Commercial Boiler Stack with Economizer - This is not a normal commercial boiler stack in this boiler room. It has a bypass stack for a commercial hot water economizer. All boilers have make-up water to make up for water lost in the systems especially for domestic hot water use.
Commercial Boiler Stack with Economizer | HVAC Heating
This hot water boiler system also served the domestic water needs for the local community where these boilers provided heat. Notice the dampers on the stacks (both the vertical and the horizontal stacks). These are controlled by a direct digital controller, located in the boiler room, and cause the hot gas to be diverted to a commercial hot water economizer instead of outside. Inside the boiler economizer were coils where the cold water supply water from the city was routed. This cold water supply was for domestic hot water use.
Domestic hot water use is hot water for showers or the sinks for washing dishes or your hands. The water supplied from the city was typically fifty degrees Fahrenheit. After running through this cold supply water from the city through the boiler economizer the water was almost ninety degrees Fahrenheit. This system saved the organization money by using the heat from the gas stack gasses. Instead of dumping it outside where it would be dissipated into the outside air it was routed through the commercial hot water economizer where it pre-heated the cold water supply for domestic hot water use. The commercial hot water economizer will help pay for itself and many other things by making the boiler room more efficient.
Commercial Boiler Stack with Economizer | HVAC Heating - Caution
It is not advisable to try this at home. When you cool the combustion gasses it causes the moisture in the gasses to condense. This condensation is highly caustic and will cause severe problems with your boiler or furnace venting system. This could be very dangerous and can also cause carbon monoxide issues. This system was engineered using special materials and controls to prevent the problems described here. Many new hot water boilers are condensing boilers and utilize most of the heat created by the boiler. If you want a system like this upgrade to a condensing boiler.
Commercial Boiler Stack with Economizer