Direct Vent vs. Powered Vent

bruce pirger

There was a thread about power venters...and not many good things were said about them. But direct vent units were called different beasts.

I am looking at a direct vent for my new installation. Is there no powered blower in these units? How is the pre and post purge then performed?

I know there is direct venting of exhaust gases and also direct taking of outside air for combustion. Is there no active blower?

John Mills_3

the way I look at it

Take a look at W-M's line.

http://www.weil-mclain.com/netdocs/rgframes.htm

The CGi would be called a power vent even though that really isn't the correct term. Induced draft is the proper term. These use a draft inducer to pull just the right amount of combustion air into the sections. The flue is a negative pressure flue and requires a draft from the chimney or b-vent. I see little point to them. They add maybe 1 or 2 points to the AFUE but are more money, more to go wrong, noisier, require a chimney liner if vented into a masonry chimney. They can be sidewall vented with stainless steel but usually aren't.

The CGs would be considered direct vent. The industry uses the direct vent term to mean "sealed combustion" where combustion air is piped in from outside. Forced air furnace makers use the same term. The boiler can be vented using a flue like the CGa or CGi or can be vented out the side wall with stainless steel. It also uses an intake pipe (usually PVC) for bringing in fresh air to burn so it uses no house air. When you get above the 80s in AFUE, you get flue gases so cool they can use PVC for venting.

This gets confusing with different terms being used. Others may disagree with my use of the terms

Bob Bona_4

the

answer is that with oil units, a DV appliance uses the burner's fan to build enough pressure to exhaust fumes. On gas DV, inducer fans do the job.

What makes a DV unit different is that the vent issue is covered by the appliances internal components. A power vented set-up uses an external device added on to blow/suck the fumes outside.

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Steve Eayrs

power vent, etc.??

Another way to look at it.....The flue gasses are either pushed or pulled. Yes, there is always a blower involved on any the units.
The power venters are usually mounted somewher close to the termnation of the flue, or mounted outside on some.
The ones with out power venters are more/less pushing the flue gasses out. Most oil burning units (of this type) will shut off the oil supply, but keep the burner blower going for an adjustable post-purge time.
To operate corectly and safely, you need to buy the boiler package, per the application you desire to have. DON"T try to convert any old thing to do what you want. Without the right components you can damage something, or even wake up dead.
Steve

bruce pirger

Thanks guys. Got it.

Yes, that waking up dead this is kinda hard...feels like I have done that a few times in the past! LOL

Unknown

Power Venting

The power vented gas system is different from direct vent even though both may have blowers on them. Many gas systems use a combustion air blower to bring in air for combustion. The Power vented units create a positive pressure on the outlet side of the power venter which means they have to have sealed connections after the power venter.

The power vented or also called mechanical venting also requires different exiting distances when exiting the building. The direct vent units can have lesser distances to openings into the building.

It has been my experience when properly installed and manufacturers directions are followed that both direct vent and power vented equipment as it relates to gas systems (my speciality) work very well. There are unique situations that arise, it has been my experince with those that special things can be done to overcome the problems.