Carrier Infinity 5-Ton # of Zones Help

[bigzaj]

I just had a complete carrier infinity system installed. It is a 5 ton unit and currently has two zones, upstairs and downstairs. The upstairs zone is roughly 1200 sq ft and the downstairs is 1800 sq ft.

I have a media room upstairs approximately 400 sq ft that is closed off to the rest of the upstairs when the door is closed. It currently has 2-10" registers and a 12" return in it, however it still gets uncomfortably warm with 4-6 people in there watching something as the thermostat is outside in the upstairs hallway and doesnt kick the AC on when this room gets hot.

I want to add a 3rd zone to the system and separate the 400 sq ft room off on its own zone. The AC guy who installed it tells me I can't do this as the room is too small to be a single zone on a unit this size. I was under the impression the carrier system would send some air into other zones using the modulating dampers so that it would optimize air flow for a zone.

Can I zone this one room or is my HVAC installer right?

[BaldLoonie]

There is a limit to how small of a zone to have. Many would do it regardless of how it would perform. Infinity zoning is the ultimate but you are still trying to stuff maybe 1700 CFM on low cool into a 800 CFM (if fed by 2 10" metal pipes) zone. If the other 2 zones will bleed excess air and risk overcooling, you probably won't have noise issues in the theater. Otherwise moving twice the correct amount of air could get rather noisy. Might be less of an issue in heating if you have a MVC or modulating furnace.

We can speculate and I'm sure this will be a long thread with lots of opinions but remember, your dealer is the only one who knows the house and duct system!

[beenthere]

A mini split for that room, is probably your best bet. Why run a 5 ton unit for a little 400 sq ft area.

[bigzaj]

I guess my struggle is the Infinity System can be up to 8 zones, the advertised and common appears to be 4 zones. In their ads and brochures they show offices and bedrooms as zones. Even on a 2 ton system having a 150 sq ft zone seems to fly in the face of each zone hitting the minimum CFM for the unit. So is their advertising wrong or is the system capable of handling zones that do not (by themselves) meet the "minimum CFM requirement" of the unit?

[beenthere]

Is your A/C 2 stage?

[bigzaj]

Yes it is a 2 stage unit.

[beenthere]

A mini split is till your best option for that room. There have been people that posted here that have had small zones on the Infinity zoning system, an they have had temp over shoots.

It can be done, but won't be an ideal set up.

[skippedover]

The issue isn't the number of zones, it's how BIG is each zone relative to the total MINIMUM airflow that can be tolerated by the system. Here's the numbers.

Total minimum CFM for the entire system on 2nd stage = 1750 @ 350 CFM/ton
Total minimum CFM for 67% of 2nd stage = 1st stage = 1173 CFM @ 350 CFM/ton.

Doing the math 1750 - 1173 = 577 CFM. Using 350 CFM/ton, that's 1.6-tons of cooling capacity that must go somewhere. What you cannot tell from the marketing pictures is the temperature of the room and the noise in the room. It all looks nice and when properly designed and installed, it is nice. If you're stuck on using the main system to cool the theater area, then I'd recommend installing another supply outlet (return too if there's none in that room) to reduce the excess air by an additional 200 CFM, which will minimize the excess air to something that should be tolerated by the other zones. I wouldn't recommend relying on the Infinity system to overcome the 577 CFM excess air, it's just too much IMO. Or as alternative, you could replace the 2-stage outdoor unit with a Greenspeed HP that will eliminate the excess air issue entirely as it can reduce its operating capacity down to approximately 700 CFM, thus eliminating the excess air issue.

As others have stated, a minisplit would be the ideal solution. It not only will provide a separate zone with almost no noise at all but with inverter technology will match the load from maximum to absolute minimum for those times when you're watching a movie all alone!

[woody19]

Although the Infinity system is a great zoning system capable of 8 zones and as many as 40 dampers it is not necessarily adaptable to every situation. As others have stated a mini-split system would be ideal for your application.

[bigzaj]

I don't really want to spend an additional several thousand dollars on a mini-split at this time, the entire system was quite expensive. I do however think that I will move the T-Stat into the media room.

Is it possible to have two T-stats on one zone if only one is functioning as the thermostat, but giving them both the ability to change the temperature?

[second opinion]

I don't really want to spend an additional several thousand dollars on a mini-split at this time, the entire system was quite expensive. I do however think that I will move the T-Stat into the media room.

Is it possible to have two T-stats on one zone if only one is functioning as the thermostat, but giving them both the ability to change the temperature?

Use remote zone sensor averaging can used, if you move zone controller to that room it will probably over cool the rest of the zone. By using multiple zone sensor averaging it will consider the theater room in the decision to heat or cool

[jpsmith1cm]

quickcat46

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[wahoo]

We've had good luck with wire-less thermostats for "hard to heat/cool" areas. The HO simply set the thermostat in the difficult area (this was a child's room), and the rest of the house would vary a little more. We've used VenStar #T1100 and worked well numerous times. The sending unit mounts where original stat mounts, and battery operated t'stat can sit anywhere. Might solve your problem cheaply!! I think same stat is available thru Carrier supply houses also.:.02:

[woody19]

We've had good luck with wire-less thermostats for "hard to heat/cool" areas. The HO simply set the thermostat in the difficult area (this was a child's room), and the rest of the house would vary a little more. We've used VenStar #T1100 and worked well numerous times. The sending unit mounts where original stat mounts, and battery operated t'stat can sit anywhere. Might solve your problem cheaply!! I think same stat is available thru Carrier supply houses also.:.02:

Those are, indeed, useful stats however they are not compatible with the Infinity system.

