Looking for some advice on replacing system

[jwcalla]

Hi all,

I had a problem last year where I wasn't getting enough cooling (11°F split across air handler), despite the system running all day. After having somebody out a couple of times and doing much research myself, to no avail, I decided it would probably be impractical and too expensive to try to identify the exact problem. Since the outside condenser unit is relatively new (<5yrs?, a 2-ton, 10-SEER Goodman -- blech!), I'm pitting my hopes on the evap. coil being the culprit: either too dirty, too old, or whatever. The whole inside unit is the original equipment, 1987 York, 2 or 2.5-ton evap. coil with a single-stage 65,000 BTU furnace.

So I have received 4 estimates for replacing the inside unit (I'm trying to salvage the condenser). I've eliminated two of the estimates and am now trying to decide between the final two. Both companies are reputable and I don't have any problem dealing with either one of them.

The main difference is between the furnace/blower offerings. I'm trying to determine how they will affect my A/C operation. One is a 2-stage, multi-fan speed York. The other is a 2-stage, variable-fan speed Carrier. The first estimator, upon giving me a York brochure, immediately skipped by the variable speed offering, saying, "You can forget this, it's overkill for this place." The second company that recommended the Carrier (which also installs other brands, including York), believed firmly that variable speed fans are the only way to go these days. He also mentioned the blower as one of the most-overlooked parts for good A/C operation. The difference in price between the two is about $800. This is the difference between the Carrier and the York, not a difference between the two estimates.

The first question I have is:
How will the variable-speed fan affect my A/C operation? (Resolving my A/C issue is my #1 concern, forget the furnace for a second.) Will it provide better cooling than just a single-speed fan? This is how I anticipate using my A/C: maintain the temp. at something moderate, like 80°F, for most of the day if possible, then bring it down to low-70s and maintain that for when I'm home. Leave it off when I go to bed. Is the variable speed going to get me anything truly beneficial? Will the coil work better at removing heat/humidity because of this fan? Or does it really not matter?

The second question I have regards the furnace. I'm a little bummed about this new-fangled "2-stage" furnace idea. My understanding is that it runs for 15 mins or so at half the BTUs, then kicks up to the second stage if needed. I think it might also try to "learn" based on past history and operate accordingly. In this way it's trying to be "smart", but sometimes I think I'm smarter. This is how I currently use my furnace: leave the thermostat at something absurd like 55°F. Come home from work; jack the thermostat up to 68°F; set it back to 55°F before going to bed; then run it for an hour, full-blast, when I wake up in the morning (so I don't freeze in the shower). This works great for me. (I'm a freak, I know.) If I get a 2-stage furnace, does this mean I have to wait for the furnace to ditz around for 15 minutes before I get "real heat"? Will the second stage be any louder than my current single-stage furnace? (Noise is somewhat important since the furnace is located in the living space. And I get the idea that all the brouhaha in the brochures about quiet operation only applies to when the blower/burners are barely on.) I really have no qualms with my current furnace (it works great), except for the pilot light and it's a little noisy.

Third question: I have a programmable, digital Honeywell CT3500 thermostat. It looks rather new. Does anybody know if it would work with a 2-stage furnace? How about a variable-speed fan? Will I need to get a new thermostat?

So I guess that's it... just looking for other peoples' opinions before I take the plunge. I live in a condo, 2nd floor, multi-level, 1300 sq. ft., and only expect to live here another 3-4 years. For that reason I want to avoid "overkill", but also want to be at least somewhat sensitive to the needs of future owners, all the while being focused on solving my A/C problem the best I can.

Thanks all,
John

[Grady]

Where were you measuring the temperature split? If measured at the air handler the fan speed could be too high or a problem with the refirgeration system. Measurements taken at registers take into accout the system as a whole & include heat gain thru the ducts. To get a better picture of what's going on, you need to do both. Unless the source of the problem is identified, you may wind up in the same boat you are in. Has anybody done a heating & cooling load calculation? Without one being done, everybody is guessing about equipment sizing & you are behind the eight ball before you even start.

[jwcalla]

Suprisingly enough I got an 11°F split both across the air handler (measured before the filter and right after the coil) and between the return/supply temps. I was surprised that they were the same. I was hoping for a much higher temp. at the filter to point to a leaky attic return duct, but alas, the temp. at the filter was about the same as on the t-stat. Likewise, the temp. at the coil was about the same as the supply.

None of the companies that came out and gave an estimate did a heat load calc. The basis for that was that the builders did one already for all the units in the complex and if the undersized the systems, we would know. Also, it ties their hands a bit when I asked (and some agreed with me) to keep the condenser, since it's new.

I simply can't afford to do both inside and outside at this time. Even doing just the inside is a huge dent in the wallet for my current state of life.

I understand that I might shell out some big $$$ and not even solve the problem, but it's a risk I've accepted.

