Replacement of system to help with dehumidifcation and temp shifts
I have a question regarding replacing my current HVAC equipment. Below is a breakdown of my current system /setup.
- Rheem 2 Ton 13 SEER w. 45k BTU 80% efficiency horizontal flow furnace (located in my attic) servicing my second floor which consist of three bedrooms, two bathroom, and a hallway. This area is about 750 sq. ft.
- Rheem 2.5 Ton 13 SEER w. 65k BTU 90% efficiency upflow furnace and an AprilAir 500 humidifier (located in my basement) servicing my basement which has a large family room as well as my first floor which has my kitchen, family room, dining room, and powder room. This area is about 900 sq. ft.
I want to change out my system because I notice a noticeable temperature shift between the different bedrooms. We also notice a HUGE temperature shift between the floor and the middle of the rooms on the first floor (I'm guessing this because my vents are closest to the floor). The other issue I noticed is that during the summer the relative humidity in my house is about 50 - 60% and during the winter its about 25 - 30%.
I was told that a new system with a two stage AC unit and variable speed air handler would help dehumidify the air in the summer and not dry up the air so much in the winter. In addition they told me a variable speed air handler will also fix my temperature shifts so I wanted to reach out to the pro's to see if this is indeed the case. The system that the HVAC contractor is offering to install is an American Standard as he feels this is a better brand than Trane and Rheem.
Any advice would be greatly appreciated.
Your biggest challenge with any two stage or variable speed system is getting an installer that will set it up properly. Otherwise you're wasting your money on a system that essentially performs like a crippled single stage system most of the time.
Also, if you change out the heating and cooling components of your system but your ductwork is crap, you won't see much benefit to going with more expensive and higher tech equipment.
First thing I'd do in your shoes is find out why the air distribution from my existing setup isn't meeting my comfort needs. It may be a combination of ducts, heating and cooling components, and your house insulation and air leakage levels. An energy audit performed by a seasoned auditor can help reveal a lot of things along these lines, as well as HVAC pros who understand air distribution and other issues that may be negatively affecting your current system's performance.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.
I'd get the ductwork/installation issues fixed first then think about new equipment.
The benefits of a new VS and 2 stage system probably don't justify taking out perfectly good equipment. Some high SEER 2 stage units dehumidify worse than a good single stage unit like a Rheem. Usually temp balance issues, like the hound says, are duct related. Too many salesman push variable speed as a magic cure and IT ISN'T. Finding a dealer trained in airflow diagnostics will do lots more than just throwing new equipment at the house.
And the dealer saying American Standard equipment is better than Rheem & Trane loses credibility right there. A-S and Trane are the same product with a little different cosmetics outdoors. I think he just wants a commission check, not to help you.
And the dealer saying American Standard equipment is better than Rheem & Trane loses credibility right there. A-S and Trane are the same product with a little different cosmetics outdoors. I think he just wants a commission check, not to help you.[/QUOTE]
My first question always is, what does the Manual 'J' calculation show for loads? I may be all wrong as I'm just guessing but for 900 square feet and 750 square feet, you seem to have a lot of cooling. That's a total of 4.5-tons for 1650 square feet of space. I say it seems like it's oversized because I just did a load on a 2,611 square foot, 2-story residence that requires 3.5-tons. Now you may have entirely different (hotter, wetter) weather where you are located but it sure seems like a lot for that space.
I'd highly recommend a Manual 'J' calculation analysis before any other money is spent. Once that's known, a good diagnosis of the duct system is in order (Manual 'D' along with Manual 'T') to determine where the problem really is hiding.
If you really want winter and summer humidity control, include a whole house humidifier and dehumidifier as part of your package. I would include fresh air ventilation as part of the comfort, IAQ pkage. A ducted whole house ventilating dehumidifier will get controlled fresh air ventilation to purge indoor pollutants and renew oxygen. The dehumidifier will maintain 50%RH during spring/summer/fall.
Originally Posted by CoquiLostInNY
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
When trying to "fix" comfort issues in a home always start with the home first.
If the humidity is hard to control inside the home then there is a reason that the humidity is either getting in or out. If you don't address the leaks first the new equipment may be able to make up for the leaks, but you're just going to spend more energy dollars and installation dollars to solve a problem that might have been fixed with something as simple and inexpensive as caulking cracks or sealing leaking duct work.
Same thing applies to rooms that don't cool or heat as well as other areas of the home. Maybe those rooms were additions or original to the home and aren't insulated as well. Yes, sometimes changing out equipment can make the bad situation better, but again you're going to pay a lot of money to change out equipment and pay the utility bills to operate it which will almost every time be much more costly than finding and fixing the root cause instead.
After fixing issues with the home, next is the duct work/ air distribution components. Maybe the trouble areas don't have the right amount of air moving into or out of them to be able to condition properly. Your heating and air conditioning system can be working perfectly, but if it can't move air from the equipment to the spaces needing conditioning in sufficient amounts to transfer the needed amount of energy, you're going to have too cold or warm of rooms.
Variable speed and multiple capacity equipment is on the market to serve one main purpose and that is that the weather is not constant. Most every home experiences a wide spread of temperature swings through the year. A single sized AC or furnace is installed to handle the extremes that happen a very small percentage of the days in a year. The rest of the time the equipment is too big to do a "perfect" job. Variable speed or multiple stage equipment is an attempt to get multiple sizes of equipment in one piece and widening the range that the system is close to the actual outside conditions throughout the year.
Look at everything first and once all the information is gathered then and only then can you make an informed decision as to what needs to be done first, second and third....... and be assured your hard earned money is being spent wisely.
Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.
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