higher efficiency=less moisture?
There is a radio talk show here in Houston where the host always talks about the negative effects of having too much efficiency. He says that a high efficency split system will not pull enough moisture out of the air because it does not run long enough. I am under the impression that if a Manual J load calc is done and the system and ducts are all sized properly then the only thing that would change by having an 18 SEER system versus a 12 SEER is your electric bill would be lower and you would probably have a much quieter system. Does this overpaid radio guy know what he is talking about?
higher efficiency=less moisture? CORRECT in some cases.... i have seen what your talking about where inccorect sizing or poor ductwork can have adverse effect...
18seer will use less energy than 12 seer correct..and Variable blower will be quieter if set up correctly and proper ductwork..and that radio guy does not know what he is talking about..high seer units with variable blower are designed and programmed to run the fan working with a humidistat spacifically to keep humidity at lower levels...he may have had poor install and just be all huffy, call him and tell him to look up the facts and change his moist diaper...
Jason J Saylor
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East Coast Division
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Moist Diaper, that's funny. Thanks for the tips!
I am a homeowner in Fulshear and get the Houston radio programs. Could you give a clue or two when I might hear this program?
Long runtimes are a function of system sizing and probably have nothing to do with SEER. There *might* be an issue with SHR, Sensible Heat Ratio but that is not what you quoted. To get the max SEER a system can be built with high SHR which means low latent heat removal -- this is all theoretical to me and I cannot promise it actually happens. It would seem to me the ideal system for Houston climate will use the highest SEER condensor component, but choose a coil which runs colder, which means more humidity removal, which means not the highest SEER system.
Best wishes -- Pstu
He says that a high efficency split system will not pull enough moisture out of the air because it does not run long enough.
A split system rated at 36k BTUs @ 95F/80F indoor/outdoor removes 36k BTUs per hour, whether it's 6 or 18 SEER.
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As you go up in efficiency you can find less moisture removal. Varies by brand and model. For example, most 13 SEER Rheems have a sensible to total ratio of 70% meaning at ARI conditions, 70% of the capacity is sensible, 30% latent. I looked up a 16 SEER recently, on high it had a 75% sensible ratio. I've seen that in other brands too. A-S/Trane is rather low on their 13 SEER units as well. But then some brands have a 13 SEER ratio of 75% sensible so they would be no better than the high end of other brands.
Some brands on low have an even higher ratio so the time spent on low isn't removing that much moisture. So don't buy a 2 stage always expecting better humidity control.
So, as always, key is not oversizing, blower speeds below 400 CFM/ton and if going with a variable speed blower, use a VP IAQ or similar and hook up the dehumidify on demand.
install a humidistat or iaq and use the blower to your advantage. many of these units do have a higher instance of sensible heat removal by a single digit percentage, but add the humidity control and make it do what you want. if your latent load is not real high, you can run at high speed without worry. when rh goes up, the system takes over, drops fan speed and performs dehumidification.
The show is on 700am ksev on sat from 2pm till 4 i believe..called the "thirty green radio show" with a guy named Gary Parr. I listen to that station all the time and have heard his show numerous times.
Originally Posted by pstu
He does have a web site by the same name.
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On an a/c unit longer runtimes do help with efficency. The first 15 mins of operation for a unit is very inefficient, reducing that by sizing properly and multiple stages helps reduce your cost.
Originally Posted by pstu
If I lived in Houston and was on the radio, I'd be talking about leaky ducts and leaky buildings and stupid things done all the time that make homes and commercial structures expensive and clumsy to keep comfortable.
Number one maxim for hot, humid climates: you can't condition air that you can't contain!
Make it tight, ventilate it right. Give the building the high SEER number.
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 am acquainted with Gary Parr and would like to give him the chance to say he was misquoted. Certainly he knows about ACCA methods and should know better than that. Used to listen to his show especially when it was just him and called "Gary on the Air", but with his recent "Thirty Green" team approach it seems to have become more generic and less interesting. For what that's worth.
Best wishes -- Pstu
Sounds like Gary Parr may have listened to David Debien, who also used to have a talk show in Houston. Some of David's methods were sound, for the Houston area. David and I clashed when he started telling contractors in my area his methods, which can harm equipment in my area.
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David Debien influenced a lot of people in this area and was a real asset to the Houston community. I especially enjoyed his well articulated opinions which sometimes clashed with conventional wisdom. It would be interesting to hear which of Debien's opinions were a poor fit for conditions in your area.
Originally Posted by RoBoTeq
I am actually going to defend Gary Parr in this particular thread (not to be construed as defending him in every aspect). His radio statements about improving the building envelope, are very much in line with what Shophound has said. I have not heard him dissent from ACCA wisdom, and I think if one asked him directly whether high SEER air conditioners have poor humidity removal, he would give a reasonable answer and not a half-truth. He would probably say "it depends" and follow up with truthful examples. Listening to a radio show it is sometimes easy to hear something different from what the AC guy is trying to say. Now if we were speaking about the other radio guy in the area, I have heard Tom Tynan deliver some real howlers on the subject of AC, sizing, and humidity. Tom listened to David Debien when he was alive, but he only heard the simple version and sometimes misunderstood.
Regards -- Pstu