A direct vent gas boiler is a unit that includes a closed horizontal piping system that goes through a side wall right to the outside for exhaust and intake air. This is essential in creating an air-tight combustion system. Today there many boilers of this type available on the modern market. The question is whether they’re worth your attention. Let’s see.
What’s the difference? Direct venting uses a special pipe that is at the back of the fireplace. It normally exits the side of one’s home. This is a very short horizontal pipe, which sucks the air and lets the smoke escape. The air from the house, however, is not pulled into the fire. Such units have covers to seal them. The heat radiates through the glass and can be pushed into the room with a fan at the unit’s bottom.
Plumbers install a direct vent gas boiler in case an air-tight construction of one’s home makes it pretty difficult for a heater to draw sufficient combustion air from the inside. The horizontal design helps to avoid multiple problems with blocking. In this case the installation of a chimney or a vertical exhaust vent is impossible. These units manage to utilize the outdoor air for combustion and keep the warm air that is inside the house, where it should be.
If you choose conventional venting, it’ll use a vertical chimney, allowing the smoke leave and provide the required amount of oxygen to the fire. The system like this allows connecting several different fuel-burning appliances to one chimney, but you’re not allowed to mix the fuel type. So, wood-burning fireplaces and gas units can’t use the same chimney.
For how long have you been using your old boiler? Even if it runs pretty fine, there are still drawbacks worth your attention. Normally it has a metal flue connected to a chimney. The unit itself relies on a natural/atmospheric combustion. If you have a direct vent gas boiler, you use the appliance that is specially designed to extract a lot more heat from the same fuel quantity.
So much heat is extracted that the gases are cool and can vent outside through the pipe. It means there’s no need to use chimney. The boilers are characterized by pretty high AFUE ratings – 85%-90%, thus they offer a much better performance a user can expect from an old venting unit. The AFUE rating is higher, because the units take more heat before exhausting the gases, thus the latter ones are cooler. The fuel gases should be exhausted to the outside, as well as in case with a clothes dryer.
The majority of direct vent gas boilers both vent right to the outside through a plastic pipe and get the combustion air from the outside. This is the type that is commonly referred to as a ‘sealed combustion’ unit that is mainly recommended in those places, which have been upgraded to be much more airtight. In fact, these are the boiler units that are recommended for homes that have more than four families or four stories.