Dehumidifier only cycles off for EACTLY 2 minutes then back on again

[jay]

I bought a Friedrich 40 pint dehumidifier. This has electronic controls, and I very firmly believe is made in China by L.G. Electronics (which is the same as Goldstar, and the even Kenwood Sears units are made by them now).

I have the humidity setting at 45%. I happen to have a separate digital hygrometer in the basement too. This morning I noticed that my hygrometer was reading 39%. What I find strange, is that, this morning the dehumidifier would run with the compressor and fan on for, say, roughly 10 minutes, and then shut completely off for EXACTLY 2 minutes and turn completely on again. Then after maybe, say, another 10 minutes if would shut off for EXACTLY 2 minutes.

It seems to me that whomever designed this thing was trying to be a bit too clever. Without having seen it in action much I'm assuming that, instead of simply designing it to behave as if controlled by an ordinary humidistat, they designed some complicated algorithm so that, if the humidity gets BELOW the target level, will begin introducing "2 minute off" periods, and then gradually increase the frequency of these "2 minute offs" until it stabilizes near the target. (or alternatively maybe they'll gradually increase the "2 minute off" to, say, a "3 minute off").

Hmmm.....call me paranoid, but....maybe they deliberately chose to always use "2 minute off" intervals because maybe it's just long enough not to

*overtly* damage the compressor, but short enough a cycle that it will add more wear and tear so that the unit DEFINITELY would not last any more than, say, 6 years (the compressor portion of the unit is warranted for 5 years). In other words, they to short cycle it so that it doesn't last, say, 10 or 15 years. Am I crazy for thinking this?

J.

[jay]

Actually, I experimented with increasing the humidity setting and it appears that, so far, the unit *always* uses "2 minute off" intervals *unless* the room humidity is 15% or more below the target setting. If the room humidity is, say, 6% or more below the target setting, then the unit will cycle on and off, with the OFF intervals always being exactly 2 minutes.

Since I see that the minimum "on interval" is also 2 minutes, then it seems that, if the room humidity were substantially below target (say, 10% or more, but less than 15% below target), then unit will eventually reach a point where it will cycle on for 2 minutes on and then off for 2 minutes. I can only hope that the unit is smart enough to then gradually increase the length of the OFF intervals without needing the room humidity to be an entire 15% below target before it does this. (Who the hell wants a unit that cycles 15 times per hour....time will tell if the unit is going to be smart enough not to behave that way!)

J.

[Joseph Meehan]

I would guess the 2 minutes off is to allow any frost to melt. The 15% humidity just sounds like the sensor is not too exact, which is not at all unusual. I might also suggest that your method of measuring the humidity may not be all that accurate. Even if it measures a static humidity well, when it is changing it may well have a delay in recording the change. The de-humidifier may be responding to the change faster since it has an air flow to measure.

Generally just about any tool you are going to find, other than wet-dry bulb is not going to be very accurate.

[jay]

The hygrometer is a digital model. I actually have two different brands and the readings are close between the two of them...and they respond very quickly to changes in humidity. I don't know what the level of accuracy is supposed to be. Anyway, it seems that the dehumidifier likes to settle into a level of room humidity (measured by the digital hygrometer) that is 6% below the target setting.

J.

[jay]

Actually, I take that back....it seems that the dehumidifier isn't doing much in the way of measuring room humidity. The damned thing cycles on and off too frequently even at higher settings. Even at a very high setting of

70% the thing is on for 2 minutes and then off for 2.5 to 3 minutes. There is no way that my basement has 70% relative humidity and the thing still turns on at a 70% setting. Room temperature is in the lower 70s so I doubt frost is an issue. Last night I had the dehumidifier set at 65% and this morning the digital hygrometer said 44%.

Frankly I trust the digital hygrometer more than I trust the dehumidifier. The dehumidifier probably just has some preset algorithm that causes it to be running slightly less at higher settings without measuring room humidity. At lower settings it probably just shuts off if the evaporator coil temp gets too low.

The way this thing cycles on and off so frequently it would be really annoying if I had this thing in an area I actually used as a living area rather than just the basement.

Maybe the mechanical models are really the better ones if they have an actual humidistat and respond to actual room humidity?

J.

[m Ransley]

Frequent cycling is usualy a sign of to large a humidifier, but yours just cycles so its defective or a bad design if frost is not building on the coil which you can look see. What is your temp, Most units freeze at apx 65f. If you are over 70 Ice should not be an issue. Your manual will say its operating temp low. I bought a Kenmore last year as my old one is fine but the new one , some redesigned junk had 2 defects and I took it back. But Sears does have the only model that can run to 45f. I dought it will last long with frequent cycles. Sears has a 3 or 6 hr setting and you may want to consider a smaller output unit so it cycles longer, if it removes humidity quickly. Sears is good on returns and just gave me my cash back after 3 months as they were out of stock. Id say get your $ back and try another brand, wait to long and they will only repair it and take a month trying.