Water Source Heat Pump Deep Pump Sizing

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Bob NH

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If I had a good gravel aquifer with water at 25 ft below the surface, with enough space to reinject the water about 100 ft away, I would use it. If you have that kind of water source, you can extract or add heat with minimum pumping power. The water would not be exposed to air so it would should not increase precipitation of iron.
 

Speedbump

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I suppose if it's done right, the water wouldn't have to see any air. I've seen the pipe going into a well seal then running the rest of the way down the casing through a column of air. With iron in the water you can imagine what the inside of that casing looked like.

bob...
 

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The problem arises when the return line is just stuck through the top of a well seal with no droppipe into the water below. This allows for a lot of oxidation and a real nasty looking casing in a short time.

bob...
 

Bob NH

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speedbump said:
I suppose if it's done right, the water wouldn't have to see any air. I've seen the pipe going into a well seal then running the rest of the way down the casing through a column of air. With iron in the water you can imagine what the inside of that casing looked like.

The problem arises when the return line is just stuck through the top of a well seal with no droppipe into the water below. This allows for a lot of oxidation and a real nasty looking casing in a short time.
bob...
Someone can always find a way screw it up, but with the vast amount of information available on the internet, the knowledge is available to do it right.

http://www.energystar.gov/index.cfm?c=geo_heat.pr_crit_geo_heat_pumps
http://www.geoexchange.org/
http://www.geoexchange.org/publications/maryland.htm
 

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In your opinion Bob, do you think the GWHP's (ground water heat pumps is how I remember them) are actually worth the extra money and maintenance required? I had one not too many years ago and didn't see any savings whatsoever. The only reason I didn't change it out to air/air was the fact I was in the pump business and could keep it working cheaper than the average homeowner.

Do you think they save that much in electricity in heating and cooling?

bob...
 

Bob NH

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speedbump said:
In your opinion Bob, do you think the GWHP's (ground water heat pumps is how I remember them) are actually worth the extra money and maintenance required? I had one not too many years ago and didn't see any savings whatsoever. The only reason I didn't change it out to air/air was the fact I was in the pump business and could keep it working cheaper than the average homeowner.

Do you think they save that much in electricity in heating and cooling?

bob...
Air-to-air heat pumps don't work well when the air gets down near freezing. Water to air heat pumps work well for heating if the incoming water is above about 45 F (warmer is better), and they work well for cooling if the water is a few degrees less than ambient air.

Ground water heat pumps have a coefficient of performance greater than 3 (see first link in my previous post). That means that you get more than 3 kiloWatts of heat effect from one kiloWatt of power. That is a big saving if you are using electric heat. With fuel prices going up, it approaches the cost of gas or fuel oil in some areas.

It will become even more important when we implement a coordinated energy and environmental policy that includes building more nuclear power plants to reduce both oil imports and production of greenhouse gasses. Also, the can't export many nuclear power plant construction jobs to China.

In cooling applications the ground water systems have energy efficiency ratios (EER) in the range of 14 to 16 BTUs per watt-hour, which corresponds to a coefficient of performance of about 4.1 to 4.7.
 

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Here; everything is electric and gas and very little gas. This keeps the electric costs less than they would be in the north.

I am just curious with all the maintenance required with the well, pump, solonoid valve, return water (depending on where it is discharged) etc. Is it really that much of a savings. And the added initial expense for the installation.

bob...
 

Bob NH

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speedbump said:
Here; everything is electric and gas and very little gas. This keeps the electric costs less than they would be in the north.

I am just curious with all the maintenance required with the well, pump, solonoid valve, return water (depending on where it is discharged) etc. Is it really that much of a savings. And the added initial expense for the installation.

bob...
If I had a good source of ground water as I described earlier, my design for the ground water source would be as follows:

The source pump would be a low-head submersible in a well in a shallow aquifer where the static water level is not more than about 30 ft down. The return pipe would be into the same aquifer around 100 ft away (that is just a guess without calculation), and the pipe would be submerged in the aquifer. That would keep the pressure at the top of the return pipe above zero psi absolute and would allow recovery of the elevation head. The energy cost would be the inefficiency of the pump, the losses in the pipe and heat exchanger, and the inlet and discharge losses in the source and injection wells. The pipes would be large enough to keep the pipe losses small.

The pump would be matched to the heat exchanger requirements and there would be no flow control. The pump is on or off depending on demand.

