Home>Discussions>INSULATION & HVAC>Venting a Natural Gas Fired Boiler
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JacktheShack
Re: Venting a Natural Gas Fired Boiler

I agree; your neighbor's vents could be anything from a hot water heater vent to who knows what.

It was inaccurate of me to say there is NO vent required on condensing boilers.

The condensing boilers I'm familiar with DO have a 2" or 3" PVC condensate vent that is usually routed thru the roof or the masonry chimney (if nothing else will be used in the chimney), in addition to a 2" pvc drain pipe to the cellar drain.

Otherwise, a separate 2" pvc pipe is routed thru the roof.

Most codes do allow for a 2" or 3" side-vent pvc pipe at least 24" above the snow line, but preferably as high as possible above grade, local codes may vary.

My boiler distributor and other techs I talked to
claim there is no noise or odor associated with the side vents.

That's why I tend to think the neighbor's vents you refer to may be attached to some other type of appliance.

My recommendation is still to vent thru the roof & not the side of the house.

JimDorp
Re: Venting a Natural Gas Fired Boiler

It's not just one neighbor -- these noisy vents are all over the neighborhood. And I highly suspect they're for boilers, since they're obviously venting gas exhaust, and they only run in the winter. I also suspect they're for condensing boilers -- that would explain the low exhaust temperature, as well as the noise, which would come from the fan which is necessary since the exhaust isn't hot enough to flow up and out by itself.

jason baptiste
Re: Venting a Natural Gas Fired Boiler

There are a number of gas boilers which have the Energy Star rating. The Freedom Gas Fired condensing boiler is the ultimate efficiency heat source for any home. This boiler has a 95% AFUE rating, and provides lower heating bills. The Freedom boiler also has a cast aluminum mono block design and a concentric vent to prevent additional heat from escaping the flue gases.

A variety of venting options are what makes the Revolution easy enough to adapt to practically any home plan. The Freedom boiler also has a cast aluminum mono block design and a concentric vent to prevent additional heat from escaping the flue gases.

RJordan
Re: Venting a Natural Gas Fired Boiler

You should use a condensing boiler. It takes air needed for combustion from outside. This is a good thing. If your house is tight, there may not be enough air for combustion inside your house. Also, it is possible to backdraft the boiler by a dryer or kitchen exhaust fan. With a condensing boiler drawing its combustion air from outside, there will be no backdrafting as this is a sealed system. A backdrafting furnace or boiler can bring carbon monoxide into your house.

Jacktheshack misspeaks when he says a 95% appliance burns 95% of the gas. It extracts 95% of the heat produced by the burned gas. All furnaces or boilers, hopefully, burn 100% of the gas. Carbon monoxide is the result of incomplete combustion.

Sten
Re: Venting a Natural Gas Fired Boiler

Jacktheshack is right, if you have a 95% furnace it burns that amount and the remaining 5% goes out the exhaust. Follow the link for more info

http://www.consumersearch.com/furnaces/review

RJordan
Re: Venting a Natural Gas Fired Boiler

Hera is a definition of AFUE: http://highperformancehvac.com/gas-furnace-afue-ratings.html

AFUE is a rating that reflects how efficient a gas furnace converts fuel to energy. A gas furnace with an AFUE of 95 means that approximately 95 percent of the fuel is utilized to provide warmth to your home, while the remaining 10 percent flows up the flue and into the atmosphere. Therefore you are actually using 95% of the fuel you are paying for and the other 5% is being wasted up the flue vent.

AFUE is not about how much fuel that is burned. It is about how much of the energy in the gas that is converted to hot air that is used by the house.

So a 75% efficient furnace only burns 75% of the gas? The CO would be off the charts.

canuk
Re: Venting a Natural Gas Fired Boiler
RJordan wrote:

Hera is a definition of AFUE: http://highperformancehvac.com/gas-furnace-afue-ratings.html

AFUE is a rating that reflects how efficient a gas furnace converts fuel to energy. A gas furnace with an AFUE of 95 means that approximately 95 percent of the fuel is utilized to provide warmth to your home, while the remaining 10 percent flows up the flue and into the atmosphere. Therefore you are actually using 95% of the fuel you are paying for and the other 5% is being wasted up the flue vent.

AFUE is not about how much fuel that is burned. It is about how much of the energy in the gas that is converted to hot air that is used by the house.

So a 75% efficient furnace only burns 75% of the gas? The CO would be off the charts.

95% of the heat from the fuel burned is being extracted for using to heat the home while the remaining 5% is part of the by products of the exhaust which is difficult to seperate from the gasses ---- also there is a certain amount of heat needed to carry away the gasses from the burning.

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