I no longer cycle off on pressure!

tmw

Please see my thread:  "Down-firing my boiler".  In essence, I went a few sizes smaller in nozzle--from 1.5gph to 1.35 to 1.20 and my system no longer climbs in pressure and cuts off before the thermostat is satisfied. In fact it seems to stay at  1.8 oz indefinitely until the thermostat is satisfied. Tried it last night after shutting the system down for 6 hours. It satisfied a 5 degree setback in 79 minutes and the stack temperature stayed at about 400 deg.



When I used the two larger sizes, 1.5gph and 1.35gph there seemed to be little if any difference in system function. Pressure would reach my cutoff (13 oz) in about 35 minutes and then short cycle 1 minute off, 3 minutes on until t-stat was satisfied.



So, is it OK to use this small nozzle if everything seems to work well?  It takes about 15 minutes to generate steam (the other two larger nozzles take about 14 minutes and generate higher stack temps of about 510-520 deg) and the radiators then get hot as quickly as before. 



What I really like is the way the pressure holds steady for over an hour at 1.6-1.8oz...



Steamhead had mentioned to not go below 1.35 (he's seen my setup and knows the boiler) so I'm concerned that perhaps this may become problematic...



anyone?

RAF

Lets see

1.20 nozzle burner on for 79 minutes = 1.58 gallons of fuel

1.35 nozzle off for 1 minute on for 3 = 59.25 minutes of run time = 1.35 gallons of fuel for 79 minutes

what do you think

RAF

I wonder

If you had your pressure control set to turn on at .5 and shut off a 2. I wonder how long would your cycle times be.

Steamhead

You should be OK

the stack temp is high enough that it shouldn't condense, and the steaming time is reasonable (though not in MegaSteam territory!). Just out of curiosity, what were the rest of the combustion test results? Did he use a digital analyzer or an old-style wet kit?



RAF, the system in question is an Arco Model K Orifice Vapor system, so higher pressures won't work.

tmw

I gave an innacurate description....

RAF: sorry for the confusion. I really did not do an accurate test (yet) for fuel consumption at a specific setback using the smaller nozzle.  I kept my thermostat at about 80 degrees just to see if I could get the burner to shut down on pressure. I realize that I said  " it satisfied a 5 degree setback in 79 minutes"  actually, I increased the house temp by 7 or 8 degrees before I ended the experiment as the house was getting too hot!



The numbers using the 1.35 (and 1.5gph) nozzle were obtained during the morning recovery from my typical night time setback of 3-4 degrees. Now I need to see how long it takes the small nozzle to do the same thing.



Steamhead:  the numbers were obtained with a digital analyzer when I still had the original 1.5 gph nozzle installed.  temp=514 ,  efficiency=83.6,  CO2=12.3.



Do I need to repeat them with the new nozzle?



p.s. check your pm, I sent you a few pics, best regards, Todd

tmw

Hey Steamhead

Steamhead:  the

numbers were obtained with a digital analyzer when I still had the

original 1.5 gph nozzle installed.  temp=514 ,  efficiency=83.6, 

CO2=12.3.







Do I need to repeat them with the new nozzle?







p.s. check your pm, I sent you a few pics,

 best regards,

Todd

Steamhead

Yes, you do

Every time you change something, you must test it. In this case, the air/fuel mixture is probably a bit lean. Verify this and adjust as needed. 

tmw

A/F adjustment, I'd like to read about burners....

Can anyone suggest a source to read about a/f adjustments, measurements, and how to use and interpret a digital combustion analyzer?  

RAF

To much of a good thing

At what point is low pressure reduced nozzle size and high co2 numbers to much of a good thing ?  

It seems to me that matching a nozzle size to run your boiler at a steady pressure isn't the way to go yes it worked for him yesterday but by me it was 40 degrees outside what about tomorrow when it is 10degrees. Is his boiler going to run all day long to match his heat loss?

O2 and co2 are great as long as smoke is 0 has he checked smoke ?

Maybe things have changed but as I recall set back shouldn't be more than 10 degrees and you shouldn't under fire more than 10% on most boilers . Is 1.50 his recommended input or is he already under fired.

At what point is short cycle a matter of pressure or vapor control verses a matter of boiler sizing there has to be a trade off at some point I would think.

Just interested in your opinions.

tmw

Great questions..

I would love to hear Steamhead's responses. Obviously I'll check my burner's run times when the temp drops again. This 45 y.o boiler was installed in a 250+ y.o. house which has recently been insulated and had 44 new windows installed. The ceilings are between 6' and 6'8" high. We have much less thermal loss than we used to. So I'm thinking that perhaps the boiler is now very oversized?



We typically use setbacks of 3-4 degrees. Recovery time this am was about 55 minutes with the burner firing continuously at about 1oz. of pressure. Typically, with the larger 1.5gph nozzle we recover from setback in about 60 minutes. 35 minutes continuous and then 1 minute off, 3 minutes on for the next 25 minutes. Pressure cuts off at 13oz w/larger nozzle.



