ReplyYes, as lower humidity makes higher temps "feel" cooler, correct? Whatcha got in mind?Originally Posted by teddy bear
God Speed, Jim. We'll miss you - 2-26-23
[QUOTE=gary_g;1985803
I know what you're thinking: I can benefit from a 2-stage condenser because average summer temps in Baltimore are in the 80's, and I'll run on first stage a lot. I would also be able to raise the setpoint a few degrees because of lower humidity in the home from running on first stage.
Take care.[/QUOTE]
Actually, thats not what I was thinking.
I can't track my run times with the stat either.
But, did check it several times during various ambients. Both during the day, and some evenings. Just to double check its cycling. And capacity at the different ambients.
Along with using several different stats on it, to see what effect they had on it, and comfort.
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Yes, as lower humidity makes higher temps "feel" cooler, correct? Whatcha got in mind?
Sponsor & Professional Member*
I promte the ability of maintaining <50%RH without operating the a/c during wet cool weather or when the home unoccupied. By using a whole house dehumidifier with enough capacity to ro remove 4 lbs per hour of moisture regardless what the cooling load is, comfort and IAQ is assured.
During high cooling loads, your properly set-up a/c will keep your home dry. During wet, cool weather with low/no cooling loads, the dehumidifier removes the moisture for a fraction of the cost of cooling. The results of all this ideal temperature with ideal %RH eventhough you have extra capacity for hot weather and extra company. thermastor.com Ultra-Aire. There are others. Regards TB
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"
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Been away a while.
Gary G., thanks for the insight on how SEER is calculated, and the EER suggestion. I'll check out my current ratings on the AHRI site.
pstu, you bring up a good point regarding top tier single stage vs entry level two stage systems, I'll have to look at that more closely as purchase time comes closer, and I start requesting local quotes.
The Infinity stuff is nice though, and looks like it is along the lines of what I'm interested in. I havent found a dehumidifier in that line-up though?
Which dehumidifier are you using? How much higher do you set your thermostat when you are running the dehumidifier?
Not quite up to speed yet on the Manual J, I'll get there.
I'm sure all of this will make sense soon.
Thanks guys.
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tbear, thanks for bringing that product line to my attention, I'll certainly keep it in mind. Definitely another area I need to study.
Simple question- does variable speed imply two stage? Variable speed relates to fans, right? And two stage to compressors I think, but do single stage systems benefit from variable speed fans?
Is there an FAQ somewhere that explains the basic theory behind HVAC? I've got a ton of stupid questions. Thank you.
Last edited by *SSS*; 09-14-2008 at 05:55 PM. Reason: Repeatedly repetitive
God Speed, Jim. We'll miss you - 2-26-23
VS blowers enhance the performance of single stage A/Cs also.
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"I bought this house in June, 2.5 stories, 3500 sqft, built around 1998"
Your rich,,, why do you care? Call anyone local and get a price. simple.
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Useless post.
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This is my opinion as a homeowner, so it may cause upset to some of the professionals here. Sorry guys, feel welcome to comment on my opinion.
The blower motors on higher end air handlers (the indoor part of the AC system) have the ability to adjust their speed and are rightly called variable speed. They typically demonstrate this feature by slowly ramping up to speed at the start of a cycle and ramping down at the end of a cycle. This adds to comfort by making the operation of the system less obvious - it seems quieter when it just creeps up on you instead of starting with a rush.
Comfort is also obtained by the ability to run at reduced speeds to just circulate air since this will tend to eliminate hot or cold spots.
However, the control of the fan speed is never given directly to the user because the majority of systems rely heavily on using all the cooling capacity being generated by the outdoor condensing unit, which has at best only two capacities it can operate with. Some two stage units do it by having two separate compressors, some by running a single compressor in a reduced power mode.
The consequence of this is that the indoor unit has to handle the cooling capacity being supplied which means that the volume of air being passed has to meet a minimum. Here is where the variable speed motor shines because it is easy to set it up to move a given weight of air per second regardless of how many restrictions there are to the smooth flow of the air.
Poor (undersized) ductwork, dirty filters, closed dampers can all impede airflow, and a variable speed blower motor will automatically increase its speed to overcome the restriction and so meet the need of the outdoor system to have the heat removed from indoors match the heat being dumped outdoors by the condensing unit.
If the airflow is insufficient then bad things can happen like indoor units icing up or liquid refrigerant being returned to the compressor causing it to slug and eventually self destruct.
Until recently the AC industry did a good job of making their products work over an increasingly wide range of operating parameters. Thermostatic Expansion Valves feeding evaporator coils, variable speed blower motors, multi stage compressors all allowed the systems to respond in a limited way to changes in ambient conditions but the user in the end was limited to either getting cooling when the thermostat called for it or no cooling when the thermostat found that the setpoint was reached. There was no way to tell the compressor to run in smaller steps than OFF/PARTIAL/FULL capacity, and the best the evaporator coil could do was to monitor pressure and superheat with a mechanical TXV so as to have some limited control over refrigerant flow.
Recently the rest of the world looked at the problem and applied modern technology to allow the user to control the speed of their fan! A modern minisplit system can control the speed of its outdoor compressor precisely (usually by powering it with a variable frequency power source), and this allows the outdoor unit to match the cooling load presented by the indoor unit. The user has control of both the fan speed and the temperature setpoint of the indoor unit, so the cooling load is not dependent on only the indoor temperature. The user might ask for a small temperature drop at a high fan speed which would make for a high cooling load, or a huge temperature drop at a very low fan speed which would be only a small cooling load.
I know my top of the line Trane XL19 system does not give me the option of making those choices. I'm going to get either 1.5 or 3.0 tons of cooling at 600 or 1200 cubic feet per minute, and which one I get will be decided by the system - my only input is to tell the system what temperature I want to get to. The system controls the blower motor (600 or 1200 cfm), and the blower motor is smart enough to work a little harder as my filter accumulates dust, but I get no control over how much cold air I want supplied.
The floorplan of my (mid 1950's) house is such that the central AC system creates a zone covering most of the living space and is not effective for the kitchen or my office. The best way to cover those areas was to instal a minisplit, and this is why I now see the value in being able to control both temperature and airflow and have come to a belief that my expensive central system is positively agricultural in its simplicity compared to the microprocessor controlled minisplit.
In my opinion to industry need to take a close look at their products - I see a distinct parallel with the way that Detroit marketed their V8s and ridiculed the funny little Honda boxes that started to appear once upon a time.
God Speed, Jim. We'll miss you - 2-26-23
If your contractor would have used the correct stat, and wired it in properly, then your 19i would run at 4 fan speeds.
A VS blower does NOT over come all bad duct designs.
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