Loud screech / hot pump

[rschmitty]

Short version: I had no idea what I was doing (and thus should not have fiddled) but thought I should adjust this pump:
http://img297.imageshack.us/img297/8...closeupne6.jpg
I first turned the middle screw in the direction of the arrow thinking it meant 'open' but it just kept turning and eventually water squirted out. I figured that wasnt good so I screwed it all the way back in. I turned on the radiant heat system again and about 10 minutes later I hear a loud screeching sound for about 10 seconds. I went downstairs and shut off the system again and that pump was very hot to the touch.

What does that screw do, what does the arrow mean, and how 'tight' should it be?


Long version:

We have these radiant heaters in lower level:
http://img144.imageshack.us/img144/4...seboardjo0.jpg
They have not been getting warm so we asked a plumber to take a look. He said they never installed a mixing valve on the water heater so you could turn up the heat on the water heater to get really hot water to radiant but still keep it around 120 for the kitchen sink.

Here is the system:
http://img140.imageshack.us/img140/7...tsystemip7.jpg
http://img150.imageshack.us/img150/3...toutputmd9.jpg
http://img264.imageshack.us/img264/3...urnpumpaw0.jpg
http://img156.imageshack.us/img156/6...ngvalvebo8.jpg

Now the reason I tried to fiddle with the pumps is I thought there wasnt much if any flow through the system. Putting my hand on the pipe by the water heater is very hot (duh) but walking a few feet over to where it inputs into the radiant system the pipe isnt even a bit warm.

Is this something I can attempt to fix or should I just call the plumber back up?

[valveman]

That screw on top of the motor is to purge air out of the motor. The arrow is the direction of rotation for the pump. It is a water cooled motor, which means you probably have hard water or mineral deposits in the motor which lock it up. Running dry will also make the pump squeal. Probably just need a new pump.

[rschmitty]

thanks, so after air is purged should it be tightened all the way back?

and when water comes out, i know the air is fully purged?

should the pump be running or off when purging air?


would just like to make sure im covering all the bases

[valveman]

There is an o-ring under the screw so it doesn't have to be very tight. If your pump was right side up, that screw would purge all the air. On it's side, the air just has to work it's way out with the water. With the power off and that screw removed, you can try to turn the motor to see if it is locked up.

[kingsotall]

It would have been nice to have ball valves on both sides of the pump(s).