Care to offer an opion on a replacement system?

[rickbaro]

We have a 3,400 square foot house with three a/c units. A 2.5 ton for the 1,400 upstairs, a 2 ton for the 500 feet in the master suite, and a 2.5 ton for the remaining 1,500 feet of the main house. The upstairs is half bedroom/ bath, and the other half is high ceiling, with about half of that very close to the roof (little or no attic space). Additionally, the staircase is a large area, so the up cannot be closed off from the down.

We are located in the Dallas Ft. Worth area, and our last electric bill totaled 12.3 cents/ KWH (including all taxes etc.). The units run lightly beginning in April, and are running heavy in August/ September as we hit 100+. Usage tapers off in October.

The upstairs unit is dying (cracks in the evaporator). I have two bids; one for a Trane 19I, variable speed fans, and two pump compressor. The other is for a Rheem SEER 16 with a two-stage pump.

I understand this is a little bit apples to oranges, but I like both of these contractors, and have asked them to recommend as though it were their house. Money is not tight right now, but with college approaching, I would like to have small electricity bills over the next eight years. Comfort is secondary, as we (the adults) don’t go upstairs much, however, all that conditioned air runs down the steps making this unit the hardest working unit in the house.

These are not inexpensive units, but with the Trane, I have the option to replace the A/H now, and the compressor later (understanding the strain placed on the existing compressor, and understanding that I will not receive the full efficiency benefits until the compressor is changed. Hopefully I can get one more summer out of it). I also think I like the idea of a variable speed blower; seems like it would be quieter.

The Rheem is less expensive, but the contractor wants to install the complete unit so that he can put in the new refrigerant (sorry, cannot recall the name). The Trane would use R-22. This means I have to do the “Full Monte” rather than put in the rest later. The Rheem also does not have a variable speed fan.

Both gas furnaces appear equal.

Whew! If you’re still reading this, thank you for your patience. :o As professionals, would anybody care to weigh in with an opinion or two?

[falling down]

I just got out of Trane Boot Camp 2 Weeks ago, awsome class I would recommend it to all. THe 18i is an awsome unit. The 2 Coompressor's will do so much for you. The smaller is 50% is of the larger, and is normally all that is need to matain comfort, and helps the elec bill out at the end of month. Did the Trane contractor explain how the a longer cycle heps wring out the humidity, and the oppisite of that is short cycling? I do not have specs on the Rheem unit, it could be as good as the Trane. You said it is a 2 stage compressor, so it runs 100% on one stage, but the other stage, did he mention what percentage it ran at? Did either of them do a room by room load calc? I almost wonder if you have too much in some of the areas, then again, im in IL, and your in Texas.

[beenthere]

I wouldn't get a 2 stage A/C without the indoor VS blower.

Ask the Rheem contractor to give you a quote with a VS blower.

[Superdark]

I wouldn't get a 2 stage A/C without the indoor VS blower.

Ask the Rheem contractor to give you a quote with a VS blower.

VS = Variable Speed?

[Daltex]

VS = Variable Speed?

Yes.

[Superdark]

Yes.

Thank you.

I would appreciate some insight as to why a VS blower is desirable with a 2 speed system.

I am in need of a new unit, and thanks to this great forum, I have requested that the HVAC professionals quoting my job include units with a dual-speed compressor. I also now understand that the installation is the most important thing about choosing a new system.

I am a professional myself, and recognize the skill and training required for HVAC work. I made it clear up front that yes, I would be seeking three quotes, and no, I would not share quotes between the submitters. Price is just one of the many factors that will decide where I spend my money.

I want a fair price that we BOTH can live with. I want a HVAC man that I can call for the next 20 years if needed and look him in the eye knowing that I didn't beat him down over what amounts to pocket change in the long run.

Sorry for the long-winded speech, but in today's "LOWEST PRICES GUARANTEED!!!" world, I feel many people are missing the big picture: Make sure the honest people who provide excellent service can afford to continue to do so in the future. You never know when you will need them again.

[Daltex]

The VS blower is a comfort issue. The unit will blow full speed when needed but will cycle down to a much lower speed when approaching the thermostat set point. This will allow the unit to run longer to remove more humidity but also, you won't feel the air blowing on you. The sound is much softer on low speed also. The rooms tend to be more even as far as temp. is concerned as the low speed blower keeps it circulating. The pros may have some additional thoughts but I hope this helps.

