Does 2 plus 3 equal 5 tons in air conditioning for a new home???

[mrbluesky]

I'm having a new home built south of San Antonio, TX. The builder surprised me by installing two a/c's without asking what I thought or wanted. I had thought he would install a 5 ton as that was what was being used in the same floor plan built by another builder. He said 2x3 was better than the 5 alone. Physically they are mounted in the attic on each end of the house: east 3- west 2. They are suppose to be heat pumps with electrostatic filters. The manufacturer is Ruud from Ft. Smith AR. I called them for help, they said they don't test their units that way, so they won't comment on whether the 2 and 3 are as good as the 5 alone. Of course builder swears two are better than one. I cannot find anyone that can comment. A a/c rep in Dallas said he needed more than 5 so he went with a 3 and 3 and that worked for him. I cannot find any information on this matter. Please advise.

[NoNickName]

If they aren't inverter driven, than 2 is better than 1, in terms of energy saving.
Also air distribution is supposed to be better, because it would be more evenly distributed.

[Tiger 05]

At least if one breaks down you'll always have one part of the house conditioned.
But knowing a/c they will both have a dummy spit at the same time.
Seriously if his done it and its not an issue its a good idea for the reasons stated by no nick name

[frank]

How can a BUILDER decide that 5 ton or 2 + 3 ton is sufficient. ?

Why hasn't a specialist been consulted.

Would you trust the DECORATOR to tell you how to build the foundations??? :eek:

[Larry2]

I think that two systems are better than one large one because you have redundancy. That way you won't be totally without of cooling when one develops a problem. However, the sizing of the two units should be professionally calculated. Without professional calculations backing the design, you may end up with problems like I have, with one system too small for it's task and no way to get the excess cooling capacity of the other system where needed.

You can't compare another home having the same floor plan with yours. It's design may have been guess and bygolly, so how do you know it's correct? It could be too large or too small. Too large is an important mistake too, leaving the home without adequate dehumidication.

The orientation of major glass makes a big difference. The rooms with high solar gain will need additional cooling and therefore additional registers for air flow and proportionally more of the system dedicated. The ventilation and cooling is an engineering problem, not something to be winged by a builder using "rules of thumb".

You would be wise to invest a few hundred dollars now and have a disinterested HVAC engineering professional calculate heating and especially cooling loads for your specific home taking into account the orientation of major glass areas with respect to South and West. If your systems proves unsatisfactory later on, it becomes a pissing contest as to weather the house is comfortable and properly load balanced through out your home. What if the size is wrong and where you need 3 tons you have two and where you need only 2 tons the 3 is installed? Then you are one ton shy because 2+2=4. Find someone who will run the calculations and provide you with a copy of his work justifying his figures.

[mrbluesky]

Thanks for replies, especially Larry2, this is a real life situation-I had expected to get Trane, builder shot me down by having his a/c man put in Ruud and then expained that he could not get the 5 up to seer 14, but 2 + 3 was better all the way around, for all the reasons. Mainly after talking to several dealers and experts it boiled down to money, 2 + 3 was cheaper than the 5. These are supposed to be heat pumps with variable speed handlers and electrostatic filters. He knew one of my reasons for wanting the Trane is that their elec. filter is the best on the market. I can not even find out anything about the Ruud. I actually have talked to Ruud at the plant, they don't even test their units against each other: such as, 2 + 3 compared to 5 ton, same seer rating, same level of model, not cheap vs expensive. I have not found any engineer willing to say 2 + 3 equals 5. The best answer was from a Dallas dealer who said he had the same problem so he insisted on 3 + 3 and it turned out a smart decision, Dallas has been having a string of hot days, it's funny now the county is giving away window units, no one is thinking downstream about power load and capacity. I had really wanted geothermal, but the builder wouldn't even consider it. I'm just gonna have to fix it after I move in, I think I picked the wrong builder.

[US Iceman]

...but the builder wouldn't even consider it.


I think this then begs the question of: how much control does the builder have? Were there contractual obligations as to what you wanted and what your costs were based on?

It does sound as if the builder has pulled a fast on. My question is, was any of this in writing?

I had a lot of similar problems with my builder. Not so much an the AC side of things, but more contractual obligations. After closing he decided to choose which ones he would do, and which ones he had no plan to address.

When he was forced to read the contracts closely, he certainly did not like to ante up the cost difference between what he wanted, and what he was legally obligated to do.

My feeling about builders is similar to used car salesman. Not too high on the personal integrity points.

I think you have some very good points here from the other RE members. If this appears to be headed in a legal direction, start early on your homework and keep your cards close to you. Put the other guy on the defensive.

Best of luck to you...

[Larry2]

I don't know what your original duct routing was planned to be, but you're taking a terrible efficiency hit with them in the attic. I'm measuring around 20% lost in my suppy ducts alone during this summer heat. That's 20% lost to the utility for every day it is switched on. I wish I had thought about the ducts for my home before I allowed the HVAC contractor to put stuff up there in hot/cold unprotected space. I paid for SEER 13 units in 1993, R19 walls, R30 ceilings, housewrap, low-e glass and high end windows that control infiltration. All this was defeated by leaving the HVAC gear up in that space. I can just imagine the temperatures in your attic in Dallas.

This would be a good time to have your contract reviewed by an attorney, unless you already know you don't have any recourse and the materials are not specified. The point at which the finishing touches go on the home is where the greatest room for builder skimping and fanageling comes into play. If you accept this HVAC substitution to the tune of several thousand additional builder's profit, why wouldn't he subsititute low grade flooring, cheap plumbing fixtures, cruddy landscaping and such during completion? Plumbing fixtures range from $20 to hundreds for one faucet. "Oak" floors have a wide range of grades and prices that vary over three to one. Tile or granite selection pricing will range thousands between lowest and highest end stuff. If you accept this substitution without demanding correction or compensation , he has your tacit permission to put lower end goods everywhere as the job progresses.

I share Iceman's disdain for builders. I contracted with a builder for time, materials and markup and had to fire him the day he was digging the foundation. He broke ground at 7AM when I visited and when I visited at lunchtime the roof of the loader was below the top of the hole. He dug the hole two and a half foot too deep! I had to make my foundation walls ten foot tall to get the house back up out of the ground. That mistake cost me an extra $10,000. It could have cost me more if I had not fired the incompetant. This man had scheduled masons to build a ten foot tall cinder block wall that would have failed code and ordered demolished. I had several other builders either bid 50% excess or "no-bid" when I presented specifications for materials and workmanship.

I wish you the best. This is a horrible, stressful time. No one is looking out for you, not even the building inspectors. We have homes built on fill dirt here that later had to be torn down. "Inspected from the comfort of the inpection office" is what was later determined in court. Other homes were built nearby just last year, five foot from the street where the county that signed off now wonders how it happened. Then they hit the builder with a "stop work order" after homeowners have moved in! Someone got paid to allow that extra housing density. I hope they never have a fire because the fire truck's ain't getting in.

Hire some professionals to look out for your own interests. Have a qualified architect look over the job during completion before it's closed in. Have an electrician check out the wiring to codes and have an HVAC man verify your systems are as contracted, at least in terms of performance. This is probably the largest expense of your life. Don't get taken.