Dehumidifier anti-icing switch
Matt
Lately the evaporator has been icing up so that no water is produced.
Inspected the anti-icing switch while it was iced up: the base of the
switch was pretty well covered with ice. The evaporator coil to which
it is clamped was covered with ice too of course. There was some
corrosion between the coil and the switch.
I removed the switch and hooked it to a continuity tester (digital
ohmmeter actually). At room temp the switch is closed as expected.
When I put it in a freezer (-4 def F or so) it opens as it is supposed
to, which is unexpected. I mean the switch seems to be working, when I
don't have any other explanation for the ice-up.
Should it be enough that the base of the switch is embedded in ice? I
mean that should be enough to open the switch, shouldn't it? Or does it
need to get colder than ice?
Has the switching temperature of the switch changed over time and gotten
too low, even though it still opens at very cold temps?
I was thinking maybe the switch didn't have good enough contact with the
evaporator coil, but gosh, if it is embedded in ice ...
Doug Miller
>Whirlpool household dehumidifier, about 12 years old.
>
>Lately the evaporator has been icing up so that no water is produced.
Clean the evaporator coil. I have two Whirlpool dehumidifiers of similar age
(9 and 11 years), and that's what causes mine to ice up: dust building up on
the evaporator.
Matt
Model AD40G1
Looks like this:
http://images.fixya.com/W/Whirlpool/177x150/20825845.JPG
I fix a section of furnace filter inside under the grill, and change it
every year or two, so both the evaporator and condenser stay pretty clean.
Matt
I just tested the switch in ice water. It does not open in ice water.
Evan
> >> Whirlpool household dehumidifier, about 12 years old.
>
> >> Lately the evaporator has been icing up so that no water is produced.
>
> > Clean the evaporator coil. I have two Whirlpool dehumidifiers of similar age
> > (9 and 11 years), and that's what causes mine to ice up: dust building up on
> > the evaporator.
>
> Model AD40G1
> Looks like this:http://images.fixya.com/W/Whirlpool/177x150/20825845.JPG
>
> I fix a section of furnace filter inside under the grill, and change it
> every year or two, so both the evaporator and condenser stay pretty clean.
Just because you have a filter inside of something doesn't mean that
the
thing the filter is installed in never has to be opened up and cleaned
every once and a while...
As to the switch you described not working when installed on the coil
subject to the icing condition but working under your ideal test
conditions
and then again not working when you submerged it in ice water,
could it be that some of the ice on the coil melts and flows into the
switch ?
You could try replacing the switch but it also sounds like cleaning
the coils with HVAC coil cleaner more often than never would be
a good idea too...
~~ Evan
Matt
> Whirlpool household dehumidifier, about 12 years old.
>
> Lately the evaporator has been icing up so that no water is produced.
http://www.appliance411.com/faq/dehumidifierfrosting.shtml
> The most common cause of complete and even frosting of the evaporator coil is too cold of ambient room temperature. Most dehumidifiers are not meant to be used when the room temperature drops much below 70°F and certainly not below 65°F (depending on humidity level). There are however some models called "basement dehumidifiers" (see the link below) which are and could be used in cool room conditions.
>
> Good air flow required! Another possible cause of complete frosting is poor air flow through the unit. If the fan motor is not turning fast enough (or at all) or the evaporator, condenser or filter (if used) is plugged, each could result in poor air movement.
Matt
> On Apr 17, 1:04 am, Matt <m...@themattfella.xxxyyz.com> wrote:
>> Doug Miller wrote:
>>> In article <XX9yn.11008$Db6.5...@newsfe05.iad>, Matt <m...@themattfella.xxxyyz.com> wrote:
>>>> Whirlpool household dehumidifier, about 12 years old.
>>>> Lately the evaporator has been icing up so that no water is produced.
>>> Clean the evaporator coil. I have two Whirlpool dehumidifiers of similar age
>>> (9 and 11 years), and that's what causes mine to ice up: dust building up on
>>> the evaporator.
>> Model AD40G1
>> Looks like this:http://images.fixya.com/W/Whirlpool/177x150/20825845.JPG
>>
>> I fix a section of furnace filter inside under the grill, and change it
>> every year or two, so both the evaporator and condenser stay pretty clean.
