Warning/FYI about CHHC-4 and RH ...

I have tested the accuracy of the Sentinel CHHC-4 for RH, temp and Co2 measurement. In terms of RH accuracy, it fails miserably; the same goes for the Titan Controls "EOS-1" Humidify/Dehumidify Controller.

I also tested the Sentinel Digital Master Timer and HydroInnovations IceBox Thermostat for temp accuracy.

RH:

To check accuracy of RH readings from CHHC-4 and Titan EOS-1, I used a high quality HAAR analog hygrometer; it's a synthetic hair hygrometer and NIST certified accuracy. I calibrate it weekly. Accuracy is +/- 3 points RH.

Both the CHHC-4 and EOS-1 are at least 10 point too high! Ex., when the 'real' RH is 50% both the CHHC-4 and EOS-1 show RH of (at least) 60%. The inaccuracy seems to range from 10-13 points too high.

When I use either of those tools to automatically increase or decrease RH I make sure to set the RH 11 points higher than I really want it to be. That accounts for the poor accuracy of those tools.

Temp:

To check accuracy of temp readings I used a good IR temp gun on a white piece of paper, not in direct light.

All tools tested for temp were within a few degrees (F) of the 'real' reading according to the IR temp gun. So, that makes me happy that the CHHC-4, Master Digital Timer and IceBox Thermostat are 'close enough' in terms of accuracy.

Co2:

To check accuracy of the CHHC-4 I put my CHHC-4 outside on five different days, for two hours each time, at different times of the day and night. I wanted to make sure the CHHC-4 gave Co2 reading close to what I know is the 'real' ambient Co2 in my location.

Where the CHHC-4 excels is in accurately measuring Co2, not so much when measuring RH and temp. The Co2 reading was within ~25-50 ppm of the 'real' ambient levels of Co2.

Thanks for the info.I was planning on buying a Sentinel,but now I might go with a different controller.Do you know of any dependable and accurate controllers?

I highly doubt any of the ones that are less than a grand to a grand and half, will have accurate hygrometers. I think you could do well to use the CHHC-4; just account for the RH inaccuracy as I do.

There are better controllers than the CHHC-4; but they are marketed to greenhouse growers/industry, not cannabis. A main 'feature' I dislike about the CHHC-4 is it can either humidify or dehumidify, but not both; which is why I bought the Titan EOS-1.

I have noticed this too.. Guess a hygrometer is just another thing to add to my shopping list
.

I never used a dehumidifier but plan to purchase one soon.If I just plug it straight into a socket without using a controller, can the unit itself keep my room at around 45-50 rh, utilizing its own controls.Im trying to set up my first sealed room.

@ SMOKE-ONE,

Yes, but I would not count on the accuracy of the hygrometer within the dehumidifier.

I would buy one of the quality hygrometers I listed in the thread "Hygrometers: models you *should* buy and use" (link to thread). And then verify the accuracy of the hygrometer in the dehumidifier against the calibrated hygrometer. Then do what I do: simply add (or subtract) the difference in accuracy from your goal RH, and set your dehumidifier to the new RH goal (i.e., the adjusted RH to account for inaccuracy).

@ SMOKE-ONE,

I forgot to mention that I use a manual control dehumidifier, not a digital dehumidifier. That way I can set the manual control of the dehumidifier to turn 'on' at a very low RH (ex., 20%), and then connect the dehumidifier to my CHHC-4. I set the CHHC-4 for separate day and night RH, so the CHHC-4 will allow power to flow to the dehumidifier, or not, depending upon day and night RH with respect to the day and night RH setting I use for my CHHC-4.

For humidification I use a commercial size (impeller) humidifier. I set the Titan Controls "EOS 1 Humidity Controller" (link to product page) day RH to 55%, it has a factory preset 4% RH "split differential"[1] (aka "deadband"). For the night RH I use 40% RH, with the same split differential.

For dehumidification I use the CHHC-4 with separate day and night settings. For day dehumidification I set the CHHC-4 to a day setpoint of 61% RH with a 1% split differential (I plan to mess around with that setting to optimize it, soon). For night setting I use 46% RH setpoint with a 1% split differential.


[1] The "split differential" (aka "deadband") is the difference between 'on' and 'off' setpoints on a control. For humidity, it is the difference in RH between the humidifier's (or dehumidifier's) on and off setting, Ex:

• If you set a dehumidifier with a 1% RH split differential to a setpoint of 61% RH, it (the dehumidifier) will supply power (i.e., remove water from air) at any RH above 61% and cut off power at 60% RH (1% RH below the setpoint).
• If you set a humidifier with a 4% RH differential to a setpoint of 55% RH, it (the humidifier) will supply power (i.e., add water to air) at any RH below 55% RH and cut off power at 58% RH (4% RH above the setpoint).
• The goal with using a dehumidifier and humidifier, in the same room, is to not have them running at the same time. So it's important that the split differentials are not so close (for the dehumidifier and humidifier) that the dehumidifier and humidifier are not running that same time. I think at least 2-3% RH between split differentials is a good goal; 5% RH is probably a good ideal benchmark.

Note #1: I really dislike the Titan EOS-1 because it's not digital and does not easily allow one to set RH at points less than 10% RH. Ex., setting it to 55% or 57% RH is not easy/possible. But setting it at 50% RH or 60% RH is possible. If I had known that limits of the Titan EOS-1 I never would have purchased it.

Note #2: It's important to not let RH get above ~60% if using a carbon scrubber (for smell). Activated carbon does not remove smells once RH reaches ~65% RH.

cannascholar said:

I have noticed this too.. Guess a hygrometer is just another thing to add to my shopping list
.

Click to expand...

Please see the following thread I wrote just for your type of situation, i.e., those that need to buy a good hygrometer

Spurr: thanks for the excellent info.

Interesting. I have the CHHC-4 too. And I was thinking I needed a new Dehuy cause my readings were reading around 50-55%. I like to set my humidity around 40-45%. I noticed that my cheap walmart dehuy reader would display 45% while the Sentinel would show about 50-55%. makes since now. Thanks I will keep in mind the difference. That sucks just read the manuel again and they dont offer a calibration mode on the humidity. All and all I am very pleased w/ my sentinel CHHC-4.