Dehumidifier that doesn't...

tcmtech

Joined Nov 4, 2013
2,867
For my two bits If it was me I would go looking for one of those old heavy built older window AC units. I have several that are 30 - 40+ years old that run just fine still being they were built to last back then. All they need to make them into a good dehumidifier is to drill a hole in the condensation trap/tray so that the water can drip out before being picked up by the condenser fan and spit back into the room.

Years ago we had a 12,000 BTU unit in our house that had a pinhole in the bottom so it dripped its condensation out and that could easily fill a 5-gallon pail and then some in a good days run.

I say watch your local yard and garage sales for old beater AC units and see what you can find for $20. Pretty good chance it the thing is 30+ years old and the cheap front plastic face is busted up or missing all it needs is a good cleaning and the fan motor lubed up to make it into a pretty durable high capacity dehumidifier.

Thats how I get most of mine every year. They work good but due to their front face plates being busted up or missing they get tossed out for nothing more than being old ugly and needing a good cleaning. :cool:
 

#12

Joined Nov 30, 2010
18,224
I would go looking for one of those old heavy built older window AC units. I have several that are 30 - 40+ years old
You will dump more water per electron with a high efficiency A/C and there have been serious increases in efficiency in the last 30 years.
Not so much in the last 10 years.
 

tcmtech

Joined Nov 4, 2013
2,867
You will dump more water per electron with a high efficiency A/C and there have been serious increases in efficiency in the last 30 years.
Not so much in the last 10 years.
Experience has shown me otherwise. I've bought a few brand new high-efficiency units over the years for my bedroom or have installed the for friends and family and I have never found one to be a fair match to an old unit of equal BTU ratings or durability.

12K BTU new seems to be comparable in cooling and power consumption to 8K BTU old style so either those old units are underrated or these new ones are way overrated and durability wise they are a joke. 2 - 4 years before their plastic fans fall apart or the POS fan motor locks up or their aluminum tubing corrodes and looses the freon charge.

No thanks. I'd rather burn that extra 100 watts an hour and have a machine that can do what it's rated for and last for several decades while doing it even if it means it has a face made out of cardboard and duct tape.
 

#12

Joined Nov 30, 2010
18,224
Experience has shown me otherwise.
As far as durability, you're right. as far as BTUs per watt hour or quarts per BTU day, I'll bet my 45 total years of experience and my 30 years of design work with a State Certificate of Competency against your "experience". I've seen the math proved out in reality to 3 digits (and sometimes better). Just be clear about which aspects you are describing.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
Maybe you could add an external fan to boost the air flow.
What is the room temperature where it's located?
What happens if you just let it run. Does it frost enough to clog the coils?
I've been watching it carefully. I let in run all night to see what it would do.
• It is placed in the same spot where it's been sitting, working fine, for the last 6 years (not in winter). I suppose my basement is in the mid-60°Fs. Without the DH it can get up to 70%RH or so and the DH (a 50 pint model) can take it down to 35% in a day.
• Little water was collected overnight and the coils are completely frosted over. A big, flat, white cake from side to side and top to bottom.
• It blows air across my basement, so it's not a lack of fan per se.
• It has a filter before the coils. My wife cleaned it after the problems started. It looks clean but I have removed it completely now.
• The owner's manual says the frost may be due to recently turning the unit on, or having it in a room below 41°F. Neither is relevant.​

Does this fit with a low-freon condition?

Unless someone has a magic wand, my only recourse at the moment is to buy something else. #12 has hinted :p that an A/C might be a better choice, so I'm starting to shop for one.
 

#12

Joined Nov 30, 2010
18,224
More better information would be provided if the changes in frost patterns are observed, as compared to waiting until it's completely frosted over, thus occluding its own air flow. It might not be, "broken". It might be that the frosting is happening because the intake air is 65F and the evaporator coil must be below that temperature to accomplish any water condensation. This takes me to, "bad design" where the Freon regulator is a fixed diameter hole, so the machine can not adjust to conditions present as the room gets cooler. How about you try temporarily adding a heater to keep the room at 70F?
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
I could only do that by moving it upstairs, which could be worth a test once it thaws out again. Increasing the basement temperature isn't practical and a bad idea this time of year. When I get a chance I'll see how it freezes up. Bottom line, though, is that it worked fine for 6 years and now doesn't, under essentially identical conditions.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
Anybody know how to roughly match a dehumidifier capacity in pints to an A/C capacity in BTUs?

