I've seen the question asked (but not answered specifically) and GPM discussed by users here, but I haven't found an answer for instruments/sensors that can be used for measuring GPM using a one-wire system (WEL). I'd also like to couple that with PSI tracking. My system's loop connections have (I don't know the official term) connections for inserting gauges in to the line at a brass elbow where they enter the compressor box. I assume there's something out there which can be installed into these insertion points. Anyone have suggestions on products that work with a WEL? I see some of you are tracking GPM so I'm sure it can be done. I'd like to track PSI as well, as I'm interested in loop pressure trends for keeping an eye out for leaks, loop compromise, etc. Thanks, Colin

Colin,

As far as I know,  there is nothing that will track GPM with a WEL.  The two ways that I know of to track GPM are an inline flow meter    or by measuring the pressure drop through the heat pump and looking at the chart for your heat pump to determine GPM. 

Below is a gauge that is used to measure pressure through the  P/T ports on your heat pump

I also would be interested in a one wire pressure sensing device .

ok, so I'm getting the idea that GPM is a costly retro-fit and p/t port 1-wire sensors are hard to find. I did find one interesting side project some one did to create a 1-wire PSI sensor:

1-Wire PSI Gauge Hack

Colin

 

Actually, it's not any different for water flow as it is for electricity flow - they're both 'flows' that can be monitored based on the frequency of a pulse stream, and the WEL ( http://www.welserver.com ) handles this quite well.

The WEL has multiple types of inputs - not just accommodation for 1-wire sensors.  It also has hard wire inputs, and inputs for measuring pulse streams.

The WEL has 4 inputs available for any instrumentation that represents flow via a pulse frequency.  While the most commonly connected pulse output instrument is a watt meter, certainly anything else measuring a flow with a variable frequency pulse stream can be connected to the WEL.

I believe a watt meter is the most common because it's an easy installation.  While the hook up of a fluid flow meter to a WEL is no more difficult than a watt meter, installation of the fluid flow meter is another (much more difficult) story.

My advise to a number of individuals recently has been that if you're going to want to measure water flow real-time, you really need to get the flow meter installed as part of the GSHP closed loop piping installation.  Otherwise, as a retrofit subject, you're looking at opening up the water loop, making connections to HDPE pipe, and then re-purging / pressurizing the system again.  Unless you've got these skills already, you're probably looking at some amount of installation expense.

The difficulty with putting in a flow meter doesn't end, though, with installation.  Yes, there are many fluid flow meters on the market today that have as their output means a variable frequency pulse stream, that the WEL can easily accommodate.  But, another hard part of the subject is finding one that accommodates small (1 - 2") pipe and simultaneously doesn't impart a signficant pressure drop.

And once you've found such an item, finding it at a reasonable cost just made the subject even more challenging.

Thus, for most people that I know who have WEL units, they manually measure the flow with a pressure meter like what Dewayne illustrated above, look up the flow in provided tables, and then assume the flow is constant in spite of EWT variation.  In fact, this is what I'm doing (i.e., I've got 14.2 gpm flowing through my 3 ton unit).

My observation, over time, is that the manual pressure measurements don't materially change over time.  And thus the approximation that flow is constant seems reasonable.

What I haven't seen yet is a product that enables flow measurement via a pulse stream that can be connected via the P/T port.  If it doesn't exist, looks like here's an invention possibility.

Best regards,

Bill

P.S., my WEL publicly available data is at http://welserver.com/WEL0043 .

Wow, I'm impressed with the creativity of the gentleman who created this.  Just think, implemented for a GSHP, you could monitor in real-time the pressure drop across the heat exchanger, as a means for being alerted if there's a problem.

Thanks for sharing this.

Best regards,

Bill

Exactly my thought, this summer after my system was commissioned we left the p/t PSI gauges in place to watch the PSI, and we saw a slight pressure drop after several days of running. The installer charged up the lines with a bit more water and it stayed steady after that.

So my thought was a having a way to do this with my WEL and set an email alert would be great.

Side question, and this maybe a can of worms, what's the typical PSI for a lines "standing" vs. running? I recall mine around 10-12 PSI standing (not running) with a drop down to 5 or 6PSI during run. It's a bit hazy what the exact numbers were, but just off the top of my head.

Regards,
Colin

Colin, my static pressure is 60+ psi, but, Dewayne is helping me get this down to around the 20 psi mark.

See my WEL 'system page' for plumbing connection details ( http://welserver.com/WEL0043 ).  I've already turned off the continuous supply of 60 psi water.  Now watching to see if pressure holds over a few week time span (i.e., no leaks).  So far this has been the case.  Next step is to drain some water, slowly over time, from the loop, to get the psi down to around 20 psi.

Hope this helps.

Best regards,

Bill

Interesting, thanks for the info. I've found a lot of academic discussion on the PSI topic, however it seems this is a system by system setting. Mine seems to run fine and only cycling a maybe once an hour for 10min or so run times, two on cold evenings, but I'm always interested in optimizing ;-)

Back to the PSI measurement, I found some higher-end industrial PSI gauges that have voltage outputs for connection to electrical monitoring systems. One of these http://www.indautomation.com/pdf/wika/eco1.pdf could probably be adapted to a WEL input to work quite well. I bet there's even a differential meter out there that will do the delta for you and produce a relative differential value.

In the end, probably cheaper and easier to use estimation in my case (for COP) and just hook up manual read gauges to check now and then, but for larger or commercial installs, getting it wired would be useful.

Colin

Posted By silversurf on 12/10/2008 3:48 PM

In the end, probably cheaper and easier to use estimation in my case (for COP) and just hook up manual read gauges to check now and then, but for larger or commercial installs, getting it wired would be useful.Colin

Colin, agreed.  And thus my guess is most WEL owners (particularly non-commercial situations) opt for the manual method.

For commercial situations, pipe size gets large, increasing the availability of of pulse stream gpm meters, and tolerance improves for transducer associated pressure drop.
 
Best regards,

Bill

I emailed Phil  ( the developer of the WEL ) and asked about this.

He said : 

" Hi

I've not seen one, although it's possible to hook a regular pressure gauge (that puts out 0-5V) to a 1-wire voltage input.
Warning... This is one of those "in theory" comments that I'm prone to make ...

Phil."

Any of you guys know how to do this?

This would do the trick nicely:

http://www.wika.com/WIKAWeb/Product/pdf/OT-1.pdf

Not sure on cost, but I think because this is a transmitter, it puts out continuous voltage (4mA-20mA or 0-10V) that can be calibrated on the PLC side (http://www.wika.com/WIKAWeb/Support/pdf/TRONIC_Reference_Manual.pdf). So if the WEL or similar interface can take a voltage input like this and calibrate it, this might work. This would NOT be used for the 1-wire but probably another input type on the WEL or similar PLC

Colin

Ultrasonic portable clamp-on flow meters are available from GE, Dynasonic and others. They measure GPM from the outside of pipe. I'm not certain if they are compatible with WEL. I'm sure they are not cheap. One place to look them up is instrumart.com.
Regards, Masoud

FYI - Here is another similar inline flow meter that I found.

http://kingsolar.com/catalog/mfg/letro/flow3s.html

-=Steve=-