short cycling or normal

Motivated Amateur

I had the very same problem 2 years ago when I had my original 1930 boiler replaced with a new Dunkirk (one pipe steam). Not knowing much about steam back then, i didn't understand what the incompetent installer did - he piped the boiler without making an equalizer pipe. This caused all the liquid water drops to go right up the headers, causing fast condensation, which meant pressure increases instantly. After fighting with Sears [NEVER USE THEM], they sent a knowledgeable contractor over to repipe the entire boiler, adding an equalizer and increasing the size of the header. Check the piping on your boiler- or post pics on the wall for us.

ljh_2

Is this short cycling or normal?

New boiler this year, programmable t-stat and house was air sealed and insulated, but the fuel consumption (therms used not $$$)has not gone down.
The boiler comes on at 5:30 am/62 degrees (outside temp is 20 degrees), burner is on for about 15 minutes then shuts off (pressure cuts out at 2psi). All the rads are hot, t-stat reads 63 degrees. Pressure drops to .5 psi in about 1 minute and then for the next hour it's on for 3-4 minutes (till pressure is up to 2psi) and off for 1 minute (till pressure drops to .5psi). At this rate the temp rises about 1 degree every 10 minutes till it gets to 70.
This constant on/off seems inefficent to me? Is this the way it's supposed to work? Shouldn't the boiler wait a bit for the heat that's in the rads to radiate out a bit before trying to put more steam in? The air vents all seem to be working. I had two replaced when the new boiler was put in....perhaps I should have all new ones put in? They are adjustable and all are in the full open position (I believe).
Thanks for any input

gerry gill

its hard to say..many variables..

how big is the boiler? stage fired? how well are the vents? try this tho- go a month without thermostat setback and see if it makes a difference on mcf of gas used..as it sounds like your complaint time is when coming out of setback...

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bob W._3

My old boiler used to do that. It was oversized and undervented. Post some detail, like the size of your boiler vs. the amount of installed radiation (in sq. ft. EDR), and the length and diameter of your mains and the type and size of your main vents. One of the steam guys here will probably have some further suggestions for you.

wfc

short cycling of older boiler

I have an old coal fired boiler (circa 1910) coverted to oil (circa 1937) and maintained with replacement components and burners as required since. Current problem for last 1 1/2 to 2 heating seasons is what I believe to be short cycling i.e. boiler runs approx. 15 minutes then shuts down for a few minutes then back on for a few minutes for 45 to 90 minutes depending on outdoor temperature or heating load. From my observations the pressurtrol (pressure switch)is shutting down the boiler then letting it refire when the pressure drops. This started after I had to have some late night service work when the burner would not run at all. I watched the service man, as is my standard practice, and I believe he inadvertently changed the nozzle from 0.8 to 1.3 and that the burner is firing hotter and/or faster than it should generating steam faster than it can move through the one pipe system - return through supply pipes - thus building pressure in the boiler to the point it shuts down.

The oil dealer naturally claims that such short cycling is normal and that his service man could have never installed the incorrect burner nozzle.

If some one has experienced the same or a similar problem please confirm or refute my theory. I was unable to find the answer in Dan's book "We Got Steam Heat". The service man is due on Monday 1/16/06 for a belated annual cleaning and service visit.