mini splits to supplement existing HVAC in old house?

arlosmomJuly 13, 2012

Our house was built in 1905 and has balloon framing. When we moved in eight years ago, we replaced the old forced hot air furnace with a Carrier Infinity system that gives both heat and A/C. We used the existing ductwork (absolutely no idea when it was installed or how well it was installed), and I do not believe that there is a return on the second floor. The system does a very good job heating and cooling the first floor, but it's far less effective heating/cooling the second floor bedrooms.

We are now looking for the least invasive way to improve the heating and cooling in the three second floor bedrooms and the third floor attic bedroom. We really, really do not want to rip open walls to mess with the existing ducting or to add a second floor return.

We considered a high velocity mini duct system like Spacepak or Unico, but I think that only provides A/C and does not provide heat, right? Would a mini split system with 4 inside units be a good solution for us? I'm not thrilled about the look of the mini split units on the walls, but I guess I could live with that. Do they do a pretty good job at both heating and cooling? I've read conflicting information about how quiet they are. Does anyone know if the lines to the outside compressor and for drainage can be run inside our balloon framed walls rather than on the exterior of the house? (The walls do not have insulation and we've been able to easily run electrical and cable in them.) Is there another minimally-invasive solution that we should be considering? We're in Maryland, by the way.

Thanks in advance for any insights you can provide.

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High velo will heat.

I like my 7 mini-splits very much (Three outdoor units). Look up some posts in this forum for more info. They are not cheap, but very efficient (no duct loses) and the inherent zoning can save you money by not conditioning the rooms when you are not in them. They also throttle well as the room approaches your desired temp.

Necessary lines and cables should be able to be run in the walls. (Mine were run in interior walls,but I am single-story.) You will probably not get an outdoor unit for each room, but cluster them. That means running lines horizontally as well and that might mean in your basement or around the foundation. That is something to discuss with your installer. Finding an experienced installer might be a problem.

If you don't like the high-wall units, consider the mini-split options with short duct runs if you have a place to tuck a small air handler or two. Ceiling cassettes are an option too. You might like the wired controls for those better than the remotes. They will cost more than high-wall. Look at Mitsubishi, Toshiba, Sanyo and Daikin web sites for a view of what is available.

    Bookmark   July 13, 2012 at 7:28PM
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The mini-splits do heat and cool but look at the specs. They have an operating range. For heating my Fujitsu units are specified to operate between 14-75 degrees F. For a unit that is bigger than the ones I own the heating operating range is 0-75 F. For cooling the operating range is 0-115 F for all the sizes. We live in Colorado and the system is only back-up heat for us but I think it had a lower temp. range than some of the competing products I looked at. Check to see what the range is of the products your considering.

I may be wrong but I think to put the lines in the walls for either high velocity or ductless mini-split you have to rip them open. The contractors we talked to for the high velocity talked about all the drywall repair we would need to do. We elected to not do this so ours run through the attic to the outside where they are covered with materials that looks like gutters running down the house.

We have run ours for heating and the heat pours out. We also find them incredibly efficient for cooling.

    Bookmark   July 13, 2012 at 10:00PM
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