Small Permanent Dehumidifier?
What are some good options for a permanent dehumidifier that only needs to squeeze out ~13 pints/day? Basically I’d like it to drain itself, not take up floor space, and perhaps be quieter and more efficient than my portable unit.
This could fit the bill, but it is expensive:
https://www.santa-fe-products.com/product/ultramd33-dehumidifier/
This is similar, expensive, and has an ionizer that I do not want:
https://www.innovativedehumidifiers.com/shop/
Background:
We finished the upstairs of our 1940’s Cape Cod in CZ4 a few years ago. Every summer until this one the brand new minisplit would intermittently put off a foul odor starting after about a week of running. I believe the odor was present when the indoor coils were being blown dry because I could avoid it by running in “dehumidify” mode, which continuously cools at low power. This was ok, but led to overcooling. My best guess is that the root cause is high moisture load. In addition to being upstairs, the space is ventilated with a Lunos e2 HRV. So this year I added a portable dehumidifier which keeps the space at ~45% RH and have had no issues.
The overall space has a cathedral ceiling but we added a bathroom that has a flat ceiling where a dehumidifier could sit and have access to an exposed vent pipe (I assume it is ok to drain a dehum into a vent?). Or an in-wall unit could drain directly into a drain pipe.
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A dehumidifier is a super-efficient heater with a COP over 1 and generally a Band-Aid applied to a gapping wound.
In some climates when it is very humid but not really very hot much of the time a dehumidifier can be useful.
I think you need to find a way to keep the conditioned air inside a tight well-insulated thermal envelope.
Old capes are notoriously drafty and poorly insulated. The way there are constructed makes it almost impossible to really do much short of spray foaming the hell out of them.
Most capes are so drafty that the idea that one needs 1 HRV is laughable and a second would be crazy. My guess is most capes blower test would show the air gets completely changed 10 time per hour at 50 Paskals.
Note the sloped ceiling are cathedral ceiling you might find one of the 5 in this article that will work for you.
https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work
https://www.greenbuildingadvisor.com/article/insulating-a-cape-cod-house
Walta
Walta, I'm writing today from Newport County, RI, where earlier in the week the outdoor thermometer reported a temperature of 80F and a relative humidity of 100% -- there was condensing fog. That's a dewpoint of 80F. In my home of Washington, DC, the dewpoint hit 77F this week. In this weather, if you don't have a dehumidifier it's going to rain in your basement. It's just not hot enough for the air conditioning to run long enough to remove enough humidity out of the air.
I agree that the product offerings when it comes to dehumidifiers are lacking, it may well be because they are often used as stop-gap measures.
I've always thought that the Daikin Quaternity was a clever solution -- a minisplit with two coils in the indoor head. The coils can be used for either heating or cooling, and if you configure it as one of each it acts as a dehumidifier, neither heating nor cooling. Unfortunately I've never actually seen one of these in operation, nor have I ever met anyone who has. And Daikin seems to not be emphasizing the product. Since I spend a lot of time in places where this would be an ideal solution I have to conclude that there must be a catch.
Walta, right, I leaned heavily on this site when we finished the space. The roof and upstairs walls meet or exceed 2016 code for insulation using flash & batt and Bonfiglioli strips. The first floor is cellulose-filled 2x4 walls and the basement is uninsulated.
Anyway, the house was measured at ~3 ACH50 and the upstairs air improved noticeably after I installed the HRV (it's probably more appropriately called one HRV made up of 2 through-wall units. I've edited the initial post to clarify. See https://475.supply/products/lunos-e-kit?variant=44680063975697). The max rate is just 22 cfm, but it does little to temper humidity and dumps all of it upstairs. I suppose I could try turning sealing off the HRV to see if that eliminates the need for the dehumidier...but like I said the air quality is noticeably better with ventilation on.
The HRV “does little to temper humidity”
When ever the outdoor dew point is higher than the indoor dew point running the HRV will make your humidity issue worse.
The real question is where is the moisture coming from and can you eliminate the moisture.
It does sound like your cape is much better than most.
Walta
I have a cheap dehumidifier in my garage, mostly because of dampness in the winter. It has a pump as well as a tank so it poots out some water in the driveway every so often.
For the money, I cannot see why anything more complex is needed.
You need a trap between it and any plumbing, so not so simple to plumb into a vent.
You could probably sneak it into the back of the toilet tank and no one would notice.
Other than that a dishwasher drain 'T' on the bathroom sink would work but would be very large
The problem with consumer-grade dehumidifiers is keeping them running. If you're relying on them to protect the building they're just not reliable enough.
They tend to last years. I have little confidence that increased cash outlay increases reliability. If they are in a public space it will be obvious if they are working or not.
It's not that they don't last, they don't run reliably. There are a few common design flaws. The most common is not restarting when power is interrupted. Or if they do restart, not restarting with the same settings as when the power went out.
It's very common for them to shut off because the drain hose has gotten kinked or blocked or airlocked.
The air filters are universally awful and clogging is a common problem. So is the evaporator getting clogged because the filter didn't do its job. This is problematic too because typically the fan is undersized for the job it is asked to do.
What's frustrating is that if you look on Amazon there are literally thousands of models of stand-alone dehumidifiers and they all share these design flaws. To get one that doesn't you have to pay at least triple the price of a consumer model.
My basement dehumidifier is probably 6 years old now. Cheap box store unit, runs pretty much continuously from spring till fall. Simple gravity drain from it to a floor drain. I can't see spending more money on anything fancier. About the only issue I had with it is the cheap garden hose for the drain kinked overtime.
The one thing I have found that helps is using an external humidistat for controlling it. This generally means much longer runtime on the unit and since the unit is completely off between cycles, no re-evaporation from the coil. More efficient and less wear on the unit.
For a basement I totally agree nothing fancier is necessary. This is in finished space with no good way route to a drain, especially by gravity. Perhaps if I were still single I'd elevate it or get a condensate pump, but either way I'd be routing to a sink, tub, or toilet, and it would be a bit in the way. Anyway, if the going rate for a permanent unit really is > $1k like I've seen, then I reckon I will just keep the setup I have.
My unit might be about 6 years old too. It has a built-in humidistat which seems pretty accurate (or at least in agreement with other sensors). I guess I don't know if it has any re-evaporation from the coils as-is, but I don't think it does. Come to think of it, why don't the dehumidifier coils start to stink after a while? Are they just cleaner due to a better filter? Or the dehumidifier keeps the humidity lower than the minisplit alone does?
The best way to plumb a dehumidifier drain is to use an existing trap and tie in above the trap. That way whatever fixture is on the trap will keep it full and you don't have to worry about it drying out during the part of the year when the dehumidifier isn't running.
This, incidentally, is exactly how a dishwasher is plumbed, so you can use a dishwasher tailpiece to tie in above the trap.
Santa Fe UltraMD33 removes moisture from basements, crawl spaces, and other areas up to 1,200 square feet. It removes up to 33 pints of water per day which is more than what you need. However, it is an in-wall dehumidifier that drains directly into a plumbing line and runs quiet.
So 33 pints is laughably small compared to consumer stand-alone models. At $1700 it's about ten times the price of a floor dehumidifier with twice the capacity.
What that money is buying you is something that has a large enough fan to run quietly, and can be hard-wired and plumbed for reliable operation. It's not going to do any better of a job at removing humidity.
“ and have access to an exposed vent pipe (I assume it is ok to drain a dehum into a vent?). Or an in-wall unit could drain directly into a drain pipe.”
If you end up with a dehumidifier it would be a code violation to drain the water to a vent pipe and any connection to a drain line would need to be after a trap.
Walta