OT: Keeping water out of impulse line

TheWaterboy said:

I went with the high loop and condensate drain.

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With a high loop, the only way you can flow up the 'loop' and back down again is if a differential pressure exists between the tank wall and somewhere along the length of the impulse pipe. If fluid collects in the pipe, indicating flow through the loop, use some soapy water along the impulse pipe to look for a leak.

OkiePC said:

VEGA Makes an electronic DP setup too. I'd shy away from rolling your own with two sensors and PLC math unless your tolerance for error is large.

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The electronic DP is going to have the same issues with error as a roll your own. For this case where you have 130PSI static, you would need sensors with probably 150PSI range.

The true wet/wet DP sensor in a 0-5FtH2O range is obviously the best course of action if the wet "dry" line can be fixed.

Note: If the "dry" line has issues with condensation, a few things that you can do:
1. Increase the size of the tubing. If you are using small tubing (1/4") the water droplets can more easily bridge the gap of the tubing and through off measurements.
2. Use a heated sample line as the "dry" line. The heated sample line would be heated to a temperature above the dewpoint of whatever condensate you are fighting. Keeping everything in a gaseous state.

If condensation is an issue, then the simplest solution is still to fill and keep full (e.g. small pump and loop at the top) the "dry" (reference) side with water. Then the system always "knows" the pressure above the water level to calculate level from the DP measurement.

If condensation is not an issue, then the sloped/high upper tap and the drain valve should be good enough, although it does add maintenance and monitoring requirements.