I'm a chemical engineer and could eventually figure it out but maybe there's a rule of thumb?

Looks like 8000 BTU gives roughly 50 pints dehumidification.
 
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tcmtech

Joined Nov 4, 2013
2,867
As far as durability, you're right. as far as BTUs per watt hour or quarts per BTU day, I'll bet my 45 total years of experience and my 30 years rating I have seen may of design work with a State Certificate of Competency against your "experience". I've seen the math proved out in reality to 3 digits (and sometimes better). Just be clear about which aspects you are describing.
Well, what more info do I need besides seeing first hand that a brand new high-efficiency unit of equal rating as the 40-year-old unit had trouble keeping up in identical running conditions? o_O

Also I have seen many on their efficiency listed as having lower amp draw which is due to having a power factor correction capacitor in them where the old one didn't yet the actual wattage draws were within a few tens of watts of each other according to an actual watt meter measurments and I have suspicions that most of the wattage savings was due to the new units having crappy underpowered 50 watt or less fan motors VS the old style units having large 100+ watt robustly built ones. :rolleyes:

The thing is the way I see it the laws of physics dictating the phase change actions of the refrigerants being used is a fairly fixed energy transfer for energy used ratios and the only major efficiency changes to be found are in either the compressor stage, compressor motor or high side/low side pressure differentials relating to either expansion valve design or condenser/evaporator design of which even that only has so much improvement that can be made which although can be used to cheat up the EER rating a good 25% by using a different testing conditions and measurement method than the old unit were run under the actual energy used VS energy transferred works out to less than a 10 % gain at best.

In all honesty going from an estimated EER of 11 - 12 to 13 - 14 is not a huge energy savings on the input end of things back period is several times the realistic life expectancy conservation pay so when the energy especially of the unit itself.

My old window AC unit used about 100 - 150 watts more than it's $350 high-efficiency replacement (EER ~11 Vs EER ~14) which for $350 that would take some (3,000,000 / 150 = 20,000) running hours on the energy savings break even which would at my normal 500 - 800 running hours a year take about 30 -40 years to break even despite the fact that the new unit lasted barely 1000 running hours before the fan fell part and the blower motor seized up and burnt out which would have cost me another $150 to replace. (And then the old beater went back in and stay there for another 4 - 5 years or so before bing moved to my workshed when I put in central air for the house.)

Now as far as certifications go you darn well I've dealt with enough certified idiots with contractor licences (many certified to no less than 15 decimal places of stupid at that!:p) to never take a piece of paper to mean a darn thing relevant to a guys actual knowledge and skill sets. :(
 
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#12

Joined Nov 30, 2010
18,224
Bottom line, though, is that it worked fine for 6 years and now doesn't, under essentially identical conditions.
That's pretty convincing evidence that it's, "broken"
When air conditioners are low on Freon, but not too low, they can ice up. Maybe the same holds true for dehumidifiers.
These two machines are almost the same as each other. Almost everything that applies to air conditioners applies to dehumidifiers except SHR (Sensible Heat Ratio). That is, the amount of energy devoted to changing the F temperature of the air compared to the amount of energy devoted to condensing water.
Anybody know how to roughly match a dehumidifier capacity in pints to an A/C capacity in BTUs?
I'm gonna have to look this up. It's in the first book in the course, and that was a very long time ago.;)
 

#12

Joined Nov 30, 2010
18,224
Now as far as certifications go you darn well I've dealt with enough certified idiots with contractor licences (many certified to no less than 15 decimal places of stupid at that!:p) to never take a piece of paper to mean a darn thing relevant to a guys actual knowledge and skill sets. :(
It sounds to me like you should get involved in the certification procedures of the HVAC industry and straighten out their flawed calculations and measurements. They obviously don't have a clue about how these machines work and need your help.

