Boiler Stack Pressure Compensation

[MNMaint]

Hello,

I have three natural gas, commercial condensing boilers with forced draft burners. The stack terminates aproximately 30 feet above the boilers. They are experienceing too much draft and are cutting out on flame failure. Currently, there is no barometric damper in the breaching to the flue.

An engineer reccomended against a barometric damper and called, rather, for volume dampers in each of the boiler exhaust connections. In fact, he said the barometric damper would void the manufacturer's warranty.

I've never encountered this before. Any opinions / comments?

Thanks

 

[chicopee]

What does the installation or operators manuals of those burners say?

 

[fjm3188]

Boiler manufacturers have the last say in barometric dampers. It depends on their UL approval. Using condensing boilers though, you are probably running a positive stack with AL29-4C venting (BH series).

In most cases barometric dampers are not allowed due to the positive draft however (cat IV), modifying the stack could increase the pressure in the stack to desirable levels.

A stack draft controller, although expensive is the best option for correct operation. It's ability to constantly adjust for pressure allows the burner to fire against it's correct design pressure therby prolonging it's life and reducing maintenance costs.