I am working with mod #SFHGD114P1447 that I am not sure why the heat will not come during the daytime. Unit is being controlled by a alerton type control system. unit runs fine in the summer time but in these temps the alerton controls will switch on the heat thru the changeover contacts .this shows up on the HI on the roof as heat at 0%. the bas shows heat on with set point at 68deg. The main problem is the dat can be way lower when the econo is at the 10 percent min or the co2 controls start to drive open the osa. On the gbas board it says the input voltage of 1.27v and that is about 68 deg.
The morning warm up works fine when the mod burners, are not in lockout, another issue, but the control guy does not know what the 68 degree set point he has given the unit what it responds to IE return, mixed or dat. the bas switch's between the heat and cool commands, based on the number of boxes over a adjustable amount that need heat or cool. This 68 degree set point for the heat is the highest the heat is allowed during the day, that is programmed in the bas, why that temp no one knows, just the way it always been, but it can be adjusted higher.

The way the daytime heat now is being done it is not working. the 4 unit's total between the two bld's basically stay in the heat mode all day long at these temp,s. I am sure there a better way to do this besides what the control co says ,it was designed this way and it's always been this way.