So Boiler is Oversize, What are my Options?

Neil_5

Have a Burnham Series 2 130KBTU unit (104 net), gas.

Heat loss calculated yield 71KBTU needed, with 95% on the information being accurate and on the conservative side.

Based on my therms/degree days from Oct 04 to Feb 05, and a design day of 10*F. I used the calculation found on the wall here to figure out my boiler size should be 77-79KBTU (that included the 80% eff)

Cycles: ON=3 mins OFF=7 mins

So it looks like I can heat my house down to 10*F with an 80KBTU boiler.

What are my options,if any, to use my boiler as best as I can? I have a separate 50g tank for my DHW.

Neil

don_84

Only two

that I know of.You could replace dhw tank with an indirect and use the indirect as a buffer and then mixdown the dhw
side.

Or you can get outdoor reset control,that will turn the boiler on and off as necessary to maintain a given outlet temp.

Then there are other option like having more kids.

Neil_5

Don

Thanks for your input, the 50g DHW tank is new with the boiler only 6 mths old, so thats out.

Have a Tekmar outdoor reset, so thats in place, so I should be somewhat ok eh?

Well the more kids (actually non so far) will affect only hot water and thats separate already.

Thanks for your feedback,
Neil

Joe Brix

Outdoor reset doesn't help

an oversized boiler. It will probably make the short cycling even worse since the boiler won't try making 180° water all the time. A straight buffer tank will give the system more mass to heat up extending the burner cycles. Those extra BTU's will take longer to be released into the home so you boiler cycles should be less frequent. Efficency increases with fewer/longer cycles and hopefully the life of the boiler increases also.

Neil_5

Buffer Tank

I can see how that will work, essentially making the water volume on the boiler end larger. Could anyone direct me to any links that illustrate this some more?

That would alos have to be an insulated buffer tank eh?

Neil

Ron Schroeder_2

An Outdoor Reset will help IF it has a larger high limit differential to allow longer run times.

Can you change the jets and under fire the boiler?

Ron

lchmb

check

I would check with Burnham and see if the unit can be downfired. Even if only by 5% it would also help....But call them, then have a service tech in to do the work.

Mad Dog

Maybe you should have sized the boiler yourself

who did anyway? Mad Dog

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S Davis

Tekmar

Neil,

What type of tekmar do you have and how many zones? if you have a outdoor reset control that will handle a zone control that might be a good option because tekmar zone controls will do zone coordination to make the boiler run longer cycles.
This might be a cheaper option than repiping your systen for a buffer.

S Davis

Apex Radiant Heating

Neil_5

Tekmar

Model 256, I have 2 zones, the large zone is for the entire house and the small zone is for the basement.

Neil

Neil_5

Boiler

MAD DOG:

Before July last year I was a renter, so had no interest in boiler etc, then I bought my house and did some background, had 5 companies in, went with the guy with good ref, middle price and made me feel comfortable here in LI. After which I found out when they wired the Tekmar 256 it was wired so when the boiler fire, only then would the circulator turn on. I rewire that and all is well. Prior to the bids, I was not aware of heatloss and load etc and most of all of this site. I started to educate myself after the fact becuase I wanted to know more about the system.

The company is a midsize here on the Island, the job was neat, the guys are friendly, but now I see they all lack the skill that should have been incorpoarted into my system. I fugure they are the pros, they would do what they know best and give me options.

Neil

KCA_2

Also


You can cut back on the "Manifold pressure"

That will cut back on the BTU output.

Short of buffers (I liked the suggestion of using the domestic side arm as a buffer. I've done that for years with little or no respect from my peers)

It's the most economical way.. Manifold pressure.

:-) Ken

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Neil_5

Manifold pressure

Throttle back the gas?