The pressure on my boiler is about 12, and the altitude reads 30. The radiators in the attic get slightly warm if I put the heat up very high, roasting us. I have been bleeding the three units in the attic, and very often get air followed by water out of 1 of them, and air followed by no water out of the other 2. One of the radiators on the second floor seems to have no air in it, but really doesn't get all that warm unless the thermostat is set very high.
If we raise the psi, will it raise the altitude? The house is probably higher, from boiler to 3rd floor radiator, than 30 feet.
Could the lack of heat in the second floor radiator have anything to do with the 3rd floor?