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Does Anyone Have The Cap Ppm-4?


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I just got the new CAP PPM-4 CO2 Controller. CAP has a great reputation and you can't beat the $199 price tag. I usually research a product prior to buying it but no one had owned it or tried it out because it was so new.


I really like the concept of the controller but I seem to be having trouble with it. When I plug the sensor into the controller, the LED CO2 estimation light goes on but it doesnt seem to transmit that information to the controller which activates the CO2 tank. I have to twist and turn it for it to activate the tank which defeats the purpose of having an automated system.


There is also some question to the acuracy of the controller. There are three LED indicator lights on the sensor. Green indicates a level of CO2 between 0-900 PPM, Yellow indicates a level of 901-1450 PPM and red indicates 1451+ PPM.


Many times after evacuating all of the old air out of my tent, the CO2 LED will be Yellow indicating a level of 901-1450 PPM of CO2 which I know is not possible. I have calibrated it several times.


I'm just trying to figure out if it's my own niavity or if it's the controler.


If you own this unit please share your thoughts. Thanks

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  • 11 months later...

Completely unnecessary bump here, but I just found this thread in a Google search around the CAP ppm-4.


I've had one installed and running for about 3 crops now. It's in a 10x10 room, well sealed, 4x1000W open HPS lamps, CO2 from a 20 pound tank. Usually about 15 large plants in the room.


I was nervous buying this controller for two reasons. First, it's too cheap -- how can it be less than half the price of other controllers? Secondly, CAP doesn't seem to have the best reputation on the Internet.


What I like

  • Price! -- try and find another production unit even close to this price.
  • Sensitivity - I can usually hear the CO2 valve click open 20 seconds or so after opening the door to the room. That gives me a clue that there is a pretty narrow hysteresis to the controller.
  • CO2 life -- A $20 bottle lasts nearly 3 weeks in my room.

What I don't like

  • No adjustments possible -- hope you like a 1450ppm setpoint
  • No current measurement readout -- it would be nice to have a meter telling me current CO2 concentration


Anyway, my unit has been plug-and-play and forget about it reliable. CO2 tank life says that it's roughly in the right ballpark, but without a CO2 concentration meter I don't really know for sure how accurate it is.

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