... it's possible the A/C has been not been running continuously for those 22 hours..

Why don't you install some sort of device to help you log the periods at which the A/C is running? Or would that complicate things too much for you?

 

Fresh data: 38 cups in the last 22 hours. That's 20.7 ppd, down from the initial value closer to 30.

The humidity in my basement has fallen to the set point of 45% RH, so it's possible the A/C has been not been running continuously for those 22 hours.

But I also suspect that the A/C is less able to pull water out at lower humidity, compared to a dehumidifier. Maybe the A/C coil doesn't get quite as cool as a genuine dehumidifier? It would make sense. A DH should be designed to run in a basement and needs a cooler coil to wring out the water even when the humidity is below 50%. An A/C is designed to move as many BTUs as possible from one side to the other, with generally warmer air.

Still, I'm happy with the experiment so far. Just gotta see how things look 10 years from now.

Our new DH has real trouble getting humidity below 45%. I think your A/C is fine as a DH.

 

Yeah, it wouldn't really add to the functionality. In fact I just turned it down to 40% so that it doesn't stop.

 

I just turned it down to 40% so that it doesn't stop.

I take it electricity is not that expensive where you live ...

 

Our new DH has real trouble getting humidity below 45%. I think your A/C is fine as a DH.

Our old one had a minimum setting of 35%. I think it did get there at times, but probably not in hot weather like now. You may be right about the DH. I never paid much attention before.

 

I take it electricity is not that expensive where you live ...

Typically 2-3¢/kWh. The average is much higher due to a very few excursion up over 20-30¢ on hot summer afternoons. Occasionally it even goes negative!

 

Typically 2-3¢/kWh. The average is much higher due to a very few excursion up over 20-30¢ on hot summer afternoons. Occasionally it even goes negative!

What the... negative you say? How can that be even possible? Also, how many kWh does your A/C consume? That is, how much do you think it will cost you to keep it on 24/7 ?

 

It's drawing just under 400W, so less than 10kWh per day. That's only a quarter per day, assuming I can avoid rate spikes on hot afternoons. Well worth it to avoid dampness in the basement.

My rate is subject to real-time pricing. It rarely goes negative but when it does, it's usually in the early morning of a day predicted to get very hot. I believe this causes the utility people to bring extra capacity online in anticipation. But while demand is still low, they'll pay me to take it! When rates spike over 14¢, my central A/C compressor cuts out.

 

When rates spike over 14¢, my central A/C compressor cuts out.

How's that? Does your A/C have a controller connected to the internet that constantly monitors the actual electricity rate?

 

It's got a switch installed by the power company that allows them to reach out and shut off my compressor. I don't think it's internet enabled, but I honestly don't know. They offered some incentive to accept that switch, but not consuming a lot while the rate is sky high is incentive enough.

I don't think my electricity meter is internet-connected either, but does log the consumption profile against time. When they come to read it, they get the whole history and then the hourly rates are applied. I think.

 

It's drawing just under 400W, so less than 10kWh per day. That's only a quarter per day, assuming I can avoid rate spikes on hot afternoons. Well worth it to avoid dampness in the basement.

My rate is subject to real-time pricing. It rarely goes negative but when it does, it's usually in the early morning of a day predicted to get very hot. I believe this causes the utility people to bring extra capacity online in anticipation. But while demand is still low, they'll pay me to take it! When rates spike over 14¢, my central A/C compressor cuts out.

Is it on windy, sunny days when all the alternative energy is fed into the system (without restriction)and they need someone to consume it? This is a major issue in Germany in recent months, paying Poland to take the excess and now Poland is going to stop taking the excess because it is screwing up their coal industry.

 

I don't know, but I don't think so. I'm in northern Illinois. There are windmills not far away, but I think most of our electricity is nuclear, coal, natural gas, in roughly that order. Of course natural gas is growing while the others are contracting.

 

Well, it was great until it wasn't.

