High Stack Temp Woes

RopeaGoat

I'm in a pickle and could use some outside advice. I'm working on a Burnham V8 boiler with a Beckett AFG burner and a TJ SS2 Powervent. Last tech that fooled with this really screwed her up. It had a .75 80* A nozzle, a pump pressure of 90 PSI, a draft of .075, air adjusted way out of wack, and was VERY sooted up. Upon initial diagnosis I got a stack temp close to 950*F, a 4 smoke (easily), and an CO2 of 7 or 8. So I took the burner book out and set it up according to the listed specs, checked the pump, replaced the strainer & filter, Vacuumed out the combustion chamber, removed the top & sides and brushed and vacced the whole unit, cleaned the vent pipe and tore apart the PV and cleaned it with he vac and carb cleaner. Reassembled everything, fired her up and she purred. THE ONLY ISSUE... still have a stack temp in the 550*-600*F range... no smoke, CO2 of 12, draft above flame of -.02. ANY ideas of how to lower that stack temp? I've replaced nozzle w/ a .65 60* A. (book recommended a .85 60* A) Thanks in advance for any info.

HeatPro

Actually that isn't a bad temperature, rather usual for oil burner heaters over decades, one reason for having oil burner venting different from gas venting. However, many do run at lower temperatures.

It's a bit difficult to analyze from here, but some things to consider are:
1. Are all parts and nozzle the same as in the Burnham catalog that the boiler was tested with at the factory? The 60A Delavan nozzles are shown in page 96 Table 6 of the catalog:
http://www.burnham.com/PDF/V8_I&O.pdf

2. Is a small nozzle baffle required for that burner?

3. Is the pressure at 140?

It is possible the flame is being drawn through the heat exchanger to the breech faster than heat can be absorbed due to the power vent and burner part settings, so further adjustment of the head and draft might be necessary.

RopeaGoat

Everything is set up per the book except the .65 60A nozzle. The book called for a .85 60A but I swapped it to a smaller one based on some info from my supplyhouse rep. He mentioned that the .65 @ 140PSI was similar to the .85 @ 100-120 PSI. By swapping it out it knocked about 75-100* F off the huge stack temp I had initially. It also helped to quiet the unit down.

Right now I'm at ~77-78% efficiency. My goal is 83-84%. This is my target for all my tune-ups. The kick in the teeth is that this unit is my own boiler.

HeatPro

The reason the 60A nozzle is selected at the output at 140 psig is a result of the testing a Beckett in their labs for some days to come up with the best nozzle. The output QUANTITY might be the same with another but not the pattern. If the factory found that other nozzles at other pressures were satisfactory, they should publish them all. I do remember the days 40 years ago when there was no testing of that sort when building a chamber. The allowable standard for smoke in the 1950's was a #5 smoke.

DuMass

"THE ONLY ISSUE... still have a stack temp in the 550*-600*F range..."

RopeaGoat.
I think that is about normal for PV oil fired systems.
By it’s very nature the PV pulls a certain amount of heat through the flue and into the breach.
Even my own older Burnham 80% oil fired boiler with Field Controls SWG-5 PV usually runs at about 550-600F stack with 0-smoke and all the other numbers within spec. Seems it is just the nature of the beast.
Another poster mentioned possibly changing to different baffles to help slow down this heat loss. That might be a viable option for your newer unit to help gain back some of the loss in efficiency because of the PV.

Josey Whales

I think you have to much air stack temp will go up and CO2 will go down hope that helps