w/ my unit), and connected the R and W wires just as they were identified in the original thermostat. Heat never came back to the 2nd floor.
The boiler is in the basement. (As my install guy explaned it) the heating water coming out the front pipe, splitting into two, and one going to the first floor zone, the other going to the second floor zone. After the water makes it's way around, two pipes come back down to the basement, each with a small pump. These pumps are hooked up to the box that also connects the cables from the thermostats. The pipes after the pumps join into one pipe and go back into the system. This is the loop of warm water. Touching the pumps they are both running.
I noticed the back pipe coming down from the second floor was cold, while the one coming down from the first floor was hot. I took this to mean that the hot water wasn't making it's way around the system. I 'bled' the system to get rid of air in the 2nd floor zone (you could feel air being forced out the pipes while it was being 'bled'). Now both pipes are warm, which is good... but no heat upstairs yet!
Tracing the front pipe that pushes water from the boiler into the upstairs rooms, I find that it starts off scolding hot, and the first floor section is scolding hot all the way till the pipe leaves the basement. Following the split for the second floor, it is hot initially, but as I move farther away from the split it gets cold (even before it leaves the basement).
What the heck could be going on? Could it be the thermostat causing issues still? Tomorrow I'm going to pick up a voltage meter and make sure the connections are good. Apart from that, what else could be going wrong? I was quite surprised that the 2nd floor front pipes were cold, given that the corresponding pipes at the end of the loop (w/ the pumps) were warm. I made sure my installation guy explained everything to me. Could I be misunderstanding how the system works? How could there seemingly not be any hot water going up to the second floor, but the pipe at the end of the loop is warm? Is the loop flowing the other way instead (pumped up the back?)? The manual for the unit is useless.
Ok... that's about it. I'll be eternally greatful for whatever guidance you can give me.