Refresher: The cheap consumer-level dehumidifiers are very poor for reliability. They rarely last much beyond their warranty and many don't even last that long. If you read the warranty carefully, they often require the user to pay freight both ways to get a warranty repair. These things aren't light and only cost $150 or so. Those freight charges approach the cost of a brand new unit, and that's what most victims do.

My experiment in using a portable, window insert type of A/C instead of a dehumidifier was done based on the generally higher reliability of air conditioners. For whatever reason, A/C units often last years and even decades. So I thought it made sense to give one a try. I knew that it should work because an A/C is very little different than a DH. The biggest difference is fan speed. A DH uses a relatively slow fan so that there is time for the cold coils to pull more moisture (latent heat) out. An A/C uses higher airflow to maximize cooling (sensible plus latent heat), not just moisture removal. My results showed that under the conditions of my basement, a 5000 BTU A/C is roughly equivalent to a 30 ppd dehumidifier. It worked fine although that was a little too small for my basement. I should have gotten one a bit larger.

The cheapest A/C I could find (that still seemed like a legit unit) came with a 5-year warranty on the sealed parts. I'm approaching the three year mark and my unit is out of coolant. I think it was probably low already at the end of last summer. Anyway, the Frigidaire (Electrolux) folks are going to replace it, so that's cool. All I have to do is send them the service tag and a picture of it with its plug cut off. I get to keep the rest for - whatever.

 

The quest continues. While waiting for a warranty replacement of my little Frigidaire A/C, I went ahead and bought one of double the capacity, 10,000 BTU. Just like the smaller one, I had to punch a small hole in the bottom to let the water drain out. Unlike the little one, this larger one has fancier features including a remote and a digital control panel. It also has a sensor that prevents it from running the compressor if ambient air is below 62°F.

That's a problem! My basement hasn't warmed up yet this season and I initially thought the new A/C was a dud until I figured this out. Once I found the sensor (on the front of the coil) and put my finger on it, the compressor finally kicked on.

So right now I've rigged a small lightbulb right in front of the sensor and this is working to keep it running. It's pulling out about 2L per hour, so that's great. Now I just need to figure out a more elegant way to fool the sensor.

About warranties: I could not find ANY other dehumidifier or window A/C with the 5-yr warranty that Frigidaire offers. Most are just one year. In my experience these things never last 5 years, so getting a warranty that long is a decisive factor in choosing that brand. They were also easy to work with when it came time for the replacement.

 

Now I just need to figure out a more elegant way to fool the sensor.

maybe you could move the sensor to the compressor (hot) side of the a/c?

 

maybe you could move the sensor to the compressor (hot) side of the a/c?

My first choice would be to leave the A/C as unchanged as possible, but yes I may have to alter the sensor. I'm hoping to find out what type it is and perhaps I can just tweak it. One complication is that, I think, the ice-on-the-coil sensor is right there in the same spot. I'm not sure if it's the same sensor or if there are two side-by-side. Anyway I don't want to interfere with that.

 

Here's a closeup of the sensor. Anyone recognize it? I believe it's a thermistor and is called the "ambient sensor". There is also an "evaporator sensor" and I don't know if they're both there.

I need a strategy to hack it, but as I sad I would like as minimal invasiveness as possible. I think I'm going to go snip that cable tie and see what happens.

 

Well now I feel silly. There are two little clip prongs you can see in the picture. Squeeze those together and the thermistor is released! It appears to be a single thermistor and it’s now loose in front of the A/C. The air filter and front grill are back in place. Now I just need a warmer. I’m using a small light bulb but I’m sure I can rig a lower wattage one.

 

What is the refrigerant? R134A, R12?

As for a warmer, get a 2 watt 62k resistor and wire it at the end of a 110V cord. Plug that in and it will give you a constant ¼ watt or so of heat.

 

What is the refrigerant? R134A, R12?

R410a is more typical these days.

As for a warmer, get a 2 watt 62k resistor and wire it at the end of a 110V cord. Plug that in and it will give you a constant ¼ watt or so of heat.

I'm thinking of one of those tiny neon lamps they used to use before LEDs. I like the visual feedback of a light. But I've got a box of old resistors too. It'd be great to put one to a good use.