Gas and Oil Home Heating Furnaces - Yearly Maintenance on AFG

Hi Folks...been lurking here for years, but just now registered. I've learned a lot already, and thank everyone for their great sharing of knowledge.

I have a SlantFin Boiler with an Beckett AFG oil burner. Pretty standard tankless setup with remove 70 gal HW tank and 3 heat zones with separate pumps and a HW-priority-based zone controller.

I've been doing my own yearly maintenance for a couple years now, and I wanted to run my procedure by the team here and see if anyone has any additional advice.

I have an old-school Bacharach test kit for testing/adjustment. Got on Ebay for $120 (needed CO2 tester rebuild kit), which paid for itself first use I figure.

Here's what I usually do:

Before starting, check flue temp, overfire draft, smoke, and CO2...record for before/after comparison.

1) Change oil filter and clean filter housing (usually quite clean but I wipe it anyway)

2) Check fuel pressure with a regular pressure gauge, set to 100psi, +/-5 (only needed adjustment once).

3) Pull nozzle assembly and clean. (replaced nozzle last year to factory spec).

4) Clean and reset electrodes (also replaced last year, kinda rounded)

5) Haven't touched CAD cell, but will clean this year (had a recent random lockout, but reset it and burner seems fine by all measures). Will get a replacement to keep on hand...burner is going on 15 years old.

6) Clean and vacuum heat exchanger with factory brush. Used Soot Saber on first cleaning, but haven't needed it since.

7) Remove and inspect/clean/vacuum flue. Usually pretty clean. Has 6" Metalbestos chimney to roof (see question below).

8) Clean and vacuum firebox. Usually pretty clean. I get some red crud in the bottom which I assume is fuel related.

9) Button everything up, and test fire

10) Check/Set overfire draft to spec (usually fine)

11) Smoke test across a range of air shutter settings, look for minimum smoke condition, open a little more.

12) Check flue temp and look for reasonable reduction before/after...maybe 50F as I recall.

12) CO2 test with liquid Bacharach tester. Tweak air if needed. I usually can't quite reach factory CO2 spec (don't have data in front of me...I think the spec is 12, and I get 11 1/2 or so as I recall)

13) Feed my woodstove so I don't need the boiler anyway... Beer 4U2

This year, I'm planning to downfire the burner with a smaller nozzle (1 GPM to .7 GPM). My boiler spec's a smaller nozzle as an option, and actually doing that makes it Energystar.

Reason for downfiring is I get only 2-3 minute burner cycles which seems short to me. Hoping smaller nozzle drives a little longer cycle and a little more efficient operation.

A few questions (sorry for the long post):

A) My burner parts guy recommended changing the oil strainer in the pump. My cartridge filter is usually pretty clean, so I haven't worried about the strainer clogging. Is that something that needs regular changing?

B) I read a few posts about the pump shaft coupler going bad. Should I change it? I'll get one this year to have on hand...but I'm thinking let it run to fail.

C) Does the chimney ever need cleaning? Its usually pretty clean, but has some buildup over the years.

D) Any other common failure modes I should be addressing?

E) Any other advice anyone?

Thanks!!

One other question...

What does the group think of slightly lowering oil pressure as way to further downfire the burner a little more?

I'm thinking setting it for about 90 PSI, to get a further 10% reduction in oil flow. This would drive about .63 GPM from a .70 GPM nozzle.

I think these kinds of nozzles operate in a sub-sonic mode so flow rate is relatively proportional to pressure. Anyone have any experience with this?

Might be a mute point...I'll see what the burn time is with the .7GPM nozzle. If its say 3-4 minutes, I'll probably stop there...Beer 4U2

Thanks!

Do not drop the pressure below 100#. To do so will really foul up the spray pattern. BTY, pump pressure to flow rate is not a one to one relationship. http://www.delavaninc.com/pdf/total_look.pdf
The whole booklet is interesting but if you look on Pg. 13 there is a chart on pressure vs. flow rate.

The pump screen should at least be inspected. My standard for replacement is: If there is anything on the screen it gets replaced. A new gasket should be installed anytime the cover is removed. Gaskets come with the screen but can be purchased separately.

Pump couplers usually last a long time but they are cheap so keeping one on hand is fine.

Look up the chimney with a mirror on a sunny day. That will tell you if the chimney needs cleaning or not. On a modern burner it's very rare to have to clean a chimney especially on a factory built chimney.

Sounds like you do a good job. Keep it up.

Thanks Grady.

100 PSI it is. Makes sense...didn't know the nozzles roll off under 100 PSI. Glad I asked!

Anyone know what the best burn time is for "peak efficiency" (I know that's subjective). Mine runs 2-3 minutes per cycle which I wouldn't call "short cycling" but seems on the short side.

For checking the CAD Cell, I saw a few posts that indicate it's good if its under 400 ohms with a bright flashlight, and over 4000 ohms in the dark. Does that sound right? I'll test when I do the PM next week...

Any other suggestions for yearly maintenance items on the burner?

Burn time is going to vary with outdoor temperature.

I prefer to check a cad cell under operating conditions. In the dark the resistance should be greater than 20,000 ohms. With the burner running you should read less than 1,000 ohms (less than 800 is preferable). I often see cad cells showing around 400 ohms.

Thanks Grady...I'll check the CAD cell in place. Sounds easier anyway.

What's the best way to temporarily jumper the controls to do this test? I recall seeing that attaching a resistor across after ignition is one way. If so, what resistor value?

Any other methods? It has a standard Honeywell control with only the red button (no LED's)...about 10-15 years old.

Thanks....

It will run better at 130 PSI and a .75 nozzle

You don't need a resistor. A simple jumper will do just fine. In a pinch, I've been known to use a paper clip. :D

What is the model number of the boiler? I can check Beckett & Slant Fin's websites for any updated nozzle/pump pressure info.