>
>
> Just because you have a filter inside of something doesn't mean that
> the
> thing the filter is installed in never has to be opened up and cleaned
> every once and a while...
>
> As to the switch you described not working when installed on the coil
> subject to the icing condition but working under your ideal test
> conditions
> and then again not working when you submerged it in ice water,
> could it be that some of the ice on the coil melts and flows into the
> switch ?
It looks to me like the switch is sealed and is supposed to be
waterproof. There is a sealant like epoxy or silicon around the wires
where they go into the housing.
http://www.appliancezone.com/ShowProduct.aspx?id=3824&AspxAutoDetectCookieSupport=1
P/N 1168777
> You could try replacing the switch but it also sounds like cleaning
> the coils with HVAC coil cleaner more often than never would be
> a good idea too...
I am not opposed to that idea, but I don't know how to tell whether they
are dirty enough for that. I can tell you that I can see between the
fins easily.
There are some patches where dust is building up a little here and
there, and I will remove that dust with a vacuum cleaner, but I think I
can say that that is not going to increase the flow rate by 5% or
probably even 2%.
To be brief: the coils look clean enough to me.
There is considerable dust on the filter. There are some small side
vents anyway where air can bypass the filter.
Regardless of what is causing the icing, should it not be shutting down
before it ices up?
>
> ~~ Evan
ransley
I bet it needs Freon, its old.
Stormin Mormon
have the cover off. I'd suggest a generous spritz of Simple
Green. Wait five minutes, and rinse with warm water. Do this
a second time. Use a nylon brush or tooth brush to remove
any visible dirt and grime.
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"Doug Miller" <spam...@milmac.com> wrote in message
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Stormin Mormon
can be purchased?
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"Matt" <ma...@themattfella.xxxyyz.com> wrote in message
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Matt
> It's clearly not doing its job.
I am inclined to agree, since the switch stays on when immersed in ice
water.
It is hard to think of a way that you are wrong on that point.
Somehow we are not getting much agreement though.
> Perhaps a replacement switch
> can be purchased?
It's about $20, including S&H, which I am happy to spend if that will
fix it.
tra...@optonline.net
Did you verify that the the rest of the system that the switch is
connected to does what it's supposed to? Don't know how they all
work, but one I recently worked on has a reversing valve, which
actually reverses the system so it becomes a heat pump that warms the
evaporator coils. I'd try connecting and disconnecting the two wires
while it's running.
Also, the unit I worked on was icing up and the cause was the blower
motor was shot. Normally, they should not be icing up unless it's in
a cold environment. That's the difference with the low temp models,
they have provisions to defrost if needed.
Joe
>
> Lately the evaporator has been icing up so that no water is produced.
>snip<
Older dehumidifiers are real picky about ambient temperatures. When
your basement or whatever gets over around 60 F or so, the unit will
be just fine. Keep it clean and warm and it will likely work for a few
more years. Go ahead and put everything back together and get back to
spring chores with a clear conscience.
Joe
Matt
> On Apr 16, 10:31 pm, Matt <m...@themattfella.xxxyyz.com> wrote:
>> Whirlpool household dehumidifier, about 12 years old.
>>
>> Lately the evaporator has been icing up so that no water is produced.
>
>> snip<
>
> Older dehumidifiers are real picky about ambient temperatures. When
> your basement or whatever gets over around 60 F or so, the unit will
> be just fine. Keep it clean and warm and it will likely work for a few
> more years. Go ahead and put everything back together
So you don't believe the anti-icing switch should go off when immersed
in ice water? How is it going to prevent icing if it stays on at the
freezing point?
BQ340
> How is it going to prevent icing if it stays on at the
> freezing point?
They are not precision calibrated switches, it may open slightly lower
than freezing. Some have the operating range printed on them, any
numbers on it that have a F after them?
MikeB
Matt
duh ... good question ... thanks ...
