New Unit Central Unit vs. Seperate Air Conditioner

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Old 03-10-16, 10:32 AM
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New Unit Central Unit vs. Seperate Air Conditioner

I live in a very hot an humid climate, that can get quite cold in the winter sometimes. It's a tri-level house built sometime in the 1970's.

That said, my current central unit is approaching it's 23rd birthday.

At the same time, I'm converting a sunroom intro an extra room. It has no venting currently.

So I'm faced with a choice.

1) Either get a separate unit for the new room and replace the central unit later + not mess with worrying about piping in new venting.

2) Or finish the room and replace the unit and at the same time and buy a new unit to handle the extra load and get the venting in as well.

I'm torn because I can see pros and cons of both. Any advice is greatly appreciated.
 
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Old 03-10-16, 12:36 PM
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I think in the long run going with two separate units will be more expensive though it will offer you more flexibility especially if you want to close off the sun room sometimes. You can't get away from the fact that your old HVAC is 23 years old. You should be financially prepared for it to die and need replacing at any time. It's won't care that you just spend $2k on a split system for the sun room.
 
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Old 03-10-16, 04:03 PM
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I'm planning on replacing the unit regardless of which option I go with.
 
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Old 03-10-16, 07:38 PM
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As long as you're replacing the main unit, I'd tie the new room into it and not mess around with a separate unit.
 

Last edited by stickshift; 03-11-16 at 08:07 AM. Reason: typo
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Old 03-11-16, 05:21 AM
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"Tying" another room into an existing system would require a specific amount of air and an appropriately sized duct to properly heat and cool the space.
You would have to run the duct to this space right back to the furnace plenum and have the air conditioning system up-sized to match this increase in the cooling load.
There is also the possibility that the furnace and/or blower would have to be up-sized to provide the additional airflow to satisfy the new space.

It will not be as easy as extending an existing duct and sometimes a mini-split heat pump is a simple but effective solution.
You would need to do a load calculation to determine what to do.
If you will hire someone to do this get several estimates because it is not always easy to find someone that is competent in this area.
 
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Old 03-15-16, 10:09 AM
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I am planning on getting this done (one of the few things I'm not doing myself), so just get various quotes and see what the overall opinion of the vendors are?
 
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Old 03-15-16, 12:59 PM
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Yes. Getting multiple bids will lead to questions on your part to ask the contractors and us here as well.
 
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Old 03-15-16, 01:19 PM
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For sure.......more information is better.
However you need to be prepared for opinions that could be skewed by a contractor's limitations.
Many who offer advice here do this sort of thing for a living and because we will not be your vendor can offer advice that has no gains attached.

My take on your situation is that if your current system performs well leave it alone and install a mini split heat pump.
By increasing the area your existing hvac covers you could wind up with a situation where the area where the thermostat is located does not properly satisfy a different zone.
Many homes that are either large or have a high use area will have a separate zone, often a second air handler.

A mini split would be your second zone.
 
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