At an energyefficiency ratio of 14 for cooling, a 5 ton (60,000 BTU/hr) unit would require about 4.3 kW, or about 15,000 BTU of electrical power, so the heat exchanger would have to remove 75,000 BTUs per hour.

At a temperature difference of 10 degrees F, it would require 7500 # per hour of water, or about 15 GPM. If you take 40 ft of head loss through the water system, that is 300,000 ft-# per hour or 0.1515 HP or 0.113 kW. With a pump at a wire-to-water efficiency of 40 percent, the pumping power is 0.283 kW.

Add another .283 kW for each additional 40 ft to water. For that condition, skip the injection well unless it is necessary to recover the water.

That number tells you how much is saved by the return well. If there is enough supply so the water can be wasted without reinjecting it, then maybe 20 ft of head is recoverable with the injection well. The additional pumping power to discharge it at ground level would be about 0.14 kW. If the water can be wasted and the cost of the return well (probably just a 2" pipe driven into the aquifer) is more than about $1000, it is probably not worth it.

The advantage of groundwater cooling for A/C is that you are operating at far lower temperatures in the condenser, and therefore, with much less power for the compressor.

The economics of the system would have to be calculated. I suspect that for the large multi-million dollar places that I see reported in Florida, a ground water source would be economical. I don't think it will be economical for a 1200 square foot place that uses one condensing unit.
 

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That was the answer I suspected.

In the million dollar + homes that are being built here, the other problem would be the water itself. We have requirements that are constantly changing. 25 years ago if you had a GWHP, you could discharge the water through sprinklers anytime of day or night any day of the week. Everyone else had water restrictions. Now, (last I checked) you have to reinject it into the aquifer. And you will do everything their way and that means more permits etc. etc.

Of course if these folks in the million dollar + homes are worried about their heating and cooling, they should be far more concerned about their taxes and rising insurance costs. That's what's killing everyone.

bob...
 

mbartosik

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Geothermal HP and well questions...

I have just had fitted a 5 ton (two stage) heat pump with open loop.
The spec sheet for the heat pump says 7 gpm on stage 1, and 14 gpm on stage 2. Stage 1 is about 3 tons, stage 2 is another 2 tons.
The water supply will be two stage (tomorrow) by fitting a second valve for stage 2 demand from the heat pump.

The well driller said that the well is capable of much more, so I presume that there is minimal draw down.
The source well is 56 ft deep and the motor is sat in plenty of water (about 20ft I think).
The discharge well is 70 feet away from the source, with about 50 ft of pipe between each well and the heat pump.
I have a large rubber bladder tank in the water circuit.

I have a few questions about optimal operation (my aim is to conserve energy).

The well motor is 3/4 HP variable speed with a Franklin Monodrive. The pump and motor appear capable of more than the 14 gpm required for heat pump. Most of the time I only use stage 1 of heat. At 14 gpm a current clamp on the input of the mono drive shows a steady 5.2A (1.25KW power factor is 1.0). If I reduce the flow to 7 gpm the current flow drops to about 2.8A (varies between 2.6 and 3.2A or 0.67KW). If I reduce the flow to 6 gpm or lower the pump cycles off for a second or two each minute (bad).

1) I am a little bothered that the pump motor has been over sized an I could have used a 1/2 HP or even 1/3 HP motor. Any comment?

2) Are the heat pump manufactures (Flordia Heat Pump) asking for too much gpm? (Higher gpm makes their COP value look better, but wastes KWh on the well pump)

3) Would a 1/2 HP or even 1/3 HP variable speed motor use much less KW? A smaller motor would work closer to its upper limit more of the time which is typically more efficient, or is the difference marginal?

4) I saw a post that the Franklin Mono Drives ramp the speed of the motor up and down. What's the alternative? I'm already unhappy with the Franklin Mono Drive because it consumes 40W constantly on standby (energy efficiency is my aim). It is probably too late to do much now, but I'd like to hear the alternatives.

5) I would like to conditionally switch the Franklin Mono Drive on when the heat pump or irrigation system call for water. The aim is to avoid the 40W standby loss of the Mono Drive. I could do this via a relay powered from the fan control of the heat pump and the pump control of the irrigation system. Any comments?

6) I'm planning on connecting the irrigation system to the well. My plan is to use only the one pump. Local permits are not a problem. The question is should I connect on the supply side or the discharge side of the heat pump?

