I have a problem with my heating system. I have a Laars "Newport" high efficiency direct vent oil boiler that is fairly new, installed when the house was built in 2003. The whole house has hydronic baseboard heat. The house has two zones - Zone A feeds bedrooms & bathroom. Zone B feeds dining room, living room, kitchen. Both zones are on one floor, boiler is downstairs in finished but unheated basement. Zone A has a standard dial thermostat. Zone B has a new RiteTemp digital/programmable thermostat. Zone A is up to temp and very comfortable. Zone B wont get above 50°F (Brrr!). Hot water is from a storage tank that feeds off the boiler, and I have plenty of hot water. Hydronic baseboard pipes in Zone B are stone cold. Outdoor temps last couple of days ~30°F high/10°F low The Zone B thermostat is about 1 year old - it's battery operated and the batteries in it are fresh. I usually program it so that the heat goes down to 50°F during the day when I'm gone, and then comes back up to 68°F when I'm home in the evening, and then goes down to 60°F overnight. I started having problems about a week ago when I would come home from work. The thermostat would be set at 68°F but the temp would be cold - 50's. I would override the program temp and crank the digital thermostat up, and after a few minutes the boiler would come on and that zone would be comfortable until the next night when I'd have to do the same thing. Now that thermostat won't trigger heat at all, and I'm guessing the only heat in that area is what radiates up off the boiler itself, which is directly below. Zone A has had no trouble maintaining a comfortable temp. I usually keep it set at 60°F all the time, but since Zone B crapped out, I've been keeping it at 68°F (and camping out in here to keep warm) I'm guessing either the thermostat is faulty or the circulator pump has gone bad. I haven't done any work anywhere that might have pierced the wires, and I've recently bled the fuel line to the burner make sure there's no air pockets. It's worth noting that my problems roughly coincide with a switch to burning dyed diesel, which in my part of the country is significantly cheaper than fuel oil right now, and it's also available in a quantity I can afford. I am told that it's interchangeable with #2 fuel oil (please tell me I didn't destroy my boiler!) I thought part of my problem might be the diesel starting to gel out in the fuel tank, which is in the unheated garage. I put an electric heater next to the filter at the outlet end of the tank, but that hasn't seemed to help. This could be minor or nothing, but I figured I'd throw it in the mix. Even though Zone A is comfortable, when I set the working thermostat in Zone A to a higher temp, it doesn't automatically trigger the boiler to come on. And when I set it all the way up, the boiler doesn't run continuously to get up to temp. It comes on, runs for 15-20 mins, shuts off, and maintains a lower but comfortable temp in Zone A. It's also worth noting that when I looked at the boiler last night, the flue pipe coming out of the boiler had somehow come unlodged at the elbow to the pipe leading outside. Whoever installed it (not me) didn't actually use screws to tie it into place, they just shoved the pipe into the elbow and left it. I'm grateful that downstairs isn't habitable space, because anyone down there would have probably been overcome by CO. It looks like there are some sensors going into that pipe. I don't know what they do but I wonder if that could be part of my issue.

Hi again, I have another question. What temperature must water be for it to begin circulating through the hot water heating system via gravity? I have a circulating pump, but I don't want to aquastat for the pump set higher than the temp needed for gravity to begin moving the water. Any thoughts?