Seriously, if these guys don't know the difference between true power and apparent power, they have no business pretending they can set the standards for the whole planet.
 
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#12

Joined Nov 30, 2010
18,224
Anybody know how to roughly match a dehumidifier capacity in pints to an A/C capacity in BTUs?
It depends.
Yeah. I know that sucks for an answer. The best I can do is to give you some education.
Look at the PDF.
Find S/T. 4th column, among things like MBh, AMPS, and Hi PR
This is the sensible heat ratio.
Run over to the right side under 115 (Outdoor ambient temperature)
Down to the 3rd and 4th group corresponding to IDB (Indoor dry bulb temperature) in the third column, Fahrenheit temperature of 80 and 85
Under these conditions, the sensible heat ration is 1.00 and that means 100% of the energy is being spent on changing the F temperature of the indoor air. Zero is dedicated to turning humidity into liquid water.

Now the fifth column under 75 Outdoor Ambient
Indoor wet bulb temperature is 67F
Correspond to IDB = 70 (F) (That's pretty soggy air at 90% Relative humidity.)
In that condition, the SHR is 0.43
That means 43% of the energy is spent lowering the F temp of the indoor air and 57% of the energy is spent turning humidity into liquid water.

This shows that a 3 ton air conditioner (36,000 BTUs/hr) can use 20,520 BTUs per hour to make water.
Heat of vaporization is 1050 BTU/lb of H2O
That's 6.51 pounds per hour per ton of air conditioning.
If, "A pint is a pound, the world around." then a ton of air conditioner can produce 156 pints per 24 hour day if the indoor temperature is 70F and the outdoor temperature is 75F and the indoor wet bulb temperature is 67F.

There you have it. Zero to 156 pints per day per ton.

It seems to me that the "standard" conditions for a dehumidifier rating must include relative humidity and indoor air temperature.
 

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tcmtech

Joined Nov 4, 2013
2,867
It sounds to me like you should get involved in the certification ocedures of the HVAC industry and straighten out their flawed calculations and measurements. They obviously don't have a clue about how these machines work and need your help.

Seriously, if these guys don't know the difference between true power and apparent power, they have no business pretending they can set the standards for the whole planet.

How many things do we have in our lives now where standards being made are being set by people who have no clue about the actual science, physics and engineering and such of what it is they are setting the standards for?
Then on top of that how many things do we all see in our lives that have supposed ratings yet when put to work clearly can't come close to matching the old gear it is supposed to replace because of questionable testing or marketing practices that either no longer match the sets of standards once used or are based on a totally arbitrary set of working and testing conditions or standards that have near no relavance or meaning to the actual devices true performance?

In my life's experience of fixing most anything far too often I come across stuff that has been or is majorly screwed up by the guys who have the pieces of paper that say they are supposed to be knowledgeable enough to fix it and unfortunately the majority of those clowns belong to the electricians and HVAC industry.

I can't count the number of licenced electricians I have met over the years who can't answer basic electrical circuit or physics questions like the difference between watts and VA or anything like that about that work they do for a living.
Same with HVAC techs who can't convert BTU's to watts or any other measurement and certainly have no clue about how the systems they service actually work other than whatever it is is going to be expensive to fix it.:(
 

#12

Joined Nov 30, 2010
18,224
And here it is: 80F and 60% humidity.
http://www.basementsystems.com/base...difier-learning-center/energy-star-label.html

Let's relate that to the air conditioner specs for a machine with SEER of 14.
69.9F wet bulb temperature.
Extrapolating the available condition of 71 F wet bulb temperature from the A/C performance chart.
Extrapolating the outdoor F temperature between 75F and 85F because 80F is the indoor drybulb temperature and it's also the intake temperature for the condensor of the dehumidifier
The answer is.....(drum roll) 0.53 SHR.
47% of a ton is 5640 BTU/hr
1050 BTU/lb.
129 pints per day per ton. (129 pints per 12,000 BTUs)

I guess a "rule of thumb" might be 1% of the BTUs is how many pints per day.
That's about 7.5% low, but the machines are not going to run at, "standard" dehumidifier rating conditions all the time.
 
