On a 4 ton GSHP with a titanium heat exchanger, run as a 'pump and dump', the manufacturer, Palm, says the water source side needs 17.6 gpm; The Load side needs 10.6. Are these numbers high on average? My ground water temps are a bit less than 40f. The system is in design stage, and I am specing out a Tsurumi LB480 pump http://www.tsurumipump.com/prods/Submersible-Pumps/Single-Phase-Pumps/LB-Series.aspx for the source side as the performance curve will give me the flow needed at 20' to the pump, and 14 more feet' to the boiler room (34' total head, using 2" fpvc). b

Where are you that groundwater temps are so low? Are you sure they are sub 40*f? How far below 40?

Exceeding 4 GPM per ton on the sorce side seems excessive, but if groundwater is truly in the 30s, higher flow is needed as a cushion against freezing

Oh, just a little bit o God's Country here in Willow Billy Land, Willow, Alaska. We live next to the Nancy Lake State Rec Area, canoeing, snowshoeing, high powered snow machines, dog sleds.
-149.9775086579095
61.67627027078562;
Nice place, a little cold sometimes...
Fun Fact: I'm a volunteer water quality monitor -wow - and checked some params of the lake two days ago:
Ambient air = 16c (This is Summer Time, Beach Boys on the stereo, BBQing time here!)
Surface temp of the Lake = 11.5c
4 meters depth temp = 5c
18 meters depth temp = 4.4
PH range = 7.7 to 6.5
DO = .20
I have a shallow well i jetted down last summer. Surface of the water in the well, which is also the ground level, temp was 10.4c, 3 meters down it was 3.4c.
So, for groundwater temps at 20 feet, my engineer says to expect 40 Fahrenheit. There is a rumor of 170f water under us at 300-500 feet. No one usually goes that deep for water here as it is available a lot higher...I would like to explore for that hot water someday. The State says the one well drilled @170f was an anomaly, but there is lots of Helium in the soil here, which for some reason indicates warm water.
http://www.osti.gov/bridge/purl.cover.jsp?purl=/6858784-SVrOuy/native/6858784.pdf
Page 34, Red Shirt Lake Study in the Lower Susitna, showed geothermal potential.
Anyway, I am off target. What I am planning is to just go to 25', 8" casing, 6' of screen and set my Tsurumi pump down in there and bring up some o' that cold water, that will turn hot in the GSHP.

So, 17.6 on the source side seems excessive, but may keep things from freezing, OK.

There is a fundamental disconnect between the needs of a geo unit operating with an open loop and the domestic water system for the house...required pressure. The geo system needs a great deal of water but at relatively low pressures, 5-10 psi. The house needs much less water but at much higher pressure, 30-50 psi. Pumping 10,000 gallons per day up to 50 psi so that the house gets its 100 gallons and then throttling the flow of the other 9900 gallons per day into a geo heat exchanger is a huge waste of energy, not to mention very hard on the well pump.

If for argument's sake a geo heat pump operating with 40 deg inlet water provides 10kbtuh per ton and extracts 8 kbtuh per ton from source water, then 1 GPM per ton will result in a 16 deg F water temperature drop, clearly a non-starter with 40*F inlet water. 4 GPM per ton results in a 4 deg water teperature drop, which may be required to provides some headroom against freezing.

Be sure waterside heat exchanger is rated for the velocities such a high GPM / ton flow will cause and be sure of pressure drop across said heat exchanger while operating at that flow; zpecify pump accordingly.

ic what you mean... So, lets say the Tsurumi pump has a pump curve apparently suitable for the head and flow and wil be dedicated for geo, so it looks like an appropriate pump for pumping through the titanium heat exchanger in the GSHP. Would you spec a pressure tank and switch, or just a Spring Check Valve.

Would you be inclined to spec a deltaT monitoring controller for a variable frequency controller to the pump?

I would add a booster pump to get the pressure needed for domestic use.

