choosing a small vs. large volume boiler

coldupstairs

I'm selecting an oil-fired boiler for a hydro-air coil to backup a heatpump, as well as indirect HW, and possibly another hydro-air coil in the future. Heatloss of main hydro-air zone is about 70K btu at design temp. I plan to turn off the heatpump in the winter. Indirect will be sized between 40-60 gallons...I'm trading off maximum recovery rate for more of a dump capacity because of the way we use water. My contractor favors Burnham or WeilMcclain boilers.

My question is: would a boiler like a Burnham V8 series (probably 83 or 84) be a reasonable choice for this type of application, or would I be better off choosing a boiler from one of these lines with a smaller water volume for this type of cold start application. Would it be wasteful to have the larger volume boiler in the non-heating seasons.

Thanks!

Bill Nye

Lee

Burnham has nice low volume boiler, the LE. You can even direct vent it, assuming you have no chimney.

Try this link http://www.burnham.com/residential/51210.cfma

BOB_23

burnham le (chimney vent)or ledv (direct sidewall vent model) would be a great boiler for this job along with a burnham alliance indirect water heater. the burnham v8 oil boiler is a great boiler if you want a cast iron boiler.

Unknown

Hi Bill

It's nice to see you back on "The Wall" so soon after your surgery. I hope you are not over-doing it though. Best to get some rest and get strong again so we'll get to see you in Baltimore! I hope you are still coming.

Glenn

coldupstairs

Thanks for the replies so far. I looked at the LE literature. Sounds like a good product. Are there any rules for deciding when to choose a cast iron boiler like the V series vs a small volume steel boiler like the LE. I assume that during the heating season the cast iron boiler with a larger volume of water would retain alot of heat between firings and might not have to cycle on and off so much (a good thing), whereas during the summer it would have to fire longer to warm up all the mass/volume when the indirect calls for heat, and then a good bit of heat ($) would be lost as the boiler cooled down slowly before the next call from the indirect, possibly hours later.

Am I thinking about this correctly? I live in central PA, and realistically I would run the boiler for heat between november and march. The other 7 months it would only cycle on for hot water.

Mark Hunt

HEY BILL!


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Welcome back!

Mark H

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Joe_13

Since condensation will occur

in a cold start app on startup, I would vote for a small volume steel boiler. If you had a longer heating season, I would have gone with CI. No matter how well insulated a boiler is, there's still the flue pipe for the heat to escape. Get a good set of Tekmar controls to post-purge the heat out of the boiler after firing.

Earthfire

Bob Eck

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coldupstairs

Thanks.

I just sent for the LE literature.

Anybody know, with little lighter weight steel boilers like the LE around (from such a reputable company), why would one still choose a cast iron boiler(assuming that the correct size steel boiler exists). The installation much be easier with a smaller, lighter unit. Is the lifespan different? Is there some obvious advantage of cast iron or a larger volume that I don't know?

Many Thanks

And sorry for asking what must seem like such basic questions on a site where the experts clearly outnumber the newbies like me.

Joe_13

High efficency

comes from longer burner cycles with less time between burns. So cast iron takes longer too heat up and longer too cool down. Great if you have a long winter season and use the heat a great deal. Now with an indirect, you want hot water NOW, so letting the CI cool too much will make hot water recovery take longer, so you have to maintain a min temp in the boiler. In the winter you're doing this anyway, but in the summer and like you where the boiler is the backup heat system, the boiler's spending more time in stand-by mode then making heat. I've seen many old style dry base steel residential boilers leak at the tankless coil flange in less then 10 years. Probably a steel boiler expands and contracts more, but the new low mass steel boilers don't even offer a tankless coil option. Low temp/high mass radiant systems usualy don't do well with non-modulating non-condensing low mass boilers because then they'll realy short cycle. The 3 pass CI boilers like Buderus, Crown Freeport and Biasi have horizontal flue pipes and heavy insulation to retain the heat in the boiler so cold start almost means warm start. I like the Laars MAX steel boiler. It's small volume means getting a reverse indirect like an ErgoMax, TurboMax, or Dunkirk Artesian tank that acts as a buffer by holding 20-30 gals of boiler water to create mass. I'd still rather have the heated mass sit in an insulated tank then be in a boiler with a flue pipe.