Heating Help

Intermittent Rough Running Beckett AFG

The problem, as described by the homeowner, is the burner runs nice and quiet 80% of the time.  The other 20% of the time it sounds like a truck running down a rough road.  It has loud short detonations/mini explosions that make the draft regulator door move.  The burner will run smooth for hours, then rough for one cycle, then smooth again.The boiler is a Burnham V8H4W provided under warranty to and installed by the homeowner.  The Beckett AFG with F Head was taken of the old boiler and reused.  The burner specified by Burnham is an AFG with L or V head and a 1.10 60 B nozzle.  The burner now has a 1.00 60 B Hago nozzle in it.  This replaced a .85 70 H that was found installed.  No explosions were noted when this nozzle was in use.  The boiler has been cleaned.  The tank filter, fuel pump, pump strainer and nozzle have been replaced.  The electrodes have been adjusted to spec and the drawer assembly set using a Beckett Z-Gauge.  Fuel pressure is set at 140 PSI and did not fluctuate, as verified on the installed gauge, when the mini explosions were taking place.  Note that the gauge accuracy was verified during the burner tune-up.  Running vacuum is 0" HG.  Vacuum Leak Test back to the tank showed vacuum dropped to 1.5 - 2' HG and held steady at that point.  Combustion has been set using and HEI Analyzer that was serviced and calibrated by the manufacturer in October 2010.  The intermittent nature of the problem has me baffled.  Any help is greatly appreciated.  Thanks,  Bill

motor?

Is it interrupted or intermittent ignition type?  Also, did you check the fan motor and coupling?  I've had some where the fan motor runs rough sometimes and causes problems.  Maybe do a resistance test on the motor leads to see if it is on its way out.  

also check

overfire draft should be -.01" to -.02"

nozzle

Change the 60 degree to 80. F heads run best with 80 degree spray angle nozzles.

feedback

Thanks for the feedback guys.  Primary Control is intermittent ignition (4184).  Overfire draft is - .015 to - .02 "WC.  Smoke 0.  I'll check the motor and possibly experiment with the nozzle spray angle later.  I don't want to change too many variables at once. 

Was that V-84

a replacement for a failed V-74? If so, that explains the F-head. The Beckett OEM spec manual shows the AFG using the F head on the V-74 but the V1-0 head on the V-84. This might be due to tighter flue passages in the V-84.

Order the correct air tube assembly from Burnham and install it. I'll bet that solves your problem.

Replacement Boiler

Yes, the V-84 replaced a V-74.  I will get the correct air tube and head combination.  That makes sense, but I still wonder why the noise is intermittent.    

The intermittency

is a bit strange, but it could be caused by a borderline static-pressure condition over the fire. I believe the V1 head can fire against a higher back-pressure than the F head can, but don't have the numbers here.

Also remember the V1 head uses a 60° nozzle rather than an 80°. The OEM spec guide shows a 1.10x60°B Hago nozzle at 140 PSI for the V8H4W. Hagos are hard to find these days, at least in my area, but a Delavan B or Monarch R should work- check w/Burnham to be sure.

And if you haven't added a CleanCut fuel unit or oil-delay valve, do so.

I don't think

that an AFG won't work on the V-8, There is little to no difference between the boilers. I have mounted AFG's to V-8's when customer wanted block only warranty replacement, and they ran as a Beckett should. 

AFG's

If the boiler had the burner package that Beclett and Burnham suggest, the problems would go away. It sounds like delayed ignition on start up.
You can pull this off with a Carlin but not so easy with a Beckett with all their head and tube configurations. What happens when home owners who aren't qualified, start trying to re-engineer products they have no understanding of.

V-series

Burnhams have had alot of different brand burners on them, Beckett AFG is one of them. This will work just as good, if not better/quieter I've found with F head/tubes. There is little to no change V-7 to V-8 series that would require the noisy burner. JMHO