Well, that's my current dilema. Let me try and explain...
Bought this house last year, moved in in July. 2 story house, approx. 2200 sq. ft, 3.5 ton Bryant central heat (gas) and air, house built in 2000, so 5 years old. 2 bedrooms, 1 full bath, half bath, and 400+ sq. ft bonus room above the 2 car garage on the second story. The problem is that the upstairs bedrooms never really cool. The unit can literally run all day and freeze the downstairs out, but these bedrooms get minimal airflow from their vents. In TN so in case you don't know it can get 90+ easy and always high humidity in the summer and fall. Last year I just bought a couple of window units for the bedrooms figuring that would be a bandaid until I decided what to do with the central AC.
So I finally started calling around to some HVAC companies for some suggestions and quotes on getting this problem solved. Had the first guy out this afternoon and he suggested zoning the system. Real nice guy, and he did a thorough job of explaining everything, but I'm still not sold. He'd replace the thermostat downstairs w/ a new digital one, and then put a new digital thermo. in the upstairs hallway. The one bedroom that really doesn't cool is on the side of the house where the unit is. He explained that the duct work runs under the house to the other side, then up, and then back down to the upstairs side the unit is on. This bedroom that never cools is the last vent on the chain. Literally, you can feel no airflow in this room's vent. I guess my thought is if the unit was running, and it was also running downstairs (i.e. the damper was open to the downstairs vents) then wouldn't I still be facing the same problem? Is the benefit that I can set the downstairs thermostat to a higher temp so it doesn't run much, then set the upstairs to a cooler temp to make it (in theory) force all of the air from the unit upstairs (and hopefully force air to this last vent) and then cold air falls, so that would help cool the downstairs?
I know I'm probably babbling here. I guess I just wanted to get a general consensus on how people here feel about zoning. I thought my only option was to put in a second unit for the upstairs (which he said would take on another $3500 to the price) and that he didn't recommend it. He said that would cause problems with the 3.5 ton unit now cycling on and off too much because it's trying to cool way less area than it's designed for. I'm just afraid I'm going to drop ~$2500 to zone a system and it not work.
Thanks in advance!
Here's my opinion, take it for what you will.
Zones systems are really nice when they are designed for a certain application (ie huge houses, office areas ect). Using a zone as a bandaid to fix and airflow problem might work, but it's still a bandaid.
2 units are great in a 2 story house... but it costs more. Also with this being an old home (not in the process of building), I'd avoid this simply for the fact you'd have one unit thats really over sized and the added expense.
To me it really sounds like the ducting needs to be re-worked or balanced. Unfortunately this isn't the easiest thing to do, so it will take a contractor with some good experience designing/trouble shooting duct systems. If the duct is easy to access, and there's enough room to make size changes as needed, or install dampers in other areas of the duct to push the flow to where it's needed, then this is the best answer (again, in my opinion). On the really extreme days, both hot and cold, you may have to run the fan all the time to help keep the air circulating, but thats not a big problem.
Are there any return runs in the problem areas? If not, this could also help fix the problem aswell.
Thanks for the reply!
Duct access, unfortunately, is not going to be easy. The crawl space under the house is only about 2 feet high, and upstairs in the attic probably about the same, maybe 3 feet in some areas where the roof peaks.
The ducts already have manual dampers installed. In fact, when we moved in, the couple that sold us the house (the original owners) had actually closed the damper completely on the duct leading to the vent in the master bedroom downstairs. The first contractor we had out when we moved in discovered that when we complained of no airflow to that room.
The only return in the house is downstairs near the thermostat. Is that what you're asking about?
So would I be correct in saying that it sounds like the only true way to resolve this issue would be to remove the 3.5 ton unit, and replace it with 2 that are sized appropriately for the two floors? I can only imagine what that would cost! I've got a guy coming out tomorrow, and then another one Thursday, so I'm going to see what they say before making any decisions. Heck, I may just say forget it and use window units again this summer. Not the route I'd like to go, but I also can't spend 10 grand on new units.
Two units may not solve your problems. I had a zoning system set up in the old house, then moved to a new one, with two units - much better units - my life is miserable now, and it's just a matter of time until I install the zoning system again.
With multiple units, all you have is the temperature control at the points where the thermostats are installed. The rest of the house will be at the mercy of air distribution. In other words, unless you fix the root cause (ductwork problems), you'll be suffering from the same problem.
