Honeywell Humidicalc Recommended Instead of Outdoor Sensor? (Automatic Humidity Control)

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Is there a consensus whether Honeywell's Humidicalc is better or worse than using an actual outdoor sensor, as with Aprilaire humidifiers that automatically adjust the humidity?
The following is from a Honeywell PDF manual: "The HumidCalc+ software inside your automatic humidity control is designed to measure or infer outdoor temperature and automatically adjust the humidity based on the frost factor setting that the homeowner sets to allow for variances in furnace size, window type and insulation."
In trying to find info on the web, I found this:
"Honeywell humidistat wins 'Seven Wonders' Engineering Award. Contracting Business, April, 1999
"No outdoor sensor needed for most applications Honeywell's new humidistat has earned a Seven Wonders of Engineering Award from the Minnesota Society of Professional Engineers. The H1008 Automatic Humidity Control with HumidiCalc+[TM] Software is the first standalone humidistat to control to dewpoint instead of relative humidity."
http://findarticles.com/p/articles/mi_hb3071/is_199904/ai_n13102640
Thank you very much for any helpful information.
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Is there a consensus whether Honeywell's Humidicalc is better or worse than using an actual outdoor sensor, as with Aprilaire humidifiers that automatically adjust the humidity?
The following is from a Honeywell PDF manual: "The HumidCalc+ software inside your automatic humidity control is designed to measure or infer outdoor temperature and automatically adjust the humidity based on the frost factor setting that the homeowner sets to allow for variances in furnace size, window type and insulation."
In trying to find info on the web, I found this:
"Honeywell humidistat wins 'Seven Wonders' Engineering Award. Contracting Business, April, 1999
"No outdoor sensor needed for most applications Honeywell's new humidistat has earned a Seven Wonders of Engineering Award from the Minnesota Society of Professional Engineers. The H1008 Automatic Humidity Control with HumidiCalc+[TM] Software is the first standalone humidistat to control to dewpoint instead of relative humidity."
Thank you very much.
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Since the dew point and condensation on your windows and inner walls is directly related to outdoor temperature, I personally can see no compelling reason to prefer a software algorithm which attempts to "infer" when the humidifier is called for or not.
The Aprilaire, in addition to using the outdoor sensor, has a consumer adjustable control to correct for the individual effects of furnace size / blower speed / insulation / etc. This in concert with the outdoor sensor measurement very nicely compensates for all of the external and internal effects of importance.
It is my personal belief that the Honeywell solution has one and only one virtue.....it allows the installer to not have to deal with running a wire to the outside, drilling a tiny hole for the wire to pass through, mounting the sensor, and thus spending another hour putting it in.
Having lived with older, non automatic humidifiers, and now using the Aprilaire and outdoor sensor in a widely varying northeast climate, I would never want to do it any other way. This Aprilaire just works superbly and with no issues whatsoever. The extra hour spent running the outdoor sensor was very well worth it.
Smarty

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It raises the fuel bill. Airsealing can raise the indoor RH, while lowering the fuel bill.
Nick
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It really doesn't raise the fuel bill, since the furnace cycle is exactly the same whether or not the humidifier is installed. The humidifier has a very small fan inside which does draw a negligible amount of electricity, but this is the only "fuel" required. Since the Honeywell humidifier also draws electricity, I don't see how the Aprilaire using an outdoor sensor can in any way whatsoever use any additional energy / fuel when compared to the Honeywell.
If your point is that adding ***ANY*** humidifier requires energy, (in this case a very small amount) versus better sealing of the house, then I agree that airsealing the house does raise the relative humidity. In my case, I still need a humidifier even when the house has been carefully insulated, weather-stripped, and sealed.
The original poster is merely trying to compare the merits of the Honeywell which does not use an outdoor sensor versus the Aprilaire which does use an outdoor sensor. I know it would be very attractive not to use any humidifier whatsoever, but in the area where I live where subzero temperatures occur commonly in the long winters, the only way I have been able to get a comfortable house which has no dew on the windows but is nicely humidified to avoid dry throats, dry noses, itchy skin, huge electric shocks when walking on carpet, sticky doors, sticky drawers, etc. is to use a powered humidifier and to control it with an outdoor temperature sensor.
Smarty
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Wrong. It takes 1000 Btu to evaporate a pound of water.

