Closed horizontal loop pressure

[geome]

Just had our 12 month system check. We have a closed horizontal loop. At what loop pressure would you consider increasing the pressure, and what would you set it to?

The tech said that he would not increase the pressure if the reading was 40psi or more (it was in the mid 30's.) Do you agree with this? He raised the pressure up to the mid 50's. Low 60's is probably our max since our pressure tank (for our potable well water) is set to that. Thanks

[Palace GeoThermal]

There is nothing wrong with what the tech has done. There is no hard and fast rule on system pressure.

I have seen them as low as 5 psi and as high as 60 psi.

They all work.

[geome]

Thanks Dewayne!

The tech had an analog pressure gauge that went into the PT port. It was a Weiss gauge, maybe 4" round. I'd like to pick up a pressure gauge to do more thorough system checks myself since the tech used an IR thermometer to read loop temperature and no water flow (gpm) and heat of extraction/rejection was calculated.

What pressure gauge (to check loop pressure) would you recommend for a homeowner (accurate, sturdy, but not necessarily the most expensive)? I'd preferably to buy one ready to go into the PT port since I don't need another project right now.

[docjenser]

Just had our 12 month system check. We have a closed horizontal loop. At what loop pressure would you consider increasing the pressure, and what would you set it to?

The tech said that he would not increase the pressure if the reading was 40psi or more (it was in the mid 30's.) Do you agree with this? He raised the pressure up to the mid 50's. Low 60's is probably our max since our pressure tank (for our potable well water) is set to that. Thanks

Keep in mind that the plastic expands slightly because of the pressure, so a fresh installed loop will loose pressure. Even more pressure change comes from temperature changes. Given the fact that we use now widely non-pressurized systems, which work like charm, I am not sure that I would change too much unless I get negative pressure (and who says that even this would not work).

We use analog 5 inch gauges, they are accurate enough for the purpose of determine performance within specs. Digital ones are not more accurate and significantly more expensive.

[Bergy]

I'd like to pick up a pressure gauge to do more thorough system checks myself since the tech used an IR thermometer to read loop temperature and no water flow (gpm) and heat of extraction/rejection was calculated.

Geome;

If a heat of extraction/rejection was not done, the tech has ZERO idea about the system's performance. I would ask the contractor for a complete report to be kept with the Geothermal unit.

An IR thermometer is not the recommended way to check water temps because a shiny surface will give false temp readings. Any pressure gauge reading up to 100 PSI with single PSI marks will work fine.

Bergy

[geome]

I'll speak to the owner the next time he calls me for a reference. Included in the installation price was one fall and one spring check. Not much of a check without knowing about system performance (and having accurate readings.)

Thanks for the feedback on gauges. I'll post results as soon as I get readings.

[Looby]

Geome,

For what it's worth, here's what I did for a P/T port pressure gauge

http://www.geoexchange.org/forum/gen....html#post3440

Total cost (gauge + snubber + P/T port adapter) was about $140.

BTW, digital gauges aren't necessarily more accurate than analog,
but they do have higher resolution than even a large analog gauge.

IMO, that makes it easier to get good differential readings in the
presence of a high (and fluctuating) static pressure background --
especially when delta-P across the coax is as small as it is with
the WF Envision (only about 3 psi @ 8-9 gpm for my NDV038).

The ability to select various pressure units is also kinda handy.

Looby

[WF_Inc]

geome,

The typical operating loop pressure is 40-70psi with no air present in the system. Loop pressure will fluctuate with the seasons; therefore, it is normal for a technician to verify that the loop pressure is above 40psi while on service calls. We would not be concerned until the pressure is below 15psi. Even then the unit will still run; however, it may not be as efficient.

[geome]

WF,
Thanks for the info. Our system will be 1 year old in a few weeks. It was explained to us that we may need to have pressure added to the loop, possibly several times within the first year or two (more so toward the beginning than the end of this time frame). Our loop pressure was close to the mid 30's if I recall correctly (my notes are on a different floor.)
Does WF teach it's installers to calculate the heat of extraction/rejection as part of normal service visits and/or at system startup? While I am extremely satisfied with the installation that was done, I am a bit surprised (based on other installers here typically calculating this) that I have never received this information from our installer.

Looby,
Thank you for the link and for your thoughts. It looks like you have assembled a very nice unit. I wouldn't mind assembling these parts, but is there any way to get more specific information on the P/T port adapter that I would need to connect to the other parts? Figuring the type of connectors that I would need is not my strong suit.

[docjenser]

geome,

The typical operating loop pressure is 40-70psi with no air present in the system. Loop pressure will fluctuate with the seasons; therefore, it is normal for a technician to verify that the loop pressure is above 40psi while on service calls. We would not be concerned until the pressure is below 15psi. Even then the unit will still run; however, it may not be as efficient.

Could you tell me why you would loose efficiency at lower loop pressures?
More and more installs are now non-pressurized systems, including mine at home. I measure 13 psi between flowcenter and heatpump, and 4 psi leaving source pressure after the heatpump, which gives me a bit over 19 gpm flow.
(one of your Synergy 3D 6 ton units).
The heat extracted is 40,500 at 32 F degree EWT, which given your COP of 3.6 in the second stage gives me a total capacity with the compressor heat added over the 50000 btu/h which you have published for the 2nd stage. So overall very pleasing, with performance nicely exceeding over factory specs.
Very pleased with the performance of your unit!
So are you telling me that the system would run more efficient as a pressurized system? Why?