Lucas formula and tds/ppm meter question, HELP!

[smknfire]

Just switched to Lucas formula 0-8-16 in rockwool after many sucessful runs with H&G in a UC. I know the target ppm in RO water is 1300ppm but i'm not sure what setting to have my meter on. It is a HM COM-100 and has the following settings:

Switching EC Modes:
The COM-100 has three different modes for EC: KCl, 442TM, and NaCl. Note that this setting only changes
the ATC coefficient that is used. To change the EC mode:
1. Turn the meter on by pressing the ‘ON/OFF’ button.
2. Press and hold the ‘HOLD/MODE’ button. The meter will cycle through the
following modes:
a. EC – KCl
b. EC – 442TM
c. EC – NaCl
d. TDS – KCl
e. TDS - 442TM
f. TDS - NaCl
3. When the meter displays the desired selection. Release the ‘HOLD/MODE’ button.
4. The meter is now ready for use in your selected mode. The meter will keep this setting until
changed again.
Switching TDS Modes:
The COM-100 comes with three TDS modes, each with its own EC to TDS conversion factor and Automatic
Temperature Compensation coefficient. To change the TDS mode:
1. Turn the meter on by pressing the ‘ON/OFF’ button.
2. Press and hold the ‘HOLD/MODE’ button. The meter will cycle through the
following modes:
a. EC – KCl
b. EC – 442TM
c. EC – NaCl
d. TDS – KCl
e. TDS - 442TM
f. TDS - NaCl

That is pulled from the manual.

thanks!

smknfire

 

[St3ve]

I would NEVER run that hot in rockwool. To answer your question.. just use EC. I mean the TDS reading is just the meter converting the EC number to something else.

I have run exactly what you're doing.. rockwool with regular lucas. For me, I would never go higher than 1.3 EC or so. (Which is around 850-900 PPM)

 

[JPLord01]

I think for rockwool it is like 7/14 I think. Im in coco so I run 6/9 my PPM are 720 water is 50 PPM to start. Thats is at .500

 

[smknfire]

thanks guys!