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#12

Joined Nov 30, 2010
18,224
I can't count the number of licenced electricians I have met over the years who can't answer basic electrical circuit or physics questions like the difference between watts and VA or anything like that about that work they do for a living.
Same with HVAC techs who can't convert BTU's to watts or any other measurement and certainly have no clue about how the systems they service actually work other than whatever it is is going to be expensive to fix it.:(
In this case, you aren't talking to an HVAC tech. You're talking to the State Certified Designer, and I just proved it with posts #33 and #35. As far as I'm concerned you can go blow your horse feathers up somebody else's bloomers.
 

#12

Joined Nov 30, 2010
18,224
Now let's look at a Consumer Reports, Top Rated, Energy Star Efficient, dehumidifier that sells for $300.
That's 70 pints/day on 820 watts.
820 watts at an efficiency of 14 BTU/W-hr (Giving the dehumidifier an unfair advantage by pretending it has some serious efficiency) = 11480 BTU/hr...96% of a ton of air conditioner.
The dehumidifier can make 70 pints of water and 95.66% of a ton of air conditioner can make 123.4 pints per day.
The $300 dehumidifier is 56.7% as effective as an equal sized air conditioner.

At Best Buy you can spend $100 less to get a 6000 BTU air conditioner that is NOT energy Star Rated.
http://www.bestbuy.com/site/frigida...hite/4791809.p?id=1219824088428&skuId=4791809
http://www.plessers.com/Frigidaire/ffra0622s1.htm
It's real power use is 540 watts. It's efficiency is 11.1 BTU/watt-hour

That cheap-@$$ A/C will drop.......... 72.68 pints per day for 540 watts and cost $100 less than
a top rated dehumidifier that drops... 70.00 pints per day for 820 watts

I have never done this math before and I am happy to see that my experience and instincts were correct.
It's nearly impossible to buy an air conditioner that won't out-perform, out-price, out-efficient, and out-last the best dehumidifiers you can buy.

Oh look! Did I find YOUR dehumidifier because it is Top Rated by Consumer Reports, not because I was looking for that "dh" you mentioned in post #25. I thought you meant De Humidifier, not a DH model by Honeywell.
 

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#12

Joined Nov 30, 2010
18,224
• The owner's manual says the frost may be due to recently turning the unit on
Let me clarify. Months of disuse allows the refrigerant to dissolve into the oil. The refrigerant becomes unavailable in the gas form. After running the machine for a few hours, the refrigerant is boiled out of the oil and resumes participating in the pressure/temperature exercises.
 

tcmtech

Joined Nov 4, 2013
2,867
In this case, you aren't talking to an HVAC tech. You're talking to the State Certified Designer, and I just proved it with posts #33 and #35. As far as I'm concerned you can go blow your horse feathers up somebody else's bloomers.
Yes and around here I can't say I have ever met any HVAC tech that could do the basic math you are doing to show what you are showing either and as far as designing them I don't doubt your abilities but I do doubt those of the people who design and build many of the new high efficiency units I see on the shelves most everywhere.

As far as horse feathers go how exactly do you explain how someone buys an equivalently rated unit to replace an old one and the new one doesn't come close to being able to cool as well? Shouldn't 12,000 BTU rating give equal cooling capacity regardless of who made it?
Or do air conditioners fit into the same rating system as small engine HP does where it takes a 12 HP Briggs and station to replace a 10 HP rated Koller or a 9 HP rated 40+-year-old Wisconsin? Nameplate HP should be HP regardless of who makes it right yet we all know that's not the least bit true?
 

crutschow

Joined Mar 14, 2008
34,285
I've been watching it carefully. I let in run all night to see what it would do.
• Little water was collected overnight and the coils are completely frosted over. A big, flat, white cake from side to side and top to bottom.
• It blows air across my basement, so it's not a lack of fan per se.
•------------------​
Does this fit with a low-freon condition?
I don't think it's a low-freon problem if it completely frosts over, which indicates it's cooling very well.
From what I understand, low freon will cause poor cooling and possible frosting on the refrigerant line, but not on the evaporator coils.
There may be a fan blowing air across the room but is it all flowing through the evaporator coils?
I think not very well.
 
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