What is the most important reason for knowing EWT and LWT to and from the heat pump? Is this a required element in typical system installation? My installer did not install these temp gauges, however gauges were installed between the heat pump and the storage tank.

Anyone have suggestions?

Thanks,

The numbers are used to calculate the "Heat of Extraction" and "Heat of rejection". Temperature differential (Delta T) X Pressure Differential (Delta P) X 500 (for pure water) or X 485 (for methanol and glycol loops) However, you can not use two different gauges. They must be taken with the same temperature gauge and the same pressure gauge. If those numbers are within factory specs, the service tech does not have to put gauges on the refrigerant side of the unit.

Bergy

Thanks BERGY,
Just seems like the EWT/LWT from the field would be needed for troubleshooting/analysis pruposes.

My system has temp gauges installed between the stotage tank and the supply manifold to the radiant tubing as well as a temp gauge betwee the return manifold and the storage tank also, which seems right for monitoring the radiant tubing. The gauges between the heat pump and the storage tank seems a little bit of a lower priority.

I am always looking to get educated here, so the more responses the better.

Thanks,
Rick

you are correct, but most installers opt for p/t ports where gauges can be attached,rather than permanently installed.

As bergy said PT ports are installed to get both pressure and temperature readings. These readings need to be accurate and permanently installed gauges will fail over time so the PT ports work best. 

I have one temp gauge on the incoming line (after pressure tank on SCW system) before splitting to the two units, and then each return line has a temp gauge. I'm using big 5" Ashcroft stainless industrial process gauges.  They are 30-130 degree with large 1 degree ticks so that even fractions of a degree can easily be determined.  They are around $90/each but I found a lot of 5 brand new for $30 total from an industrial surplus supplier. I couldn't be picky that they have 12" stems, but no big deal to have those copper extensions on the piping.

I like having instant easily seen data. Seeing the outgoing temp instantly lets me know my delta T is normal and all is well. But bimetal temp gauges are expensive and the only reason I see they are not used in an installation.

However, I've also seen electronic units with 2 probes that could be attached to outside of pipe and insulated for around $30.  These are less likely to be very accurate though.

Those will get you close... accurate information is needed to calculate heat of extraction/rejection.

Bergy

Calibrate the Ashcrofts with ice water before install. Long stems could pose an accuracy issue - 'live' part of probe needs to be in the process stream

One benefit of knowing your EWT, and tracking it over time, is to be able to assess the 'health' of your water loop, particularly if it's closed.

I.e., you can look up what your 'down deep undisturbed' earth temperature is, for your geographic location.  And then watch EWT to see how much the swing is above and below the baseline earth temperature.

For example, my baseline earth temperature is 68° (F) (Dallas climate).  And from the chart I started buuilding for EWT, shown below, I now know my EWT summer high was 83°, and winter low was 63°.  This is a 'swing' of 20°, and it tells me 2 significant things:  (1) my loop is performing quite well, and (2) my loop is probably oversized for my needs and thus I probably spent more money than I needed to.

As another example, if my chart were to show an 80° swing, with a projected high of 113° and a projected low of 33°, I'd know to be worried that my loop was either 'short looped' or broken in some fashing (i.e. no grout and no earth/water in contact with the pipe).  (And that antifreeze may be needed!)

Another benefit of knowing EWT, this one even longer term, is to assess if you have long term heating of the earth.  After I get some multi-year data, I'll easily be able to see if my earth is gradually heating up.

Hope this helps.

Best regards,

Bill

I use simple indoor / outdoor thermometers. I bought 6 of them and then put them all in the same body of water and matched them up. I used two of the matching ones for the geo in and out. 5 of the six were within .2 of each other the 6th was about a degree off.

But in reality it isn't the accuracy I was looking for, more for an over view of what the system was doing. I just collect data by looking at the low incoming and outgoing temp on each line once a week. It is interesting to see last year temps compared to this year.

The biggest real advantage is consistency or inconsistency, you can see if something changes a lot from what the "norm" is.