We have a gas boiler that replaced an existing boiler. When we put it in we consolidated several heating chores. The new boiler has a coil in the ducts for the forced air part of the house, and also heats our domestic hot water. The house is 25 years old, and is not very air tight. Including the basement, it's 3 floors, but the part of the house over the basement only has one floor above it. The net result is that the b-vent stack is above the local roof, but is some 8 feet shorter than the two story part of the house. We have a wood cooking range and a wood space heater that we use extensively. We have 6 zones in the house, including the DHW one. Three of the zones have never come on. One comes on only in severe cold weather. The boiler is a medium efficiency unit, electric ignition, with a powered damper plate at the bottom so that there is no continuous draft up the chimney when the boiler shuts off. The boiler short cycles: Typically it will come on for only two minutes at a time, then be off for 15 even in mid winter. Because of the stack effect of the wood chimneys, and air leaks in the upper part of the house, the basement space is always at negative pressure. If I leave the outside vent open the room gets very cold -- I worry about freezing the pipes near the boiler. I blocked the outside vent, and installed a CO detector. It has never gone off except when testing. This has worked for several years. HOWEVER, with the short cycle, the chimney cools off. When the boiler starts, there is serious condensation in the cold chimney, and it doesn't run long enough to dry it all out. The net result is that I am faced with replacing the entire b-vent stack. That I can do. My question is: How do I keep this from happening? Answer 1. Set the boiler to run with a greater differential. Unfortunately, this is not setable in this unit. Answer 2. Install a buffering tank across the output of the unit, so that a fraction of the water pumped through the boiler went through the buffer tank. (In effect a permanently on zone with very large volume, but no radiators.) In this way, when the pump comes on some of the water in the buffer tank is also circulating so the boiler has more water to heat before it can shut off. Answer 3. Modify the cleanout cap at the bottom of the B-vent by drilling a hole in it. This hole should be of a size that there is some flow up it all the time. However, because of the stack effect on the rest of the house, I suspect that as the vent cooled, flow would reverse. Then when the boiler fires, there would be flue gasses coming into the room until the stack was filled with warm air. In principle a damper on this opening could prevent this. Answer 4. Modify the cleanout cap and put a tiny fan at the the bottom of it to force circulation up through the stack. (A 5 watt CPU cooler fan should be addequate.) Again this should have some kind of damper on it so that if the fan fails, I don't get flue gasses in the house. Things that won't work: 1. Make the house tight. While this is a good idea generally, the fact that we use two wood burning appliances, one of which has a chimney exit 12 feet above the boiler chimney means that the basement is always going to be at negative pressure. Other ideas?

Hello All, Heres my situation: I have a 5 zone system installed in a 4 flat with the basement split into two sections sharing a single valve (see the bottom zone-a-flow-valve in the picture link below) . All 4 zones for the upper floors work fine, i.e, pipes are extremely hot . The basement zone is the one I am having problems with. The electronic valve works fine but the pipe stays cool when the valve is open. In turn the motor runs nonstop. For Images please visit:[URL="http://www2.uic.edu/~crusin2/"]hydronic zone system[/URL] Can someone please describe step by step on how to completely purge the system. Also can someone explain the pupose of the air purger shown in the last picture, can this part be checked/cleaned for proper operation. Thanks in advance.