Gas and Oil Home Heating Furnaces - Circulation question

We recently bought a house that has an older original house and a rear add on roughly equal in square footage to the front original house. The central air sits on top of the front. The problem we have is the front is freezing but even with all front vents closed we get very little cool air in the rear. I am pretty sure the central air unit has the capacity/power, etc.

My question is, is there such a thing as a booster fan or other device that would force more air to the rear? Also, since we spend most of our time in the rear, is there any method for diverting all the air, or a majority of it, to the rear, other than closing vents?

Thanks in advance for your thoughts and ideas.

jklegseth:

If closing the vents to the front of the house does not increase flow to the rear then increasing the duct sizes to the rear may be needed.
Are return air grills located in the rear and are they unobstructed?

Booster fans will not significantly increase the airflow.

Hey Greg,

Thanks for responding!

"Are return air grills located in the rear and are they unobstructed?"

Okay, you hit the limit of my knowledge here. I believe the return vent is the intake vent?...if that's the case, it is located in the front part of the house, almost directly under the unit. In the rear we have three AC vents for three rooms and that's it.

Yes, return grills and intake vents are the same thing.

It is verry difficult to offer suggestions when one cannot see the layout of your home.
I think the best thing you can do is get qualified contractors to size up the situation and give you a quote on what it would take to fix the problem.

Thanks Greg. I do plan to have the system inspected. I was trying to get as much info as I can because, frankly, I don't have blind trust in contractors. The more I know the more I can hope to avoid rip-offs. I know that's cynical but more and more that's the way contractors operate. I have busted auto mechanics, electricians, plumbers, and other contractors because I have enough knowledge in many of those areas to be on guard. If you have any recommendations about organizations that certify, etc. I'd appreciate it. And thanks again for your assistance.

Hello: jklegseth

If the roof top unit has the capacity to cool the front house as well as you claim, then it can be reasonably assumed it was added to handle both houses square footage.

The problem is most likely the physical location of the unit besides the duct sizing. Duct sizing is important as Greg mentioned. Most units where already installed then the addition was made.

In most cases unlike yours, to save costs of adding another unit when the addition was completed, the contractor simply extended & or added duct work to the original existing furnace.

The results where not enough capacity to handle the added load. Your case appears to me to be the complete opposite. I could be wrong based solely on what I am reading in your postings.

What I mean in other words, is the two houses existed but when the currect unit was installed it was done so in the original location of the prior unit.

The new unit was capacity sized correctly but not centrally roof top located to save costs. It was simply install in the exact location of the original and the compensation was made in the ducting diameter size.

The lack of a second intake was yet another mistake often made by some contractors to save costs. But not always a contractors fault either. Done so to save costs by customer requests.

If I am correct than installing a damp into the existing ducting plus and a return intake in the rear area may work better. Location of the thermostat is also critical.

Two T-Stats on the same unit will not work so that thought is useless. Damps are only a cure for a symptom mind you and a thought.

Dual units, two seperate & totally individual heating & A/C units would be ideal. Cost effective over one unit running when one area of the house isn't being used and over the long term.

Regards & Good Luck.
Doityourself Web Site Host & Gas Appliances Forum Moderator. Energy Conservation Consultant & Natural Gas Appliance Diagnostics Technician.

Hey Sharp Advice,

Thanks for the lengthy response! I appreciate it. Between you and Greg I at least understand some of the issues I may be facing. I hadn't thought of a separate rear unit but in some ways that is ideal, as you say, because even if we solve the circulation, we are cooling rooms we are seldom in. The question there will be cost. In the meantime I will explore the other things you guys suggested.

Do you have any advice on finding qualified and fair technicians?

Thanks again.