The problem goes like this. I have a Hydro air system that uses a fuel burning boiler. On the 1st floor -When the thermostat calls for heat, the boiler starts waits for the aquastat allowing the coil to heat up before turning the blower on. This is like a 10 to 30 second delay from the time the blower starts blowing hot air. When the thermostat reaches temp the boiler turns off. But the blower continues for 8 to 10mins blowing cold air and then shuts off. Everything is working fine expect for that 8 to 10mins delay of the blower – blowing cold air. Does anybody have any ideas on how I can fix that 8 to 10min delay? Thank you for looking at my post...

Working from what I know a little about, toward your system. Forced air furnaces use a limit switch or timer to delay the blower starting until the air warms, and to cool the furnace after the heat shuts off. However that is much less than the 8-10 minutes. Likely you system works the same way. Start with relay that controls the blower. If it is on circuit board, likely it is controlled by a timer on the board. The only reasonable repair may be big bucks for new board. If it is just sort of inside the unit, and wires go to near the coil, it could be a bad limit switch. If it has the temperature marked on it, it may be easy to replace. Otherwise, you may need to have somebody figure it out from the model number.

I have a very similar system with 3 zones. My take on your situation is that there is a energy sayer in the circuit that allows the blower to clear all the residual heat out of the coil. It can be changed over to instant blower and instant shut off but you would have to be in the HVAC industry to figure out how to do that. BTW mine is wired with a special system that uses a variable motor that changes the speed in relationship to the heating demand. A very expensive system. The motors and controlers cost me wholesale 632.00 each. That's 1900.00 just to have piece and quiet. Well worth it.