Fix the ductwork, you may not even think about zoning again (though I should tell you, life is a dream when you have it
When you think about zoning systems, think of each room as a zone. The more zones you have, the better control you can achieve - but only if you go with modulating dampers.
Google is your friend - look up "temperature zoning".
I guess the easiest solution to your problem is neither. A balancing damper might help but would have to be adjusted seasonally. Far better than window units. Ultimately you have a duct issue but as long as the system has proper airflow some balancing might help.
To reinforce what Amick and Doc said: You MUST fix the ducts. A zone system put on top of undersized ducts will cause as many problems as it solves. The ducts to your upstairs bedrooms are obviously undersized for your summer needs. A zone system would try to force literally all the system's air through the upstairs’ undersized ducts. As a result you'd have way less air through the equipment than they're designed for and equipment failure would eventually result. If the contractors talked about a bypass duct as a solution to maintaining airflow, don't be fooled. Bypass ducts are a piss poor solution at best and NEVER result in good overall performance.
I'd suggest getting the ducts fixed and balanced for summer operation. In other words, have the ducts sized so that they deliver enough cool air upstairs without the downstairs duct being dampened down. Then you can either use hand operated dampers to choke the upstairs in the winter or you can put a zone system in to do it automatically.
Thanks everyone for your replies!!
I guess my question (and point of frustration!) is how can you all agree that it's a duct work problem, but none of the people that came out and have actually looked at the setup (at least 3 last year and so far 1 this year) have even approached that as a problem? Am I just getting people out that either don't know what they're doing and/or are trying to sell me another solution that may not even work? I mean, I've explained everything to them exactly like I've explained in this post, and they've looked at the unit, duct work, measured room size, etc... and none of them have even mentioned ductwork. That's just frustrating.
Irascible: You hit the nail on the hit regarding the bypass duct. The guy that came out yesterday mentioned that would be one of additions if I chose to go with zoning.
Too funny. You can't imagine how classic a scenario this is. Think of it this way:
1) Ducts are a pain to deal with.
2) Ducts are high labor and fairly low materials cost items. As such they take man hours that an often understaffed shop doesn't have and they don't have the high margins that equipment sales have.
3) To really make a good and specific recommendation on your ducts would require that someone crawl around and see what you have. The salesman doesn't want to do that to be sure.
4) The equipment upgrades will likely make some improvement - perhaps even enough to make you happy. And problems to the equipment may happen far enough down the road that you don't affix blame to the zone system for your future troubles.
5) A lot of salesmen and even technicians don't even understand how to design proper duct systems. Their entire focus is on fixing and replacing the box.
Given all that, there's little motivation to really want to deal with ducts.
The bypass damper is considered legitimate by the zone system makers so long as everything else is in line. But what happens is that a huge percentage of your conditioned air loops right back around and gets re-cooled (or re-heated in winter). As a result the air temperature coming out of the system drops like a rock. Often times the system will run less than five minutes before it will shut the compressor off. There's often a temperature sensor that protects the system by not letting temps get too low or too high. The problem is that the typical zone system relies way too heavily on the bypass damper. As a result the temps drop fast and the equipment cycles off and on, off and on. That's not good for your compressor. But it can often take that abuse for years, so you're none the wiser. Ducts are supposed to be oversized by 25% when you have zoning to allow the open zone(s) to take a good percentage of the air lost to the closed zone(s). That eliminates a lot of the bypassing. As we already know, yours are undersized even for a non-zoned system.
There are homeowners who get a ton of bids cause they’re cheap suckers looking for something for nothing. Then there are the homeowners who get a ton of bids looking for that one unusually competent tradesman. Maybe you’ll be in that second category and get a bunch more bids until you find a company that addresses all of your problems.
Irascible, thanks for that explanation!
I found it funny, and ironic, that you mention how the bypass system might make the compressor cut on and off too often. The guy that was out yesterday recommended against adding a second unit for the upstairs because he said it would make the then oversized unit for downstairs cut on and off too often. To hear that his proposed solution of zoning might have the same effect makes me wonder if he really knew what he was talking about. More and more I'm starting to feel like he was just trying to sale me a solution that he doesn't understand, and that may not even work, and could potentially cause me problems down the road.
