proper venting of boiler

tm · October 2005

I am installing an oil fired Biasi hot water boiler. The trim kit does not include a barometric draft (only included with the gas burners). It says in the instructions that for some 2 story and 1 story buildings a baro draft is not required as the Biasi is designed to be pressure fired. How will I know if I need one? Should something else be consided or would I pipe it direct to the chimney with nothing inline? Thanks

Ron Schroeder_3 · October 2005

Viessmann oil boilers come with barometric dampers

The reason for the barometric damper is of course draft control. Without a baro you might indeed have positive pressure on start-up. When the vent warms up however you will probably swing over to a negative draft situation. It is difficult to set up a power burner optimally when the overfire pressures change at each firing.

I would be concerned about a vent that was two stories all that did not have a barometric damper to aid in controlling excessively negative overfire draft. Combustion characteristics can change significantly under these circumstances.

An additional concern is that condensation occurs within a vent at much higher temperatures if the vent is pressurized than when it is not. Condensation must not be allowed to occur in venting and chimneys that are not designed for such operating conditions.

My third concern is that special positive pressure rated venting will have to be used if it is possible that the appliance will operate in that mode. The increased cost of this material will easily offset any savings that might have been realized by not purchasing a barometric damper.

Just my thoughts in the matter.

tm · October 2005

so basically it can't hurt in any way to just use one.??

Maine Ken · October 2005

All of my Biasi installs have barometrics... except for the dv's.

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proper venting of boiler

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