So: 53 minutes @1.5gph= 1.325gph

       55 minutes @1.2gph=1.1 gph



I'm wondering if perhaps I've overdone things a bit. I'll try a 1.25 nozzle later this week.



This system was designed to run at 3oz.



thanks,

Todd

Unknown

Boiler Efficency

Hi - Just a couple of thoughts. It seems to me that unless a change is obviously in the wrong direction, I would consider trying it out for a while. If you change things too frequently you don't really get a good picture of what is actually happening. The other thing that came to mind is that you may want to get a Hobbs meter so you can accurately log your burner's running time and then you can compare it with your fuel bills. I believe jpf is using one so you might want to ask him about it.

- Rod

tmw

great..

thanks

RAF

55 Minutes

55 Minutes of constant run time does not seem reasonable to me to raise your home 3-4 degrees.

You say Steamhead has seen your system My guess is you and he figured your EDR out what's it looking like as far as boiler size goes.

Great that you have new windows and insulation but you still have to be able to fill your radiators with steam.

I am having a hard time rapping my arms around the fact that in 1900 an Engineer designed your system to run at 3OZ of pressure. How did you arrive at that number.

What I am wondering  here is, is your short cycle caused by a boiler who's EDR is way to tall or is it being caused by your control settings or is your system actually condensing a full head of steam in one minute and having to run three to make up that steam. How does it run on a normal call for heat.

I am not trying to step on toes. I work in the fuel oil business and if I can learn somthing that can save my customers some money I will use it as this will help me keep accounts.

jpf321

hour meter .. not hobbs

here's the hour meter I have installed ..

http://picasaweb.google.com/jpf321/Fitzgibbons400Boiler?authkey=Gv1sRgCNOPnfifvI7MNA#5415686969374511410



i'm quite happy with it .. and it was under $20

tmw

RAF..I am a complete novice who...

didn't even know that I had  a steam system until last  fall.  That's when I came to this board  and started reading Dan's books. Steamhead came by for an hour a few weeks ago and gave me lots of very useful advice on where to add main vents, repipe cold radiators to make them hot, etc. He still needs to do a bit of repiping and "big" stuff that I don't dare touch. In any event, I certainly have no problems with skepticism or criticism. I'm learning a lot from all of this and am delighted that you're taking the time to talk with me.



My Arco Model K vapor orifice system (LAOSH p. 268) was probably installed in the early 30's and from what I've gleaned on this board, was designed to run at about 3oz.



My thermostat (old round mercury) sits in an awkward area in a hallway. It is never quite accurate but usually we feel the house become more "comfortable" after 35-45 minutes of turning up the t-stat in the am. I need to get a more accurate setup before I start throwing numbers around again.



I think my short cycling is caused by a number of factors. Quite possibly all that you mention.



BUT: When I started working on this system it ran between 4-5 lbs. and short cycled constantly. We were either hot or cold, never comfortable.  The radiators in the basement (old house-bank barn foundation-kitchen and rec room in basement) were incorrectly piped and stayed cold unless a vent (which you DO NOT do on a 2 pipe steam system) was stuck on a radiator. Then it would get warm and spit water.  Now those radiators work beautifully!  My wife and I have never been more comfortable in this old farm house. And my fuel consumption has decreased by 15% since I began my tinkering.





Please forgive this rambling. This system still has plenty of problems. Steamhead has plenty of work ahead of him. And I have many many things to learn about heating.

But it has all been a blast, and I look forward to hearing from you. Perhaps Steamhead will chime in and lend insight.



best,

Todd

Unknown

Hobbs Meter = Hour Meter

Thanks jpf!  I can see where that might be confusing. My age is showing. LOL -I also call all facial tissue - "Kleenex" ! 

- Rod

tmw

All of my information has been incorrect....

I installed an inline fuel pressure monitor last night and discovered that  my oil pressure was at 75 psi !!  I am somewhat perturbed that my "burner guy" didn't discover that last week before he ran the combustion analysis. Which, I realize, is now completely invalid.



So: last night I adjusted the fuel pressure to 100 psi. The nozzle is 1.25 80deg. solid core.

I set the t-stat to 66 (4 deg. setback) before going to bed



This am I awoke and radiators were warm, mains hot but not burning, boiler off.

I set the t-stat to 70 deg. and was at 2oz of pressure at 9 mins. I held at 2 oz for 18 minutes then pressure started to climb.  7oz at 21 mins. 11 oz at 26 mins. cut out 13 oz at 28 mins. I cut back in at 4 oz, 1 minute later, and burner stayed on for another 5 minutes before it satisfied the t-stat. 



So, this time house temp increased by 4 deg. in less than 35 minutes. All well and good, but my question is:  Is it OK for a vapor system to climb like this and cycle off on pressure? Or would it have been better to stay beneath the pressure cut off point only cutting off when it satisfied the t-stat?