Peter Seddon - Jul 17, 2014

Understanding the Swirl Plate in your Boiler or Water Heater

                Swirl Plates are a staple in the design of high efficiency boilers and water heaters. They are present in most, but not all, gas burning units.  The majority of our units use the Swirl Plate. It is found in most cases attached to the outlet plate of the gas valve and sandwiched in between the gas valve and the blower (inducer) housing. Swirl plates provide a vortexed air flow supply to the gas coming out of the gas valve outlet. The swirl plate adds turbulence, mixing the gas and air to provide a blended mix to the blower.


                Swirl plates are plastic, are different colors, are round like a “plate” and have fins and orifice openings of different sizes. The swirl plate is open to the atmosphere at the gas valve outlet as our valves are negative pressure valves that only emit gas with the presence of blower “vacuum” drawing on the valve. The blower at the same time draws air into the swirl plate openings which are on the circumference of the plate. The air/gas mixture is then “swirled” around together and drawn into the opening in the plate and on to the blower.


                Swirl plate problems occur for several reasons, but mostly swirl plate failure is the result of exhaust gas recirculation. The corrosive nature of the exhaust gases which can be drawn into the intake air piping and sent to the swirl plate as clean intake air, when it is not, can begin to erode the swirl plate eventually rendering it cracked, broken, disintegrated and even in very rare cases almost completely gone!


                It is important that the swirl plate be inspected at least annually, along with other routine inspection of the boiler or water heater combustion apparatus. If you see that the swirl plate has discolored it is wise to remove it and check its condition. There are several of our boilers and water heaters that have the swirl plate contained inside a housing or “cowling” cover that is a round black plastic cover which comes apart in two pieces. Inside the cowling is the swirl plate.


                To ensure that your boiler or water heater is maintained properly and gives you years of trouble free service, we suggest that the swirl plate be part of your annual inspection.


Above is a new Munchkin 140M swirl plate in pristine condition.


Above is the same swirl plate, in poor condition.

Written by Peter Seddon