If I connect the irrigation on the supply side, then the well pump will likely be able to provide for the heat pump on stage 1 and irrigation together, and then the irrigation can work independantly of the heat pump. For stage 2 (which is rare) the heat pump may be short changed, but demand from stage 2 would be hyper rare at the same time as irrigation.

If I connect on the discharge side of the heat pump, then the heat pump will always have enough flow for both stages but then I either need to have the heat pump on to operate the irrigation or have the irrigation system open the heat pump's supply valve. Also unless I shut off the pipe to the discharge well with another valve the pressure seen by the irrigation system would be lessened.

thanks
Mark
 
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Bob NH

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Are the heat pumps really staged (discharge of one to suction of the other) or are they in parallel (both operate off the same evaporator)?

Monodrives allow vendors to avoid matching the pumps to the system and cover any errors in head loss or flow calculations. You pay the bill for the monodrive and they avoid the engineering effort and risk of screwups.

If you look at my posts on this thread you will find that my recommendation is that pumps used for heat pump systems should not be selected or operated to produce enough head for irrigation. That is a waste of energy.

I discussed how a combined system should be set up with a second pump to take water from the heat pump source for irrigation, and manage the irrigation and heat pump operation with controls. You can set heat pump or irrigation priority and the system will water the lawn and heat the house without your intervention.

A 3/4 HP pump is probably more than you need unless the heat exchanger is sized to produce a lot of pressure drop. A 3/4 HP Goulds 10GS07 delivers 14 GPM at 175 ft of head (75 psi). A 10GS05R (really a 1/3 HP pump) delivers 14 GPM at 80 ft of head (35 psi). I don't have the service factors on those motors so they may be operating at more than the nameplate horsepower.

The only reason I can see for selecting a 3/4 HP pump would be to be able to irrigate with the same pump, which is an inefficient way to operate a heat pump system. That is also the only reason that I can see why you would have a bladder tank. If a variable head pump can't be matched to a heat pump system without a bladder tank, then the designer should get some engineering help with his design.

Your MonoDrive pump may not be operating at its most efficient point. I made a calculation for a 5 ton heat pump source in my post of January 10. You can substitute your own numbers.

The pipe to your injection well should go all the way down into the static water level so that you recover the available head from the heat exchanger down to the water level in the aquifer. The pipes should be large enough to keep velocity, and therefore pressure loss, low.

I can't tell you exactly what pump you need because I don't know the pressure drop in the heat exchanger. If it is all one heat exchanger, then the pressure drop will go up dramatically when you double the flow.
 

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Bob, first thanks for the reply.

I couldn't find your post from 10 Jan, the closest I found was your post yesterday (17 Jan). I think that I understood most of that post. Key to that post is if you are injecting back to the same depth as pumping then the head pumping energy is only the friction losses (although power for priming is needed although not often).

In my case the two stages of heat pump are as I understand it in are parallel. I understand about the not sizing the pump for irrigation, it wasn't sized for that, the ability to use for irrigation is only a bonus, and will be relatively small percentage of the usage. The irrigation is only likely to be one or two hours a week for 3 months of peak summer use, compared with 25 to 40% duty cycle for the 3 or 4 months of heating season for the heat pump. So a second pump does not appear worth it. However as you see further down I think that lowering the pressure is practical for the GSHP (but that would make irrigation impractical).

The well pump is Goulds 13GS07, and the motor is 3/4 HP 3 wire Franklin 214 5079 004S.
As I understand the pump selection
13GS07 means optimal rate is 13 gpm (with a range of 4gpm to 20gpm), and 07 means 3/4 HP. This data is from the manual.
A 10GS may have been better with a range of 3 to 16gpm (given that 2nd stage heat rarely kicks in demanding the full 14 gpm).

Given that the well is 56ft deep and the pump is in 20 feet of water, I assume that means a static head of about 30 feet. I'll round up to 40 ft to allow for some draw down. Although since I have an injection well the friction loss is the key thing.