Wrong. That's a tiny part of the fuel requirement.

Wrong. How much energy do you need to keep your house RH 50% at 70 F with an indoor humidity ratio wi = 0.00787 pounds of water per pound of dry air when the outdoor humidity ratio wo = 0.0025, with 200 cfm of natural air leakage?

Sounds like you need more airsealing. How much fresh air would you need for wintertime DEhumidification, given Andersen's estimate that an average family of 4 evaporates 2 gallons per day of water indoors by breathing, showering, cooking, washing floors, and some green plants?

Wrong. Given your natural indoor humidity sources, you might keep a more airtight house at a comfortable indoor RH with a lower fuel bill with simple ventilation controls.
Nick
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Nick,
Let's go through this point by point.

I disagree. Since the furnace cycles exclusively on temperature and the burner cycle is determined by the thermostat, the only way your claim would have the potential to be correct would be if the moist humidified air requires more energy to heat than the same air if it were to be dry. If this is indeed your argument, then your claim is wrong and specious, since your alternative "airsealed" humidification approach would, in fact, require this additional energy as well. Whether the moisture was added by my humdifier or retained naturally by better weathersealing, the incremental cost of energy to heat the same moisture-laden air which is aritificially humidified with the humidifier should therefore be ***the same** as the energy to heat the moist air resulting from better airsealing.

Again, I disagree. This is the ***ONLY*** incremental energy use, since moist air requires the same energy to heat regardless of where the moisture comes from.

Nick,
I have used and applied all conventional methods of both blown-in and stapled-in insulations, weather-stripped everyplace, have excellent windows throughout, and still come up extremely dry. Your "typical" example is worthless in my case.........I have no family of 4 since my kids moved out decades ago, do very little cooking since I eat out daily, vent my dryer to an external outside vent, have no plants, no pets,.....and most important, know from very practical experience that without supplemental humidification that this place is dry as a bone in the winter months.
I therefore reject your entire set of counter-arguments entirely. Even if I were to accept your premise that the evaporation of a gallon or so of water per day was an incremental cost of a five or ten thousand BTU daily, this is still on the order of way less than 1% of my daily heating consumption.
Smarty
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Really? :-)

Nick
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Hint: 70 F air weighs about 0.075 lb/ft^3.
Nick
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Nick,
You answered your own question several times now. It takes 1000 BTU of energy to evaporate a pound of water. It matters not whether this energy is expended in my hot water tank, dryer, or any other contributor to the moisture in my house.
If my humidifier supplies moisture rather than my cooking, drying, etc. the net energy penalty is precisely and exactly the same.
The house is a closed system, as closed as I can make it with all sorts of "airsealing"." Any incremental energy needed to raise the humidity has to come from someplace, and it matters not whether this is the humidifier, bathing hot water, or any other friggin source.
I have 2 degrees in engineering, and have plenty of thermodynamics in my education, so if you want to discuss this in terms of entropy, enthalpy, sensible heat, or any terms, let's go at it.
Smarty
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So now you disagree with yourself? :-)

If that were true, you would need DEhumidification in wintertime.

So this should be a piece of cake:

