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Repair or replace? 5 ton residential unit - 12 years old

Repair or replace? 5 ton residential unit - 12 years old

Repair or replace? 5 ton residential unit - 12 years old

(OP)
Sorry for the long post..... but I'm in a delima......

I have a 5 ton RUUD split system installed in my house. It is a 10 SEER with a scroll type compressor. I think my compressor is bad and that it has probably contaminated the rest of my system with acid from the burn out. Date on the unit is 3/99.

It was installed when the house was built in '99. I bought the house in '04. Since then, I have replaced the run capacitor twice, the outside fan motor, the contactor, and the inside fan motor. I had also put in a KS-1 hard start kit a couple years ago when I first had issues with the start capacitor.

OPTION 1:
Should I try and replace just the compressor? I would assume the tech would have to flush the rest of the system to get the contaminants out. I also assume I would probably want to put in suction and liquid line filters/driers at the same time.... as there are currently none installed.

I think I can still get the R22 compressor but it is around $1100. I assume it will cost $500 or so to have it installed along with the filters and flush the system out.

OPTION 2:
Replace the current system with a new 5-ton system. I would probably opt for a 2-stage unit with a variable speed fan. Looking at the current tax credits, I would shoot for a 16 SEER system and try and get the full $1500 tax credit on my taxes next year. If I do that, I need to reconfigure my system to have 3 zones. My current 5 ton system has 1 zone for a 2400 sq ft house with a 430 sq ft bonus room upstairs. It is a joke IMHO. To accomplish this I would need (the way my current ducting is set up) around 5 dampers, a bypass, a zone controller, and a programmable thermostat for each zone. I might also need to install a new return into one zone (Master bedroom) that currently has no return there.

OPTION 3:
Scrap the current 5-ton and replace with 2 smaller units. I would probably put my MBR and my upstairs (approx 830 sq ft) on a 2 ton system with two zones (one for the MBR and one for the bonus room upstairs). The rest of the house could possibly be on one zone on a 3 ton system. Obviously this is a more complicated and more expensive way to go.... but at the end of the day..... probably better suited.

The way my house is now.... with one 5 ton unit.... no separate zones.... if I have the downstairs at 72°.... the upstairs is probably 10 deg hotter. To band-aid this.... I put a 12,000 BTU 115v window unit in my bonus room so we can turn it on when we are up there. It make the space much more comfortable.

Any thoughts?

I live in MS where it is pretty hot during the summer months.

RE: Repair or replace? 5 ton residential unit - 12 years old

IMHO, option No. 1 would be a no go.  12 years on anticipated 15 life cycle doesn't make since to repair.  Three reasons for me come to mind, age, R-22 and the third, its a RUUD (not a huge fan of theirs).

While a zoned 5-ton system looks good on paper and would be cool to show off to your friends, I personally would go would two systems for the simplicity of operation.  Tow speed compressors for both is a great idea too.

Andy W.  

RE: Repair or replace? 5 ton residential unit - 12 years old

5 tons sounds like a lot for 2400 sf house.  We have a 2200 sf house in the Los Angeles area running a 3 ton system.  Since utility rates are continually increasing, getting a newer, more efficient system would seem to make sense.  If you can drop the tonnage a bit, the system might run even more efficiently.

TTFN

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RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
I'm about 1950 ft downstairs and 430 ft upstairs.

My 5 ton takes hours to drop from a 76 deg setting to a 72 deg setting. Maybe my current system isn't doing what it is supposed to be doing?

My house is on a slab. No basement. Bonus room upstairs. It always seems HOT in that room in the summer.

 

RE: Repair or replace? 5 ton residential unit - 12 years old

Mine's only two story, no basement.  There'll always be a delta between the topmost floor and the ones below due to solar loading on the roof.  Your upstairs might also be extremely poorly insulated, particularly if the house is pretty old.  It might be worthwhile looking at upgrading your insulation.

How cold is the air from the registers?  A typical AC system should be putting out 55ºF-ish air into the ducts.  My spouse was/is always complaining that the AC air is too cold, but that is as it should be, usually.  I would think that a 4ºF drop should take less than an hour or so, at least, for the air temperature.  Your walls might still be convecting heat back into the rooms, since their thermal masses are larger.

TTFN

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RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
Well, I got a "TRANE" guy that lives near come by and get me some pricing on several options.

1.) A new 5 ton 13 SEER Trane condenser unit.
2.) A new 5 ton 13 SEER Trane condenser unit and matching a-coil (keeping existing furnace and air handler)
3.) A new 2 ton unit to install for my upstairs that would allow me enough capacity excess capacity that if I put another room upstairs, I would just run a few supply ducts to the new room.

He also priced a Goodman condensing unit to replace the current (now dead) 5 ton RUUD unit I have.

He also priced me a 15 and 16 SEER 5 ton complete Trane split system.

I kind-of had sticker shock. Prior to me getting the prices mentioned above, I called a buddy that is in that business and he "offered" to get me some American Standard stuff.... or anything else at his cost and could hook me up with a guy that installs near where I live that would do it on the side.

