Central air problem

[John]

Hope this is the right forum where someone can shed some light on this problem I have. I have a 1200 sq. ft home, well insulated all around. The furnace is about 25 yrs old(meyers), the AC(2 ton trane)about 8 yrs old. On a hot day, my AC runs all day and well into the night and never gets the house down under 80 until late in the evenings. I measured the temp at one of the registers and it was about 52 degrees and the temp at the floor register for the return air was about 73, but the house temp at the controls was over 80. I had it checked by a tech. who said everything looks good on the AC unit but thinks the return air duct is too small(10"x18")and that the belt driven blower is not able to push enough air. The house did not originally have AC. There's about 8 registers throughout the house. He suggested enlarging the return duct to about 10"x25" and would need to update the blower and motor which realistically means replacing the furnace which I don't mind doing since it's past it's expected life and is inefficient. I had several heat/ac sales guys come through the house and had several opinions - few of which suggested keeping the current AC unit. One suggested that I needed to install more return air vents in the house. One suggested replacing the inside coil with a 2.5 ton along with a new furnace and some gadget that attached to the coil and fed more fluid to the coil to speed up the cooling process. One suggested a 2.5 ton AC unit which I think is too large. Several of the furnaces required 2 PVC pipes to be vented horizontally out the side of the house which I never heard of before. The Lennox guy didn't mention anything on this however. There were all 90-93 efficient furnaces. I guess I know I have an air flow problem and it would probably be corrected by installing a new furnace with a bigger and better blower/motor. I was wondering if I really needed more return vents or just increase the return duct size? Would it make sense to replace the inside coil with a 2.5 ton coil when the outside unit is a 2 ton or even replace it at all when nothing is wrong with it? Kind of strange that my furnace doesn't stay on all day during the winter. I live in central IL.

[CBHvac]

Ok..no one..nada, on the internet can tell you what the right solution is..

that said..

Get an HVAC company out that knows what in hell a manual J and a manual D are, and then, and only then, can ANYONE tell you what the answer is.

Period.

[TURTLE]

This is Turtle.

John you need to stop right here and stop all the parade of salesmen and newbee techs guessing on your system and get a real grown up hvac tech to check your system and tell you what is wrong with it.

By what you have said here, I think you have a plugged up evaperator coil and you got a bunch of kids working on your system. If you have a real 52 degrees discharge temp and a 73 return temp. it can't be 80 degrees in your home. If your really getting a 52 degree discharge temp. off your system. Your not moving enough of air or you got a plugged up evaperator coil or a dirty filter. The tech that looked at it and said that a 52 degree discharge temp was OK, well fire his ass.

When a tech tells me that the return air for a 2 ton cooling system is too small with a 10" X 18" return line. I would run his ass out of my house and call somebody else that might know what he is doing here. First fire everybody and call a Good service company to repair it and tell them I do not want a new system and to fix the damn thing. The first time any of them says you need a new condenser, furnace , evaperator coil , or a larger return air line. Fire their ass.

You must have a bunch of turkey hvac companys in your area. i need to know where you live at and move my business to there and make a killing just fixing system and not changing them.

TURTLE

[Joseph Meehan]

I agree with the others. A good tech will have the same answer as another good tech. The fact that you are getting different answers tells me at least some are not doing their job, and likely don't know how.

Follow CBHvac as to finding a good tech.

From what you have said I do have a couple of observations. First when having that kind of problem and having a 25 year old furnace, makes me think you should consider replacing the entire system. In the long run I suspect it will save you money with increased efficiency while your enjoy the increased effectiveness.

Second it is almost certain that you need changes to the distribution and return systems.

One more item. Make sure your insulation is up to the job. If not do what you can there without tearing the house apart to do it. It is a good investment for saving money and increasing comfort.

[R]

If everything that you have said here is true, then you have no A/C problem

10x18 is plenty for 2 tons...21 degree split is awsome.

Once again, all I have is what you have said.

You need more insulation

and that the

[John]

Thanks for the feedback. I've had 6 people out to 'evaluate' the problem and give a solution. I called a different tech to do a service check and evaluation since I didn't want anyone giving a quote on new equipment to do repairs or check the systems because I feared they might just say I need a new system even if I didn't. All talked about doing a manual J to determine the needs. I don't recall any mention of a manual D. What's that? I've got good insulation. It's a brick house with 3 1/2" R20 on all outside walls and about an R50 in attic. The filter is new and the 'squirrel cage' was cleaned. The return air vent opening size is 8"x24". Nothing blocking air flow from return air vent to blower. I thoroughly cleaned the outside units fins. If I'm getting 53 degrees air at the registers, would there be any problems with the inside coil? Would the inside coil have anything to do with the air flow? I realize I'm not going to find a complete answer or fix over the Internet, but would like some feedback as to what you think could be the problem. I'm sure anyone responding would do at least as good as the people I've had over to see things first-hand! :) Thanks.

CBHvac wrote:

[BSAKing]

You don't say if it was previously working ok. If so, then what has changed since last time it worked correctly?

[John]

Oh, one more question ... I have ceiling fans in all living areas of my home. One guy told me that I shouldn't be running them because the warm air trapped in the attic causes the ceiling to be warm and I'm only blowing warm air around. Said it was better to have a floor standing fan. Seems to me that if a fan is running, it doesn't matter at what level it's running since it's moving the air throughout the entire room. Is it better not to run my ceiling fans at all during the summer?

CBHvac wrote:

[Joseph Meehan]

In theory he has a point. In use, I don't think it is much of an issue.

