Blend Air ll

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Old 06-13-17, 06:48 PM
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Blend Air ll

My manufactured house by Fleetwood (no longer in business) has the Blend Air ll system.
Does this system provide adequate attic ventilation?
As the roof shingles need to be replaced, now would be a good time to change or increase ventilation if needed.
What do you think?
 
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Old 06-14-17, 10:57 AM
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I have seen the blend air on Coleman furnaces, I don't think they have anything to do with attic ventilation.
 
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Old 06-14-17, 09:42 PM
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Blend Air ll does ventilate the attic.
 
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Old 06-15-17, 05:12 AM
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I'm familiar with attic ventilation but not the Blend Air so did a search:
Troubleshooting Coleman's Blend Air Systems - Mobile Home Repair

Apparently the Deluxe model also ventilates the attic.

So, my question is what other ventilation openings currently exist, soffit, gable, ridge, or roof vents?

Relying on powered ventilation means it is only contributing when the system is running, unless there is a separate control for the attic venting function and we need to know where that powered vent is pulling in its replacement air.

Bud
 
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Old 06-15-17, 10:24 AM
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Blend Air ll

There are 4 "turtles" one at each lower corner of the roof, and the Blend Air duct located near the peak but at the 1/3 length of the roof.

According to the Blend Air installation and owners pamphlets, the system vents the attic on a 4 hour on, 4 off timer, unless the furnace or A/C is running. Then it continues to run as long as they do.
Also, the information says the system blows fresh air into the attic and out the vents. This is where I don't understand their logic, as it pushes hot air down to the lower vents going against thermal flow.

I would think the engineers at Fleetwood and Coleman know what they are doing, but, I still question this setup.
 

Last edited by deano379; 06-15-17 at 10:41 AM.
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Old 06-15-17, 11:01 AM
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The ventilation you have is all mechanical, 4 hrs on and 4 hrs off isn't bad from a moisture point of view (that's the primary purpose of attic ventilation) but for the secondary reasoning, removing excess heat, those 4 hr cycles may not line up with the temperature objectives.

Pushing down against the thermal flow isn't a real problem as the lift created by a temperature difference is tiny compared to the pressure created by a fan. However, either pressurizing or depressurizing an attic has been shown to be very expensive by either forcing hot attic air into your home or pulling cool air out. There are a lot of unexpected air leaks between house and attic and those should be sealed. Add up all of the little leaks and it comes to about a one foot square hole.

Passive ventilation would require a lot more NFA (Net Free Area) with half locate high and the other half down low.

Your climate location will dictate the ceiling insulation and perhaps any moisture issues.

Bud
Sorry just spotted the UT.
 
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Old 06-16-17, 05:27 PM
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Blend Air ll

I received a reply from the manufacturer of the Blend Air system. I thought it may be of interest to others.

"The blend air 2 has a flex duct that attaches to the top of the furnace to a vent on the roof so when the blower in the furnace runs it can allow fresh air into the home. It has an attic motor as well that works with soffit vents to ventilate the attic.

The blend air systems are an accessory that is mounted to our furnaces as well as having a motor mounted in the attic. The blend air 2 and other motorized damper models and ones that incorporate an attic motor for attic ventilation are obsolete and some of the replacement parts for them are no longer available. The only one used currently only has the duct that attaches to the top of the furnace for fresh air in the home, attic ventilation is handle by other means.

With the blend air 2 and some of its parts being obsolete, I would recommend they look into other means of ventilating their attic."


Thank You
Johnson Controls
Manufactured Housing Dept
 
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Old 06-16-17, 06:30 PM
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Quote "With the blend air 2 and some of its parts being obsolete, I would recommend they look into other means of ventilating their attic."
So, with the new shingles going on are you looking for other means to ventilate the attic?

Apparently that unit also acts as a fresh air intake through the furnace. In homes that are well air sealed (air tight) it is often necessary to provide a source of fresh air. Whether your home needs that is to be determined.

I'm not sure if the fresh air source is also providing combustion air for the furnace. Is anyone familiar with that unit, skaggsje?

Bud
 
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