John

[Grady]

I hate to see anyone spend a bunch of money on a system to cure a problem without knowing where the problem lies. Two tons for 1300 sq.ft. sounds small but without knowing where you live & more about the construction, I'm guessing just like everyone else. Has anyone done a superheat measurement? If replacement is what you are going to do, I think two stage &/or variabe speed would be a major waste of money. Since the outdoor unit is Goodman, I would suggest a Goodman coil indoors.

[TigerDunes]

[QUOTE=jwcalla]Hi all,

After having somebody out a couple of times and doing much research myself, to no avail, I decided it would probably be impractical and too expensive to try to identify the exact problem.


First of all, you have to recognize that you have a mismatched system, Goodman AC outside condenser with York single stage furnace. I would suggest you verify the model number, size, and age of above and also find out exactly what you have with your evaporator coil. The evaporator coil must be properly matched with your outside condenser to get your efficiency ratings and for effective cooling. Generally speaking Goodman equipment has been categorized as budget/builder models with dubious reputation. Has your AC ever worked satisfactorily and have you given up on finding out what the problem is? You definitely should insist on a written Manual J heat/cool load calculation for verifying equipment size both in cooling and heating. I would not even consider a new furnace with blower without first finding out what is behind your AC problem.

I am a big proponent of variable speed either in a furnace or an air handler. They are less expensive to operate, quieter, improved air quality with media cabinet,and provide better comfort with even heat and cooling. Some manufacturers also say they contribute to better dehumidification with a matched system. As you know, variable speed is also more expensive. I would not consider variable speed in your case because you indicate you will only live in home 3-4 more years and also because if you keep your Goodman AC, you will still have a mismatched system.

On question 1, you may be creating more of a problem and stress on your AC condenser by moving the thermostat up and down, on and off as you say you plan on doing. False economy? You do not mention the area of country you live. Many homeowners run the variable speed fan continuously because it helps provide more even temperature room to room and is much less expensive to operate than a conventional single speed blower. I would not waste my $$$ for a variable speed furnace with a Goodman AC condenser.

On question 2, two stage furnaces are becoming more popular but if you intend to manually work the thermostat and only stay in existing home for 3-4 yrs, then I would not waste my $$$ on this either.

Concerning your existing thermostat, Honeywell has a site on the web that you can direct that question to.

I agree with Grady. A 2 ton AC condenser may be borderline adequate. Again, I think the key is finding out what is wrong with your cooling and at a minimum get a matched Goodman evaporator coil if you plan on keeping your existing Goodman AC condenser. Do your current quotes include new evaporator coil?

Good Luck!

[Ed Imeduc]

To stay there just 3 or 4 more years and you got 4 bids .Id go for just the indoor coil and be done with it . Could be bad TXV if you have one or the wrong orifice on the coil.


ED :thinker:

[jwcalla]

If the thermostat is on the cool setting, but not currently calling for cooling (because the t-stat temp. is satisfied), will the air handler still run the fan on the variable speed blower to "keep the temperatures even"? If so, I would consider that a huge downside, since I have high ceilings and that would only serve to bring warmer air back down into the living space.

I agree for heating it would be an advantage.

[jwcalla]

Could be bad TXV if you have one or the wrong orifice on the coil.

Where can I get more info. on this? I know the coil has a #59 orifice, but not sure what that means.

Thanks,
John

[mattison]

3 or 4 more years I think I would 1st find the problem it's probably something simple. If you did just replace the furnace and coil, just go with a matching Goodman 80%. The way you operate your stat in cooling season you'll have a pretty humid house. The system needs to have long run times to get rid of humidity.

[Grady]

Has the system ever worked properly? If it has, was anything done to it prior to the problem showing up? Presuming the coil to be a York & you can get a model number, I suggest calling a York dealer & ask him about if orifice size is correct for your outdoor unit.

[jwcalla]

I bought the condo in January 2004, so last summer was my first taste of it. And no, since I've had the place, the A/C never worked right.

It looks like the previous owners replaced the condenser and left the original inside equipment. The two might not want to play with each other since there is a vast age discrepancy (1987 vs. >2000). They probably didn't replace both at the same time due to financial issues.

I think they replaced the condenser either because the other one died or maybe they had a leak in the refrigerant lines, because they ran whole new lines. The new refrigerant lines are at least 30 ft. longer than the originals, since the new ones had to be run through the attic instead of the crawlspace. (Altogether about 110 ft. long.) I did have somebody out last year to investigate, and he checked the charge and came up with an overcharge and took some freon out, but I literally noticed no difference. Most of my condo neighbors have their original condensers.

I think I'm going to go with the York 2-stage furnace instead of the Carrier variable speed. I'm sure the variable speed is a nice technology, but it might be just a bit too high scale for a small condo. If it was a place that families live in for years, it might make more sense.

John