Heat will Not Turn Off

One step at a time. Heat continues with thermostats "off"? OK. Remove thermostats from wall and disconnect. Heat stops? Bad thermostat. Heat continues? Go to other end of thermostat wires at control, and disconnect BOTH wires (or all three (note where they go). Heat stops? Bad wires. Heat continues? Now you can start investigating the control.

Does it connect to the primary control on the oil burner? The relay in the primary control might be welded shut and it won't shut down with the thermostat or any safety that is on the low voltage side

Is there a schematic of the furnace inside the blower door or somewhere else? Can you take a picture of it? Usually there is a low voltage control to the primary control (the control on the oil burner itself) but not sure how it does 2 stage, could be 2 low voltage controls to the primary control for high and low.

If disconnecting W on the furnace control board doesn't do it, TT on the burner primary goes through 3 and 6 at the 9 pin molex. If you remove one wire from TT at the primary, the burner should stop. From there, with the power off, you can back track and see what's closed using continuity.

Here is the diagram of the two yellow wires from the 9 pin plug to the Primary control.

Turn off power. Remove the yellow wires from the primary control screw terminals. Then power up the furnace…. Burner stops?

Yes = Bad fan timer control

NO = Bad primary control

That will not matter on this set up. The HZ311 is a zone control panel for one stage heat and one stage cool, so there will be no wire from W2 on the Thermopride to the HZ311. There is no place to put the W2 wire on the zone control panel.

By removing the wire from W terminal on the HZ311 they have eliminated the Zone control from being the problem. The burner keeps operating because of something inside the Thermopride.

Next step for @Mac18 is to take a picture of the circuit board inside the Thermopride and post it here for us to see what is going on in there. Can you do that Mac the Knife?

I may see a problem. need to do more research.

Can you verify the yellow wire with the blue connector on the R terminal is going to 9 pin plug? And if so which number on the 9 pin plug, 3 or 6?

I think you have the Riello Oil Burner and this is your diagram

Remove the Yellow wire yellow wire with the red connector on the C terminal of the Thermopride control. That should stop the oil burner.

If that stops the oil burner, then the Thermopride control board is bas and needs to be replaced.

If the burner continues to run then the small black relay is bad and needs to be replaced.

(unless the wires connected to the Riello burner are not connected properly. That would be another picture needed with the burner cover removed.

Tapping of that black relay tells you that the relay got stuck. That may happen again. I would order a replacement relay and have it on hand for the future.

As far as the blower operating for 4 minutes after the call for heat from the zone control is satisfied, That can be adjusted. Do you get uncomfortable cold air (during heat season) at the end of each cycle, then you need ot adjust the dip switches on the Thermopride Fan circuit board.

From the manual. It appears that switch 3 is in the on position and switch is in the off position. if you don't have a problem with comfort, then leave it alone. (If it ain't broke… Don't fix it)

Where is that relay in relation to the safety chain of the furnace? If the any safeties control that relay rather than the line voltage power to the burner, you want to make sure that the relay is properly functioning otherwise it could cause a fire if it prevents a safety from stopping the burner.

mattmia, I believe that the L1 from the field supplied power switch goes to the circuit board at S1 on the right had side of the board. From ther it feeds several locations on the board including #1 on the 9 pin connector that goes to all the high limits in series on the furnace before returning to #4 on the 9 pin connector. From there #4 feeds a signal to the onboard software that the limit switches are closed and therefore the #2 pin on the 9 pin connector is powered. #2 on the 9 pin connector eventually connects to one of the orange wires that go to that relay in question, and then return to ultimately connect to the oil burner #5 terminal also labeled L1. Following that path, the 120 VAC must go thru the High Limit(s) before it gets to the orange wires that feed the burner thru the relay that was defective.

That relay getting stuck closed still have the high limit(s) in the series circuit. I know this because that is how the limits are configured when the Beckett burner is used on that Thermopride and the limits are the same on that system. So the limits are where they should be regardless of the burner brand used.