Non-expert homeowner here. My open loop system runs on 42 deg F incoming water at 3 GPM/ton (4 GPM/ton sure sounds right at 40deg incoming water). I'm using a goulds 3/4 hp 25 gpm submersible well pump hooked up to a pressure tank and both domestic and heat pump water use in exactly the energy-wasting way that engineer describes. (30-50 psi household water pressure throttled down through the heat pump with Dole flow-restricting valves.)

That Tsurumi unit appears to be a 2/3 hp, 110v "dewatering pump" rated for continuous use. I'm not a expert, but that looks more like a submersible sump pump type unit rather than a submersible well pump - not sure if there's any efficiency/performance differences that you need to be aware of.

Do I understand correctly that 110v pumps are less energy efficient than 240v pumps?

If the well will be just used for the heat pump, then I wonder if you could get a pump with flow and pressure closely enough matched to the heat pump requirements that you could just control the well pump with an accessory switch/relay somehow tied to Y1, instead of needing a pressure tank and switch on the well pump and a flow control switch and flow restrictor valve on the heat pump?

There's been some discussion around here about using variable speed pumps like the Grundfos SQE, or variable speed controllers like the Franklin MonoDrive or SubDrive, as well as booster pumps, and other gadgets like CSVs. Any of these add extra costs and complexity, and I haven't seen anything concrete enough yet to convince me that the benefit will outweigh the costs.

Tsurumi Rated current is 6.1/3.0 (110/220v)
High Volume/ low head, pump looks like it's application is good for water transfer applications, High capacity, low pressure applications. I bought the 220v LB480 model, so about 3amps draw. The 220 model looks to be a bit more efficient by about 11 watts, or about 1.5%.

Engineer Wrote:

The geo system needs a great deal of water but at relatively low pressures, 5-10 psi".

So, this pump may be good for my pump and dump. Unless I go deep to a possible hot water layer and I will reconsider. The problem/or fun with this project is that there are a lot of unsolved variables...This Tsurumi does require much more maintenance than I am familiar with in pumps. I expect the GSHP to be On most of the Winter to keep up with the Heating Load, so the pump is a critical part, rt?

JME:

If the well will be just used for the heat pump, then I wonder if you could get a pump with flow and pressure closely enough matched to the heat pump requirements that you could just control the well pump with an accessory switch/relay somehow tied to Y1, instead of needing a pressure tank and switch on the well pump and a flow control switch and flow restrictor valve on the heat pump? "

Matching the pump to the requirements is a good idea. What is your opinion on a Check valve as being adequate on the supply? Perhaps a small pressure tank on the source side in addition to a spring check valve? This Heat Pump has a wired controller with connections, what I read are at 230v for the Source pump and the Load pump. I could use some help reading the wiring diagram.

What is the head to your system? Is your Goulds a shallow well or deep well pump? Amperage?
Good input on the speed controlling, thanks. I thought about locating a 'GSHP House' at the pond, which would save me 14 feet of head, but if I can't control the pump frugally, I am putting the GSHP in the utility room at the cost of a lower flow, but I won't have to build a new building and flow curve still matches the design. Building down at the pond might save from possible line freeze-up. The house is located on a rise, overlooking the pond with the Lake beyond...State Lands at the lake; I am not going with loops in the lake.


JONR: A Booster Pump sounds like a good idea! Our Domestic water well has great water now. So, I plan on keeping that system seperate from the Source well.

You seem like a quick study, so I thought I'd pass along the rather unorthodox approach I took. I have a semi-open (standing column) system with a 100 foot deep water table. My EWT runs as low as 40 degrees on long runs (3 ton system). I pump at 7 GPM and have never had a lockout (though I've been close!!!!). What also might be of interest to you is that I run the house off the same well and pump - at a different pressure and flow than geo. In fact, to reduce my pumping head, I actually pump at 20"hg vacuum through the unit using the suction created in the drop pipe. Using two pressure transducers, the pump spools up to supply the pressure tank when necessary, then drops back to vacuum "pressure". The upshot is, I'm only drawing about 275 pumping watts. Contrary to conventional wisdom, it is not necessary to compromise between house pressure and geo pressure and I'm happy to share details.... I've had two years with this and no problems (after I got the bugs worked out, anyway). If you are dumping to a lake at lower elevation than the unit, it is possible to use that suction discharge to greatly lower pumping energy. Of course - no installer in their right mind would recommend this let alone want to be liable for the results - but if you can find someone a little bit nuts, it's totally possible. (sorry for the formatting, apparently my browser doesn't know how to include paragraph breaks!)

