Beckett cuts out after 14 minutes-then starts again- CF800

tman9

I have a Beckett burner, CF800, in an construction heater and it is cutting out after 14 minutes...recyles then restarts. At about 14 minutes the fuel pressure bounces once then goes to zero, cad resistance goes to 50K. I am not sure what is happening first though. If the burner motor is going off hence the fuel oil pressure drop and that causes the cad resistance to go to 50K. Or maybe fuel pressure drops due to fuel pump or some other sequence.

I replaced the Genysis 7505-452M controller, nozzle, electrodes, filters, cad cell and holder, fuel line cut off solenoid. Screen in fuel pump is nice and clean. There is another heater running off the same fuel tank and it is having no issues although it has a different pickup in the fuel tank.

I am wondering if it would be fuel pump, blower motor, or bad ignition(or once running this would not matter?) or even junk in the fuel tank. It starts beautiful and runs smooth. Fuel pressure is 145 PSI and looks great until it dies. For some reason very close to the 14 minute mark seems to be when it takes place. Then it restarts perfect again. On this heater I am not able to watch the flame in the combustion chamber but when running it runs perfect and starts very nice. I do not think it is an air/fuel mixture issue.

Any suggestions
Thank you
Todd

tman9

Sometimes after first restart it will go for up to 22 or 23 mintues. But first stop and recycle and restart seems to happen around that 14 minute mark.

STEVEusaPA

Must be a big heater. Don't know why you replaced all those parts without testing them. If you get the contractor tool you can put it on the primary control and see if it tells you why it locked out.
I suspect either vibration or heat affecting the wiring.
Do you have a vacuum gauge attached?
Usually there is not much of an air adjustment.
That is a tricky one. What happens if you take the pick up to the fuel pump and stick it into maybe a clean 5 gallon can of fuel and see if you get past the 14 minute mark.
Maybe a little air is getting in the pickup or a slight vacuum leak, giving you a hiccup. I assume it's two pipe?
Edit:
What other controls are on the heater, besides the burner. Did you check there for loose wiring, overheating?

HVACNUT

It also could be a restricted oil line. It will go into recycle with an increase in vacuum and higher resistance at the cad cell eye.
If you start the burner, jump FF on the Genisys, then leave your ohm meter on the yellow wires for the cad cell, you should see the resistance get greater and greater. If that's the issue.
Are the oil lines filtered?

EdTheHeaterMan

How many hours are on the burner? it may be as simple as the burner motor coupling. After 14 minutes of operation the worn coupling may overheat ... expand enough to lower the pump pressure... causing the flame signal to drop out... shutting off the fuel... Genisys control goes into recycle... restarts after 90 seconds, then repeat

Or ... what everyone else said

tman9

Thank you everyone for your suggestions. Yes it appears it was air getting in. I put a clear fuel line on in the same shape as the existing fuel line. An air bubble starts to build but can't quite get through the bottom of the U shape it is in. At about the 14 minute mark that air bubble is finally big enough to go past in one big movement. Then it all shuts down. Now I have to find where the air is getting in. I have to check through two inline filters one with a primer and a heater(probably the culprit) and tons of hose and connections that are hard to reach. Not sure the best method of doing this...maybe I will just take the filter with the primer and heater out of the circuit and retry it.