Just finished with a new second floor addition. Upgraded to two zone heating from single zone. When heat comes on after expected delay for temp to rise the blower comes on for fifteen seconds then kicks off and comes on again in about two or three minutes, and kicks off again in fifteen seconds, on and on the cycle goes. The contractor claims this is normal, he did do some checks on the system. I can't believe this to be normal, the system never operated this way before. To me, heat being generated is sitting in the chamber waiting to be blown out into the ducts. Energy is wasted with the blower motor kicking off and on, also sortening its life. The unit is running longer since the heat is not being pumped into the living spaces. Our building contractor is unsure what to do, I want to bring our Service contractor in if this can't be resolved, but I would like to know first if I am wrong or right, and what should I tell the contractor to look for or inspect. I believe that they as the installer should fix it. The control panel is a NCN-300, and the furnace is an oil fired Thermo Pride about ten years old. Any help would be appreciated. Thanks.

labman

The on and off definitely is not normal, and is very hard on the blower motor. I guess the limit switch could be shutting off at too high of a temperature. It heats up, starts the blower, cools, shuts the blower off, and starts another heat cycle. If you have a setting for fan on, you could run a heat cycle with the fan on. If the fan runs continually, that suggests the limit switch is bad. If the fan still cycles on and off, look at its relay and the motor itself.

slls

What I would do is check to see what the fan control is doing. Remove the front furnace panel where the burner is located. In the upper right or left corner is the fan control, it has a silver cover that you remove by squeezing the sides and pull out. you will see a dial marked in 10 deg increments starting at 50 degs and up to 250. There are 3 adjustments tabs , #1 fan off setting, #2 fan on setting and #3 overheat shut off. #1 is normally set to 90 deg, #2 -110 deg, and #3- 190 deg. With the cover off watch the dial to see what the fan control is doing. Not sure about the 2 zone, I assume it’s control dampers.