My brother's Central AC for a rental?

[Wild Leg]

I've got two brothers-in-law I'd swap.

Wanna trade?

[ombre]

Nope--

[pstu]

Allow me to ask a naive question, I am just a homeowner who tries to follow what the best pros are doing and understand it.

The Trane 5.0 ton system is a two-stage unit, is it not? And the 1st stage will be sort of equivalent to a 3-ton unit, is that about right? And the house was cooled OK when it had a 3.5 ton system installed?

It seems reasonable to speculate that most of the time, that Trane will run on 1st stage and do its regular job of humidity removal (yes I agree a 4 ton model would do it better). So will this necessarily be inferior to the older system which appears to have been properly sized?

I understand that without big ductwork improvement, that Trane will make extra noise on those few times it is in 2nd stage. And it seems that the only way to cool that sun room will be to add lots of ductwork to that load, and no doubt its own return. We *do* know it has a terrific heat load, even though we don't have it in numbers.

Does this sound reasonable to you all?

Thank you -- P.Student

[ombre]

Originally posted by perpetual_student
Allow me to ask a naive question, I am just a homeowner who tries to follow what the best pros are doing and understand it.

The Trane 5.0 ton system is a two-stage unit, is it not? And the 1st stage will be sort of equivalent to a 3-ton unit, is that about right? And the house was cooled OK when it had a 3.5 ton system installed?

It seems reasonable to speculate that most of the time, that Trane will run on 1st stage and do its regular job of humidity removal (yes I agree a 4 ton model would do it better). So will this necessarily be inferior to the older system which appears to have been properly sized?

I understand that without big ductwork improvement, that Trane will make extra noise on those few times it is in 2nd stage. And it seems that the only way to cool that sun room will be to add lots of ductwork to that load, and no doubt its own return. We *do* know it has a terrific heat load, even though we don't have it in numbers.

Does this sound reasonable to you all?

Thank you -- P.Student

A lot of good points. I am an old fart technician who has been out of the trade for over 12 years-----so I know very little about 2 stage compressors (did they ever actually do that--I know they were working on it?), or 2 separate compressors---and how they work exactly.

One reason I come onto this forum---is to try and keep up.

Again you make good points. If there are actually 2 compressors in that Trane monster-------I would assume with a light heat load, that only only one of the compressors would be working. No need to disable the second compressor at all.

That Florida room facing south with 3 sides of almost all hurricane windows was always impossible to cool. ------The best solution would have been to install a highly efficient 15-18000 BTU, and, if you want to spend the money, fairly quiet running, wall unit in that room--close it off and turn on the wall unit when you need it, leave the unit off when not necessary---Which would make everyone, especially renters--- HAPPY HAPPY HAPPY ---

---Which is exactly what I kept suggesting to my brother---Not that he ever listens to me. He has this horror of holes in a wall. (I think holes in a wall do have their place.)

And so now that 5 ton monster might even cool the Florida room, although, I think rather inefficiently---They did actually install 2 rather large discharge ducts into that room (there was just one teeny discharge before)--

-and the return is back through the rest of the house--through a very large sliding glass door, which can be easily closed.

The fact that that room can be so easily closed off from the rest of the house is the main reason I suggested an expensive, but highly efficient and very quiet wall unit specifically for that room.

Hell, my brother spent $11,000 for the oversized absurdity he has now---He could have bought one hell of a good wall unit for 1/20th of that price.

One possible problem I see, the way it is now is that-------the rest of the house will tend to overcool just to make up for that monster of heat gain in that silly Florida room.

And I think excessive noise from both the blower inside next to bedrooms and that monster of a condensing unit outside the main bedroom--Plus the serious possibility of a very damp house------will have renters seriously upset.

But we will all find out this summer.

I know there will be a problem when my brother calls me and says--- "Kenny---can you come over?"

[Edited by ombre on 03-22-2005 at 07:30 PM]

[Shophound]

A lot of good points. I am an old fart technician who has been out of the trade for over 12 years-----so I know very little about 2 stage compressors (did they ever actually do that--I know they were working on it?), or 2 separate compressors---and how they work exactly.

The Trane XL19i uses two compressors. Lennox has a new high SEER model out that uses a modulating scroll compressor, like the Copeland UltraTech Scroll shown here:

http://www.emersonclimatecontractor....ics&User=false

I saw one of these at a recent RSES conference. It uses an internal solenoid operated by DC current to move a plate that covers up or reveals a hole in the lower scroll to effect capacity control. It appears destined for two stage systems and to me would seem ideal for when the homeowner wants to use the A/C for dehumidification on cooler but muggy days.

P. Student:

The Trane 5.0 ton system is a two-stage unit, is it not? And the 1st stage will be sort of equivalent to a 3-ton unit, is that about right? And the house was cooled OK when it had a 3.5 ton system installed?

It seems reasonable to speculate that most of the time, that Trane will run on 1st stage and do its regular job of humidity removal (yes I agree a 4 ton model would do it better). So will this necessarily be inferior to the older system which appears to have been properly sized?

Good point, P. This may indeed work out to be the MO for this system. Only time will tell, since apparently it was just thrown together, hoping for the best. If it performs adequately it will be more from luck than engineering.

[docholiday]

Im not going to try to make heads or tails of the specs but for the most part this is not a good practice since generally you may find poor latent capacity when the unit is running at low stage and suggesting it will performt the same as a regular 3 ton system may not be as accurate when looking at latent sensible ratios.

[beenthere]

When its in first stage cool, you'll have a 3 ton compressor running with a 5 ton evap, giving you a warmer evap coil and not condensating like a 3 ton condenser, with a 3 ton evap.

So on mild temp days you still have short cycles with higher humidity then with the old straight 3.5 ton a/c.

[ombre]

OK--

Makes sense.