baseboard heat air in sys


Old 04-09-04, 09:20 PM
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Unhappy baseboard heat air in sys

had a pipe break and replaced it, but had to drain complete sys, pipe was in basement floor. All fine with pipes now , but have air in sys and doesnt have any bleeder valves, in any of the baseboards. boiler is a dunkirk rad pwb-70, it heats 3 floors usually (counting the basement ) all have baseboard heat. it has 1 zone in basement-1 pipe in and out, main floor has 1 pump but divides into two pipesin and back, same for top floor. I have lived here only a year, this is first winter just passed. worked great. until i replaced that pipe with a GIANT AIR LOCK I guess. Its a hot water not steam 3 pump system, originally installed in 1956 when new, boiler 3 yrs ish old. has the auto fill valve, I turned it on but not sure where to start, do i bleed by ??? expansion tank is in joists and has no water in it or just a very little feels and sounds empty, lost lost lost, i understand the system but dont know how to get the air out....please please help. still been cold in chgo at nite
thanks Dan
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Old 04-10-04, 08:22 AM
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,815

Is this a multizone system? Does it have more than one thermostat in the houe? If it does, you have to bleed one zone at a time. The bleeding is done without the pump operating. The water supply fill valve, is it on the supply or return side? Normally the supply is on the top of the boiler and the return comes in low. When the bleeding is started you need to valve off the return from returning into the boiler using a gate valve and there should be a purge valve spigot for each zone before the gate. In purging air from the piping, you're attempting to push the air through the pipes overcomming its natural boyantcy to try to rise using system pressure. To do this, you will need to override the water pressure regulator with the small lever on its top, being careful not to hit the 30# mark on the boiler tridicator gauge or the safety relief will dump water on your floor.
As to the expantion tank being empty sounds like a valve is closed somewhere OR it was full. Does it have a gauge glass?

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