R7284B (Oil primary) Setup

valve on delay lets the burner start and run for 15 seconds to establish oil pressure , ignition and draft and it allows a cleaner start of the burner. Burner off delay at 45 seconds will shut off the oil flame when the thermostat is satisfied and run the burner with no flame for 45 seconds cleaner shut down.

Those are not problems those settings are ok.

I wonder what your nozzle assembly looks like?

You may have something that is not really a problem.  When oil burns it gets really hot and can leave some signs of that heat behind.  If you burner operates like most homeowners, then an annual tune up and maintenance is in order.  Have a professional with the proper combusting testing instruments perform that service for you.  Light usage can often get by with every two or three years of operation. But at least every 300 gallons of fuel usage. With the proper settings and adjustments your nozzle assembly may look like new after a year of operation, but I found that to be the exception, not the rule.   As long as you can replace the nozzle and clean up the ignitors and polish up the metal parts of the assembly, you can get years of life from that burner even with some black stains on the parts.

The primary control that is set to NO for the thermostat contacts turns that control into a 120 VAC control only. That means when you get both the LIMIT and the L1 powered by 120 VAC, the control will operate and does not need a thermostat input. The Thermostat YES setting is usually used on furnaces that are connected to ductwork. The 24 volt thermostat will call for heat by closing the T T contacts to start the burner. Then the fan limit control will operate the fan and stop the burner if there is a over temperature condition in the furnace.

Since you burner is on a boiler, there must be some boiler temperature measuring control that is connected to the LIMIT terminal of your Primary control. It may be an electronic control that has a B1 terminal that is connected to the primary's LIMIT, or it could be the L8148 or L8124 that has a B1 terminal. There MUST be some control that is measuring the boiler temperature. that control will also be where the thermostat is connected. Can you see where your thermostat is connected to on your boiler? What is the part number or model number of that control? Or better yet, take a photo and post it using the Photo icon next to the smiley face at the bottom to the comment box.

You could still have a boiler.

Your "domestic" HW (stinks, shower etc) is electric. But if you have radiators or baseboard (steam or HW) you have a boiler.

If warm air gets blown out of registers into the house, you have a furnace.

So your system is connected to ductwork. Then you most likely have a newer furnace that utilizes a ST9103 fan timer. That is the control that you connect the thermostat wires to. In that case there are several different ways the primary control may be connected depending on the manufacturer's wiring design. Some use the ST9103 to call for heat on the R7284U with two wires from the 9 PIN plug in connector to T T on the R7284U. Others may not use that design. The bottom line is to look at the R7284U and see if there are any wires connected to T T that go to the ST9103.

If there are no wires connected to T T on your Primary control then NO is correct. If there are wires connected to the T T on your primary control then YES should be set for T T. see the illustration

Now there is an exception to this. If the ST9103 has a defective switch circuit that fails to make the call for heat from the thermostat, transfer to the 9 PIN connector, the you might need to have the ST9103 fan timer replaced. As a money saving adjustment, I have made the change from T T = YES to T T = NO as long as all the other safety functions of the ST9103 fan timer are operational. You would need a professional technician that is familiar with the proper safety circuits that include the high limit and flame failure safe guard.

So you are saying that you have t wires connected to the terminals marked T and T3 like I showed you in the photo of the primary control in my previous post... Is that correct?

Then you should be able to set the T T to YES and it will also work fine. There are three different things that will keep the oil burner from operating with that control under normal conditions:

1. No power to the L1
2. No power to the LIMIT
3. T T set to YES with no call for heat from the thermostat or control connected to T T

The ST9103 Fan timer has a way to turn on the LIMIT and the T T on a call for heat. With the T T set to NO on the primary control, the ST9103 only has one way to shut off the burner, that is the LIMIT having no power. that might be just fine but you are bypassing the ability for the ST9103 to also shut off the T T call for heat. Unless there is a problem, I would set my R7248U's T T setting to YES.

The R7284U also can shut off the burner if there is a flame failure. It can also keep the burner form starting if there is a flame signal when there should not be a flame signal. Depending on the inputs from the thermostat, limit, 120 L1 and the amperage of the motor ,valve and ignition, and the cad cell Ohm reading during operation and trial for ignition, there are several diagnostic messages you may encounter from that control. Those messages can help you determine where to look for a no heat call from the oil burner,