Make up air

Rich Kontny_5

or makeup air, this is a common oversight in residential and even commercial applications. Check your owners manual for the Crown boiler it should have minimum makeup air requirements.You need oxygen for combustion and you do not want to create an oxygen starved interior room or basement etc.

Gravity combustion air used to be 1"/1000 btus fired.The gravity systems are the most foolproof unless they get blocked (either inside or outside)Power fresh air systems need controls such as pressure switches etc. to prove the air is present prior to ignition.

Have seen many gas fired appliances buried in enclosures or closets. This creates not only combustion problems but safety concerns.

It is also common to have too tight of a home where negative pressures can become a problem.


Rich K.

Make Peace our Passion while Supporting our Troops!

Ed Lentz_2

I have a Crown boiler that is heating the house and also my DHW. It has run fine for about two years now. I noticed something today and I am wondering if I need to provide my Crown some extra air. I replaced an old entry door this afternoon. I haven't finished insulating around the new door yet. I noticed that when the boiler is running I get a pretty good draft around the door. This draft subsides when the boiler shuts down. Last fall we had new windows installed. Since we are slowly tightening the house I wonder if we shouldn't run some PVC about ten foot to the outside wall to get it some air. The room it is in is about 10 X 20 with two new windows. Thoughts or suggestions?

Thanks

ttekushan_3

yes. Good idea.

of course, you could get one of these:

http://www.tjernlund.com/Retail/inforcers.htm

Or you can go lower tech and install what you are talking about. It works. Take a 4"min PVC line and drop it in the general vicinity of the boiler. But realize that you are only minimizing the pressure differential with the passive vent. Without a pressure differential, make up air won't flow. But realistically speaking, this is usually good enough to prevent terrible drafts, or carbon monoxide being pulled back through the chimney. However, active devices can maintain a zero pressure differential.

The negative pressure can become an issue when you tighten up the house. Especially while running the clothes dryer in the winter. All the air infiltration from the old windows and doors provided enough leakage to prevent much a negative pressure. When I gasketed all of my steel casement windows, the doors seems to leak more. When I updated the door weatherstripping the fireplaces began to backdraft. So I put in a makeup air duct. Solved the problems. Should have put the make up air duct in first!

As an aside, since I'm stuck with forced air at the moment, I then improved on the design and piped one portion of the makeup air into the return system of the furnace. I can control the amount of fresh air thats sucked into the return air to adjust for equalized or slightly positive barometric pressure in the house. It mimics the active device as long as the blower is on.

-Terry

Ed Lentz_2

Thanks Rich and Terry for the replies. I will look into the manual and go from there. But, if I read between the lines I would not be doing wrong in getting some fresh air to the boiler at any rate.

Thanks

Ed Lentz_2

Thanks for the replies guys. Last night I took a 4" Dryer vent tube and routed it from outside to just beside my boiler. I noticed a draft as soon as the boiler fired up. Not so much that it made me think I should have done this long ago, just a reassurring one. Thanks again for a very informative and helpful board