As I am sure a lot of you have been reading about my complaints and ordeal regarding terribly insufficient cooling capabilities of my home’s 2nd floor system, I have to wonder what might the alternatives be instead of paying $5,000 for a replacement system.
Right now it was determined by some that the 2nd floor system was mistakenly installed with a 2-ton system, and the first floor with a 3-ton system. The 2nd floor vs 1st SqFt is 1230 vs 1326, but 379 SqFt is two-story elevations open to the second floor. For heat loading, this is like 1609 SqFt 2nd floor and 947 SqFt 1st floor.
That’s a 3-ton basement located system for 947 cooling SqFt, and a 2-ton attic located system for 1609 cooling SqFt. Obviously this is nuts. Even without migrating SqFt in the heat load cooling determination the 1st floor isn’t 50% larger in cooling SqFt than the 2nd floor.
So, to get beyond the peak warm days (weeks, months) I wonder if an alternative is available than simply baring the expense of replacing the 2-ton system with a 3-ton system for $5,000. The two rooms that need the cooling the most are two bedrooms converted to ‘other uses’.
These two bedrooms house a home theater (nice analog CRT projector, amplifiers, receivers and other electronics), which is above the garage, and a computer room with multiple computers, printers, CRT monitors, and other computing and network equipment. These two other bedrooms get a lot of use by the wife and I, and I do a lot of my free time in them (hermit).
So, why can’t a targeted solution for just these two rooms be conducted? I am in an HOA community, and the idea of installing window units would certainly get me a lot of hot air (from the HOA board responding to neighbor complaints). I can understand this, and do not wish to ugly the street appearance, either.
So, why can a 1 or 1.5-ton AC-only unit be installed into the attic, with their own dedicated supply and return ducts to these two rooms? I am not suggesting altering the existing system (eliminating their original ducts), but adding to them on a second ‘booster’ system?
Replies
Your existing unit is fighting to cool because of heat gain. Sure one way is to add more "power" in the form of bigger cooling but it will never pay for its self and odds on be just as ineffective as what you have now.
I suggest you work it the other way and look to reduce the heat gain. Add extra insulation to the outer walls of the rooms, install more insulation in the attic, if no attic add to the roof deck and re-roof.
Use a foam type of insulation for this as you are looking at running costs and comfort. Find the gaps and air leaks and close them up. (outer wall sockets etc.)
What type of lighting do you have, are the bulbs very bright and could you drop the wattage 10-20% with little effect?
Nuke, been reading your other threads re: HVAC and was wondering the same as Nigel. Why so much heat gain? Why so much heat retained through the night when OAT (outside air temps) drop. Have you already checked into how the house is inuslated? Not many options for research of this and fewer for fixing it.
I cannot answer this question. I only know that no HVAC contractor would ever consider coming over to my house in the mid to late afternoon and have an experience for themselves. They always want to show up at the crack of dawn, the coolest part of the day, and when the system is performing at its best.
I'd buy dinner for the guy that shows up at, say, 4-6PM to take on the experience. Of course, I may need to call 911 to pull his limpless body from the attic. :)
Yeah, but inuslation of the house is outside the realm of HVAC.
Talking about insulation is not on topic with "Add to an existing HVAC system". I asked about adding a booster AC system to target two rooms and the response had nothing to do with adding a supplemental AC system.
HVAC contractors are scred of my house at 5PM. :)
Edited 8/18/2007 9:56 am ET by Nuke
bunch of other issues could be masked by by focusing solely on the HVAC. HVAC is calculalted on the assumption that the house is insulated properly. HVAC calcs also figure limited air leakeage to limit the loss. IMHO a lot of houses in GA are underinsulated especially in the attics. You already know that your house was built by the cheapest bidder for all subs, HVAC, insulation, windows. Who says the last 2 were done correctly?
