A mystery of hard starts, firing rate and draft

oldhouse11

Hi,

I have a problem--a new oil boiler that sometimes hard starts and kicks puffs of smoke out through the barometric damper. The oil company (which does the service) says there's an issue with the draft and the burner; the boiler installer says it's a venting issue; and the chimney installer says the burner is not properly adjusted. I can't figure out who is right! Or even what questions I should be asking to home in on a solution.

Here's the situation:
-One pipe steam system in an old house.
-New boiler (Burnham Commercial V904A with Carlin 301CRD burner) and new stainless-steel 8" chimney liner installed in 2019. The chimney stack height is 36 feet.

The system ran fine in the beginning, but last winter we had a ton of these hard starts. The oil company would come out, do some things (replace nozzle, change filter and so on) and it would run fine and then a few days or weeks later the hard starts would happen again.

Over the summer, the tech spent a lot of time servicing the boiler and for the first month of so of this winter things were good. Then the hard starts happened again. This time the tech who came out tried lowering the burner firing rate from 350 to 325. He measured the draft at .02 and said that was too low for this kind of burner but that perhaps the lower firing rate would help.

It did--it seemed to run beautifully for about a month, then a few hard starts and quickly the burner locked out because it failed to fire. This time the tech said it wasn't draft, it was a clogged oil line not delivering oil the burner. He flushed the line and changed the filter and, fingers crossed, everything is running nicely again.

But I still don't understand what is going on here.

-Is it OK to run with the lower firing rate?
-Is .02 really insufficient draft? (One suggestion was to replace the Carlin burner with a Riello burner capable of operating with lower draft. Obviously I'd rather not replace a two-year-old burner...)
-Is the clogged oil line maybe the key here? Or a red herring?

I should say that I have no problems with the heat itself--when the system is running the radiators get plenty hot.

Grateful for any wisdom!

EBEBRATT-Ed

Sounds like the clogged oil line was the problem but it took the service company a long time to get their.

Did they do a combustion test after the last work was done? Can you post it so we can have a look?

oldhouse11

Thanks! Should I not worry about the draft/firing rate?
And does it make sense to clean the tank? The tank is old and I have no idea when it was last cleaned. 

Combustion test: I don’t see the little printout from the last one but there are notes on the service record. (Last line is the visit where they lowered the firing rate to 325.)

STEVEusaPA

You should worry about draft. That’s a very big steamer, and I’m sure the job was quite expensive. I’d ask the installer to come back out with the manufacturer of the boiler and the burner and go over the set up.
Got any pictures?

oldhouse11

It was indeed quite expensive! 

Here are some pics, hope I captured everything important. 

STEVEusaPA

You’re getting a lot of odd info from your techs. There’s nothing wrong with the burner, don’t change it. You shouldn’t down fire that burner, you’ll make things worse. Draft is key. Here’s a snippet from the manual about draft.
You have a very 'hack' oil line set up. Too many fittings, iron, copper, a coupling, a firomatic in a weird spot, and a two pipe set up with flex hose on the return. That filter could’ve been mounted to the jacket with flex or hard pipe to the burner, not two pipe.
Your tech could call Carlin Tech support and have them walk the tech thru a proper set up.

retiredguy

You said that the oil nozzle plugs up so I have to ask; Is the oil tank an existing one, has anyone checked the oil tank to make sure that it clean are free of debris, is the customer buying good quality clean oil. Is that gray cylinder a strainer or a filter. On small burners like that I never would install a strainer. They work OK on large burners but not on smaller burners. I would check the tank, check the oil supplier to insure that it is of top quality, and do what the others have said.

oldhouse11

Thanks @retiredguy and @STEVEusaPA for the great info. I will definitely have the tank checked and focus on the draft. I'm a little confused about the draft situation, though: As you pointed out, Steve, the manual notes that this boiler should be operated with *positive* draft (over-fire draft?). The tech was telling me that the draft was ".02" and that that was too low and it should be .04 or .05. Does this mean it is not negative enough or not positive enough?

EBEBRATT-Ed

oldhouse11

As far as the draft goes I think you are fine. That boiler is supposed to run positive in the fire box. That is not controlled by the chimney or the barometric damper it is controlled by the slide damper built into the smoke hood on the boiler.

The somke pipe is not designed for positive pressure and that is fine as it is in a chimney with a barometric damper.

As long as the chimney barometric damper and slide damper allow for the boiler to run positive in the combustion chamber and negative in the flue your ok.


I also noticed while the tech reduced the nozzle size he upped the oil pump pressure so your firing rate may not have changed much.

Why he did that maybe he was trying to improve combustion. I didn't pull the Carlin manual to see what they want

Steamhead

@oldhouse11 , that does look like a positive draft reading- if it were negative it would read -.02.

The manual for this boiler, here:

https://www.burnhamcommercial.com/wp-content/uploads/2019/08/V9A-8142958R23-3-21.pdf

and the brochure, here:

https://www.burnhamcommercial.com/wp-content/uploads/2019/08/v9A-brochure.pdf

specify a positive draft of 0.1 inch of water column, measured at the breech (where smoke pipe connects to boiler). There is a removable plug there for inserting the combustion analyzer probe. They don't show a specific procedure, but on some other models they have you adjust the burner for 12% CO2 and zero smoke with the breech damper open, then close it enough to get that positive draft reading and re-check combustion.

The actual specified firing rate of that burner in that boiler is 4.2 gallons per hour (GPH), using a Hago 3.50x80SS nozzle (rated 3.5 GPH at 100 PSI and having an 80° semi-solid spray pattern) running at 150 PSI. The previous nozzle on the service record was a B (solid spray pattern) instead of an SS, which is wrong. Hard to tell which type they put in most recently. At 150 PSI, a 3.25 GPH nozzle would fire just shy of 4 GPH, so I doubt that's your problem.

After that, the head and electrode settings should be checked to see if they conform to Carlin's specs. The electrode settings can be found in the 301CRD burner manual. Often, if the settings aren't spot-on, the burner will experience these hard starts.

Where are you located?

oldhouse11

Thanks @EBEBRATT-Ed and @Steamhead. Steamhead, I am in Westchester County, NY.

I am going to ask the tech for more clarity on what he meant when he said the draft was too low--perhaps he meant that the draft in the flue was not negative enough to evacuate the combustion gasses? But I'm not sure why that would cause the rough starts.