From my personal prospective, if a home has a good HVAC system it does not need ceiling fans for comfort, and they don't fit my style.

[Joseph Meehan]

If the existing unit was properly sized to start with, I doubt if you could add a 12x24 area to the load. If it is properly sized now it may have been too large to start with. It would take an on site calculation to determine that. Too large a unit is NOT good.

[MF]

Seems to me that it is moot whether or not the fans blow the warmer air down, because if it sits at the top of the room, eventually the heat would radiate further down, so the fan is not doing any damage. Remember, though, I am a layman talking, and a rather undeducated one at that, just have an opinion.

As for ceiling fans I do get a kick out of people that believe fans cool a room. They do give the illusion of it because the air is moving, but no cooler. Think of the breeze blowing on a 95 degree day. It's still 95 degrees, but that breeze feels good.

I personally like air hitting me, so the ceiling fan is a good idea in my book, but I don't have the illusion that it is helping me with heating or cooling.

Maury Wylie, TX

ps. If the attic is so hot that it is warming the air at the ceiling level, then attic ventilation and insulation needs to be addressed. In an ideal situation, the attic will be no hotter than the outside air, and then the temperature of the air at the ceiling would be no different than the outside walls or doors.

[Joseph Meehan]

Left to its own devices the air at the ceiling will be warmer than the air at the floor. Remember hot air rises, hence hot air balloons work.

With a fan the hot air at the top is forced to mix with the air closer to the floor, making all the air close to the same temperature. So the air around you is likely to be a little warmer with a fan. Even if it feels a little cooler because it is moving. Also take into consideration that when the AC is on it will cause some mixing anyway.

Now if left alone the air at the ceiling will be a little warmer and less heat will transfer from the attic area which is warmer since the difference will be less.

[CBHvac]

Well....depends..

I am of the train of thought, that ceiling fans are great in conjunction with central air. You remove any stratified air caused by bad air flow from bad design of duct systems, and you keep the air moving, and that is what you want... Make sure, however, that in the warmer months, your fans are blowing DOWN, and in the cooler months, they are pulling UP in reverse mode.

Ceiling fans also give the illusion of cooling, due to evaporitive cooling..direct airflow on the skin, as in the down flow mode, will make it appear cooler than it is, and help you actually set your stat a couple of degrees warmer in some cases. In the winter months, if you use them flowing up, so that the airflow is actually being pulled up towards the fan, and the warmer ceiling air is being blown down the walls, you do not get the direct air flow on you and it seems a bit warmer...particularly since you are moving the air you heated that headed up back down to floor levels.... Remember...cooling more direct air flow and faster...heating, indirect and slower..

[Ray Kostanty]

Four considerations.

1. Garages aren't particularly well insulated. Did you add insulation to the new family room walls and ceiling? What did you do with the old garage doors? Replace them with real walls, made from 2 x 4s, insulation, sheetrock, etc.?
2. Until you mentioned that it worked okay the first year (was that year as hot as this year?), I would have mentioned the placement of the ducts in the rooms. To illustrate by an extreme case, if the return duct were located very close to the supply duct, the supply air would be sucked right into the return duct, leaving very little mixing of air throughout the room. Ideally you need the supply and return ducts at opposite sides of the room, and at different heights.
3. Sometimes proper return flow depends on the clearance at the bottom of a closed door (if that room has no return of its own). Are you closing more doors that you used to? Have you added carpeting (or elevated the floor), thus reducing the clearance?
4. How's your attic ventilation? Could some of the vents be blocked, causing increased attic temperatures that would radiate into the rooms below? Also, you might add an attic fan (not a whole-house fan) at one end, with a large opening at the opposite end.

[John]

- I put a 2x4 wall up and insulated all walls(r20)and ceilings(r50).

- Can't remember if it was any hotter than normal the 1st year. The return vent is not near any of the supply vents. One salesman thought it would be better to have an additional vent near the ceiling for summer since my one return vent is on the floor. Sounds like a good idea so it will pull the warmer air near the ceiling out.

I leave all the inside doors to rooms open to allow air to circulate so I don't think that's an issue. I actually have more clearance under the doors because I replaced the carpet with laminate flooring.

- This might be an issue that I've wondered about. I don't have very good venting up there. I think I might install an attic fan. It's extremely hot up there.

Thanks for your input Ray.

[John]

- I put a 2x4 wall up and insulated all walls(r20)and ceilings(r50).

- Can't remember if it was any hotter than normal the 1st year. The return vent is not near any of the supply vents. One salesman thought it would be better to have an additional vent near the ceiling for summer since my one return vent is on the floor. Sounds like a good idea so it will pull the warmer air near the ceiling out.

I leave all the inside doors to rooms open to allow air to circulate so I don't think that's an issue. I actually have more clearance under the doors because I replaced the carpeting with laminate flooring.

- This might be an issue that I've wondered about. I don't have very good venting up there. I replaced all the insulation that was up there during the remodeling. I think I might install an attic fan. It's extremely hot up there. My AC doesn't kick on until after noon which makes me think it's because the house is well insulated. But then later in the afternoon it never shuts off. This might seem to indicate, as you pointed out, that the heat trapped in the attic is radiating down.

Thanks for your input Ray.

[John]

You were right Turtle. I finally broke open the inside coil and found it to be almost completely blocked. Cleaned it all out and it worked great ... for about 2 days and then found that the connections on the outside compressor had fried and which didn't leave enough good terminal to make a good connection anymore. Guess I'm shopping for a new AC after all.

TURTLE wrote: