FPX Model 44 Elite - Positive Pressure

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woolleyr

New Member
Dec 8, 2005
13
I have tried and tried but I cannot get positive pressure through out the whole house. Its in a 2700 sq ft house with a really open floor plan and 9-12 foot ceilings, with about 1/3 of the space on the second floor. The great room is 20x20 in size and 26 feet tall at its highest. Its a new house and pretty tight as I have to be careful when the furnace runs or I get back drafting when I first light the unit up because there is a big cold air return vent on the first floor. (once the doors are closed no problem). The house is also zoned forced air and the air is not balanced very well hence the negative pressure problems when it runs. I try not to use the furnace when burning wood anyway as that is the point of burning wood. (ps we have a CO detector at each bedroom).

Anyway my real point is when the furnace is not running but the fireplace is and is blowing air from outside the home aound the fire box and into the house I can still not get positive pressure. I definately get a convective current to set up inthe great room as the celing fan will spin on its own as the hot air rises...we also get to experience the cool air coming from the floor vents of the HVAC system which I suspect is coming from warm air going in the upstairs vents.

Been back and forth with the HVAC man and he claims have 380cfm of air leakage is common in a house this size...Me and my calking gun are best friends but alas no success. I want to get a blower door test done to check the actual leakage but no one in this part of the country does anything like that...I have looked.

I have been thinking about adding more capacity to the incoming circulating air by adding another duct and fan and then connecting that to the existing line past the original fan but before it enters the fire box jacket..any suggestions?
 

annette

Member
Nov 19, 2005
166
the Indiana Riviera
...
I'm confused by some of what you wrote, because air leaking into your home will help you have positive pressure. Yet it sounds like you are trying to eradicate these leaks? Your stove needs that air--that's why it's sucking it in! Some people crack a window or add an outside air feed so they can operate their stoves with a good draft and no smoking. Does your stove smoke constantly? What do you consider "positive pressure?"
 

Chas.

New Member
Dec 2, 2005
10
Your furnace should not cause any smoke spillage into room as the ducts for the firebox should be outside of the envelope using outside air for combustion. Outside air into firebox, and up chimney with smoke. Closed system.
My limited knowledge of positive pressure is that it works like this;
It is using outside air for combustion and is a sealed unit from the house (living space) air. Just a wood heater in a room when doors are closed.
It is taking outside air from a separate duct, heating it and blowing it into the envelope that is the living space. Kind of like blowing up a bicycle tire. The idea is that it is adding air to the living space and pushing warm air through any leaks instead of pulling cold air into living space through leaks for combustion. So, if you open a window, that room should get warmer.
An old inefficient fireplace is the opposite. It draws interior air into the firebox for combustion, and it goes up the chimney with the smoke. The additional air needed to replace interior air is drawn into envelope through leaks.

I would almost bet that at the peak of your great room it is about 85*+. You need a ceiling fan to get the heat down, or a cold air return at top. Many here will say that is a no-no, but with well placed CO and smoke detectors you will have no problems as you have a sealed unit that isn't using interior air for combustion. I'm assuming it was installed as per manufacturer instructions.
I have a 44 elite and my heat has come on twice so far this season. It was only the upstairs and it was due to oversleeping! :) Most of my home is within 4-5* (68-73*). One exception is my office as it is at the base of the two story foyer. I just hit the house fan (moving around interior air, not adding or subtracting) and bring it on board.
Hope this helped, my two index fingers are tired. :red:
 

woolleyr

New Member
Dec 8, 2005
13
The unit was "professionally" installed and it seems to operate well.

The back drafting only occurrs when I come home from work and the house is cold and the furnace kisck on at the same time I begin to light a fire. If the fire is hot there is plenty of draft to overcome the furnace coming on...

As far as the furnace goes I am very confused about it as well when it kicks on I definately get a strong negative pressure set up on the first floor, I am going to have more battles with the HVAC guy I suspect, somthing just isn't set up right...has something to do with zoning forced air and excess air and so forth...

The unit pulls all combustion air from outside and all chimney air and all circulating air also come from outdoors so the burn chamber is isolated from the interior so we shouldn't have any CO problems.

With the posi pressure system I should be able to open a window anywhere on the first floor of the house and heat will blow into that room from the great room nd then out the window...much the same way Toasty mentioned its like blowing up the house like a balloon.

Just cannot get the house to blow up ie pressurize...too much air leakage for the circulating fan to overcome hence the idea of adding more input air.

Anyway that was my idea but I am worried that I may cool the exit gasses too much and cause a creosote problem inthe chimney...
 
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