He came back with pricing that appears to be pretty good. I am contemplating between the 13 and 15 SEER American Standard 2 ton and 5 ton systems. I am leaning on putting just the 13 SEER systems in knowing that they are way more efficient than my current 10 SEER system is.

I talked to the tech and he is supposed to come to my house tomorrow morning and look at what I am needing.

I think I can get some good quality stuff and get a good install done and I'd be tickled.

Thoughts?

RE: Repair or replace? 5 ton residential unit - 12 years old

Keep looking.  

When I got my AC, I talked to 5 AC guys, 4 of which wanted to get me 4 ton or 5 ton systems.  Only one guy came up with the 3 ton solution.  I would guess that you could probably get by with a 3-ton downstairs and a 1-ton upstairs.
 

TTFN

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RE: Repair or replace? 5 ton residential unit - 12 years old

Replace the lot, don't muck around patching a new A coil into the old existing indoor unit.  They will stiff you on any warranty work and it will always be some problem with the sa fan.  Does this thing have a furnace?

Return air path restrictions are common with residential systems, as well as basic balancing as everyone dicks with the dampers.  Have your guy run through the whole system.

RE: Repair or replace? 5 ton residential unit - 12 years old

blazer406:

Sounds like it could be an inefficient ducting delivery and/or return air problem to me too.  

Have the same problem in my house and it would take bookoo bucks to fix.  Was a bad design from the beginning.  I just have to live with it.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Repair or replace? 5 ton residential unit - 12 years old

When the tech comes to your house, get him to go room by room, and check supply and return duct sizes,also under door gaps for rooms with no return grille. Spec out the entire house from scratch totaly ignoring what you have now. Then figure your zones and air handler sizes for heat, then air. If you need to add ducts or increase duct sizes do it now
 You are already into a major replacement anyway. A few extra bucks spent now will save thousands over the life of the operating system.
B.E.

RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
IRstuff,

I agree for the most part. I am a mechanical engineer. They make us do plenty of HVAC calcs. I do understand an appreciate the importance of not oversizing too......

My "Trane" guys answer when I question him about why I shouldn't downsize the unit once I take the upstairs "load" off the unit...... he said, well.... it has been cooling it well as of now.... you might need that little extra capacity for one of those 100° summer days when a 4 ton unit would not maintain 80°......

I can't exactly say he doesn't have a point. It does routinely get near triple digits here every summer..... with very high humidity..... feels like a sauna.

I surely don't want to spend thousdands of dollars and come the middle of this summer....... wish..........I had another 1/2 a ton of cooling.......

RE: Repair or replace? 5 ton residential unit - 12 years old

My "Trane" guys answer when I question him about why I shouldn't downsize the unit once I take the upstairs "load" off the unit...... he said, well.... it has been cooling it well as of now.... you might need that little extra capacity for one of those 100° summer days when a 4 ton unit would not maintain 80°......

It sounds like a better solution would be a multispeed unit.
B.E.

RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
berkshire,

I am assuming you mean 2-stage or 2-step compressors?

I am already wanting to make sure I get the variable speed blower in the air handler.

The 2 ton and 5 ton AS 15 SEER systems my buddy quoted me have the variable speed blower but I think just single stage cooling. I have asked him for clarification. I have asked at what SEER level I need to get to get the 2-stage compressor.....

 

RE: Repair or replace? 5 ton residential unit - 12 years old

replace the unit but:
You said "My 5 ton takes hours to drop from a 76 deg setting to a 72 deg setting"
That tell me that your unit is overzised.
I think it is better to hire an engineer to recalculate your load and redesign your system.
Happy Easter for everyone
 

RE: Repair or replace? 5 ton residential unit - 12 years old

Blazer
Yes,
I meant two stage compressors, that way you get the dehumidification with the first stage and you get the capacity when you really need it.
B.E.

RE: Repair or replace? 5 ton residential unit - 12 years old

RE system size:

Remember, your family will not thank you when they are too warm.  

RE: Repair or replace? 5 ton residential unit - 12 years old

I guess what I am saying is that it makes no economical sense to me to upgrade only the Unit if at least part of the problem is with the delivery system.  The problem will still persist.   

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
Well.... The 2nd HVAC guy came and looked and agrees that I need to stay with the 5 ton for my downstairs. I have 9 and 10 ft ceilings throughout and a huge vaulted ceiling in my living room that is close to 20 ft at the top. I also have no conditioned space above any of my current downstairs.

I am probably going with the AS 5 ton with the variable speed air handler 13 SEER. Then a 2 ton for the bonus room over the garage also 13 SEER. MY budget is driving me to stay with the 13 SEER in stead of the 15 SEER. I just can't afford to do the 15 SEER right now.

The 2 ton is slightly overkill but I am planning an expansion upstairs that will need any excess capacity I will have from the current bonus room. I'm actually tempted to dump a new duct or two off this 2 ton back down in my master BR.

