how many zones for central A/C?
We are doing gut reno so can install central A/C for four story brownstone w/garden apt. How many zones should we have? right now plan calls for 1 per floor but that seems like too many. top floor is home offices/guest bedroom, 2nd floor bedrooms, parlor main living space. eager for any advice, as always!
We are doing gut reno so can install central A/C for four story brownstone w/garden apt. How many zones should we have? right now plan calls for 1 per floor but that seems like too many. top floor is home offices/guest bedroom, 2nd floor bedrooms, parlor main living space.
eager for any advice, as always!
In my experience as an hvac service and installation tech,old brownstones can work well with a unico high velocity mini-duct system or a ductless air-conditioning(mini-split)system.The unico system can be zoned but it is too costly to be retrofitted for that ,instead you should use smaller air handlers for each zone with the appropriate condenser.Mini-splits can be zoned for each area and can cost as much as the unico system.
Pros and cons
The ductless system can remove a lot of moisture and latent heat,but if you are big on aesthetics,the minisplits can be intrusive and interferes with the decor,with the exception of the LG line of ‘art cool’ductless line.
The unico system of mini-ducts measuring 2 1/2 inches diameter outlets can be hidden among the recessed lights or in the corner of the floors and even above wall shelving.In the hands of a good installer ,the system is eerily quiet and removes more moisture than most central air units and ductless air-conditioning.
If you need an estimate you can call me at 15163181172.
Aaron is on the right track.
Although you are doing gut renovation, duct work takes space, which is or should be at a premium.
Consider Sanyo slimline multizone units. You can drive up to 4 air handlers from one compressor. By clever planning regarding which living areas are likely to be used at alternate times, a 31K BTU compressor can drive more than 31K of air handlers, as they will not simultaneously call for cool. For instance you may be able to drive four twelves, or an eighteen and three nines.
Because you have walls open, air handlers do not have to be on external walls, and can often be mounted up above a closet, or other out of the location. The length on the line sets has some limits on length, but you can locate the compressors up on brackets or roof or ??
You’ll need condensate drains, but for you, that’s easy.
Price for the units will exceed cost of big compressor and ductwork, but you will save on energy from day one. It’s a better mousetrap. Central air is clumsy unless it is a large house all of which gets conditioned. Air from one part of a centrally cooled house goes anywhere once it has returned. This evens out the home, eliminating the economy of not cooling a section that will not be used.
Also consider Unico. They are pricey, and hard to zone, but they will save you the footage. They do make high SEER and heat pump units.
I have been doing computer work for an HVAC contractor, and have learned more than I ever thought I would know about air conditioning.
Bruce
Dave I agree with you, and would add the further point that separating the air handlers by floor will simplify the ducting. Central a/c isn’t a particularly good idea in a 19th century brownstone.
We are about to embark on a similiar project and I’m getting quotes… would anyone who has done this mind putting a ballpark cost range here? Also, I’m assuming people used duct airconditioning but did anyone consider the smaller “split-unit AC system’s (Mitsubishi slimline etc)? Pro’s and con’s of both?
RG does bring up a good point. With a large house (3 floors) you’re not going to get much efficiency as you move further from the air handler if you are only using one in the basement. A third floor will definitely work much more efficiently and comfortably with its own separate compressor & air handler. You’ll see the same situation with heat.
We did a gut renovation in a four story brownstone (double duplex)and put in 4 A/C compressors and handlers, one per floor. We have two floors that are exclusively bedrooms and two that are living/dining etc. We turn on the A/C on the bedroom floor about an hour before bedtime, turn it off in the morning, and vice versa on the living/kitchen floor. Because heat rises, the demand on the A/C system varies from floor to floor, and it would be wasteful (energy-wise) to cool two floors simultaneously. Also, I think (hope) that the A/C units will last longer as each is used only half a day. We discussed having each floor on a different zone, but I’m not sure about the efficiency of that system. In your case, I would definitely have the garden and top floors on separate systems (the garden floor doesn’t need as much cooling, the top floor is an oven),
and maybe combine the 2nd and 3rd floors into one unit with separate zones. Talk to Dmitri at Coolco for a second opinion.
More zones are better, up to a point. tread denton’s post below. Put the guest BR on a separate zone and then 3 others….main floor, 2nd floor BRs and then the top floor. The object is to use programmable thermostats in conjunction with the zones so that they can be regulated throughout the day when areas are not in use.