HVAC Question - How much is enough?

We are looking to replace our 4 ton a/c unit in our house. Here are the stats on the house:
1. 2200 sq ft house 2. Three attics (front, back, middle) 3. Insulation = shredded newspaper treated with flame retardant.     a. The insulation is crumbling into dust. 4. Windows on house are single paned, aluminum CHEAP windows     a. The kind used in houses in the 1960s. 5. House was built in 1964. 6. Windows are chaulked but still leak tremendous amounts of heat/cool because, as I said, they are cheap windows. (You can feel the heat radiating off of them right now.)
Questions:
1. The a/c guy only wants to replace our 4 ton unit with another 4 ton unit. His reason is that technology has advanced and a new 4 ton unit will work better and cool better. Question: Will it? 2. Our contention is that (as the a/c guy explained to us) 2200sqft/500 = 4.4 tons of a/c. Question: If the equation comes out to be 4.4 tons - shouldn't the a/c guy go to at least 4.5 tons? 3. Given all of the bad problems with the house (and yes - we should reinsulate the house and get better windows - but I'm unemployed and we can barely afford to get the new a/c) - Question: Should the a/c guy blindly follow the specs he is quoting or should he realize that, given the condition of the house, he should increase the number of tons to compensate for the conditions?
Our outlook is that, given the conditions of the house, a larger unit would work better. We might have to pay more for it but at least, here in Houston, Texas - we would stay cool inside while the temperature outside rises to over 100 degrees.
Please give me some feed back on this because we would like to be able to present some valid arguments to the a/c person (other than what we've already pointed out to this guy) on exactly why this blue book's equations can not be strictly adhered to and instead need to be modified to our needs.
Thanks in advance for any help you can give.
Mark Manning
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Please back it up, half a step. What's wrong with the old system? I've fixed systems that other people thought were forever dead. That said, an old sytem about to die seldom performs to the name plate rating. So, taking out a wimpy, pathetic, under performing system that says "4 tons" on the name plate, replace it with one really doing 4 tons. Might be major change.
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The old system was originally put in pre 1996 (when we bought the house). We replaced the heat exchanger (outside unit) in 1998 because we found out that it was a 2 ton unit while the inside unit was a 4 ton unit. So the outside unit would freeze up/trip breaker all the time. The house came with the a/c unit and duct work all insulated (but not the attic itself). However, the house (and unit) has gone through a lot and the a/c now only cools to approximately 15 degrees below the outside temperature. At over 100 degrees temperatures - we are overheating inside of our own house (which is one of the reasons I'm answering so late).
While it is true a new 4 ton unit might work - I'm used to working in heavily a/c'd areas (computer rooms) which range between 60 degrees and 65 degrees. Around 75 degrees I just begin to melt. Before I was married - all of the apartments I lived in could keep the temperature down. This house is the first house I've ever bought and the a/c, when we bought it, seemed like it could handle the heat. Unfortunately - that was late fall when we bought the house (in 1996). I should have waited to buy it until summer time. Then I would have seen that the a/c could not handle the house.
I think we actually would do better with two separate units. One for the downstairs and one for the upstairs.
Stormin Mormon wrote:

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Simulacrom1 wrote:

Hey - Mark Manning:
1. The only method to determine the correct needs of a structure is to have LOAD ENGINEERING performed by an LICENSED HVAC contractor or a LICENSED P.E. -
2. It is likely that your existing system leaks air into other spaces besides the conditioned space [your living quarters.] Most systems installed years ago leak at a rate of about 30% or more. [I just performed a duct test on two homes this week, the 4-ton leaked over 400 cfm and the 3- ton leaked just under 300 cfm.] Just think of the savings if that cooled / heated air was put where it belongs instead of in the attic. Several states currently required duct testing as part of the permitting process.
3. Replacement equipment is more efficient than the older equipment and can reduce your monthly utility cost. It has been determined that the higher efficiency equipment will pay for itself through energy / utility savings. Most utility's offer rebates reducing your initial costs.
4. Attic and wall insulation plays an important role in reducing your utility costs and can increase your family's comfort. Have that newspaper removed from the attic [which by the way is a fire hazard although you believe it has flame retardant] and have insulation bates either laved or blown in. That alone will reduce your utility costs annually. And you might be able to get the local utility to help pay a major portion of the costs.
--
Zyp



