when should I reaplace my 17 year old trane Central AC? unit

[rollandelliott]

http://www.google.com/url?sa=t&rct=j...2wSrYA&cad=rja

states that payback is only 3.3 years. I just paid $600 to add refrigerant to my AC unit. Aparently it leaked out a little after 17 years of use.

It is a 3 ton unit. If I have to pay to get it fixed again I'm deffinetely going to replace it, any recommendations for a 3 ton unit!??

[solar_dave]

Well minisplits are great but may require modification you don't want to make, most have upto 4 wall unit capable 3 ton outdoor units.

I run a Trane 2 speed and it is higher seer and a pretty efficent.

[rollandelliott]

Interesting I did not know they made minisplits that big. I always assumed they were for smaller 2 room or less applications. I guess instead of having a spiderweb of duct work in your home you replace it with a web of refrigerant lines!

Actually the mini splits have competition
http://www.energystar.gov/index.cfm?...nt.me_cac_ashp

shows some central AC units with Seer ratings of 21 and up!

[Ralph Day]

Before installing my Mitsubishi mini split I found a site that was dedicated to HVAC reviews (sorry, don't have the site address anymore, just google hvac reviews/furnace/ac reviews). Mits had 5 reviews or so, there were many (21?) pages of Trane problems. Old units were and are top of the line, but the new Trane stuff sounds horrible...run, don't walk away from it. Installers even saying they no longer carry it because of all the problems.

The concensus seemed to be, if you have older Trane equipment and it's working, keep it, but don't upgrade to new Trane stuff.

Ralph

(spoiled by Mitsubishi)

[Ken Marsh]

Your chance of getting another 17 years without recharge is not good.
There is virtually no small leaks like that.
Oil circulates with the refrigerant and coats everything. Trash in the oil plugs small leaks.
So leaks are usually cracked lines with the crack perpetuating or charging fitting, etc.
Have you frozen up the evaporator coil? This can cause a leak.

But if you can find the leak they are usually quite easy to fix.
Look for oil spot on the lines.
You got to have the equipment.

Seems like the main benefit of the mini splits is that you can run them with solar arrays.
They don't have the large inrush upon start.
In a few years all refrigeration will be this way.
Have friends in the industry who report that their R&D is full of inverter driven stuff.

I am retrofitting a 34 year old heat pump.
It is getting a 3 phase compressor, VFD and some other things.
Have it running with manual control and it looks good.
Still have to get the controls adapted.
It starts with 0 amp inrush and the amps ramp up with rpm.
Looks like it is drawing about 75% the power as the single phase compressor.

[inetdog]

I just paid $600 to add refrigerant to my AC unit. Aparently it leaked out a little after 17 years of use.

It is a 3 ton unit. If I have to pay to get it fixed again I'm deffinetely going to replace it, any recommendations for a 3 ton unit!??

One reason that the recharge cost so much is that it uses old type Freon refrigerant which is no longer being manufactured for environmental reasons. The only supply in the US now comes from recycling from older units when they are scrapped, along with stocks that people have stored. The next time you have to recharge, the cost will have gone up again.

Unlike car A/C units in which it can often be practical to switch over to a replacement refrigerant, stationary units are stuck by design with their original Freon type.
Going to a newer, more efficient unit will also get you into a lower long term cost for refrigerant in case of leaks.

[rollandelliott]

"Have you frozen up the evaporator coil? This can cause a leak.

But if you can find the leak they are usually quite easy to fix.
Look for oil spot on the lines.
You got to have the equipment."

Well I was looking over the repair guys shoulder when he did the repair work on my exsisting compressor unit, but had to leave before he put in the 2 lbs of refrigerant/r22. He could not see any leaks., but sold me some sealent he injected in for $120, said hopefully that would fix the small leak. I have replaced a car condenser so I know what you mean by checking for oil leaks. That is actually how I found the leak on my car.

My inside evaporator coil did freeze so if that is where it leaks than I'll just wait. Ripping that condensor coil out would be a one or two day job easily.

I just spoke to a HVAC sales guy and he came to my home. Quoted $9,000 for a new HVAC system. TOld me that I would have to replace my furance too! There's gotta be a way to take out the exsisting blower and replace it with a variable speed one.

Ebay has lots of HVAC high effcient units, but they tend to me incomplete. I saw a 3 ton 22SEER compressor unit, but it did not come with air handler. From everything I have read if you dont' match components than the effciency rating goes down the drain.

Ken sounds like you have experience frankensteining systems, do you know where I can get a variable blower fan?

[rollandelliott]

Since these new HVAC systems use Refrigerant that does not deplete the ozone is installing one, now a DIY possibility? With R22 I think they only sell it to people with HVAC licenses. I've recharged my Car's AC refrigerant, Doing so for a home can't be that much more difficult IF I can actually buy the refrigerant.

[inetdog]

Since these new HVAC systems use Refrigerant that does not deplete the ozone is installing one, now a DIY possibility?

It is a relative difference, not an absolute one. The newer refrigerants do not deplete the ozone layer as much on a pound-for-pound basis but they still have an effect. Regulations may still require you to pump down and recycle other refrigerants too. Check your local laws on this one. Getting the charge amount correct can still require a pressure gauge set and other equipment, and over or undercharging can damage the compressor.

Matching the compressor size to the coil size and the air flow rate is indeed important, and a mismatch can either overload the compressor or cause the coil to freeze up. So putting together a system from parts requires at least a minimum level of engineering calculations.

[solar_dave]

I just spoke to a HVAC sales guy and he came to my home. Quoted $9,000 for a new HVAC system. TOld me that I would have to replace my furance too! There's gotta be a way to take out the exsisting blower and replace it with a variable speed one.

That is a bit pricey, I had mine replaced with an air sourced heat pump 2 speed compressor system for right at $6500. My installer told me that the payback on going much higher than 17 seer is minimal and the cost is much greater proportionally. YMMV A gas fired heater system was less money BTW