[skippedover]

In some repsects, shopping for HVAC replacement equipment is like shopping for a new car. Lots of different models, features and benefits. But unlike buying a car, you're not purchasing a commodity that's plug-and-play. It's in pieces and needs to be assembled. Hopefully you hire the proper company that knows how to assemble things properly to give you the auto you think you're purchasing. I've attached my usual white paper as a guide to help you in selecting a good quality contractor. It may or may not help you decide between companies.

A variable speed blower is much more energy efficient than a standard blower. It uses on the order of 1/5th of th electricity. Any 2-stage condenser should only be connected to an air handler with a variable speed blower because you need to change the blower speed as in conjunction with the condenser staging. 2-Stage AC systems make great use of the 2-stage smaller/larger system features. Most or all variable speed air handlers also have a provision for extra humidity control. No matter where you are in the country, the nights are cooler than the days simply because there's no solar load on the home at night. That means the equipment doesn't need to work as hard. Like as no, in the morning you'll find the system operating on 1st stage, cycling on and off with the on cycles becoming longer as the day wears on. By late morning or early afternoon you'll probably find 2nd stage cycling on periodically until finally sometime in the afternoon 2nd stage is on almost continuosly. All that time the variable speed blower is ramping (we call it ramping because it's like a car driving up or down a ramp gently, rather than thumping up and down stairs) up and/or down to accomodate the changes in the system. The variable speed blower will also automatically adjust for dirty air filters (perish the thought) and/or a closed damper here and there (oops). I'd highly recommend a matched system with the complete job done all at once. Yes it's more money but most high quality companies can offer some form of delayed payment, perhaps up to a full year "same as cash". That way you can pay for the section your prepared to pay for now and then save up and pay off the loan before the year is up on the part you weren't expecting to pay for right away. That way you get the full system, reduced operating costs (save that darned utility overpayment) and put the savings into paying off the small loan.

[beenthere]

As above. The VS blower will slow down for first stage cooling, allowing it to remove more moisture. A multispeed motor, can be slowed down some, with a relay added to slow it. But it may not slow down enough.
VS blowers can also be signalled from the stat or other device to slow down in the middle of a cycle if the humidity gets above set point. Plus, as your air filter loads up(gets dirty) a VS blower will increase its speed to maintain proper air flow.

Think of 2 stage A/C as having a car with cruise control, but no speedometer to set it by. LOL... Ok, its not quite that bad. :)

[rickbaro]

Thanks everyone,

I have a feeling that if I request (insist) that the VS become part of the Rheem quote, the price will end up very close to the Trane price. That will be a bit like apples and apples then.

I better understand why I want the VS; not only for noise, but to get a better control on the humidity, and so the cooling. It does not sound like the end result of the two-stage vs the two-pump compressor is any different, they both do the same thing in different ways. Although it seems like there would be better efficiency asking a small pump to run at its own efficiency, and then later asking a large pump to do the same. A two-stage pump must run a smaller load, but still try to be as efficient as a large when needed. Kind of like driving a four-wheel drive back and forth to work when all you really need is a two-seater.

One more question if I may, does Trane or Rheem hold a "quality high ground" over the other? I understand them to both be quality units. I know there's Carrier, and Lennox too, should I be looking at those, or will I end up with something similar to what I'm already looking at?

[beenthere]

Their about the same. Heck, you didn't even mention my brand. :(
There are 3 basic 2 stage systems in residencial. use 2 compressors, use a compressor that rotates in one direction for 50% cap, and teh other direction for 100% cap, and then the unloading scroll at 70/100% capacity. Pros and cons for all methods.

Ooops, forgot the 4th method, before the IQ drive guys beat me up for not mentioning it.
There is the Inverter drive system, it can modulate from 40% to about 120% of rated capacity. From what I hear, it has a big price tag on it. But would probaly be the best total humidity and temp control system.

[rickbaro]

Their about the same. Heck, you didn't even mention my brand. :(
There are 3 basic 2 stage systems in residencial. use 2 compressors, use a compressor that rotates in one direction for 50% cap, and teh other direction for 100% cap, and then the unloading scroll at 70/100% capacity. Pros and cons for all methods.

Ooops, forgot the 4th method, before the IQ drive guys beat me up for not mentioning it.
There is the Inverter drive system, it can modulate from 40% to about 120% of rated capacity. From what I hear, it has a big price tag on it. But would probaly be the best total humidity and temp control system.

Oops, I should at least ask what your brand is after the good advice you've offered. Are you in the DFW area?

[beenthere]

No, I'm in Pa, your just a couple miles out of my range. :)

I prefer York, they have good coil selections for matching the SHR of the house. But there is nothing wrong with the brands you've been quoted, except using a standard blower on a 2 stage.




PS: SHR=sensible heat ratio.