Nate Nagel writes:

As an aside, the old dehumidifier just had the little rotating knob
humidistat on it and I'd set it for slightly higher than "normal"
humidity. It cycled on and off, more off than on. The new one has a
digital humidistat so I set it for 55% RH because I've heard that to
minimize all of the bad things that can happen to your basement due to
incorrect humidity you should be in the 45-55% range. Apparently the
old dehumidifier was actually set for about 60 to 65% RH. New unit
showed 65% when I turned it on, quickly dropped to 60, now is showing
55% but have not heard it shut off yet (granted, I haven't been in my
basement for the whole time period.)

Leave it alone for a day or two, then see if it's still running
constantly. If your old dehumidifier was set to 65%, then *everything*
in your basement that can absorb water vapour has about that level of
absorbed water. If you try to bring the humidity down to 55%,
everything is going to be "bleeding" moisture into the air for a while -
your drywall and studs, your bookshelfs, all the books, etc. Once the
humidity has been 55% for a while, everything else will stabilize at
that level, and the dehumidifier will have to run less.

So I assume that it just displays
in 5% increments and showing 55% means it's probably in the range of
52.5-57.5%. This is a 45 pint unit and based on the amount of water
it's pulled out, I don't know that I suspect that there's a problem with
the unit; more that my house is very open and it would seem that due to
the climate (this AM: almost 90 degrees and 57% RH outside; now, 77
degrees and raining) the humidity in the whole house is higher than 55%
and trying to suck it down to that is taxing the unit. Any real problem
just leaving it at 60% and letting it go, even if that isn't "ideal?"

If outside air can flow freely through your house, you are trying to
dehumidify the outdoors. That is a hopeless task. You need to provide
some barrier between inside and outside air.

On the other hand, it's not "taxing" your unit to run all the time; it
oought to be built to deal with that. At worst, it won't be able to
keep the humidity down to what you want.

Dave