Posted By jonr on 02 Apr 2012 10:19 PM
Sounds like you are alluding to another myth - that restricting the
flow through a pump increases its power draw (it decreases it).

Sometimes yes, sometimes no. Pumping power is a function of
flow rate, pumping head, and pump efficiency -- which itself is
a function of flow rate and pumping head.

pumping power = flow_rate x delta-P / efficiency

...the mythology you allude to is apocryphal,

Looby

Posted By jim peterson on 02 Apr 2012 07:48 PM
How about splicing into existing loop? Is 1" pipe easy to make a slinky coil with to fit a 42"-48"trench?

Have you considered adding a pair of 3/4" slinkies, in parallel -- rather
than a single 1" slinky?

Better yet, have you considered hiring an experienced loop designer for
an hour or three of professional consultation?

Not convinced we needed extra loop at all......

Btw perhaps if we close valves on all our loops untill fluid could barely pass, then clearly efficiency would soar and pump power plunge......it's win-win.

Lo:
Jo: and most others and of last two:
you seemigly are both going about correctly:

Over-working (wild on say 3" pipe, 1ft (1/2.3 psi) pressure drop... [ the pump w/ TOO MUCH flow (see eff curves, watch amps...) or impinging friction..
 then amps shoot up, like a vacuum cleaner motor heard slowing as you REMOVE hand-"pressure-block" is REMOVED,
but more WORK per KWH is done.
Then, with MORE power consumed:
EFFICIENT work is done (in range engineered)
but in its eff range
pumps and motors within "service factors" eff curves...all considered

doing more WORK for least (kw) per gpm [wire:water]
is what I believe you both know well, to be efficient---

b)
if IN that efficiency range
and b2)
if flow through variations in gt plastic in the piping causes sufficient turbulence ((no- not reynolds #'s))
for a RANGE of efficient heat transfer to be achieved

c)
and all diff Temps are near "efficient" that heat is moving well (enough),
 then
THEN: get a consult, get some 3/4" in that shorty...

yes a 25% difference in loop-loop, even so 'imbalanced' WITH letting the pump work in a MORE EFFICIENT range in it's CURVE will be fine-er, than ever restricting it to a "worst" circuit.

A POINT on all we know of your loop
- that can be intersected, if I am to presume a little,,,
 DESCRIBE total continuous circuit,
because I HOPE you meant 25 TDH ft of WATER pressure drop (11psi) which with 35% glycol is then ~ 55% at the pump


Other words pump may only be equal to 6gpm flow in what looks like water would have 55% more flow...chart may read 11.1/2 gpm, but for water.

you can see why typical 1" is piped to 700 ft lengths MAX; and more HI Eff under 640 ft with 16%-18% methanol/and similar other-hols...
 -let alone glycol
but sdr-11 x1"
I see chart at 100 ft and 5 gpm: .6psi and 6gpm:.84 psi
here for for glycol x 1",
I will use 1.2 psig roughly, per 100 ft (~45% worse flow)
so
use more efficient circuits near 600 foot in parallel ~ 7 psig   or  TDH of 14 to 15  ft water + fittings  + unit water coil...

Is your short loop able to be intersected more so appropriately  within a - 10% difference?

Since units I use have less than 7ft or 3 psi drops through the units and hoses to pumps with 1.1/8th inch ID 3-way valves... on glycol loops, a 10 psi loop and fittings out side the system is acceptable:  but NOT 25 psi loops.

www.FlowCenterProducts.com  is just a very low PD system  that site sells a chamber for GT FLOW CENTERS if you want more performance out of little standing reservoirs, but I used reservoirs overhead in joists: 6 gal was fine for 14, 3/4coils and 12, 1" coils: 5ft vertical pressure over the pump-low-pressure-drop-inlet-piping (of larger diameters of pipe to pump), really gives maximum flow.

This may be fine with only 18% glycol... over 2.8 gpm per "rated-ton"... loop never under 32-degrees-entering unit ( less than 16% glycol has shown organic growths in the solutions !) .
26 gallons of glycol is just under 20% by vol. on GT 1"x 2800 ft alone, my vendor.

NOW COMMON PUMPING HORSEPOWER is great at under 1hp per 20-Compressor-label-tons
Some are at 24+ COMPRESSOR ( SOME 27-28"TONS-RATED" GT) --- keeping D1 and IC at bay ---

WE WANT A BOOK!
D&L collaborate!