Also live in NH and we run a dehumidifier from May thru Sept/Oct and just set it on the auto level (have a floor drain and hose connected so know emptying required) that gets it to low humidity levels down there. Love having a basement as well. Lots of dry storage, place for boiler, laundry etc.
Well, yes, "ON" all the time is the real problem. However, the post de-energize fan time matters. Does it matter to the point of dripping humidity? No. But it may be enough to up the RH a few percent to a tipping point.
I can't find the damn reference right now and I'm on my way to church. (Shouldn't have said "damn.") The point is there is a reason this time period is configurable due to this effect.
Gotta go, roast me over the coals for not having my references. I get a "D" on this paper.
I had a freezing up dehumidifier that I tossed. I wish I'd thought of the timer thing. Great idea!
No problem, I know it may not seem like it sometimes, but we do have lives outside this forum!
But I would be curious to see any refs if/when you get time.
I think the off delay has a couple purposes. One is efficiency - might as well extract the residual heat or cold from the Heat exchanger or coils. Second, for heat, it keeps the heat exch from over-heating, which could happen if the residual heat was not drawn off, and it might help keep the coil from developing a coating of ice - those extra 30~90 seconds will draw off enough cold to bring it above freezing.
Might be a 3rd reason, can't think of it now - but I really can't imagine how a few extra seconds will affect humidity overall, it take maybe a half hour to see a change when it is running full bore.
edit/add: "The point is there is a reason this time period is configurable due to this effect." - I don't think the configuration is for that effect (which I don't believe exists!). I think the simple reason is to allow for different sized units/ducts, etc. with the same control board. The 90S setting might start blowing cold air in heat mode at the end of the cycle? And no sense running it longer than needed. Too short, and the heat exch might not get cooled off enough, and you lose some efficiency. Similar reasons for the cool side. The mfg probably want these set 'just right' for the efficiency rating tests they have to submit.
-ERD50
https://resource.carrierenterprise...._59tp6a100e21--20_article_1429461218267_en_ss
Yeah, sure ERD50, I know how you like to have references. I'm back from church, atoned for my swearing, so we can discuss further.
First: the blower delay is absolutely essential for heating mode and should always be present. You are right about that! It is important for the health of the heat exchanger, and of course is important for efficiency.
Second: this delay, and especially the fan speed must be matched to the tonnage of the unit. This is crucial, and perhaps what I might have slightly convoluted with the blower delay. All modern units have settings for speed based on cooling tonnage and heating BTU.
Even a properly sized unit that has too fast of a fan can reduce dehumidification. It is very important the installer get this correct. I wonder if OP had that looked into?
One other very oddball thing about de-humidification and blower delay is the design of the drip pan. Actual de-humidifiers drop into a bucket immediately out of the way of the air flow. Most HVAC units in the horizontal position have a large pan with drip water that lazily takes its way to find the exit. A vertical unit disposes of the condensate quicker. So I guess the problem is complex and really doesn't have a one-size-fits all solution. Vertical units may not even ever have the problem.
I did a bit of a search on stuff I found last summer when I was fixing my unit, and found that "blower off delay humidity" brings up some interesting conversations. Not everyone agrees, just as we don't here.
As for hard data, the only thing I could find this time is the Carrier marketing statement about this. It is marketing, so... take it as you see fit. I used to have this system which also included running the fan ultra-slow during humid events. It was kind of cool, but overkill. I found these modes would only rarely run only a few times per year.
Here's a pointer and quick quote to what I am talking about:
https://resource.carrierenterprise...._59tp6a100e21--20_article_1429461218267_en_ss
I don't have a floor drain, so I was emptying mine via the hose into the sump pump pit. Not ideal, since the pit is only crushed stones over dirt. So that was no doubt throwing some dampness back into the basement.
Eventually the light bulb went off - I put the dehumidifier on top of a utility shelf next to the basement sink, so the unit is higher than the sink and the hose runs into the sink drain.
You may be the first to bring it up, and it is a good point. The electricity use is not insignificant. It helps to have a high quality unit with a good humidistat.
