Here’s a quick rundown of some things to consider in trying to decide whether or not you want a heat pump dryer in your RV. After you decide you do, head on over to the next post to look at the characteristics you’ll want to consider when deciding which heat pump dryer you want.
Most heat pump dryers, while requiring very little power to run, operate at 240V. If you’re normally connecting to 50-amp shore power, that at most means wiring a new receptacle for the dryer to plug into (assuming you don’t have one already). If you want to run your dryer away from hookups (i.e. solar, batteries, generator), or on 30-amp (120V) service, you still have a number of options–the most straightforward (not necessarily the cheapest) being to select one of several heat pump dryers that operate on 120V power. A follow-up post will address other options in more detail–including a small voltage transformer, a dedicated inverter, and a few others.
The long and short here is that if you can get 240V power to the dryer, you have tons of options (including a standard dryer cord). If not, there’s a shorter list of models that will work simply by plugging them in to a standard receptacle. (Model list to follow soon!)
If you happen to have a layout where the washer drain isn’t in the same cabinet as the dryer, you’ll either have to figure out how to route the drain line, or empty the small tank every 5 or 6 loads.
It should go without saying that this water isn’t potable. It’s far cleaner than what’s in your grey tank, but it may have traces of material from clothes/detergent or other contaminants. Do you really drink the water that drips from your air conditioner? Didn’t think so.
If there’s some need to get clothes hot beyond simply getting them dry (I’m thinking of some sort of hypothetical craft project, not normal laundry), a heat pump dryer might not be for you. On the other hand, the lower temperature drying means less static, clothes last longer, and you don’t need to take them out of the dryer right away at the end of the cycle to prevent wrinkles. As someone with a dog, I’ve noticed I wear his coat to a lesser degree with the new dryer.
The other downside to not getting very hot is that there’s not much in the way of a wrinkle release cycle. I haven’t found that to be a big deal–most conventional dryers have a “cool-down” cycle to prevent wrinkles; the heat pump dryer doesn’t need one as the clothes aren’t hot in the first place (we’ll revisit this when talking about cycle times).
Compared to a conventional vented dryer of the same size, a heat pump dryer will be heavier. The model I’ve been using weighs 110 lbs, while the comparable vented model only weighs 88 lbs. That’s not a big difference, but it might be relevant depending on how your dryer is fixed in place or what cabinet it’s in.
If you already have issues with high indoor humidity in the winter, you may exacerbate the problem by not doing laundry with a vented dryer. That vented dryer depressurizes the RV interior by exhausting air, and the makeup air is the cold dry stuff that gets sucked in from outside. A heat pump dryer doesn’t add moisture to the RV, but it doesn’t exhaust your humid indoor air either.
This is a small effect, in most cases too small to notice. It’s mentioned more for completeness than anything.
Of course, the opposite is also true. Especially if your air conditioners struggle to keep you cool in the summer, or if you have issues with icing on your AC unit’s evaporator, a heat pump dryer will improve things relative to a vented dryer. You’ll be pulling in less moist outdoor air, have less condensation in your RV’s air conditioner, and have less hot outdoor air to cool again.
Again, this is a small effect overall–unless you’re doing a lot of laundry or tracking energy consumption, you probably won’t notice.
While your fabric softener in the washing machine will work the same way as before, you won’t be getting much use out of dryer sheets. They rely primarily on heat to release the fatty molecule that coats your clothes to make them feel softer. Without much heat, the dryer sheet will still contain most of that surfactant.
While a relatively minor task, you will want to stay on top of cleaning the lint screens and condenser fins. The lint screens are nothing you’re not familiar with, though you’ll generally find they have a finer mesh on a heat pump dryer. I find that makes the lint easier to remove. Of course, those screens still aren’t perfect–I’ve found that every 50-60 loads there’s enough on the condenser fins that there’s enough buildup to wipe/peel it off. It only takes a minute or two, but is important to maintaining airflow through the coils. I’d argue it’s much easier than cleaning a vent duct, but we all know it’s easier to neglect an out-of-sight fire hazard than a clump of wet lint you can easily see.
If you’re not up to the task of occasionally cleaning out the lint, you’re likely to eventually have severely reduced performance, and getting it back to 100% may require opening up the dryer cabinet to get to the stuff that’s gotten past the first 3 lines of defense.
It goes without saying that clothes dryers are plenty safe enough. It is, however, worth discussing the relative safety of a heat pump dryer over a conventional dryer. First, the lower power consumption has inherent advantages for all of the equipment used to supply power to the RV and dryer–less current through the shore power connection, less power through the breaker box, less power through the wiring in between. Electrical fires are relatively common as fire causes go, we reduce our risk here slightly.
Second, by not venting, we’re not depressurizing the RV/living space. Typically, as you blow air out and reduce the relative pressure of the indoor space, you increase the chances of what’s known as a backdraft–where a combustion device’s exhaust doesn’t go up and out, but is instead drawn into the living space. RVs are typically worse than a conventional house because of their smaller air volume, but better because the only common natural draft appliance inside is the range. You should generally avoid operating the range with a vented clothes dryer, but there’s no similar concern with a non-vented dryer.
Third, the lower temperatures reduce the risk of a fire within the dryer or in its exhaust path. Hot, dry, static-y lint in the exhaust, and flammable oils and solvents on clothes in the dryer, run the risk of igniting under the right circumstances. There’s never any hot dry lint accumulating in a vent (any lint that does accumulate on a heat pump dryer’s evaporator will be both cold and wet), and the maximum temperatures your clothes are exposed to are a lot lower, should you have something volatile still on your clothes. While not RV-specific, NFPA reports show fire departments respond to about 16,000 fires involving washers and dryers each year–with about 8,000 instances of clothes or lint being the first thing ignited. Those numbers are small, but far from zero.
Finally, while we’ve added a compressor, its motor operates in an oxygen-free environment. There’s a very slight risk added any time we add components, but this risk is vanishingly small compared to the risks we avoid as mentioned above.
I’ll probably update this post later as I think of more things that differ from a conventional dryer, but these are the ones I’ve observed so far.