So I got caught up in the real-estate frenzy and bought a house last month. Yes it's crazy out there. We have been needing to move for 3 years now and it finally happened.

The new place is a two story with a 4 ton upstairs that is in ok shape. But the downstairs living area 4 ton unit is long gone. The mbr/bath/closet is also downstairs on a 2.5 ton unit. Each one has an independent thermostat. I'm looking to replace the downstairs units (which are unrated they are so old) with a 16 seer(minimum) 5 ton unit zoned. Ideally it would be set up with smart thermostats. I've found the benefits of a zoned setup online but would like to hear what the negatives are before I pull the trigger on it.

Thanks.
-TVz

No guru here, but there are no circumstances under which I'd go from two systems to one.

Edit because I mixed up words.

This message has been edited. Last edited by: Skins2881,

quote:

No guru here, but there are no circumstances under which I'd go from one system to two.

Never would I

Typically a properly zoned system is done during design / new construction phase. Ducting design and the zoning must be properly sized. I would seek a few professional organizations for their advice. First most, make sure the equipment is sized properly with a load calculation performed and the duct work will support the equipment selected.

Have a mechanical engineer, not an AC company, spec out the compressor, handler, and duct work. This is not a case where you should get close enough and round up - an oversized system can be as problematic as an undersized one (if not more so).

First, everything is rated.

Second, is this your idea or is someone whos in the HVAC industry recommending such a catastrophe?

Make sure your able to get your vents and returns back to the new unit. If they are on separate units today, that will probably take some work.

Secondly, you should talk to someone about proper sizing. A 5 ton unit is pretty big. You will have trouble conditioning a single zone (bedroom/bath/closet) on such a big system unless it has the ability to step-down. Same thing for the larger zone. If it's 4 ton now and you're going to a more efficient 5 ton, that sounds like overkill.

My $.02

quote:

A 5 ton unit is pretty big. You will have trouble conditioning a single zone (bedroom/bath/closet) on such a big system unless it has the ability to step-down. Same thing for the larger zone. If it's 4 ton now and you're going to a more efficient 5 ton, that sounds like overkill.

Think he said the downstairs has 4 ton and a 2.5 ton units, and he was investigating replacing both with one 5 ton.

IF they are significantly older units they are not going to be as efficient as a new 16+ seer unit. Might be possible, but as others have said, get quotes and it wouldn't hurt to have an independent engineer give you an assessment on which direction to move.

Someone mentioned ducting reconfiguration and that would have to happen, return and feed ducts would have to be routed to the new system or new ducting, which might be needed anyway depending on the size and capacity of the old ducts...

Here's a cool seer comparison calculator, you put in your location current seer, size and then you can compare it to different seer levels to see what projected savings you will see.

Moving from our 13 seer to a 25 seer will hypothetically reduce our bill by 50% a year.

Of course you have to factor in the cost difference but it lets you compare your seer to other seer options..

Link

We have two zones/units here in sunny warm Florida. We have replaced them one at a time over the past few years, one this spring. A lot of advances have been made since your house was built. It also pays to have the ductwork in the attic inspected, we discovered one was leaking air into the attic. Does your state give credits or rebates for high efficiency units?

Thanks for the input. The house originally came with 3 HVAC units(not 2). A 4 ton upstairs(4 brs, 2 bath and a den), a 4 ton downstairs, and a 2.5 ton for the master bedroom suite(downstairs). All three are 21years old. I got a quote for all three and its more than I want/can spend. A second option is to just replace the single 4 ton unit. That would help with the install cost and some of the electric expense. But I know that the other two units won't last forever. Just replacing that one unit pretty much commits me to a 3 unit arrangement going forward. The AC companies I got quotes from would be happy to replace 3 units.

Going zoned was my idea. My intention is to use a high efficiency 5 ton 2 stage AC with the variable speed air handler to support the entire downstairs. There is plenty of attic space to support the dampers and additional routing of duct. This would address two of the HVAC units and maximize the efficiency if it fits the application and is done right.

I'll call the owner of the AC company and ask more questions. The rep that came to the house was concerned about the high ceilings through out the downstairs when I first posed the question. So a follow up on how they intend to set this up and about getting a mechanical engineer to evaluate the air space before I commit to the install. Their quote for the zoned setup included a substantial amount for setting up the air controller/dampers and rerouting ductwork. It's not a simple ad on charge.

As for the rating of the old systems, that was regarding my question on how would the failed 4 ton compare to a new 16 seer unit. The failed unit has a 410 evaporator coil that was converted to R22 by the previous owner. That is the catastrophe being addressed now.

Thanks.
-TVz

quote:

Originally posted by HayesGreener:
We have two zones/units here in sunny warm Florida.. Does your state give credits or rebates for high efficiency units?

When I was shopping for an electric provider for the new(to me) house I came across some type of $2500 credit when a new system is purchased with a specific provider. Damn if I can't find it now. Right now I'll qualify for a $300 tax credit with the purchase. Better than nothing I suppose.

-TVz

That's what I read, one 4 ton upstairs no issues, you want to replace the two ac units 6.5 tons total with one 5 ton and moving up in seer you probably need new ducts anyway to maximize the 5 tons capabilities depending on time of day and demand.

Sounds like you are on the right track, shop around, get plenty of quotes and emphasis should be on installer ability and follow up.

All AC units will perform the job, it's how they are put in, designed and programmed. Install is important.

quote:

Originally posted by HRK:
Sounds like you are on the right track....

...for a train wreck.

When I did my A/C for a remodel a couple of years ago, I got 5 quotes and everyone of them gave different estimates, double from the lowest to highest and every one suggested a different design.

I would have at least 3 or 4 companies come out and give estimates.

I found the one that has actual sales people were the highest estimates by far.

We had to replace both units 2 years ago. I got an engineer out. We followed his recommendations, and our house is more comfortable than before, and the energy bills are down significantly. YMMV.

quote:

Originally posted by Excam_Man:

...for a train wreck.

I thought about this comment while reading the more recent HVAC threads and have a better appreciation of it.

I'm bringing up this old post as I didn't want to step into the other threads with my question.

I've reconsidered sticking with the 3 HVAC unit setup for the house and just replacing a single 4 ton unit. The other two(4 ton and 2.5 ton) are holding their own during the recent uptick of 100 degree days. So my question is should I replace with a single stage or two stage? Variable speed is too expensive to be an option.

As the other two units are single stage, will I get the benefit of the two stage when it is this system? I will at least get a 16 seer unit. The two stage will be either a 17 or 18 seer. I can close off the area serviced by the 2.5 ton system, but the areas (upstairs and downstairs) serviced by the 4 ton units cannot be completely separate. Would I be able to reap the benefit of a two stage upgrade running along side a single stage unit?

Thanks for the input.
-TVz

Yes you will.

As you'll gain run time (dehumidification) while the outdoor temps are not demanding the full capacity.

Tbanks!