Danfoss Oil Pump Pressure

[Apodemus]

I installed a new Danfoss BFP20L3 in my elderly Rayburn 480k. The Danfoss comes pre-set to 10bar but checking the fuel pressure suggests it is giving me 15 bar. The reading on my gauge remains at 15 bar when the pump is running regardless of the positioon of the pressure-setting screw on the pump. The Boiler side of the Rayburn has a soft-start set at 6 bar and during the soft-start period, the gauge correctly drops to 6 bar, so it looks like my gauge is working properly. I can also vary that 6 Bar reading by adjusting the pressure regulating valve for the soft-start, again suggesting that my gauge is good. I'm struggling to think of any logical explanation except that I replaced the motor last year and I'm wondering if I have somehow managed to get a motor that is running too fast for the pump? Am I missing something obvious?

 

[Apodemus]

Doh! Forgot to remove the one-pipe system screw!

 

[Johntheo5]

A easy mistake to make, my 17 year old Firebird with its Riello G5X burner came with its by pass screw taped to the front page of the Riello instruction manual where it remains, to this very day.

 

[Apodemus]

Yes, taping it to the instructions might help! Danfoss have it inserted by default, so you have to remember to remove it. For some reason my (24 year old) boiler eats a pump every couple of years, and I have done the replacement so often, I had relaxed into "I can do this in my sleep" mode! But I might follow your lead and tape it onto the front of the pump, so that I see it the next time I remove the pump!

 

[Johntheo5]

Why is your pump failing after a few years? is it seizing up or what, are you letting the tank run dry often , I have seen pumps failing after 5 or 6 years due to people trying to prime them after tank empty by repeatedly pressing the reset button.

 

[Apodemus]

I'm not sure why the pumps fail - I've probably only had a couple that have reached the stage of actual failure. I'm perhaps just overly sensitive to a deterioration in noise from them and replace them when they start to sound a bit "rough". Being a stove in the kitchen, you hear these changes more than if it was a boiler in a cupboard. They have lasted longer since I started using an additive in the tank, or possibly since Danfoss made changes to make the pumps compatible with biofuels. I suspect, though, that there may be a slight misalignment between the motor and the shaft and although this is largely taken up by the rubber connecting rod, it perhaps pulls unevenly on the pump bearings. There are probably other things slightly loose in the works of the Rayburn which vibrate when the pump is not running as smoothly as it should, which make the pump sound so much worse than it really is.