Hi,

I have a TRANE XE1000 split unit HVAC system at home. It has air handler/evaporator in the attic and compressor/heat pump on concrete slab outside. This system is 20 years old now this year.

I am already looking into cost-effective solutions for when the system fails. Maybe it still has years of life left, or maybe not. My single level house is in Arizona desert and is 1251 square feet. It has no basement. There is no room to install equipment inside the house. If possible, I'd like to not work out of the attic anymore at all. Incredibly hot in summer, and cramped quarters up there. Ridiculous location for HVAC equipment. Are these options that might save me money:

1. Have myself install the units in attic and outside slab and pay technician to hook up connections.

2. Install mini-split units myself. How many would be needed?

3. Eliminate the attic altogether and place split units side by side together on slab, or backyard and route ducting into attic. Existing slab is on one side of house. So would this cause uneven distribution of heating and cooling in house?

4. Would three powerful window units cool my 1251 square ft. house sufficiently? Would these units be too noisy?

5. Can I replace one unit at a time..............or does the old equipment jeopardize the brand new unit?

My neighborhood does not have a HOA.

 

1) You could do that, be careful of warranty issues and check with an installer first
2) Depends on the layout and what you want to cool, newer mini split systems can run multiple heads with just one condenser.
3) All your duct work is in the attic and should be fine if its the correct insulated material.
4) Yes, you wouldn't need very powerful units, just sized correctly for the room sizes. Good quality units are pretty quiet.
5) At 20 years, replacement them as a set. You'll also be going to the new refrigerant which is not compatible with your older units.

 

I was thinking more about this. I am the only one living in my house. If I start out with two wall mounted air conditioners in my house, I might be able to greatly reduce the use of my central A/C thereby extending the life of the existing system.

I was applying this logic to the mini-split system setup also. I know that one compressor/condenser can power multiple air handlers. But to me it would be easier to just buy a condenser that is designed for just one head. It seems easier than extending connections to different heads around the house, Then as finances permit, I could slowly expand and add air handler/compressor pairs to this mini-split system over time if needed.

Then if central A/C finally fails, I have already started a new A/C system. Would this work out?

 

1251 Sq ft isn't very big, depending on the layout and ability to move air around, you could cool it with nice 12-15k btu window unit. Another small unit for your bedroom to run seperatly at night and you're all set.

 

Im not in your area but id guess you would be around 3 tons of cooling load. Have a room by room heat load done. this will put you miles ahead.

 

So I could really cool my house with two window or wall units?

What do think of the mini-split option for house of my square footage.......not necessary since wall/window units sufficient?

When you say 'heat load' I assume you mean have a technician do a room to room survey with some type of meter to gauge heating/cooling needs?

 

Heat load is done on a computer. You just enter the information and it does the rest. You can get the program online for around $50 are pay someone to do it.

 

Most contractors frown on just hooking-up units bought elsewhere.

Here is a Free online whole house load-calc. Have family or friends help you do it. First, print & follow directions, it is easy to do.

You could also possibly do each room separate for the window &/or ductless A/Cs.

HVAC Load Calculation - Maunualj - Whole House Loadcalc

 

Mini-splits are expensive to purchase and repair when there's already ductwork. Window units just plain suck and will lower the value of the house if/when u sell.

Best thing you can do is turn the attic into an interior space - have the roof deck insulated.

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3 tons is a heck of a lot for 1200 sq ft; but having ducts in the attic can eat up a lot of capacity.

House of that size if reasonably efficient should cool on 2 tons in a very hot climate and 1-1.5 in the northeast.

A load calc should be done - the odds of having large enough ducts for the 1200 cfm a 3 ton has to move are very low. the effective capacity could be as low as 50% of the rated capacity once duct losses and poor performance are taken into account.

 

I hear what you're saying about window units. I'm not crazy about that idea either. Plus there might be an illegal entry or burglary issue with the window unit option. But I definitely don't want a replacement system in the attic. It gets very hot up there in summer (Arizona) and it's cramped quarters with not enough space to work up there.

I just replaced a light switch and porcelain lampholder in the attic a couple days. I practically had to become a human contortionist to put in a couple screws.