Down-firing my oil burner....

tmw

Hi,



I've spent the last few months working on my vapor system (Arco model K) using Steamhead as a consultant and also using this superb site as a resource.



I've added venting to the system and this allows it to heat up at very low pressures (0-3 oz.on vaporstat.) until the vents close off.  My system should (based on my research)  reach an equilibrium at 3oz, and stay there. Instead, it will climb up to 2lbs if I allow it. I have set the cut off at 14oz w/subtractive differential of 12oz (cut in at 2 oz).



Recovery from a 3-4 degree setback takes about 25 minutes. From time of steam production to main vent closure is about 15 minutes. The vaporstat will cycle off for about a minute and then cycle back on for 2-4 minutes until the t-stat is satisfied.



I've done a lot of insulating in my old house as well as replaced all of the windows (44 in all!) this past summer.



I think (and Steamhead concurs) that downfiring may be an OK thing to do to allow the system to equilibrate at 3oz. 



I've got a "burner man" coming tomorrow to do a combustion analysis and perhaps downfire the burner. The burner guy is a terrific fellow--honest, friendly and very reasonably priced. Unfortunately he knows s--t about steam and vapor systems.



Is there anything I should be asking (or telling) him insofar as my system is concerned?  I don't want the thing overly downfired so it takes forever to make steam. Is there a way to determine a happy medium? 

Unknown

Boiler Models

I think if I were you I'd do a little research on your boiler and burner.  In the boiler manufacturer's product line quite often one size boiler and one model burner will be used to create several model boilers.  For example the same boiler and same model burner will be used on the 125,000 btu model boiler, the 150,000 btu model boiler, and the 175,000 btu model boiler. The only difference between the models being the nozzle and pressure settings on the burner.  As most  I&O manuals cover a series of boilers you can usually use it to determine which models which have the same boiler and burner model as yours.

After determining where your boiler is positioned, you will have an idea of how much scope of adjustment is available and decide on what percentage down fire you which to try.



If you don't have the I&O Manual for your model handy I'd download it from the manufacturer's website and print it out as I'm sure it would be helpful to your burner man.

- Rod

tmw

thanks..

the WM boiler is 45 y.o. and info is hard to find. The Beckett burner is within the past 10 years and should prove easier to research.



If the above info is unobtainable is there any way the combustion analysis can help guide the decision to downfire?

TomM

goto becket website

go to the becket website, and sign up for a username.  once you signup, you can get all the manuals and stuff for your burner. 

.

make sure to read the 'For the Professional' booklet.  its all about burner theory and how to measure and test your burner, etc.  it was probably one of the best things i've read besides Dan's books.

.

TomM

Steamhead

Maybe

you should wait until all the basement rads are working, or allow enough capacity to heat them once they are working.



Or maybe you got them all working now? That would be great!



Your W-M 6-62 is rated 1.85 GPH with an older-style burner. The Beckett you now have burns more efficiently and gets more heat from the fuel, which lets us reduce the firing rate slightly while generating the same amount of heat. But even with the Beckett, I still wouldn't go below 1.35 GPH in that boiler. Make sure the stack temperature is above 375° F or so, to prevent flue gases condensing in the chimney. If the stack temp is too low or the boiler takes too long to make steam, you'll have to have him raise the firing rate.

tmw

How long is "too long"?

Thanks Tom and Steamhead,



Steamhead, I showed you a pic of the one radiator that I repiped. The other two are currently getting good and hot with two varivents that I reinstalled at the bottom of the radiators, near the returns. So their capacity is currently in the equation..



Thanks for this very valuable information re:stack temp and GPH.



How long is "too long to make steam"?  Roughly? 



best,

Todd

Steamhead

In general

on a modern boiler you should be making steam in 10 minutes or so, from a cold start. Your 6-62 might take a bit longer than that, but not that much longer. You want to avoid a situation where the boiler runs for 20-30 minutes or so before making steam. That's wasteful.



Looking forward to the pics of the other rads' vent pipes when they go in. The VariValves are known to spit if water reaches them- watch your pressure while they are still installed, to keep from exceeding the "B" dimension.

tmw

Time to steam from dead cold start is about 14 minutes...

on the  old WM. My pressure cuts off at 13 oz (on at 3oz) which keeps the waterline well below the outlets of the basement radiators.

thanks

tmw

checked my stack temp..

and it is about 510-520 degrees. So I guess when my burner guy comes tomorrow (didn't make it today) we at least have some leeway within that parameter.



Does anyone have suggestions for a good high-low burner that will work well with my 40-45 y.o. WM?  perhaps something that could be reused if and when I buy a new boiler within the next 2-3 years?

Steamhead

Unfortunately

no one is marketing these as a retrofit item- yet. They do exist, but are only available on a few specific boilers and furnasties. I'm waiting...................

tmw

OK, I reduced the nozzle size

from 1.5gph to 1.35 gph.  System heats in about the same time and still cuts off on pressure (set to 13oz) at about 35-36 minutes given a 5 degree setback.Stack temperature remains the same at 510-520.  I had the system off for four hours before this last trial.



Most of my radiators are throttled down quite a bit because the newish valves don't have the orifices needed for this type of system. Could this be a reason for the pressure buildup? 



Should I consider going even lower in nozzle rate?

tmw

anyone? (Steamhead?)

should I try smaller and smaller nozzles as long as the system heats up within a reasonable time frame and stack temp remains high?