Closed horizontal loop pressure

[teetech]

HE = GPM X water deta T X 485 (brine)

There are no pressure numbers in that formula.

Grundfos recommends 2 - 3 lbs pressure at pump inlet which is met by standing water column on a pressure-less flow center.

I think Dewayne hit this on the head.

[Looby]

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?

Just those three parts, they thread together directly. Nothing else needed
except some teflon thread-sealing tape -- available in any hardware store.

Gauge is 1/4" NPT male, P/T probe (gauge adapter) is 1/4" NPT female.
The (optional) snubber goes between; one end is male, the other female,
both 1/4" NPT threads. Here are some gauge adaptor part numbers:

Sisco model# GA-125 or Petesplug model# 520

Or, ask your installer to get one for you -- he might have it in stock.

good luck,

Looby

[docjenser]

HE = GPM X water deta T X 485 (brine)

There are no pressure numbers in that formula.

Grundfos recommends 2 - 3 lbs pressure at pump inlet which is met by standing water column on a pressure-less flow center.

I think Dewayne hit this on the head.

May be you misunderstood. My point for heat extraction was that the numbers indicate that the system runs very efficient wether you have a pressurized or non-pressurized system, actually above factory specs. Since waterfurnace commented that with lesser loop pressure you loose efficiency, I was doubting that this was the case and questioning why.

[urthbuoy]

Loop pressurization is to ensure air has been removed and to prevent pump cavitation on the suction side of the pump.

I've never been an expert on pump cavitation as it can get pretty complex. Most pump manufacturers report desired minimum pressures (required head pressures). Cavitation can take place at some relatively high pressures in some cases.

If in doubt, look up the head pressure requirements for your circulating pumps and see if they are adequate.

[WF_Inc]

geome,

In WaterFurnace training courses we teach that the heat of extraction/rejection should be calculated during startup and service.

[WF_Inc]

docjenser,

We apologize for not specifying in our original post that the numbers provided were for a pressurized closed loop system. Non-pressurized systems are a little different. When using a non-pressurized flow center in a closed loop system, the minimum water pressure required by the circulating pump is maintained by a column of water in the cylinder above the pump. Pressures that we refer to are suggested operating pressures. Pumps used in these applications, only need 3psi or greater to function normally. Our concern is that the pressure does not drop below the minimum 3psi.

[geome]

Looby & WF, thank you again for your replies.

[docjenser]

docjenser,

We apologize for not specifying in our original post that the numbers provided were for a pressurized closed loop system. Non-pressurized systems are a little different. When using a non-pressurized flow center in a closed loop system, the minimum water pressure required by the circulating pump is maintained by a column of water in the cylinder above the pump. Pressures that we refer to are suggested operating pressures. Pumps used in these applications, only need 3psi or greater to function normally. Our concern is that the pressure does not drop below the minimum 3psi.

Thanks for your reply.
I understood that you meant pressurized systems, however you made a comment that you loose efficiency with lower pressure, which I questioned.
As long as you do not suffocate the pump, which would reduce flow, efficiency should not be affected. I used the non-pressurized systems as an example. Grundfos 26-99 are used for both pressurized and non-pressurized systems, it would be new for me that they differ.

[Looby]

As long as you do not suffocate the pump, which would reduce flow,
efficiency should not be affected.

I agree. I don't see how a heat pump could possibly know/care about
the static pressure of the brine. GPM is GPM; delta-T is delta-T; and
static pressure has no effect on heat capacity.

As long as the loop circ pump isn't cavitating, I see no mechanism
by which the static pressure of the brine could affect heat extraction,
pumping losses, compressor load, or any other aspect of efficiency.

[WF_Inc]

docjenser,

You are correct. The efficiency loss and will occur when the pressure is below 3psi. At these pressures we are concerned with air getting in the pump and causing cavitation, which then could result in pump failure. Pressure will change as the temperature changes. Our goal is to have enough pressure on the loop that it can go through the seasonal temperature changes and still maintain a positive pressure.