Flow rates for Goulds 13GS07 from Goulds manual

............20 ..40 ..60 ..80 ..100 ..120 ..140 depth to water -->
.........PSI
.........0................ 19.7 18.5 17.0 15.0 13.2 11.5 8.5
.........20..... 19.4 18.0 16.4 14.8 12.9 10.5 6.0
.........30 18.9 17.5 16.0 14.6 12.5 10.0 5.0
.........40 17.4 15.9 14.4 12.4 9.7 4.0
.........50 15.4 13.8 12.0 9.5
.........60 13.2 11.5 8.5

Shut-off PSI 86 78 69 61 52 43 35 26 17 8



Flow rates for Goulds 10GS05 from Goulds manual

............20 ..40 ..60 ..80 ..100 .120 .140 .160 .180 .200 .220 depth to water -->
.........PSI
.........0 ................16.0 15.3 14.3 12.8 11.3 9.0 6.4
.........20 .....15.9 14.9 13.8 12.5 10.8 8.3 4.8
.........30 15.7 14.6 13.5 12.3 10.5 7.8 4.0
.........40 14.5 13.4 12.0 10.3 7.5 3.0
.........50 13.0 11.5 9.8 7.2
.........60 11.3 9.0 6.4

Shut-off PSI 89 81 72 63 55 46 37 29 20 11




I don't know or understand what PSI value I need for the heat pump, but I know that the "Fluid Side Pressure Drop" across the heat pump is 7 psi with only one compressor (of two) running at 15gpm, so I would guess more drop with both running but maybe not, and there needs to be remaining pressure to discharge to the return well. The pressure at the bladder is set to about 50 PSI.

It looks to me like a 10GS05 (10 gallons ideal rate, at 0.5HP) could have done the job more optimally. But I don't know what PSI value is needed at the heat pump.

There is a table in the spec sheet for the heat pump:

Fluid flow Pressure drop
8 GPM 3.5 FOH 1.51 PSIG
12 GPM 7.2 FOH 3.13 PSIG
16 GPM 12.1 FOH 5.25 PSIG
18 GPM 15.0 FOH 6.49 PSIG
22 GPM 21.5 FOH 9.32 PSIG

If I understand this table right, then at about 14 GPM roughly interpolating that will be 4 PSIG or about equivalent to an extra 10 FOH (feet of head). (I think that FOH means feet of head). The measured drop was 7PSI at 15 GPM. Even allowing for 10PSI drop across the heat pump, I think that means the 0.5 HP pump is plenty sufficient.

So one of the key questions become:
What pressure is required at the heat pump. As I see it, the pressure required is the drop across the heat pump plus what ever pressure is required by the discharge well, and the discharge well is unlikely to require more than 10 PSI (it is only 40 feet deep with at most 20 feet of water in it). So the pressure at the bladder need not be more than 20 PSI (plus unknown for friction loss) 10 PSI for heat pump and 10 PSI for discharge well.

Very simply I have 30 feet of head, plus I need about 20 feet of equivalent head to push the water through the heat pump and into the return well. That's only an equivalent of 50 feet of head. The 10GS05 can pump 16 gpm at 80 feet of head and is thus still over kill but 0.5HP looks like the maximum that I need, and maybe the smallest that I can buy?

Should I adjust the pressure sensor down to 20 PSI?

If I was to ask the well guy to swap my 1 month old 3/4 HP motor and 13GS07 for a 10FS05 pump and 1/2 HP motor or even a 10FS05R with 1/3 HP motor then would that likely do the job? And would that use much less power, or does the Mono Drive mean that I've just paid for over spec motor and pump but the power consumed won't be much different?

I really don't care about paying over the odds for a larger pump and motor and Mono Drive, but I do care very much if it is using more power than it should. The entire system is net metered with a large photovoltaic solar array, and 1KW of DC power costs between $4000 and $6000.

If the pressure at the bladder is set at 55 PSI, and the drop on the heat pump is about 10 PSI plus say 5 PSI for other pipes, does that mean I'm just pooring 40 PSI worth of energy straight down the return well for no good reason?????

I've just done an experiment:
At 55 PSI and 15 GPM current draw is 5.2A so 1.25KW (at MonoDrive input, power factor is 1.0)
At 55 PSI and 7 GPM current draw is about 2.8A so 672W
At 45 PSI and 7 GPM current draw is about 2.4A so 576W
I cannot drop the pressure or gpm below this because the system cycles causing hammering.
If I interpolate to 20 PSI at 7 GPM thats about 225W, which sounds about right for 3 tons, since I read that about 75W pump power per ton is about right, and over 100W pump power per ton is bad. So the system appears to be set to use x5 the pump energy really required!

