Metered condensate return issue

Kent_Overby

Hello, and thank you for your time! I have a large building heated by steam from a distribution system. I am measuring this building's steam usage via an Onicon in-line electromagnetic meter on a 2" steel line. There are two receivers, pumping individually into this condensate return, meeting up in the ceiling of the mech room and dropping about 10' right in front of the meter.

My issue is I am getting questionable readings from this 2 year old meter. I have verified the meter with a separate ultrasonic clamp-on meter over 30 days. The meter itself has been showing an "empty pipe alarm", which is an issue with this meter type. We subsequently installed a 6" riser after the in-line meter to try to keep the pipe full at the meter, but this doesn't seem to have worked as well as hoped. How much riser do we need after the meter to ensure that the pipe at the meter stays full of water?

Another consideration I have is that one of the receivers feeding this meter is a ways away, and I'm worried that the flow is fairly high coming in from that receiver and may help to wash out the water at the meter.

Jamie Hall

The six inch riser should be enough - provided that the pipe beyond doesn't drop down below the meter level. If it does, you have a siphon setup. If that is the case, try a larger diameter horizontal pipe after the riser with a vacuum breaker on it (an open vent or air gap would be even better, but may not be possible).

Kent_Overby

Thank you @Jamie Hall! The pipe beyond the meter definitely drops below the meter level and travels quite a distance back to the central plant. I was wondering if a 5 or 6' riser and vacuum breaker would fix it. Up-sizing the horizontal pipe is more cost than I'm willing to incur without trying some other things if they are feasible. Our Utilities Director would like to avoid any open vents if we can.

Jamie Hall

Try just figuring out a way to put a vacuum breaker on it.

Kent_Overby

Will do! Thanks!