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

[Blazer406]

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.

 

[imok2]

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

 

[Blazer406]

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.

 

[willard3]

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

 

[Blazer406]

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.

 

[IRstuff]

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

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[KiwiMace]

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.

 

[berkshire]

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

 

[KiwiMace]

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.

 

[cascadehvac]

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

matt

http://www.cascadehvac.com

 

[BillyBTU]

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.

 

[boo1]

The 15 SEER plus units qualify for the 30% federal rebate. The price difference between the 13 and 15 is ~$500-$800.

http://www.budgetheating.com/15_SEER_HEAT_PUMP_SYSTEM_R_410A_s/143.htm

5 ton Goodman 15 SEER for ~$2400 plus delv

Consider change the freon lines.

 

[Blazer406]

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......