I've received several estimates from various installers to retrofit an old house with an A/C. The house has a hot water boiler heating system so there are no heating ducts to work with. There seem to be three options: 1) high velocity ducted system, 2) mini split system with units on the exterior wall and 3) a ducted mini split system with an air handler in the attic and ducts running to the ceilings of all the rooms.

The mini split systems are half the price of the high velocity system and the installation is much simpler and less intrusive. My favored system is the ducted mini split because it conditions every room while the ductless mini split system only has units in a few of the rooms.

I was told by one of the installers that they would never use a ducted mini split because there is a air handling unit in the attic and condensate with water that will eventually cause damage. My question is that true? Are air handlers in the attic problematic because of water overflow?

Thanks

 

*shrugs* It's pretty typical to install an HVAC in the attic. As long as it's installed correctly, including an overflow pan and water shut-off, you should never have an issue. If there's ever a clog, the water overflows into the catch pan and drains outside. If the catch pan ever gets clogged, the water sensor should shut off the system.
But leaks do happen, and they are mostly due to poorly installed units. The catch pan is just thrown in and never really checked to confirm it drains correctly.

I've used both high velocity and mini split systems and they both work great. I have an old house (1850's) with a high velocity system that's going on 18 years old. Though the ductwork is small, it works similarly to standard HVAC systems. It's also convenient to have ducts in every room.

Mini-split systems (with heads in each room) is great for smaller houses where you can cool the whole house with 3-5 head units. In larger houses with 4 bedrooms + 3 other rooms, it gets more expensive plus potentially more maintenance. I've been told to expect about 10 years out of these systems, so the cost-per-year might be higher or more equivalent to the high velocity system.

I've successfully used Mini-split systems in a couple rentals as it allowed me to get rid of the big cast iron radiators and switch both heating and cooling over to the mini-split system. Also, the heat-pump technology is very efficient - and will save you money compared to a traditional compressor AC system.

 

Just noticed a post about how an overflow pan is working correctly and some discussions about additional safteys to ensure it doesn't ever leak.
Condensation drain line question

 

It is quite common to put AC air handlers in an attic. I have several in my rental houses. Aside from listening to the HVAC helpers complain about lifting the equipment up into the attic they really aren't much trouble. If you live in the house and just keep an eye on the condensate drain during AC season you'll be able to easily spot a clogged drain line.

The biggest negative I see with the air handler in the attic is noise. Because it's machinery mounted on the ceiling joists you may hear some rumble in that area when it's running. But, modern units are surprisingly quiet and it's not an issue for most people. They aren't loud and don't vibrate much at all, it's just if the room is quiet you will probably be able to tell it's running.

 

Really ? The few high velocity systems I've encountered were very noisy due to the velocity of the air.

 

There's one port that is loud, I think it was connected too closely to the handler. You can hear the air moving, but it's never been much of a distraction.