[bigzaj]

The reason I got the infinity system is because my friend has it and he really loves the zoning. He has a 1800SF home with a 3 ton infinity sytem and 4 zones. I've talked to him about it a lot and this is what I know about his zones:
Zone 1 - Downstairs, approx 800SF
Zone 2 - Upstairs, approx 500SF
Zone 3 - Guest Room, approx 120SF
Zone 4 - Master Suite, approx 400SF

He has infinity smart sensors for every zone, and he says his system works perfectly. We have turned on the guest room by itself and the system runs on low power at 600cfm, and right at .8 static pressure. That room is fed by one 6" duct and has a small amount of noise when its the only one running, but nothing crazy. The smallest zone I want to create is 400SF and is fed by two 10" ducts, so after seeing his, I have no concerns that the air will be too loud.

First of all, even though his system seems to work perfectly, does anything stand out to you as problematic with that system?
Secondly, is there any other information you would recommend that I give my installer to ask him to create this since I've seen this in action and its what I want?

[beenthere]

See how much it over cools the other zones when only that zone is calling.

[jpsmith1cm]

pressures


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[bigzaj]

On the Zone Status screen of the system control it shows the following:
ZONE * * * * * * *POS * * * * * *CFM
Upstairs * * * * * 2 * * * * * * * * *71
Downstairs * * * 2 * * * * * * * * *140
Master * * * * * * 0 * * * * * * * * * 0
Guest * * * * * * *15 * * * * * * * * 385
(If you refer to my original comment about his zones, I had them in the wrong order, but this is accurate)

When we go into the upstairs or downstairs common areas, there are no signs of overcooling, and the smart sensors register that the temp in those rooms is exactly at the set point. *Is this a fluke, or do you think his installer possibly did an excellent job of sizing the ducts/returns, etc, and that's what I need to have done as well?

[beenthere]

I think you should ask him to check his static at the end of the cooling cycle when the other zones are closed.

What size is his A/c.

[bigzaj]

3 ton. Says static pressure never over 1.0

[beenthere]

1 is a high static.

How much more load does his small zone have over the other ones?

Remember, your zone you wan to add, will have a higher load then the other zones. Which is why its so hot in there.

[skippedover]

The reason I got the infinity system is because my friend has it and he really loves the zoning. He has a 1800SF home with a 3 ton infinity sytem and 4 zones. I've talked to him about it a lot and this is what I know about his zones:
Zone 1 - Downstairs, approx 800SF
Zone 2 - Upstairs, approx 500SF
Zone 3 - Guest Room, approx 120SF
Zone 4 - Master Suite, approx 400SF

He has infinity smart sensors for every zone, and he says his system works perfectly. We have turned on the guest room by itself and the system runs on low power at 600cfm, and right at .8 static pressure.

This is a very high static pressure. With an Infinity air handler and variable speed blower, he's using a lot more electricity than should be used to cool that single zone.

That room is fed by one 6" duct and has a small amount of noise when its the only one running, but nothing crazy. The smallest zone I want to create is 400SF and is fed by two 10" ducts, so after seeing his, I have no concerns that the air will be too loud.

You're missing the point there. He's got a 3.0-ton system that needs to move 1050 CFM on 2nd stage and 704 CFM on 1st stage. Even if the blower slows to 80% of 1st stage (the absolute minimum before ice forms) it would still need to move 563 CFM. You say that room is being served by one 6x6 supply outlet and it's not noisy? I find that impossible to believe unless the other zones are open. A 6x6 at 500 FPM face velocity would deliver a maximum of 90 CFM before velocity gets ridiculous. So that leads me to believe that someone is misinterpreting the data. Once each day at normaly (the time can be changed) the Infinity system checks all zones for airflow capability. What are the readings for the 4 zones? It's in the user interface history.

Now you're trying to assimilate his info or lack thereof to your 5.0-ton system. That's a size jump of 167%, so all the readings and needs of the system are different.

First of all, even though his system seems to work perfectly, does anything stand out to you as problematic with that system?
Secondly, is there any other information you would recommend that I give my installer to ask him to create this since I've seen this in action and its what I want?

You have 2-zones, he has 4. The logic of the control algorithms is like this. It "remembers" prior runs and needs. It "remembers" the airflow for each zone. It tracks the run time for each zone's demand, tracks how long it's been since each zone last called for cooling, calculates the maximum airflow that can be tolerated by any zone calling for cooling, calculates how much excess air needs to be diverted to another zone, calculates how much air can be introduced to each zone, based on past call length and time since last call and then begins to open dampers as appropriate. Dampers for zones other than the one calling can be opened part way or all the way, depending on the calculations at the start of a cooling cycle and if the trend of a zone being used as 'relief' for the calling zone is changing, another zone can be incorporated into the mix. Your friend has a total of 4-zones for all these calculations. You have 2. That makes the likelihood of NOT over cooling another zone less likely than if you had 4-zones with 3 of them able to handle most or all of the minimum airflow.

I'm not suggesting you cannot have what you want, only that it needs to be done to minimize the airflow issues. So as I said before, you should have another supply outlet introduced into that theater area and a separate zone for it. I don't know what CFM capabilities there are for the other two zones but I'm sure in combination with 3/10-inch supplies in the theater, one of the other zones at any point in time can handle the excess air without over cooling to any significant degree.

[bigzaj]

My main issue is that I'm dealing with an installer who was hesitant to do two zones because the upstairs is barely big enough to be its own zone. He says zoning this room will be inappropriate and he want guarantee the system. If there is a practical way to make this room it's own zone what the heck do I say to this guy?