Not so quick, but enduring...

On long runs

How long is that? It might make a difference to balance the suction, rt? I built a bell siphon for a flood and drain aquaponics system last month, where, if the pipe drain length and outlet pipe were not sized right, the siphon either wouldn't begin, or wouldn't stop...Is part of your system all about balance?

275 pumping watts

That is a good savings; over 50%...I heard from the Manuf who says the pressure range on this particular heat exchanger is usually 30-45psi. Funny as I was planning for 5psi.

no installer in their right mind...if you can find someone a little bit nuts

No problem there @ Willow, AK...ha

pump at 20" hg vacuum

I am currently pumping at about 17 Hg with my shallow well, but with poor flow, likely due to a bad venturi, nozzle or impeller gasket leak in the Jet Pump. Steady vacuum, no leaks in the system.
So, yep, I am interested. Your experience must have come at some expense...The height back to the water from the unit is about 15'. Think it would work?
b

"On long runs" = long run times on cold days, not "long distances". In any case, in my experience with a 3 ton system, 7 GPM @ 40 degrees works with no freeze lockouts to date. The less water you pump, the less energy it takes. As for suction line distance, mine is over 200 feet long (1 1/4 in reducing to 1 in for the vertical drop) with very little effect on vacuum. However, your are correct that there are some controls in place to regulate flow. If the siphon is lost, a vacuum switch "orders" the pump controller to operate at 10 PSI until the siphon is restored. I also use a self regulating 7 GPM constant flow valve (HCi terminator brand) and a slightly modified compound pressure transducer to control the pump speed at vacuum. The biggest challenge was taming the oscillations as the pump controller "hunted" for 20" hg vacuum when it was designed for 40 - 120 psi! Mine got complicated (with added cost) due to the double duty for domestic water. However, I believe yours can be made much much simpler if it only going to do geo duty. The KEY is going to be pump selection. (Get ready for an education if you've never studied a pump curve!) IFF you can find a pump that will pump the flow you need (less than manf. spec IMHO) at the total head (subtracting elevation change to lake, but adding back pipe and HX friction drop) AND has the capability to pump at a higher head (albeit at lower flow) to start the siphon, you're set. No fancy controls, regulators, variable frequency drives, etc. Just the physics of moving water!

I suppose one other thing to keep in mind is that a cheap pump might make your specs, but be an energy hog in its own right. By my estimate, you'd be looking for fractional HP pump. Stay away from Jet/Venturi pumps for efficiency, stick with submersible and press hard to get power curves and motor efficiency specs.

The Tsurumi pump was not inexpensive (smile)... Do you have a link to a FHP Pump, 1/2 hp to 3/4hp? Thanks! Wikipedia says FHP are motors less than 746 watts and they have an exemption from the US Energy Policy Act of 2005. I located one motor (only) the equivalent watts was 1070 v the 660 on the Tsurumi...Is curious that the 1070 watt motor found on the web is still called a FHP. I never located a FHP Pump so I could compare... I heard back from the Tsurumi Applications Engineer. he wrote: "This pump can be controlled by a VFD, but I would not use above 60Hz, as you can overload the motor, and cause damage." "This IS considered a dewatering pump."

For round numbers, on this Tsurumi, at 30' Head, it is at 20gpm (pump curve attached), and perhaps, without empirical data to back up the manuf claims, it is adequate if not 'excessive' and not knowing about, Reynolds Numbers , the pump appears to be a good fit, especially if I use right sized pipe and fittings; I'm thinking 2" FPVC... [quote]subtracting elevation change to lake[/quote] Hmnn...Until I hear otherwise from our state water regulators, I am planning on returning the water to the same aquifer, which is exposed, so I was planning on dumping lots of water over our hill. My concern is freezup. It happens every year here and, well Nancy, it is cold. Subtracting my 14' elevation rise above the pond, that leaves the pipe termination in the ice. So, I can insert another well, with issues of capacity. What controls should I be Googlin' to make a ? HCi Terminator Brand constant flow valve? Vacuum switch? Pump controller?

