improve cooling to the bedroom

[Hugh Wong]

I would like to improve the air flow to the master bedroom in my house. Presently, the air is not as cool as it should be. It's about 5 degrees warmer than the other rooms. Physically, this bedroom is the farthest distance from the main unit which is a Day and Night, 5 ton A/C. The house is 1700 sq ft. All the other rooms have sufficient flow and cooling. There are about 7 vents throughout the house. I tried temporarily installing a stove exhaust fan just outside the air duct but that didn't seem to help the air flow or the cooling. Any ideas on how to rectify this problem?

Thanks.

Hugh

[HeyBub]

Put in a window unit. You can get a new one for less than $150.

I did that and cut my cooling bills by 2/3rds, saving the cost of the unit in two months.

That was three years ago.

I'm gonna buy a mongoose with the money I saved. Or maybe something else.

[LouB]

Or, if a window unit is not feasible put up a ceiling fan. Get one with a remote control.

[Lefty]

Insulate the plenum and trunk lines with FSKL, at least 1-1/2". Also add another run into the bedroom. There is no way seven runs is enough for a house that large, unless the individual runs are huge. Also, throw out that restrictive allergy-gard filter if you are using one. You want a high velocity throw-away if a one inch slot is all you have.

Actually, rereading your post; five tons of air through seven 6" runs equals a no air flow ice cube anyway. You better have a pro check that system thoroughly.

HTH, Lefty

[Malcolm Hoar]

Was it always this way? If so, chances are the duct was undersized or poorly installed. Take a look at the duct size and run relative to the others in your home.

If this is a new problem, maybe the duct is blocked, collapsed, or leaking badly. Connections to registers, other ducts, etc. can come adrift.

It's also possible that you have a baffle splitting the air flow between ducts/registers which has moved, diverting air away from the register in your master bed.

Also consider the return path. A problem there will mean the a/c is just trying to pressurize your bedroom and air flow will fall badly. In that case, opening the bedroom door might help quite a bit :-)

In any event, I'd start by making the most detailed inspection that you can in order to figure out what is going on. 5 tons for 1700 sq ft sounds generous but we don't know what climate you're subject to.

[Bob F]

Partially close all the other ducts.

[frag]

What are you doing in there that makes it so hot?

[ilbebauck]

You could have a duct balancing damper closed for the duct run to the bedroom. Go to the main Trunk Duct off of the Blower Unit and youll see the branch ducts coming off of it ; throttle down the duct dampers about 50 percent to the rooms closest to the blower and open the duct dampers for the longer runs. Make sure your Blower is up on high speed, the air filter is clean , and the a/c is fully charged on freon. You most likely need an additional duct ran to the bedroom so you get adequate air to the space--have an additional well sized duct ran . Right off hand, 7 supply registers for a 2,000 cfm / 5 ton cooling system is not enough . Im willing to bet your air distrubition system is choked down hurting the performance .

[ransley]

A bigger supply to the room

[Ron]

It is recommended that you run your blower on the medium setting to remove humidity,

Also, I've owned 3 homes and none of them had a "duct balancing damper".

[Ron]

If this problem has just occurred, have you checked for duct leaks?

[trader4]

I see two big issues:

1 - 7 vents for the entire house can't be enough. 2 - 5 tons for a 1700 sq ft house sounds over-sized, provided the house is of reasonable insulation and the windows aren't open in Miami I have a 3100 sq ft house in NJ and mine is that size. In new houses here that are over 4000 sq ft they are putting in around 6 tons, split between 2 systems.

I'd get a pro in to evaluate the whole thing. It's likely you are throwing $$$ out in energy bills that are higher than they should be.

[jamesgangnc]

Unit seems too big with too few supply ducts. Where are you? Duct work in the attic or under the house? Ducts shared by the heating system? What and where is the return duct? How long has the unit been in place? Has this always been a problem or is it a recent problem?

[jamesgangnc]

You need to move a certain amount of air through a system based on the size to make it operate correctly. So it's got nothing to do with how many rooms he has, it's because of the system size he believes he has. Even with mediocre insulation 5 ton is pretty big for a house that small. If you don't move enough air across the coil it's temperature could drop below freezing. When that happens the condensation freezes on the coil instead of draining.

[ilbebauck]

No, you want to move the maximum cfm possible for cooling and a lower cfm for heating . If you have a home without duct balancing dampers, then you had a system that was cut corners on ; the rooms farthest away from the blower will starve for air while the ones closest will get too much .

[ilbebauck]

de quoted text -

Its possible he requires a 5 ton system for his 1700 sq ft. if he lives in south Florida or southern Arizona and has little or no shade, alot of glass facing south, and minimal attic insulation. But hes going to need more than 7 supply registers to get the 2000 cfm out assuming `14x6 " registers (or smaller) . The return is also going to be a factor too as they most likely undersized that too. I see it all the time even in very expensive homes over $1 million . Its amazing what they get away with.

[ilbebauck]

On Jul 23, 6:52=A0am, Smitty Two wrote:ui

1. Because the room size (load) might require more airflow than what one register can deliver . 2. Because the room may be configured to where a single register wont distribute the air well enough . 3. Because the heat gain of the room might require multiple registers to deliver enough conditioned air to satisfy it. 4. Because one register might be too noisy if youre trying to push too much cfm thru it . 5. Too be sure youre moving enough air over the cooling coil to prevent freezeup especially during low load on the system.

[trader4]

So that the system heats and cools evenly. I just took a quick count of my house. I have 22 outlet vents. That's in a house that's 3100 sq ft, 4.5 ton AC. Seems about right to me. So for a house of

1700 sq ft, I'd expect around 12, not 7. Several of my rooms have 3 registers each. Every house I've ever lived in, including small single story ranch, have had at least some rooms with more than one vent.

Having 5 tons of AC with 7 vents just ain't Kosher.

[ilbebauck]

Return air configurations come in a variety of ways. 1. There is the ONE huge central return air grille often put in the second floor ceiling at the top of the stairs which is ducted back to the Air Handler. 2. There are TWO large return air grilles...one on the first floor ceiling and one on the second floor ceiling...both ducted. 3. A number of return air grilles placed high on the inside walls of both downstairs and upstairs and ducted back. 4. A return air grille in EACH room (except the bathroom) and ducted back. In order to know if the return air duct system was properly sized, youd have to have a knowledgeable professional come out to determine the size(s) and how much each return air duct can handle in cfm airflow. I can tell you this fairly accurate rule of thumb : The return air duct area feeding a 2000 cfm (5 ton a/c system) such as yours, requires One 18" dia. round duct or Two 14" dia. round ducts (or equivalent retangular ducts in sq. inch area) . Hope this gives you a bit more insight. In addition, you need to make sure your air filter(s) , cooling coil surface , blower wheel ...are all very clean in addition to the system being full on freon and working properly . Ideally, you should bite the bullet and have a professional come out and thoroughly examine the entire system and equipment. Regards.

[Ed Pawlowski]

But the number of vents means nothing. The size of the vents and ducts to them is what is important. There are units that large operating perfectly with only one or two vents too. Big ones.