Radiant Heating System Newbie... Help!

I recently boutght a 1931 home and this is my first experience with radiant heat… which I know nothing about. I drained the system a while ago because I needed to move a radiator so I could re-tile a floor. I now need to reconnect the radiator, refill the system and get it working for winter. (I'm in Minnesota and it's 25 degrees right now.) A few questions…

1) It looks like a water supply line is hooked directly into the system. I would assume this is what I would use to fill the system, correct?

2) Once it's full, should the fill valve stay on?

3) Expansion tank… what do I do with that? Do I drain that after I fill the system to ensure that the whole thing doesn't blow up?

4) Any special trick to bleeding the radiators? I would assume you start at the highest level of the house working your way down and just bleed it until only water comes out.

5) When bleeding the radiators, should the system be on?

6) When reconnecting the radiator I took out, should I use teflon tape on the threads?

7) How much pressure should be in the system?

Anything else I'm missing and should know about?

Thanks!

1. Likely it is. It should be connected through a check valve so the stagnent water from the heating system can't get back into the potable water supply, though.

2. The heating system does not normally operate at the same pressure as the potable water system. If it is direct connected, it should be through a special valve that reduces the pressure to that of the heating system (normally around 12-14 pounds or so). Once it drops below that, it either adds water automatically, or you have to do it manually while watching the pressure gauge.

3. Now would be a good time to check that the expansion tank is in good shape and has the requisite pre-charged air pressure - nominally around the normal operating pressure 12-14 pounds. If it had the proper air pressure in it, when you opened and drained the system, it pushed out all of the water in it, and is (nearly) empty. If it is full, it is probably shot.

4. Often that is the case, but each system is a little different. This is a hot water system and not steam?

5. Probably best to do it off for the bulk. Dont' think you have to turn it off later unless you have big problems. The system will (should) shut down if the pressure gets too low or the water level drops too far.

6. Don't know...

7. Depends on the design, but as noted 12-14# is fairly common.

Got it working last night. Thanks!