A typical US house leaks about 200 cfm. An "airtight" US house might leak 60 cfm. A 2400 ft^2 house that meets the Canadian IDEAS standard might leak 1 cfm...
Nick
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Nick,
I did not state nor have I assumed that my house is an idealized, perfectly closed system with no flows in or out. There are, however, no longer economical ways to further reach a 60X improvement to go from my present "airtight" house to the Canadian 1 cfm "ideal" you refer to.
My original reply talked directly to the question raised by this specific thread, namely, whether the Honeywell Humidicalc algorithm is recommended versus the use of an outdoor temperature sensor. Your series of attacks and comments have not offered any insights or contributions whatsoever on this thread's topic. Since you have chosen to hijack this thread on another topic with remarks which are critical and disparaging to my original reply, I have felt obliged to respond. I do so reluctantly since my basic opinion is that this exchange does not serve the original poster in answering his question in any way, but instead, leads off in the path of your digression.
My prior comments center on the premise that energy to evaporate moisture into the home is expended regardless of whether the humidifier, the furnace, the hot water tank, the clothes dryer, or other appliance provides it.
A house with a less than perfect seal does indeed require more energy to heat and humidify, and neither of us needs to further elaborate on such an obvious distinction.....no doubt homes built to the newer Canadian standards will use less energy and require less humidification.
I have never disagreed with the physical fact that energy is required to evaporate water. My only disagreement was, and is, your assertion that a humidifier inherently demands more heating fuel, and my reasons for so believing are as simple as the observation that moisture evaporated into the air requires energy from someplace. A family of 4 (to use your example) burns additional energy in the activities you cite (cooking, bathing, washing and drying clothes, etc.) to evaporate equivalent humidity that a humidifier would provide. And in a perfect world where true adiabatic homes with no flows or losses exist, the need for either would be moot.
Perhaps in some home in the future where there is only 1 cfm of 'leak' it will be, as you assert, possible to avoid a humidification method entirely, but I, for one, will reserve judgment until much more is known about the consequential issues of mold, oxygen deprivation, smells, radon effects, and other poor air quality issues.
Since the original topic remains unanswered by opinions other than my own, I welcome your thoughts from Villanova's Electrical and Computer Engineering Department as to how a Honeywell humidistat using only a software algorithm might, as the original poster asks, compare to the method used by several other manufacturers who add an outdoor temperature sensor to allow their algorithms to adjust to outside changes.
Smarty
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Have you sought professional help with a blower door test?
Why 1 CFM? How many min CFM do we need to keep a house RH 50% at 70 F with an indoor humidity ratio wi = 0.00787 pounds of water per pound of dry air when the outdoor humidity ratio wo = 0.0025 (Phila in January) and you and your pint-a-day green plants naturally evaporate 1 gallon of water per day?
Hint1: 8lb/24h = 60CFMx0.075(wi-wo).
Hint2: ASHRAE suggests 15 cfm of fresh air per full-time occupant.

You may well find that you did, if you re-examine your words carefully, but it's nice to see you reagreeing with yourself :-)

Sure. Aprilaire's advertising ignored that for years and claimed people could save energy by turning the thermostat down, but they dropped that claim after I pointed out that the thermostat savings were 10X less than the heat required to evaporate the water, in a typical US house.

It's perfectly doable today with more than 1 CFM.

"Build it tight and ventilate it right" with a mechanical system, eg a bathroom or kitchen exhaust fan with a humidistat that turns it on when the indoor RH rises to 50% in wintertime. For extra credit, you might figure out how to automatically decrease that 50% setpoint when it's colder outdoors to avoid condensation on indoor window surfaces.

Clever Honeywell thermostats measure indoor air and wall temps and temporarily raise the air temp to compensate for initially colder walls, which can save energy by prolonging night setbacks, compared to air-temp- only thermostats. Maybe clever Honeywell humidistats are mounted indoors on exterior walls, so they can get an idea of the outdoor temp, which would be colder with a larger air-wall temp difference, but how would it know the wall or window insulation values? It might get calibration help from an owner who pushes a button when there is condensation.
Nick
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Nice try but a failing grade, Nick. Go to the back of the class.
The Honeywell Humidicalc is a duct mounted device, and does not use the exterior walls in any way whatsoever.
Smarty
http://electronicaircleaners.com/database/index.mv?Screen=PROD&Store_Code=ElectronicAirCleaners&Product_Code=H1008A1008

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No thanks, asshole :-) Then again, my two hints were insufficient for you?

http://electronicaircleaners.com/database/index.mv?Screen=PROD&Store_Code=ElectronicAirCleaners&Product_Code=H1008A1008

So they have something like that button, in the "frost control" knob. Maybe their patented Humidicalc software (what's the patent number?) estimates the outdoor temp by the furnace duty cycle, ie the percentage of time the duct air is more than (say) 120 F.

