What's the proper cfm for a 2 ton system?

[545GAlady]

Thanks for all your advice! I did ask the tech one time about zoning and the price was too expensive. Here's a look at one of the air registers in our upstairs: All the supply registers in the three bedrooms upstairs (except the ones in both bathrooms) look like this one. We replaced the registers back in August. The old ones were the typical cheap registers.

[54regcab]

Those are the good ones. As a homeowner did you notice much improvement or is it just something us HVAC guys notice?

[motoguy128]

Thanks for all your advice! I did ask the tech one time about zoning and the price was too expensive. Here's a look at one of the air registers in our upstairs: All the supply registers in the three bedrooms upstairs (except the ones in both bathrooms) look like this one. We replaced the registers back in August. The old ones were the typical cheap registers.

Yup, those ar the better ones. You can keep hte slats mostly strights to increase flow slightly.

Next to to go to a larger boot and grill. But it looks like it's only a 6" duct feeding it, so you won't gain much if anything doing that.

The imbalance is probably from a undersized main trunk and branch ducts.

The next solution might be to do the best thing and that lower hte heat gain upstairs. A cool roof design and an sealed unvented attic can probaby cut your heat gain by a 1/3. But that's not a cheap solution. Zoning is a lot cheaper.

How's the attic insulaiton again? Do you have a lot of recessed lights or ceiling light fixtures? Are those all well sealed?

[545GAlady]

Thanks. There's actually an 8 inch duct going to the register, not 6 inch. We do have recessed lights (only in the hallway) and they are well sealed. One of the techs recommended installing an attic tent to help trap the hot air from leaking out of the attic pull down ladder. The insulation was checked before the new furnace was installed and it was fine. Each bedroom has one 8 inch supply in them.

[545GAlady]

Those are the good ones. As a homeowner did you notice much improvement or is it just something us HVAC guys notice?

The new registers have made the air a little quieter and there's been much improvement from them. They look nicer as well!

[George2]

But even zoning requires that you have a minimum airflow to run the equipemnt on low stage with min&max supply temps AND that you still ahve adequate flow to each zone to match the heat loss or gain.

A good zone systme starts as a properly sized, distributed and balanced duct system for equipment sized maybe 20-25% larger that what a load calc calls for. IF you're using zoning ot correct for ductwork imbalances, it won't work as well and may even fall on it's face and be worse than non zoning at all. It shold only adjust for changes in load only. I'm not saying that not what good pros do, just clarifying.

Agreed. I was merely responding to post #22. A larger blower will help address comfort issues, but this is not the only method available.

Like all things, one SHOULD know the proper procedures for all installs. BUT, we all know, things aren't always installed properly. What do "they" say..........50-70% of home have improperly sized ductwork and equipment.

It does not speak to highly for our trade.

[545GAlady]

It will be nice to have zoning, but we can't afford it, unfortunately. The air registers are made of steel. I prefer aluminum registers of this style, but will aluminum ones actually make the air quieter coming out of the vents? You could really hear the airflow coming out of the current ones pretty good but they are still quieter than the old cheap ones. The ductwork is not causing the noise because when we replaced the vents, there was almost no sound coming out when there were no registers in the ceiling.

[George2]

It will be nice to have zoning, but we can't afford it, unfortunately. The air registers are made of steel. I prefer aluminum registers of this style, but will aluminum ones actually make the air quieter coming out of the vents? You could really hear the airflow coming out of the current ones pretty good but they are still quieter than the old cheap ones. The ductwork is not causing the noise because when we replaced the vents, there was almost no sound coming out when there were no registers in the ceiling.

Please refresh me on which of the 3 systems this is an issue? Is there one register (area) where the noise is the biggest issue?

The simple solution is to install a larger register. The supply (run) is supplying too much air for that small register. Thus the noise and the reason it's quiet when the register is removed from the boot.

[545GAlady]

Please refresh me on which of the 3 systems this is an issue? Is there one register (area) where the noise is the biggest issue?

The simple solution is to install a larger register. The supply (run) is supplying too much air for that small register. Thus the noise and the reason it's quiet when the register is removed from the boot.

Thanks. This is the upstairs system. The noise is not very loud, but there is some noise from all the registers upstairs. So you are saying that 14" x6" is too small? During thanksgiving this year we stayed in a condo at the beach and it had aluminum registers that looked the same as ours. Those had pretty good airflow and the air was so quiet (almost no sound) coming out of the vents. I quess the material that the registers are made of have nothing to do with the sound, correct?

[George2]

Thanks. This is the upstairs system. The noise is not very loud, but there is some noise from all the registers upstairs. So you are saying that 14" x6" is too small?

14x6 is okay for a 6" supply run. 14x8 is better for a 8" supply or a short 6" supply. If the area is heating or cooling okay, maybe a damper to reduce the airflow would work. But duct work in the attic is not always easy to get to.

We put dampers just beyond the register in those situations. That way, a customer can take off the register, adjust the damper for airflow/noise and reinstall the register.

To do that takes just a minute on our part but it's a really nice (and thoughtful) thing to do for the homeowner. We do it on every new house were access is limited. But that kind of consideration is rare these days.

[545GAlady]

14x6 is okay for a 6" supply run. 14x8 is better for a 8" supply or a short 6" supply. If the area is heating or cooling okay, maybe a damper to reduce the airflow would work. But duct work in the attic is not always easy to get to.

We put dampers just beyond the register in those situations. That way, a customer can take off the register, adjust the damper for airflow/noise and reinstall the register.

To do that takes just a minute on our part but it's a really nice (and thoughtful) thing to do for the homeowner. We do it on every new house were access is limited. But that kind of consideration is rare these days.

Okay thanks! Duct work in our attic actually IS easy to get to. Could installing dampers right on the start of the ducts from the plenum be a good idea?

Now the other 2 experts said that the registers I'm using are the good ones. We have some relatives that live in Louisiana and they have those round diffusers in their house. I assume those aren't good to use since they blow air along the ceiling which means they work better in cooling mode.

[George2]

Okay thanks! Duct work in our attic actually IS easy to get to. Could installing dampers right on the start of the ducts from the plenum be a good idea?live in Louisiana and they have those round diffusers in their house. I assume those aren't good to use since

Now the other 2 experts said that the registers I'm using are the good ones. We have some relatives that they blow air along the ceiling which means they work better in cooling mode.

The round diffusers are (normally) all we use for the second floor. However, they are at least double the price. Do you need to ask why your registers are rectangle?

[545GAlady]

The round diffusers are (normally) all we use for the second floor. However, they are at least double the price. Do you need to ask why your registers are rectangle?

I would like to wonder why they are rectangle. I think one of the reasons why is because the registers are installed right by the windows and also since the fact that when these homes are built, the builders don't want to spend so much money on air registers.