When to use valve-on delay and motor-off delay?

CLamb

I'm looking through the manual for the Beckett AFG oil burner packaged with a Weil-McLain SGO-3. It says that the GeniSys controller has provision for valve-on delay and motor-off delay but doesn't say anything about when they should be used. Can somebody please explain?

Big Ed_4

The valve on delay can be used for any application . The valve on and motor off delay must be used for a direct vent , no chimney , vented out the wall application .

HVACNUT

What model GeniSys? 7505A, B, or P? 
This is a late model with the Clean Cut pump? If so it should be a B or P.

STEVEusaPA

When? Always.

Steamhead

I'm pretty sure most or all oil burners in production today use valve-on delay. There's no reason not to- it makes the starts and stops a lot cleaner, and helps to reduce soot buildup. I tried valve-on delay on my own burner (Sunray FC Bantam at that time) years ago and saw the difference- now we add it to all our customers' burners that don't have it. Beckett makes a nice delay valve kit that will fit most burners.

Motor-off delay is used for direct-vent jobs as @Big Ed_4 says, also for boilers with a lot of back-pressure in their flue passages. In the latter case, the spec burner will have it enabled.

EBEBRATT-Ed

I would use the valve on delay and motor off delay. Cleaner starts and stops. + the motor off delay will cool the nozzle slightly befor shutdown to help prevent after drip

EdTheHeaterMan

As @STEVEusaPA said "Always" If there is a choice, use the longest off delay for direct vent applications. If you have a standard chimney vented appliance, the time can be set to the shortest off delay, or 30 seconds minimum. anything less than 30 seconds.. why bother? The idea is to reduce convection heat in the combustion chamber from heating the oil in the nozzle line and nozzle. This causes after drip, then that oil is baked and it forms a coating on the nozzle and electrodes

So use post purge always when available.

Yours truly,
Mr.Ed