You're asking the right questions, some of which are now beyond by level of expertise. First - what I've been hinting around at is that a 20 gpm pump is most likely overkill and will be using more energy than necessary. If you do want that much flow, this pump will probably do the trick. I personally don't like the idea of "throttling" a pump using a constant flow valve. Let's say you put a 10 GPM flow valve on your 20 GPM pump - what happens? You build unnecessary back pressure. You may or may not save energy by reducing flow because you're adding head at the same time. (There's a guy that's been banned from the site who claims you actually save a lot of energy by throttling flow - did I mention he's banned?). So, the other thing to do is add a variable speed drive - which is not possible with a two wire pump. Also, variable speed drives are likely more money than you have into your pump.

As for your freezing pipe, the tail end of the pipe can a and should extend into the lake itself (if permitted). Burry the pipe below the frost line and I'm thinking it should work - but this is nothing I've had to deal with. To better maintain the syphon, you'd want the discharge underwater, anyway. If you're contemplating a second injection well, I'm out of my league on that one. But the syphon idea still works, and at least theoretically, given your high water table, you would have almost zero pressure head once the siphon started. At 0 head, you're pumping 60 gpm with your tsurumi! I think you're pump is too big to take mazimum advantage of your situation. If you are agreeing at this point, I'm happy to point you toward some different pumps. Again, with the right pump, you don't need any fancy controls and I'm guessing we could get you down into the 150 - 200 watt category - less if you want to fork over the extra bucks for varible speed, but it'll never pay for itself.

One more thing about pump curves - what you also need to wrangle from the manufacturer/dealer is the EFFICIENCY curve. A single speed pump will have a bell-curve shaped efficiency plot. The key to lowering pumping watts isn't just to be on the curve but to be as close to the peak of the curve as possible. For variable speed pumps, there's a little more leeway, but it's still a pretty narrow target. What you posted will tell you what the pump will pump at what head, but not where the peak efficiency is.. This is no small matter with centrifugal pumps - which is why there are so many bloody pumps to choose from!

I need to school myself. Dumb A observation: It seems that there should be an easy enough way to slow a big pump down by lowering the watts it consumes. [quote] you actually save a lot of energy by throttling flow [/quote] Maybe so, if the flow is of electrons...

Plan...it is pixalated, tried to delete this post, but here it is.

It's true that centrifugal pumps do use somewhat less energy when throttled - continuing to spin the same water in a circle takes less energy than actually moving it somewhere. It's also true that all pumps are most efficient at a specified pressure and flow. Operating at other points will be less efficient.

I'm not a hydronic heating expert, so I can't really assess your whole schematic - just the lower left corner if I'm reading it correctly :-)

On throttling watts - Oh, if only it were so.... Electric motors are interesting beasts - they only draw what they need to draw to cover the load. More load = more watts. Also, motors also have an efficiency curve and most are happiest in a narrow load range. Get too far out of that range and more watts are going to make heat than drive the load.

So, in the case of a pump, there are two parts - the "wet head" and the motor. The "wet head" is the impeller(s) pushing water (it's actually more like "throwing" water, but that's another lesson). The impeller has a head/flow curve and an efficiency curve. The two together is what determines the work it takes to drive the impeller at any given point on the curve. The work it takes to drive the impeller is the load that the motor "sees" and draws the corresponding watts (given its own efficiency curve).

The upshot is, you can't throttle watts on a pump motor. A variable speed drive doesn't actually change "watts" either. There are a couple of ways of doing it, but essentially a variable speed controller alters the frequency from the standard 60hz to change the speed of the motor, which in turn changes the speed of the impeller, which in turn changes the number of watts required to do the work. It also happens not to be a linear relationship. In very rough terms, the power (watts) for a centrifugal pump varies by the cube of the change in RPM.