Dehumidifier or AC + space heater?

Cool :C (and dry) idea!

We toured the Southeast U.S. once on a long 9000 mile trip in July-August. The temperature-humidity combinations were a nightmare - but everything else on the trip was a superb once-in-a-lifetime adventure.

Our worst situation came up with high humidity, but in only mild temperatures (75-80 degrees). We ran the air conditioner full blast along with an electric heater going such that the two of them kept the interior temperature around a 72 degrees with nice low humidity. We had to fiddle with the heater setting a bit to get the balance just right between the air conditioner's cold output and the heater's heat output.

Our 30 amp RV did just fine running both at the same time. If dry camping in that situation, running a generator for incoming power would accomplish the same results - remembering that the propane furnace CANNOT replace the electric heater because in most motorhomes the heating/cooling control will allow only the air conditioner by itself or the propane furnace by itiself to be active - not both at the same time. So when dry camping the generator would be powering the air conditioner and an electric heater - just like when on hookup power.

I call running both at once a "poor man's dehumidifier" because one not need buy a dehumidifier to accomplish the same results. Just use what you probably already have in your Class C .... the air conditioner and a small portable electric heater.

The issue with humidity I've had is when the cooling requirements are marginal and the AC is cycling frequently. Night time would be good example of this-fall asleep with AC on, wake up to find it cycling and humid.

First thing IMO is to find the setting (if available) to cycle the air conditioner fan and compressor simultaneously. If the fan runs continuously, it reevaporates the condensate every time the compressor shuts off.

I certainly think if I'm in a setting where I want more compressor run time I'll set an electric heater to about the 700 watt setting to put a bit more heat in the place.

If I was camping in the Pacific Northwest and things got too sticky inside I may use the heater/AC solution for a while, but probably would eventually go with the dehumidifier. I think that would be the better overall solution if you don't need to cool the air, just remove moisture.

I found P-tuna's approach to creating a dehumidifier with existing hardware elegant and innovative. Managing the power load and time-based system hysteresis might cause me to break a sweat, however.

Thanks for the great tips, insights and ideas: low heater setting, furnace, low AC fan speed, smaller dehumidifier, etc.

DownTheAvenue wrote:
Believe me, if come to the Southeast in June, the A/C will have enough to do to keep you cool and dry. I promise you will not need a heater to do anything. The A/C will not need to be "tricked"- it will be plenty hot enough!

Guess that's what I needed to know from you guys. I'll leave the dehumidifier at home and "Fiddle with the thermostat controls" if the need arises. Thanks.

Believe me, if come to the Southeast in June, the A/C will have enough to do to keep you cool and dry. I promise you will not need a heater to do anything. The A/C will not need to be "tricked"- it will be plenty hot enough!

nomad 289 wrote:
Contemplating a trip to the South East in June. RH ~90%.

Dehumidifier is large, size of carry-on luggage, and space in a "C" is at a premium. Piano-tuna said he "tricks" his AC (into running more to remove moisture) by running a heater simultaneously, effectively creating a dehumidifier.

This seems clever, logical and appealing; any reason a dehumidifier would perform better? Slightly lower noise is the main advantage I see.

There is no reason to have a huge one as you describe.

Go to Lowes and pick up a SMALL dehumidifier. I bought one and it makes a BIG BIG difference in assisting your ac in when RV'ing in the south.

I place it midship off to the side doesn't take up any room and is not in the way. you can either empty the cup when it fills with water or run the drain line also included to the shower.

I find it hard to believe that the breaker wouldn't keep blowing with both a space heater and ac on and IMHO it wouldn't help the ac anyway.:R

Adding a small dehumidifier to assist the ac getting the moisture out of the RV does. Just saying.

I don't do cold and clammy. That is when using a heater with the air conditioner shines.

I've only needed to dehumidify a few times. Spending money on something I'd use less than once per year is not good husbandry.

SE in June you won't need to "trick" your a/c to make it run a bunch. I doubt you'd be happy with the results adding a heater into the mix. All I would do is run it on the lower fan speed settings (IF you can keep cool enough that way). Less airflow = lower coil temperatures = more moisture extracted.

The running power consumption of a dehumidifier is much lower than an air conditioner (and I assume the startup power requirements would also be less). The 50 pint dehumidifier in my basement lists 6.5A on its data plate, not much different from a typical electric heater on low. (The startup surge power draw is, of course, bigger than a heater which has essentially none.) It is rather on the noisy side, and the bucket can fill up pretty quickly if one doesn't use a drain hose.

If the temperature is such that you need/want air conditioning, you probably don't need a separate dehumidifier. If the temperature is cool enough that you need heat, the furnace will also reduce the relative humidity to some extent because warmer air can hold more moisture than cooler air, but the actual amount of water in the air remains the same.

Fiddling with the thermostat such that you can run the furnace and the air conditioner simultaneously (perhaps by installing two separate thermostats, or by putting in an override switch for one or the other) would eliminate the need to carry any additional equipment.

A dehumidifier would probably be a lot quicker at reducing the humidity than the air conditioner and heater together.

I can't speak to your amp draw... I'll leave that to Pianotuna.

What I can say, though, is "tricking" your AC into running more by using a heater is going to be harder wear on the AC. On the other hand, if you use a dehumidifier, that will help so that the AC can keep up better... making it easier on the AC. Personally, I think the answer is obvious.