Thanks moondawg. Congrats on senior member status.

Maybe I should have posted this question here since it involves preventative maintenance. Are there preferred times of the year to check for heat of extraction & rejection?

It's my understanding that pro's would normally check this whenever they visit the customer, but just wondering if there are better times (i.e. when do you check this on your own systems?).

To minimize calculations (and perhaps make the calculation more precise), I'd just assume do this calculation when the loop temperature is at one of the manufacturer's published book values (to look up GPM and Btuh specs for comparison to actual.)

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WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon.

If you're using P/T ports and HX delta-P to guesstimate flow, forget
about precision -- especially with a low P-drop WF Envision coax.

Delta-P is a small difference between two large (and rapidly fluctuating!)
numbers, so the probable error of measurement is inherently very BIG.
Even if you can measure each pressure to within a few tenths of a psi,
there will be at least a 10% uncertainty in the resulting GPM estimate.

The inherent imprecision of the GPM measurement will completely
swamp minor inaccuracies due to temperature-related effects -- but
that's not a problem...

..."close" counts in horseshoes, hand grenades, and heat of extraction,

Looby
.

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One measurement is worth a thousand expert opinions.

Thanks Looby.

What is your recommendation? I do remember the devise you use to measure pressure. Would that reduce the error in this calculation enough so that the results would be meaningful?

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WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon.

I use an entry-level digital pressure gauge (Dwyer DPGW-08) through
the P/T ports. I went with digital because it has better "resolution" than
even a large analog gauge. Resolution is more important than absolute
accuracy when measuring small differences between large numbers.

IMO, a 10%-ish uncertainty in extraction/rejection is perfectly acceptable
for checking geo system performance and watching for long-term trends.
Who cares whether it's 93% or 103% of spec?


"Not everything that can be counted counts, and
not everything that counts can be counted."
- Albert E.

.

__________________
One measurement is worth a thousand expert opinions.

So, the definitive "Looby Pressure Gauge" consists of:

Gauge: Dwyer DPGW-08

P/T probe (gauge adapter): Sisco model# GA-125 or Petesplug model# 520 Which do you have?

Pressure Snubber: PS122 (or is it PS222?) I see Dwyer has adjustable Pressure Snubbers - thoughts?

Teflon thread-sealing tape.

Did I miss anything?

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WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon.

Nope, that appears to be the complete list.

I don't know who made the gauge adapter -- my system installer ordered it
for me, from WaterFurnace. FWIW, the P/T ports supplied with the system
(presumably as part of a WF-furnished install kit) came from Sisco.

The gauge snubber is Dwyer part# PS222 ($21.75). In retrospect, it's not
entirely necessary, but it does reduce rapid pressure fluctuations a little.
I won't hazard a guess on the effectiveness of adjustable snubbers.

Looby

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One measurement is worth a thousand expert opinions.

Thanks Looby.

In the Dwyer catalog, searching for PS222 gets me to pressure snubbers. When I click on Pricing/Ordering, the closest match is:
- PS122 Pressure snubber, for water & oil service, 1/4" NPT. for $20.75

Not sure why I don't see PS222. Does the description of PS122 sound correct to you?

We have a WF system too. The yellow sticker on our PT Plug caps also says Sisco.

P.S. I see that "http://www.flowcenterproducts.com/accessories.php" has gauge adapters.

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WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon.

Check Dwyer's "virtual catalog", page 546. The PS222 is 100% stainless;
PS122 uses the same stainless steel snubbing element with a brass body.
I'd expect the performance of either to be identical (as long as you're careful
to keep your loop below 10,000 PSI).

Looby

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One measurement is worth a thousand expert opinions.

Thank again!
Don't think I want to be around a PT-port with 10,000 psi behind it. :-)

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WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon.

For some reason, Dwyer's computer system scheduled the shipment 21 days out. I called this morning and the rep said that the items are in stock and she changed the schedule - the order will ship either today or Monday. Guess it never hurts to ask. Good experience with them so far. Funny that it is cheaper (by 29%) to order from them directly as opposed to Grainger for the same gauge.

I ordered the GA-125 gauge adapter from the other company I mentioned for $11.11 plus shipping (probably about $20-$24 total.)

I hope this helps someone else making the LDPG (Looby Definitive Pressure Gauge.)

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WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon.