New Burnham gas steam boiler cycling

nicholas bonham-carter

yes you need a vaporstat to keep your pressure below 16 ounces.
the boiler may still cycle as it keeps the pressure between 4 oz. and 12, but your comfort level will go up and your fuel bill will go down.
on my 60 radiator system by 3 oz. the vents are closed and the returns starting to get hot.overpressure can also lead to other steam system maladies such as uneven heat, water-hammer, and condensate grooving; and you wouldn't want that, would you?
as to whether your boiler is incorrectly sized you will have to count up the total capacity of your radiators and compare that with the rating on your boiler specs.dan's book"the lost art of steam heating", available here, will give you more info on that.--nbc

[Deleted User]

I own a 2 family house with basement. Replaced old gas steam boiler with Burnham Independence KIN8S (245000 BTU INPUT) 644SQ. FT Steam. The boiler is cycling approximately every 30 sec0nds ON/OFF from pressuretrol settings.My pressuretrol(L404F)Main setting position indicator set @ below 2.0PSI @ Diff. position set below 0.5PSI. Verified CUT OUT & CUT IN pressure using pressure gauge on boiler (0-5PSI range). Cut out pressure measured 2.4PSI & Cut In pressure measured 1.5PSI. This calculated a subtractive differential of 0.9PSI. My question: Is my boiler OVERSIZED for my house causing cycling? Does Burnham sell conversion Kits to reduce boiler output? Is my pressuretrol working correctly? I cannot adjust the CUT OUT pressure less than 2.4PSI. Is the pressuretrol the correct model for my boiler? Any help is greatly appreciated Thanks Mike

David Nadle

But...

A vaporstat isn't going to stop the short cycling. From a cold start how long does it take to build up the 2.4 psi?

[Deleted User]

From a cold start it takes approximately 12 minutes to reach 2.4 PSI and then cycles ON&OFF every 30 seconds on the pressuretrol settings until it reaches the thermostat temperature of 70 Degrees.

JohnNY

Sounds like your boiler is oversized and/or undervented.

How did you determine the size?

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[Deleted User]

The plumber that did the job took the the btu numbers from the old boiler. I guess the old boiler was much inefficient as compared to my new one.

Charlie from wmass

mike please search threads on sizing boilers. Otherwise we will simply be repeating ourselves. The boiler maybe able to be underfired.

Unknown

Mike-
If you haven't done it yet I would strongly suggest you get Dan's Books on steam heating (See "A Steamy Deal" at the bottom of this page) They are a "must" for any steam system owner. Easy reading and packed full of information on things like sizing your boiler. As was mentioned above, use the "Search" function and read up on past sizing posts.
You might also look under the term "EDR"

The following links might be of interest to you

http://www.heatinghelp.com/newsletter.cfm?Id=162

http://www.heatinghelp.com/newsletter.cfm?Id=130

http://www.heatinghelp.com/newsletter.cfm?Id=14

http://www.heatinghelp.com/steam_burnershortcycles.cfm

pat renz

Is the boiler surging. Was it skimmed

[Deleted User]

Rod,
thanks for the info. I will read from the indicated link.

[Deleted User]

The boiler does not appear to surge. Water in sight glass appears to be very stable when steam is produced.

Unknown

Mike-
The links I gave you were for your general steam knowledge.
Sizing a new boiler on the old boiler's spec plate is a "no-no" from everything I've read as the parameters were different then. (The phrase "the blind leading the blind" come to mind) It is very probable that your boiler is oversized.

I think what I'd do is first make sure all components (main vents, radiator vents etc.) are working properly. As has already been mentioned, you need to get your pressure down for more efficiency. If all components are doing their job, the system should be heating rapidly and evenly especially with an oversized boiler.

I know zip about gas burners so don't know if they can be down fired or modulated. You might want to contact Burnham and see what they recommend. Another possibility might be to use a delay on the thermostat. Check this link. It was question posted today

http://forums.invision.net/Thread.cfm?CFApp=2&Thread_ID=60678&mc=9

I'm rather new to steam so maybe one of the pros can better help you.