Checking Pressures and Temperatures

Discussion in 'Maintenance and Troubleshooting' started by geome, Jul 23, 2010.

  1. geome

    geome Member Forum Leader

    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.)
    Last edited by a moderator: Aug 29, 2010
  2. Looby

    Looby Member Forum Leader

    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,

    Last edited: Jul 23, 2010
  3. geome

    geome Member Forum Leader

    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?
  4. Looby

    Looby Member Forum Leader

    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.

    Last edited: Jul 23, 2010
  5. geome

    geome Member Forum Leader

  6. Looby

    Looby Member Forum Leader

    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.

  7. geome

    geome Member Forum Leader

    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 "" has gauge adapters.
    Last edited: Jul 24, 2010
  8. Looby

    Looby Member Forum Leader

    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).

  9. geome

    geome Member Forum Leader

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

    geome Member Forum Leader

    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.) :)
    Last edited: Jul 30, 2010
  11. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Grainger has a huge assortment but they are not known for being the cheapest place to shop.
  12. Question

    I have a 2008 Carrier (ClimateMaster) 50YDHO26PCK301 water source heat pump.
    Would the recommendations given on this thread for gauge purchases for calculating water flow be the same for my unit? including adapters? -edit-

    I just looked briefly at the Dwyer pdf. They have 4 different choices; resolutions going down as low as 15 lbs / psig. My home well will probably never go over 50 - 60 lbs psig, ever When I stick the gauge in either the inlet or outlet port, am I expecting to hit a full 50 - 60 lbs? Isn't the actual reading much lower?
    (My thought here is to go with the lowest resolution for the highest accuracy)
    What do others think?
    Last edited: Sep 30, 2010
  13. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Do you have a closed loop system or a open loop system. Checking flow rates can differ and be addressed several ways. For open loops I prefer the flow meter over gauges.
  14. geome

    geome Member Forum Leader

    For our closed loop and system, ideal psi range is 40-70 per WF, so I bought the 100 psi model as Looby suggested.
  15. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

  16. Open loop from a 1/2 horsepower submerged motor well...I could adjust the flow by guessing, but I want to do it the right way; talk to me about the flow meter option
  17. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I like the flow meters by "whites". they are robust and long lived and relatively in expensive. It should be installed downstream of the unit with two isolation valves for ease of cleaning or maintanance. Simply install in vertical position, turn on heat pump, observe reading in sight glass, use downstream valve to throttle flow to achieve desired flow rate. Ball valves work the best and pvc provides inexpensive smart looking install. I think there are pics of the flow meters and a couple installs in the picture gallery on my web site.
    Hope this helps
  18. Where do I get it? Do I just google "whites" ?

    Where do you buy it?
  19. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Google search
    blue-white flow meters
    I like model number F110
    online purchase, ups deliver, too easy
  20. zach

    zach Member Forum Leader


    What was the total cost of the LDPG?

    I appreciate your questions and thanks Looby for posting info on this.

    With winter coming I want to measure COP throughout the season.



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