Here are the markings on the switch:
T-O-D
37TA32 31097 1168777
F53-30F J9850
Here is the product line:
http://www.tod.com/productdetail.asp?ProductID=82
> Moisture Resistant Temperature Control
>
> The 37T series of 3/4” (19mm) bimetal disc thermostats from Therm-O-Disc® offers proven reliability in a moisture resistant sealed design.
> The 37T is the most popular and widely applied thermostat in refrigeration applications such as defrost termination and ice cube maker control. It is also applied in a range of heat pump and air conditioning applications.
http://www.tod.com/loadMedia.asp?Method=Spec&MediaName=37T.pdf&ProductID=82&ReturnPage=14
I don't see anything in the product info that relates the part number to
the temperature range.
As you hinted, there is that "30F" number, but that doesn't seem to
match the temp ranges described in the product info.
Stormin Mormon
much more time in analysis.
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"Matt" <ma...@themattfella.xxxyyz.com> wrote in message
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Matt
> Since the dehum coated your old switch in ice, I'd not spend
> much more time in analysis.
Meantime I've gotten the idea that the switch might work by sensing the
temp of the coil to which it is clamped, which would have to be below
freezing to attract frost.
As I mentioned elsewhere on the thread, the switch bears a marking
"F53-30F", which might indicate a switching temp of 30 degrees.
So I guess it could be that the switch would not turn off even when
embedded in ice---if it is not making good contact with the coil. And
it could be that if it were making good contact with the coil, it would
turn off before the coil gets cold enough to attract frost---at a temp
between the freezing point and the dew point.
If the switch is not making good contact with the coil, the hypothetical
design above wouldn't work. As I mentioned, there is some corrosion on
the coil where the switch is clamped.
terry
>
> - Show quoted text -
Agree ours (located in a cool basement) and which does not have an
icing switch AFIK; ices up easily when temperature falls to about
50-55 F. But in winter, here, the humidity of the basement air drops
any way and we just keep it 'turned back'.
During warmer more humid summer (it never gets very hot here anyway)
it works better with less icing.
One change have made is to rewire the fan to run continuously while
the unit is plugged in so that if ice does start to form the moving
air melts it more readily.
Matt
You and some others (eg Stormin') were right that it was an airflow problem.
Thanks especially to anybody who suggested cleaning the condenser.
I was only looking at the evaporator, which was quite clean. I didn't
notice that the condenser was fairly dirty. The airflow was such that
air could get in past the filter when the filter got a little plugged.
I took the whole cover off and put the innards outside under the hose
and sprayed water gently though the coils. Washed out some wet globs of
dust. Not huge globs, yet of a somewhat gratifying size.
I also brass-brushed the evaporator coil where the anti-icing switch is
clamped on. There was some green corrosion that might have been
inhibiting contact between the coil and the switch.
The filter itself probably slows the airflow, maybe enough to cause
icing when the filter gets somewhat dirty. The filter is not part of
the OEM design, but is my bright idea.
See my post elsewhere on stopping the vibration on this model.
I put it all together with a clean filter, and it is running fine.
Not clear that the anti-icing switch is working though. Could be the
improved air flow is enough to prevent the icing, and the switch hasn't
needed to work yet.
I wrote:
> Whirlpool household dehumidifier, about 12 years old.
>
> Lately the evaporator has been icing up so that no water is produced.
>
Stormin Mormon
once!
Very often, a machine is designed for some air flow value.
If you reduce the air flow, you get icing. This also happens
in air conditioning devices.
--
Christopher A. Young
Learn more about Jesus
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"Matt" <ma...@themattfella.xxxyyz.com> wrote in message
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Evan wrote:
> On Apr 17, 1:04 am, Matt <m...@themattfella.xxxyyz.com>
> wrote:
>> Doug Miller wrote:
>>> In article <XX9yn.11008$Db6.5...@newsfe05.iad>, Matt
>>> <m...@themattfella.xxxyyz.com> wrote:
>>>> Whirlpool household dehumidifier, about 12 years old.
>>> (9 and 11 years), and that's what causes mine to ice up:
>>> dust building up on
>>> the evaporator.