RE: Repair or replace? 5 ton residential unit - 12 years old

Your 5 ton unit wiuld be more efficient if you installed drop ceiling fans   

RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
Well..... I got my "estimate" for the labor to replace my whole 5 ton system and install a new 2 ton system..... OUCH!

I'm going to ask for a breakdown of labor vs materials..... just to check.

I am supplying the condenser, lineset, furnace/air handler, thermostat etc. He is supplying the wiring for the new 2 ton, about 40' total of ducting (supply and return), the pad for the condenser to sit on, and the labor to install and fire up. He thinks he might can do it all in one day.... but said it might take two days.

I am re-thinking my equipment.... and am definately dropping back to the 13 SEER AS..... but now.... am considering maybe looking at Goodman for value and warranty (supposedly lifetime compressor). I might could step up the SEER a little on the goodman equipment. I am really bummed at the coin I am about to drop.

 

RE: Repair or replace? 5 ton residential unit - 12 years old

So, you thought it was going to be cheap....?

RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
williard3,

No.... but I was not expecting 2 days labor (contractor said it would take hopefully no more than a day and a half) , about 25' of supply duct, about 10' of return duct, a condenser unit concrete pad, the wiring for a 2 ton air handler and condenser unit (both very short runs under 25') and wire up the t-stats...... to be $3400. I'm already buying 99% of what is needed.

I'm always skeptical when I see what someone is charging me. I guess it is the nature of the beast.

RE: Repair or replace? 5 ton residential unit - 12 years old

Of course the 2nd AC guy agreed that you "needed" a 5 ton downstairs and 2 ton upstairs.  Why would he voluntarily cut his commission in half?  We're talking about 7 tons for 2400 sf, which is more that what we're running for a 4800 sf house in the same temperature zone.  I tend to think, in my more paranoid moments, that there's a conspiracy amongst the salesmen to jack up the tonnage on all residential systems, particularly those that do not have a PE looking over the numbers.  Additionally, of course, no one ever complains about an AC that's overcapacity, except when they might be looking at the utility bills.

I suggest that you get a quote for 3 ton downstairs and a 1 ton upstairs just for comparison.  That's still 4 tons of total capacity, which, depending on whose rules of thumb you use, is supposed to be sufficient for up to 2800 sf of space.

TTFN

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RE: Repair or replace? 5 ton residential unit - 12 years old

Actually, in a humid area an oversized unit will short-cycle on dry bulb and not adequately deal with the latent load.  The upshot is you get a humid 72degF and you still need to peel yourself off the leatherette couch.

RE: Repair or replace? 5 ton residential unit - 12 years old

KiwiMace,
Thats what I was getting at when I was pushing the 2 stage units, however the OP said he knew, about the disadvantages of oversized units.
B.E.

The good engineer does not need to memorise every formula, he just need to know where he can find them when he needs them.  old profesor

RE: Repair or replace? 5 ton residential unit - 12 years old

Berkshire - yep.
It does seem though that all the price competition is on the standard box. These dual stage, two speed, condensing furnace, electronic filter etc options cost you your first born.  Unless there is going to be a long association with you and the property it hardly seems worthwhile.  I tend to move a lot though...

Personally i am adverse to the noise more than anything.  If the unit is cycling, it drives me nuts.  Probably worth a two speed fan for this alone.

RE: Repair or replace? 5 ton residential unit - 12 years old

getting something new is really the only option.  if you want to zone, have you looked at ductless heat pumps ac?

matt
www.cascadehvac.com

RE: Repair or replace? 5 ton residential unit - 12 years old

If you move or not, I suggest to determine the house R-factors for the existing construction and perform the manual-J load calculation or run a similar computer load calc.  You also need a pro to look at your air distribution system and match it up with the stucture for the most efficient use of supply and return air.  A vari-speed fan is best for humidity control if there is compressor capacity reduction capability.  Eliminate guessing or assumptions as much as possible, it will cost you in the long run. I'm not a fan of ceiling fans when AC is running.  A 13 SEER heat pump with aan automatic programmable T-stat is fine for MS, unless you want a five to ten year payback with a better SEER.  Have the dealer give you a payback number if he'll agree too one.  Get a prepaid maintenance plan too.  It will pay for itself.  But read the fine print and know the difference between implied and applied warranties.     

RE: Repair or replace? 5 ton residential unit - 12 years old

(OP)
I ended up going with the AS equipment in a 13 SEER. I did choose to step up the inside furnace (on the 5 ton) to the furnace the distributor was specifying for the 15 SEER system....the evap coil (oddly enough) was the same from the 15 SEER to the 13 SEER.

I got the 2 stage gas valve with the variable speed fan. The only other thing I wish I had been able to afford was the two stage compressor. I think that would have been the bomb with the inside unit I went with.

On the 2 ton... it is just a reagular 13 SEER split system with a small 5KW heat strip. I won't need much heat on the upstairs room.... and in MS......
 

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