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1. The guy is (as far as I know) a licensed HVAC person. But he is dismissing the condition of the windows and attic. Glossing over those problems if you will.
2. As I said - we can barely afford the new a/c unit. There are other problems as well. Allisan flooded our house and black mold got into the ducts as well - which is also a big incentive to replace the entire a/c unit. (I can send/post a picture of one of our vents which has black mold growing around the vent.) So our choice is - insulate the attic and have black mold and bad a/c or change out the a/c, get rid of the mold, and have great cooling. We want the latter.
3. I'll have to call Reliant and see what they say about this.
4. Yeah, I know it is a fire hazard. When Allisan came through we got rid of it downstairs but then the contractor walked on us and took all of the money. So we never got the upstairs re-insulated. Since then we've been hit by one problem after another. (Funerals, extraneous bills, IRS saying we owed them $10,000.00 because a company I had worked for did NOT pay the taxes on the money I had made even though they DID take it out of my paycheck, and so on.) So we are pretty much piss-poor. So our choices are: A)Get a new a/c and forget about the need for new insulation, or B)Get new insulation and forget about the a/c. We can only do one or the other - not both. So we are going with option A.
What about the equation stuff? Even a qualified HVAC person will do some equations. The thing is - do they have to blindly follow them? Or can they adjust them according to the situation?
Thanks! :-)
Zyp wrote:

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wrote:
I am not a HVAC contractor. Just another homeowner trying to learn more about HVAC in order to make good decisions. So do your own thinking about my recommendations.
I would go with the 4 ton unit. My reasoning is that you can do some things to improve the house yourself. I would start by taking a sample of the newspaper insulation outside and see if it will burn.
Next add insulation to your attic. The cost is likely to be a little as the difference between the 4 ton and the 5 ton air conditioner.
Buy some caulk and caulk everywhere. $20 for caulk will probably reduce you electric bill by $20 over the air conditioning season. Ditto for weather stripping the doors and windows.
Buy some of those plastic sheets to insulate your windows. They tape around the window and then you use a hair dryer to shrink them so there are no wrinkles.
Switch to compact flouescent lamps. They use a lot less power and will reduce the amount of air conditioning you need. Check to see if there are other things that add heat to the inside of the house. For example your how water heater may be inside the house. You might be able to add insulation to it.
Ask your HVAC guy about more things you can do fairly cheaply. Maybe better attic venting.
Think about buying a window unit just for the bedroom so you can not air condition the whole house in order to get some sleep. Think about ceiling fans and just ordinary fans. I use a ordinary box fan bought at a garage sale for a couple of bucks set in the window to push out the hot air in the second story in the evenings. It brings the temperature down to what it is outside. Might not be any help in Houston during the summer, but would save running the air conditioner as much in te Spring and Fall.
Dan
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snipped-for-privacy@krl.org wrote:

Dan, That was excellent advice! http://www.udarrell.com/check_ac.html
- udarrell
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several things: 1. Zyp is right! all duct joints should be checked for leaks, especially after hurricane damage. 2. don't rely on one contractor's input, get several inputs. 3. were the flooded walls gutted? i hope u removed any wet insulation. if walls were opened or are still bare, u need a heat balance sheet performed on the house. 4. are your ducts in the walls, attic, under the floor, where? how high did the floodwater get? 5. with insufficient funds to work with, a new AC and a new duct system will only partially solve your temp problem (u need major insulation and window improvements) 6. pres's new ARRA (american recovery and reinvestment tax act of 2009) allows a tax credit 30% of product cost (up to $1500) for energy improvements. 7. i know u probably cannot afford it, but u should talk to a cpa or tax attorney about the irs issue (i know a guy who (though an attorney) got the irs to re-think his unusual situation). isn't there such a thing as arbitration?
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Simulacrom1 wrote:

Hi Mark,
If you can get a loan or get some Fed., weatherization money, reduce the heat-gain as much as possible!
Plug all the air infiltration places; it can be half of the heat-load. The ductwork & airflow is the next gigantic loss of cooling BTUH of your system! The install is critically important - READ & Learn what you need to know!
Make hard-copies - Print the pages linked below.
Get it all done right
On 2200-sf you ought to be able to get down to a 3.5-Ton unit. It would work with the 4-Ton coil, - if they are a similar SEER.
There is a lot to know & learn: http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html - udarrell
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Liberals are good at spending other peoples money, and increasing dependance on government. What was that, about not being a liberal?
So, you support the Constitution. Where, in there, does it say that the Fed can take my money by force, and spend it on fixing someone else's house?
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Christopher A. Young
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Stormin Mormon wrote:

It was Free Market Capitalism that brought down the economy, not govt regulation, - but a lack of effective enforced govt regs. You can't win either way, because in your mind you lose either way. If we want a future we'll have to be willing to share, work together & sacrifice. - udarrell
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