Agreed. I ave one of those POS houses that Georgia found 100% perfectly fine to issue a COO. COO inspections are five minutes at best, and not at all if you buy them lunch. :)
H3ll, I've had one 'southerner' tell me insulation ain't needed as it only gets cold here for a few weeks out of the year. The epitome of his ilk. Heck, my basement is better insulation, but then again I did the work, I didn't strive for the lowest bid, and I knew the benefits of insulation was year round.
Still, i think it would be cheaper if I paid someone's gas money and had them drive their Icynene rig 800-1000 miles to me as the prices locally are twice that of Chicage or the NE. Yessir, its considered a luxury down here.
Still, this does not answer the question posed. Can a small AC-only system be installed, with their own supply/return registers to boost the cooling capacity of two rooms? How would this be any different than the when someone on FHB tells me to stick a window unit in (HOA no can do).
I mentioned the possibility of getting a supliment system way, way back. One such would be a mini-split ductless.But first you need to know what you need.You said that you had Hvac-Calc.What does it show, ROOM BY ROOM in terms of load? I think it also shows air flows needed.Then how well does that match up to what you have?Possibly you only need to do this to one of the rooms and then redirect the extra air into the other problem room.BUT YOU NEED YOUR NUMBERS..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I have thought about this, but didn't want to introduce the idea into my original post. I see split ductless systems for fairly reasonable prices.
Anyway, here is a good excuse for a supplemental system. My 2nd floor system is no longer working. The blower is humming along. The condenser fan is spinning its heart out. But no heat is being removed from the 2nd floor, and no heat is being felt coming off the condenser. This is in opposite to what I observe with the 1st floor system (its humming and blowing along, removing heat from the floor, and blowing heat at the condenser unit).
So, a supplemental system could also be used for limited backup if the primary fails. Gee, I could have benefited from this tonight. :)
Nuke,Can you keep all this in one thread? You've got about 8 threads on this subject, and important information keeps getting missed.We don't mind if a thread gets really long, heck there's a couple of threads with over a thousand posts.SamT
If you had R-50 or 60 in the attic, with all gaps and cracks in the framing sealed, and still have problems then I'd consider further plans. It's crazy how cheap insulation is and how dramatically it can effect heat loads.
You also might not need extra capacity overall, but better circulation of the air. Booster fans can help undersized ducts supply better. A few small returns may be all that's needed in the hotter rooms to turn them around.
Totally unconnected to the hvac system, but sometimes a huge cost saver are a few small flex ducts to circulate air between warmer and cooler rooms. With a remote fan they can be essentially silent.
There's no way to get around the need for more ducts as most systems are designed with the absolute minimum and a system can be ramped up with better supply and returns. Keep in mind that larger returns in hot rooms will draw more of the hot air out of the room and that air has to be replaced--with the cooler air. I've become a huge believer in the power of good returns for upper floor rooms.
Beer was created so carpenters wouldn't rule the world.
I just wanted to second what Idahojohn said. I worked remodeling small hospitals and the inspector had the HVAC guy measure each supply to make sure it was moving enough air. I'm not an HVAC guy. Just something I observed.
Many systems are out of balance and are never checked. He used a device like a rectangular umbrella that he put over the register. It had a ball in a tube that the air had to lift to a certain level in order to pass.
They also used metal ductwork ( trunks?) and limited the flexible duct to the registers to 10' or something. The flex ducts have high static pressure and in residential work they are kinked a lot. So no matter how much you partially close registers in other rooms in order to try and pump more air into the rooms you want to cool, the ducts just have to much resistance.
My current house has a room that is upstairs and faces the south west. It is warm every afternoon/evening. I think it gets gain from a few sources that just add up. It doesn't take much. I'm going to put an overhead fan in it. ( cheap)
In answer to the tail end question you asked. Some companies make a split system intended to do what you are asking for. I think Samsung is one.
It consists of an indoor unit about 30" long, 12" high, 5" deep. Pipes for the coolant are ran to an outdoor unit. This will give you the local cooling setup you need. If the original system is tough to "improve" then this might be the way to go.
Check out this link for ideas http://www.air-conditioners-america.com/ed_SplitAC-CompareBedroom.asp