Water Source Heat Pump Deep Pump Sizing

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mbartosik

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In my region (North East USA) 2 x 200W DC solar panels will generate about 440KWh per year. It is generally more economical to reduce demand than to add solar panels. Which is why I'm keen to get the demand down.

My point was that dropping the power demand by 850W was something significant, and I consider that the installers really messed up by wasting 850W down the return well. Fixing that waste has just paid for at least 2 panels when I install the next array.


Doubling the size of the evaporator is very interesting I will discuss with the HVAC people. I will also have to do some research there. Also switching from parallel to series with the evaporator is interesting.


There are no other devices that can cause a pressure drop in the water circuit. The pipes on the inside of the house are all 1" diameter copper, and on the outside 1" PVC (same as sprinkler pipe). In the well they are 1" poly pipe, and the return well goes down to the water line and is sealed. If all the pipes took straightest line rather than making 90 degree turns I doubt that I'd save more than 20' horizontal distance in total for supply and return together. But straight lines for the pipes would have been difficult.

I was a little surprised when they fitted the sprinkler type pipe in the trench (installed with a hydraulic missle/mole). Maybe a different type of pipe or larger diameter here would have been better? That really is too late now, other than to advise others.
 

Valveman

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If you can save $288.00 per year and your $1,000.00 pump will last more than 4 years then you are saving energy and money. If it does not last 4 years, you have got to decide how much extra you are willing to spend to save energy. Except for being able to change the operating pressure, I still think you could size a normal pump for the flow and head to get about the same energy savings. If you are really looking at energy savings alone, you may have to look back further. If saving a little energy means replacing a pump every 5 years instead of it lasting 20 years, then how much energy is used to manufacture, transport, install, and dispose of those extra pumps and motors. A big part of what you pay for the extra equipment, is used for energy. It is like the hybrid cars. If you have to replace the batteries every 35,000 miles, the money you save on gas is spent on energy mining, manufacturing, transporting, and disposing of batteries. It still seems to me that making equipment last, is the best way to save money and energy.

Putting a ½ HP pump end on that 3/4 HP motor will reduce the horse power. It would pull slightly less power with a ½ HP motor but, the 3/4 motor will run cooler and hopefully last longer, which I think is going to be your problem anyway. 13 PSI of air in a tank that runs at 35 PSI is not going to hurt anything. That larger tank is not doing you any better job than a 1 gallon size tank, it is just being used as a shock absorber. You have to have a pressure bandwidth like on at 20 and off at 40 to put any water in a tank or get any out. When a drive holds the pressure steady at 18 PSI all the time, no water comes in or out of the tank regardless of the size. Normally the water in the tank stays in the tank and gets stale and contaminated.
 

mbartosik

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I've already saved the $288 per year (850W) by better tuning the pressure and flow, largely thanks to this forum.
The question is whether I can save more, I suspect that the most that I'd be able to save while the pump is running is another 250W (half the 500W currently).

Anyway I've learnt a lot from this forum.
I think that my remaining saving can come from....

1) Switching the MonoDrive on/off automatically will save 40W of standby power (240 KWh per year).

2) I'll look at fitting a second pressure switch, and use a relay to switch between 18 and 35 PSI. Saving about 100W for 2000 hours or 200KWh per year. This will also have a good effect of cycling the water in the bladder.

3) Using a 1/2 HP pump might save more, but this will require more analysis.
The difference between the Gould 3/4 HP and 1/2 HP pump is two rotors/stages (5 stages in 1/2 HP vs 7 in 3/4 HP), so I wonder if I could remove two stages, I doubt it?

The easy way to avoid the "emedded energy" loss of buying a replacement pump is to sell the existing one on internet auction, then the only wasted energy is transport for the pumps.

4) Using a second evaporator either in parallel or in series. -- Thanks Bob NH. Even better if it improves the COP of the heat pump.

5) For irrigation ground water is more efficient than street water, so I can lock the irrigation out when the heat pump is on (the two would rarely be on together anyway), I can use a valve to send the pump output directly to irrigation (without going via the bladder and locking the sensor switch on). This results in less pressure drop than on the return side of the heat pump.

Is the 1" PVC sprinkler type burried pipe between the wells and the house causing more pressure drop than another type of pipe?

6) I don't have a filter installed (thus no pressure loss from that), the water is pretty clear.

My total roof space for solar panels is 1300 ft^2, and I've already used 900 ft^2, that leaves 400 ft^2 with a max DC capacity of 4800W DC or about 5000KWh per year here. Beyond that I cannot install more solar power. So my aim is to get the heat pump and well pump to not use more than 5000KWh per year. More house insulation and replacing the drafty windows will go a long way too.
 
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Valveman

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Yes you can take out two impellers if you grind off the outside of them and use the part thats left and fits just over the shaft as a spacer.

As for the irrigation, drip would use much less pressure than any kind of sprinkler and has less evaporation. I love my drip in the garden, uses 10 PSI and 3 GPM. A yard would take more volume than row crops. More expensive to install though. Like anything else, it has got to last long enough to pay back the difference.
 

ncgeo

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In the summer, the AC is taking heat from the house and putting it into the water, raising the temperature of the water. If the water is pumped back into the well, then the temperature will slowly RISE in the summer.

In the winter, the heat pump is taking energy from the water, causing the water to be cooled, and discharging it to the house. If the water is put back into the well, then it will cause the temperature of the well supply to drop.

The most effective way to circulate the water to the ground is to inject it into the aquifer at some distance from where it was withdrawn from the aquifer. It then tends to flow through the aquifer from the injection point to the withdrawal point at the well.

If the water level in the well is much below the surface the systems use a lot of electricity you usually don't recover all of the available head when the water is reinjected.

I just found this thread and it involves the exact application I have, but not sure anyone is still reading it.

With regard to water re-injection to the well, I have a 3-way valve on the condenser water output so I redirect some of the water to a creek (rather than back down the well) on the most extreme days. That is usually only the coldest winter nights where the unit runs continuously. That redirection is done manually, would be nice if I could install some type of feedback circut (as well water temperature drops to/ rises above some level increase water redirection to creek).

The water reinjection concept is known as standing water column, where you are continually re-using your well water as heat transfer fluid. It relies on the water storage in the well and the heat transfer between the well water and bore wall to move heat.

I think of it as a less-than-optimal closed loop system. Reinjecting water may be less than optimal for heat pump efficiency but it beats pumping your well dry.
 

Thumper

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A bump from Thump :confused:

It's getting [too close] to time and pull the trigger and I'm seeking input on which way to go on the recharge well direction/reinjection pipe length questions posed in my last post in this thread.

Thanks,

T
 
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