So I think that I should ask (or insist) that the well installer to swap the pump and motor for something a lot smaller. Then I just forget about using it for irrigation also since the pressure would not likely be enough.

Does a 10GS05R require a 1/3 HP motor or a 1/2 HP motor?
Would the MonoDrive work witha 1/3 HP motor, the manual say 1/2 3/4 or 1?
Should I be looking at 1/2 HP or 1/3 HP?


thanks
Mark
 
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Speedbump

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I'm not a fan of variable speed pumps and am not sure if you intend on using this water for your home as well as your irrigation and heating/cooling. But like Bob said, using one pump to do all three is never going to be economical. If you had a large enough well, you might be able to put two or maybe even three pumps in it.

If the pipes were large enough going through this heat pump, you might be able to discharge all or some of the discharge water to the sprinklers killing two birds with one stone. I'm sure this could be done with a little engineering. This way you would only have two different flow rates for the same pump.

Three wells and three pumps is the economical solution. But the up front costs could be a bit staggering.

bob...
 

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The point about having the variable speed was to be able to match the heat pump at between 7 and 14 gpm without wasting energy.

My problem now appears to be that the minimum power on the pump is slightly greater than the maximum that I need.

Also the minimum power for a MonoDrive that is required to do the variable speed is 1/2 HP, but I only need about 1/3 HP max, since the variable speed can regulate 60 Hz pumps down to 30 Hz a 1/2 HP can run at between 1/4 HP and 1/2 HP so the energy saving with the variable speed is the difference between 1/4 and 1/3 HP (not a lot), which is probably burnt up in the overhead of the controller.

The other advantage of the variable speed pump is that the wear and tear is on the pump and the well is meant to be less (but for a complication of having the controller).


For drinking water, washing, plus toilet etc, I use street supply.

The well pump is only for the heat pump, and if I could have used it for irrigation it would be a bonus.
The current size of pump is enough for irrigation, but of course that's only about 35 hours a year, and there is no point running at 45 or 55 PSI for 1500 hours a year just for the sake of having enough pressure for irrigation and wasting at least 20 PSI all year long (at least 1500 hours) for the sake of the 35 hours.

So now I'm feeling pretty let down, but will speak with the well driller, and if he will resize it for minimal cost I'll be happy.
 
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One of the problems with variable speeds it the horse power of the motor doesn't match the pump. It's always bigger than the pump. That in itself is a waste of electricity.

Doing two or three different things with one pump always has and probably always will be a problem. Not only for the sake of electricity used, but in maintenance and longevity of the pump and motor.

bob...
 

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Why does the horse power of the motor have to be greater than of the pump with a variable speed drive?
I think that you are thinking of the SubDrive series, not MonoDrive.

I appear to have a 3/4 HP pump and 3/4 HP motor with variable speed controller MonoDrive.

From the manual from my MonoDrive:
"The MonDrive is designed to convert a conventional 0.5 0.75 1.0 HP pump system to a variable speed constant pressure system by simply replacing the 3 wire control box. Maximum pump output using the MonoDrive is similar to the performance achieved using a conventional control box. Therefore, the pump selection criteria are the same as if a control box were used. Please refer to the pump manufacture's literature for details of pump selection procedure."

However for the SubDrive the manual says use a 3/4 pump with 1.5HP motor (SubDrive 75).

From my system with a 3/4 HP pump and motor, assuming 40% combined efficiency of pump and motor, my input is a little over 1.25KW max, and at 40% that is not far off the 0.55KW that corresponds to 3/4 HP.
 
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Speedbump

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When you ramp a pump up past it's normal RPM's it will require more horsepower. So if the pump is a 3/4hp, the motor could easily be a 1.5hp or so. I don't see any other way to spin these pumps faster without having more horsepower to do so.

Unless they don't allow the motor to go over 3450 RPM's and just ramp down to keep the motor running. I'm not the expert on variable speeds, so you might want to get an answer from someone who knows.

bob...
 

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The MonoDrive ramps down (30 to 60Hz) i.e. about 1800 to about 3600 rpm.
The SubDrive ramps between 30 and 80 Hz i.e. about 1800 to about 4800 rpm (using more HP).

