Hi there.

I have a 2-zone HWBB system. One zone upstairs, one downstairs. Each zone covers
600 sqft. My boiler is only 5 years old. In the last week or so I've noticed the heat on
one end of the house is much cooler than on the other end. This had never been the case before.

My thermostats keep asking for heat but the boiler doesn't come on and the heat
doesn't seem to increase. I've placed thermometers on both ends of the house. On
one end, the temp is close to the value in the thermostat. On the other end, however,
the temperature is about 8 - 10 degrees cooler. (on both floors)

I did some snooping around, and the cooler side of the house is on the return side
of the HWBB flow. Again, the temp distribution was much better in the house even
only a week or two ago.

Is it possible my circulation pump has burned out? How could I test for that? Are
there other tests I can do? I want to try to isolate the problem before I bring in a
plumber.

Thanks for your help!!

You can use a long screw driver like a stethascope to listen to the pump. Just touch the tip of the screw driver to the pump body and put your ear on the handle to listen for rotation and water flow through the pump. It could also be a failed zone valve if that is how it was configured, or a vapor lock (air in the line)

Hi Northernheat.

I tried the screwdriver trick. A really neat idea.

I didn't hear a lot noise, but I did hear the hum of a motor. So, I have to surmise
That the pump is running.

As far as the valve is concerned, how could I check that? If I'm getting heat in
One part of the zone and not another, doesn't that suggest the valve is opening?

Finally, regarding the air in the system -- I don't have bleeder valves along the run.
All I have is spigots right near the boiler for each zone. Would purging the air be as
Simple as opening the valves (with a hose attached of course) and letting the water
Flow for a while?

Thanks very much for your help!

A hum doesn't mean rotation. If there is air in the line you can try to purge it pretty much like you said. Pumps cannot move air.

Hi NorthernHeat.

Can you help me figure out the right way to get the air out of my system? I have
Two photos of my system here:

http://www.dpsw.net/temp/picture3.jpg
http://www.dpsw.net/temp/picture2.jpg

I don't have whistle valves on any radiators, so I have to purge at the boiler I guess.

If you can help me with the step-by-step, I'll give it a shot.

Thanks so much!