Hint3: CFM = 8/24/60/0.075/(wi-wo) = 13.8.
Nick
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Nick,
Your original reply to my one (and only) attempt by others on this newsgroup to answer the stated question was dismissive, not at all to the point of how the two humidistats compare, and digressive since it answered only the question which you (yourself) posed...regarding water evaporation.
When I answered the original reply, you found it necessary to treat my answer (which was directly on the poster's topic) in a sophomoric, pedantic, and rude manner with your "I'll give you a hint" form of arrogance.
When I went to engineering school and for the 40 years thereafter, I was taught to do research to solve a problem. A mere 90 seconds of research on the poster's question revealed Honeywell's description and ads for the Humidicalc duct-mounted humidistat.....clearly something incapable of making any inference about external wall temperatures.
So now your reply, rather than addressing the topic is a personal attack. Is name-calling part of what they teach at Villanova Computer and Electrical Engineering School? It is very juvenile, and displays how angry and embarrassed you truly are.
Smarty
wrote:

http://electronicaircleaners.com/database/index.mv?Screen=PROD&Store_Code=ElectronicAirCleaners&Product_Code=H1008A1008
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"When I was a lad I served a term as office boy to an attorneys firm..."

You never learned to think? :-)

And you never learned to read? :-)

That would be consistent with their statement that we need the outdoor temp sensor with multizone systems...
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

Thank you very much for your replies, and the time, etc., spent on them. I appreciate it. Other helpful opinions from knowledgeable people are also welcome.
Thank you.
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poster3814,
Very glad to try to help you answer your question. In researching this matter, I also found your post in the home do-it-yourself web site forum, and hope you have been able to get some additional insights.
Having installed humdistats of both the "outdoor sensor" type (the later model Aprilaire) as well as those of the earlier type (Sears, Aprilaire, Autoflow), no doubt it is much simpler to install a humidistat directly in the furnace plenum with no wiring going to either a separate humidistat upstairs in the heated space or wiring going to an outdoor sensor. The time saved in not wiring, and also time saved in not mounting an outdoor sensor, adds up to at least an hour or two, maybe more. It is my belief that the Honeywell solution appeals to installers for this reason.
The extra labor invested in installing an outdoor sensor and wiring it seems to pay off well, based on the limited sample of systems I have had in this house. Not until I installed the outdoor sensor Aprilaire did I truly reach the total automation I was seeking, where the dew point is dynamically adjusted and there is never, ever, ever,.....any moisture, frost, or dew forming on my windows or anyplace else, yet the humidification is always extremely comfortable with none of the problems arising when there is too little humidity. My kids were prone to allergies when they were young, my wife complained on dry skin, we frequently drew big sparks as we walked across the carpets, and drawers and doors would begin to stick. The outside sensor eliminated any misadjustment issues entirely.
As to whether a Honeywell Humidicalc with no outdoor sensor sitting in a basement cold-air return plenum can infer enough from the surrounding air and plenum temperature / humidity to make really appropriate guesses about what the dew point is remains to be seen in my opinion. Given the option of a direct measurement of outdoor temperature versus a software algorithm which, at best, knows only current and past temperatures, and current and past humidity local to the duct, it is hard for me to imagine a superior outcome, particularly since the Aprilaire humidistat also sits in the same location when installed and also has humidity and temperature data to work with, or so it appears. Moreover, Honeywell also adds an optional outdoor temperature sensor when controlling either multizone or heat pump systems, since in either / both cases the local duct measurements are insufficient.
Good luck with your decision and glad to be of help. I am sorry for the digression which occurred in this thread earlier regarding energy needed to evaporate water.
Smarty
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It's easily seen, given the frost control knob feedback, if it measures the furnace duty cycle, ie how often the duct air is moving. A system with an outdoor temp sensor and no user feedback might do a lot worse, with no knowledge of window R-values.

That's the important part, you pompous ass :-) Caulking and humidification can both increase indoor humidity, but caulking reduces fuel consumption, and humidification can dramatically increase it.
Nick
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