So for me the MonoDrive is the more suitable, but of course that's if it is worth having variable speed at all. I think that my problem is that I'd like a variable speed on a lower HP size than is accomodated. I'd like variable speed on 1/3 HP not 1/2 HP, but I actually have 3/4 HP installed.
 

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And then there is the Cycle Stop Valve.

I don't think we want to get that discussion started again. So all I'll say is you might want to research some of the CSV discussions that have been hashed over in the past. You might want to look into them further.

For my money, that's what I would have on my well. As a matter of fact I do, on two different wells.

bob...
 

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"At 14 gpm a current clamp on the input of the mono drive shows a steady 5.2A (1.25KW power factor is 1.0). If I reduce the flow to 7 gpm the current flow drops to about 2.8A (varies between 2.6 and 3.2A or 0.67KW). If I reduce the flow to 6 gpm or lower the pump cycles off for a second or two each minute (bad)."

I have been following this post with great interest as I am in the process of designing a heat pump system for my own home. I really appreciate the explanations given by BobNH as they are very helpful. I was told by Franklin Electric that their Mono and Sub drive units are made to vary the flow rate of a pump for intermittent use only. Intermittent being taking a shower or filling a washing machine. Any long term water uses such as heat pumps and irrigation needs to be matched to the max output of the pump. When you are using 7 GPM or low flow rates the amps are varying between 2.6 and 3.2 amps. This is showing you that the (go/no go) switch used with the Mono Drive instead of a pressure transducer is causing the pump to ramp up and down about 45 times per minute. Then as you have seen, once per minute the unit does a "bump" as Franklin calls it, which increases the pressure about 4 PSI and completely shuts off the pump/motor. Then because water is still being used the pressure quickly drops and the pump restarts after only a couple of seconds. With a Mono or Sub Drive this process is repeated over and over as long as the flow required is less than the max output of the pump. When you are running 14 GPM the amps stay steady. That is because this is the only amount of water that the pump is "designed" to pump for any long term water use. What I am hearing and seeing in the field is that the continuous ramping up and down of the Mono Drive controlled pumps is causing the wire down hole to wear out quickly and even wearing holes in the side of the pump or motor from touching the casing. This motor torque is happening 45 times per minute which is a million times every 21 days of use. I am also hearing that the fan in the Mono Drive needed to cool the electronics is drawing in lint and other debris which reduces the air flow and causes overheating of the Drive itself. Not to mention the ones I have heard about that where destroyed from this air flow area being taken over by fire ants and other critters. Then there is the "stray voltage" caused by the Mono Drive or any VFD. Do a search for "VFD stray voltage" and it will give you other problems to worry about. I agree with BobNH that to save energy the pump needs to be sized for the minimum head to make things work without any kind of regulation. You certainly do not need 55 PSI or a bladder tank to make this work. However it looks like to me that when using 14 GPM, your pump is not oversized by very much. I think you should change out the Mono Drive controller for a standard control box, remove the pressure tank, and wire a relay to run the pump anytime the heat pump is on. There won't be any change of power consumption or pressure at 14 GPM. At lower flow rates the pump pressure will be much higher than needed but, the high pump pressure and low flow rate will cause the amps to drop almost the same as when using the Mono Drive. This is best for the pump/motor and will make it last considerably longer. If you have to purchase a new pump/motor and or Mono Drive every 2 or 3 years, which is all I expect, energy consumption is the least of your worries. If your pump system last 15 or 20 years as it should, you can afford to use considerably more energy and still be better off. Save a little energy and spend $1,000.00 on a new pump every 2 years, or use a little more energy and have that $1,000.00 pump system last 20 years, do the math. If the total head needed when pumping 14 GPM can be done with a smaller pump, then that is the best and maybe only way to reduce the energy consumption. Also when restricted to low flow, some pumps will reduce in amperage more than others. The Goulds pump like many others, uses a floating stack impeller design. When the flow is restricted, all these floating impellers drag on each diffuser causing the amps from lowering any further. A pump with a fixed impeller design (locked to the shaft), such as a Grundfos pump, will not allow the impellers to drag and the power consumption at low flow will be much less than floating stack impeller pumps. I have a 2 HP Grundfos pump at my home now and when the flow is restricted, the amps drop from 12 to 5.5 (using a CSV not a VFD). A floating stack pump would only drop from 12 to about 8 or 9 amps. This makes a big difference in power consumption at low flow.
 
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Hey, wait a minute.

This is awkward, but...

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