>> Model AD40G1
>> Looks like this:
http://images.fixya.com/W/Whirlpool/177x150/20825845.JPG
>>
>
Matt
> Glad to hear a kind word, now and again. Got one right, for
> once!
>
> Very often, a machine is designed for some air flow value.
> If you reduce the air flow, you get icing. This also happens
> in air conditioning devices.
You have repaid me for one time pointing to a reference about how the
human teeth are numbered.
terry
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
Interesting ........ have been following this dehumidifier thread, so
thanks for the follow up.
We have a very much used Sears type DH, got free. It worked OK for a
couple of years and then didn't.
So, in order to keep basement area drier and protect tools bought a
very similar new one. It works fine, not needed much in winter but it
runs more during our cool summers. Not sure if new one has an anti-
icing switch at all! Seems to be more a matter (with this newer one)
of setting it correctly so it doesn't form a block of ice on the
cooling coils.
last year took the cover off the older one and discovered that it was
a problem with anti-icing switch; it was operating 'too soon' or 'too
quickly'. Operating (switching to open) to cut off the compressor
almost as soon as any slight hoar frost formed on the coils. So
removed it and now the unit seems to operate OK. Must try it again as
weather gets slightly more humid. Keep meaaning to test oit out inthe
fridge/freezer to see at what temp. it opens!
On the topic of humidity. During our cool winters normal home heating
raises the house air temperatures and the relative humidity is thereby
lowered. We have electric baseboard heat which some claim is too
dry'.
One could call this a miserable 'spring'. It's an indication however
that 'something' IS happening to the climate. We are now getting more
rain into April/May, than in the past, not snow.
For example there is a local holiday in this part of Canada on May
24th, where traditionally we go trouting; the equivalent one guesses
of the more affluent 'Fly fishing'! Many people have an old fishing
pole in the trunk of the car or cab of the pickup and the spawning
season for trout is over mid month, so off we go with a few flies and
or a tail bait with a worm on it.
ANYWAY........ the point is that on May 24th the weather could/can be
anything from 50+ degrees to snow/sleet!
Also by the way; two points.
1) Is there any rule on which way the air goes through the unit?
Presumably room air is drawn in the back through the coils and
exhausted past the fan out the front? The fan motor only gets slightly
warm anyway and is also cooled by the now drier/cooler air from the
coils?
2) All the energy used by the DH (probably about 300 watts/hr?) Become
a small amount of heat within the house? Right? There's no heat pump
effect here because the whole unit is contained within the one room.
Similar, say to a fridge, which operates entirely within the shell of
the house.
Thanks to all for the postings.
Stormin Mormon
for you.
--
Christopher A. Young
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"Matt" <ma...@themattfella.xxxyyz.com> wrote in message
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Matt
> I'll admit I don't remember that moment. But, glad it worked
> for you.
sci.dentistry, I believe.
The point was it worked for you.
Matt
How do you know that that was "too soon"?
> So
> removed it and now the unit seems to operate OK.
What is your measure of OK operation? Keeps running steadily or
produces water steadily? If it isn't producing water, that is not OK,
and the evaporator may be iced.
I think my DH may have been running iced up a lot without me knowing,
since I had it connected to the drain by a hose and never had to empty
the bucket anyway. So I couldn't tell whether it was producing water.
Hopefully you mean 300W, not 300W/hr.
> Become
> a small amount of heat within the house? Right?
I wouldn't say 300W is a small amount. That could easily cost 5 cents
per hour ($36/month). And if you are using your air conditioner, it
will be another 300W extra power used by the A/C.
> There's no heat pump
> effect here because the whole unit is contained within the one room.
> Similar, say to a fridge, which operates entirely within the shell of
> the house.
It is a lot like running a window air conditioner with both ends inside
tra...@optonline.net
You said the switch opened in a freezer when it was -4F. That's
obviously a LOT colder than it needs to be for ice to form. It's
possible the ice by the evaporator never gets that cold. I wonder
what temp they are supposed to open at? Also, depending on how often
this thing runs, it might be wise to look into a new one. Todays
energy star units are probably more efficient than a 12 year old unit.
nibli...@gmail.com
Stormin Mormon
effect?
--
.
Christopher A. Young
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