I certainly like to think I fall into the second category of home owner you mentioned. I knew solving this problem would not be cheap, and while I would certainly rather spend the money on something else, I have no problem forking over the cash for a cooling solution that will actually work. As I mentioned, I have another company coming out today, and another one tomorrow. Should I mention what we've discussed here, and ask that the duct work be inspected? Are there companies that specialize in that, or would I still be contacting HVAC companies like I've been doing?
And the plot thickens...
OK, so I had another guy out here today, and here is what he said. Without me mentioning anything, he thought I might be looking at a ductwork issue...which is what all of you guys have mentioned. He said it could be something as simple as some tape being loose, or something like that. He also mentioned that before he does anything, or even attempts to give a quote, he would like to come back and do a load balance test. He said he was going to get the lot number of the house, and check the plans to see exactly what was put in before he did that, and that he would call me back tomorrow. Is this routine, or am I being fed a line? Sure, the testing of the duct work and the load balancing would run me about $125 he said, but if that will A) confirm the condition of the ductwork and B) balance the unit, then it seems like I would at least be able to get a quote on a solution that would correct the problem I'm having. Do you all agree?
I have to admit that I get a better feeling about this guy. Reading through this forum and others, it looks like a load balance test is recommended before any changes are ever done to a system. Is that correct? Sorry to keep beating this topic to death, but I just want to be a least somewhat of an informed consumer and try and learn something before I go wasting my money on something I know nothing about!!
Whether or not you should ask the contractor up front I'll leave to you. I'm no good at what you might call "contractor psychology". If you ask up front, they may tell you what you want to hear. If you don't and they tell you what you're looking for anyway, then I think that might be more legit.
Call me ignorant, but I'm not sure what is meant by load balance test. A room by room heat load calculation would tell you how much air each room needs. Airflow testing is done by people that sometimes call themselves air balancers. So perhaps he's doing a load calc and/or is measuring how much air is currently being delivered to each room. Both a load calc and a measure of the current airflow would be useful. So if you feel comfortable with this guy then pay the money. Since you're paying, the information he produces will be yours to use as you please (including giving that info to other contractors for competitive purposes).
The most fantastic system I ever put in was for a guy that I first did a heat load calculation for as well as mapping of all the existing ducts before he ever got a bid from me. In that instance my agreement with him was that if I got the job then the heat load calc would be included. If not, he was going to pay me considerably more than what you're going to for the heat load calc and survey.
OK, I guess I swapped some terminology. A load calculation is what he said. I had load balancing on my mind, which is a term I use in my line of computer work.
I still have one more guy that will be out tomorrow, so I'm going to wait and see what he says. So far I'm leaning towards this guy from today. I guess I like the fact that he wasn't trying to sell me on something before he actually understood the problem, and that he wanted to actually do testing before offering a solution...which is the feeling I got from the first person that looked at it yesterday.
So, is everyone sick of hearing from me yet??
One last question regarding this if no one minds. I had the third (and hopefully final) guy out today. After I described the problem, just like I did for the other two, and after he took a quick look in the attic, crawlspace, and felt the air from the vents, he simply said, "Yep, it's a ductwork and balance issue." This is the same diagnosis the guy yesterday gave. Today's guy even went as far as saying zoning would probably not help this situation one bit. He pointed out that with some vents blasting air, and others barely having any coming out, he needed to balance it. He also pointed out several spots in the attic ductwork that had come loose, and had "a lot of air just leaking into the attic" that would he would need to fix before balancing. Now here's my dilemma...the price! I'm not sure if it's OK to discuss prices here or not, so here goes.
Yesterday's quote was "about 2 hours, so about $125 service charge." Today's quote, a flat fee of $600....doesn't matter if it "takes 2 hours or 6 hours" to get it right. Is a price difference of that much for a job (that seems small) like this to be expected between companies??
Also, is it OK to call the guy from yesterday, saying "OK, I had someone else look at the system today, and he confirmed the same problem you did...ductwork and airflow. He said $600 flat to make sure all of the ductwork was taped and sealed, and then doing an air balance at each vent. Why the heck is your quote so low?" Would that be considered rude? Understand I'm not trying to pit these guys against one another, I'm just trying to understand why one would be 1/6 of the price for quoting me the same work. Perhaps I did misunderstand the guy yesterday, so I'm going to call him in the morning and ask him to tell me exactly what he would do, and if there would be any extra involved. It just shouldn't be this dang hard to get this fixed.
Lastly, I do appreciate all of the insight and responses you people have given. I've learned a lot more about how these systems work than I ever expected to!