Venting hot water radiators

Chilly in Wilmette

I bought ah old (1871) victorian that has a four zone hydronic system. On a recent "tune up" visit, a heating guy vented all the radiators. When my wife asked that he find a way to cool down one particular radiator, the guy went down in the basement and drained a pipe of a great deal of water. The radiator was definitely better, however it seems all the radiators in that zone have reduced heat output and some have none. I'm wondering if I can increase the output of most of these radiators by simple venting them. Reason I ask is, I have no idea if the system would need more water added to enable me to fill the radiators more via this venting or whether the system will automatically call for more water when I vent the radiators. I don't want to ruin the system but I'm frustrated with what the heating guy did and was thinking of trying to fix it myself. Looking for advice. Any tips for a somewhat handy homeowner?

Matt Undy

Re the radiators piped in series or do they individually tap off a supply and return main? If they are in parallel you can close the radiator valve part way.

Are the radiators tapped top and bottom or is the supply and return both in the bottom? He may have filled the radiators mostly with air if the tapings are on the bottom.

A modern system will have an automatic water feeder but if its very old it could be manually fed and it could be turned off even on a modern system. Note the pressure when the system is cold and make sure it returns to that pressure after you bleed the other radiators on that zone.

Matt

Chilly in Wilmette

Venting hot water radiators

Thanks for the quick reply! The supplies and returns are all at the bottom on all the radiators. The boiler is about 20 years old and is Blue but I have no idea who made it. How would I tell if it has a automatic water feeder? It doesn't seem to have a pressure indicator on the outside; I will look to see if there is something inside the housing.