Where to REALLY Install Barometric Dampers on Multiple Boilers (Avoid These Deadly Mistakes!)

The best explanation I've heard. Awesome Ray Ray! Mad Dog

Mother Nature controls draft in a flue based on pressure difference indoors versus outdoors and by temperature difference of flue gas and outdoor temperature. This is a constant change and then we can throw in wind and rain.

The amount of air that is pulled into the equipment is affected by this change and affects the combustion. This would affect safety and efficiency. The purpose of a barometric is to maintain a fixed flow or draft through the equipment. In the case of residential gas equipment, the draft should be -.02"w.c. Commercial gas equipment will on occasion require up to =.05" w.c.

Prior to the development of gas equipment, all barometrics were single acting for oil, wood and coal. When gas arrived a problem developed because of standing pilots. With wind a downdraft conditions pilots would blow out. In the beginning there were no safety pilots so when the pilot went out gas would continue to flow. Not a good thing. I have searched for some time to determine which came first, the double acting barometric or the drafthood with no luck. But it didn't take long to realize a fixed device (drafthood) cannot control variable conditions whereas a double acting barometric can.

What about safety? Does allowing equipment to continue to operate when the flue is blocked or there are severe downdrafts a smart thing? Lets add some spill switches for safety. If that is the case why do 90+% of drafthood equipment not have spill switches. No those are not spill switches on new equipment,, they are blocked flue switches, spillage still allowed.

The picture in the Field Controls literature with 3 boilers and barometrics mounted in positions A, B & C is a mechanical nightmare. I have tried for 40 years to get rid of the picture. Understand that no one from Field Controls has ever been in the field testing that configuration. In that picture C is the worst location but not because of the location but because of the design. You cannot have smaller flue connection down stream.

I always wondered why oil equipment has single acting barometrics? Don't we want an oil burner to stop if the flue is blocked? I can see with wood or coal a single acting barometric may help snuff the flames with a clogged flue but not oil.

I did do a test with Field Controls and AGA in 1993 to prove how dangerous drafthood equipment operated. Anyone that has been in the NCI Combustion class and still using drafthoods are careless, negligent and unprofessional.