Danfoss oil pump on burner

[TonOfSand]

Hi all
I posted a question about this before but am still curious to find out what the problem is. On my boiler burner I have an oil pump - Danfoss BFP 11 L3 - which heats up after about 10 minutes. It's about as hot as a very hot radiator, so you can touch it but not for long. It shouldn't be anywhere near this temperature. Here's some info:
-it's a one pipe system
-the horseshoe washer is present (present for one pipe, removed for two pipe. I presume its Danfoss's version of the bypass plug)
-I don't have the means to check pressure but it was bought new and the factory setting is 10 bar (145psi) and hasn't been touched
-nozzle is 0.40 USgal/h (for 100psi pump pressure)

My guess is that the pump pressure is too high for the nozzle but I've found charts that list the new USgal/h if the pump pressure is changed but no mention the pump heating up.

Any thoughts on this will be gratefully received.

 

[oilhead]

What burner is this fitted to? The connection of the pump to the motor varies and we need to know before offering any further advice. I see that you have already asked this question and been offered advice about pump mounting.
A pressure greater than the boilers requirements will not overheat the pump, but can cause problems elsewhere.

 

[TonOfSand]

Thanks Oilhead. The burner is EOGB.

 

[oilhead]

B9 or 2011. Either way don't tighten the screws up too much and fit a new drive dog.

 

[BoilerBob]

They need to be just tight enough so you can just move it slightly.Bob

 

[TonOfSand]

Thanks folks. I've swapped over between this pump and the old one a few times in my efforts to keep the boiler going and the old one never heated up.

 

[oilhead]

Begs the question, why change the pump if the old one works?

 

[TonOfSand]

The old pump doesn't work anymore. While diagnosing a problem with the burner I fitted a new pump (the problem was with the controller). Once I replaced the controller I noticed the new pump heating up so switched to the old one. Then the old pump stopped working properly a few years later.

 

[oilhead]

How old is your 'new' pump?
After fitting it, and replacing it with the old pump, did you fill it with oil and replace the transit plugs? If not, it probably dried out and rusted a little inside giving you your problem.

 

[TonOfSand]

Thanks Oilhead, I do appreciate your replies on this matter but it's not a rust issue. The pump was installed on the day (or day after) I bought it new. It heated up then and when I removed it I wrapped it in newspaper and kept it indoors.

 

[oilhead]

But if you did not fill with oil and plug up the inlet/output ports, the innards dry out and oxidise, or any sediment solidifies. I've seen it so many times when being presented with a pump retrieved from a replaced burner, and the customer never understands. A pump will get hot if there is any contamination in the pump, or if the connection into the motor is off centre, or the drive dog is too tight and pushing the shaft back into the pump.

 

[TonOfSand]

Thanks again. Looking at the solenoid. It seems to be the first thing to heat up, especially the cap that holds it in place and after about 10 minutes it is noticeably hotter than the pump case.

 

[Burnerman]

There will be a certain amount of heat generated by the solenoid - it is a coil, after all but if it had a problem it would fail soon enough. Nothing to stop you trying the original coil, of course!
If I may mention, the factory set pump pressure is too high, 100 to 120 psi being more the norm so I think it needs to be set, together with the CO2 level. Overfiring will burn out the baffles in the boiler.
John

 

[TonOfSand]

Cheers John. Good to have your input. I did try the old solenoid - same result. I never let this run for more than 15 minutes as this would be foolish. This is really bugging me. It would be a good idea to get the pressure set regardless but according to oilhead it won't solve the heat issue. CO2 level? I'm assuming this the air/oil ratio so you set the correct air/oil intake to get the cleanest burn? I'll have to get someone in to do that if I ever get the heat issue sorted.

Regarding the pressure. Do you think reducing it would stop the pump heating up so much?

 

[Burnerman]

A real head scratcher, this one!
I suppose in theory the higher the pump pressure the harder it is to spin but personally I’ve never noticed any difference in the heat generated......I’ve just let the burner get on with it.
The pumps do get very hot, for sure after they have run for a while and can get too hot to comfortably hold but you shouldn’t be able to fry chips on them.
On the B9 burner the pump is on the back of the motor......does the motor feel hot too?
Regarding the oil pressure, a gauge is screwed into the pump port marked P and that is cheap enough but the flue gas analysis to set the CO2 is much more expensive and the air door is adjusted to give a reading of approx 11%.
Are you so concerned about this that you don’t want to run the burner for longer than 15min?
John