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Old 10-22-15, 10:09 PM   #131
randen
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Default 5 Ton GSHP

Well yes my calculations are a little off the cuff. The proper formula for calculating the wattage of the three phase motor is this: (210V x 5.8A x .82pf x 1.732) / 1000 = 1.73 Kw
Still a little more than the power of a hair dryer.

I also realize I must calculate the efficiency of the VFD and the power the circ. pumps use.

Also as Tech Shop pointed out calculating the energy transferred in the flow rates through the HX would give a better idea of BTU output.

But reviewing the flow charts for the Grundfos Circ. pumps would still only be a guess. A true measurement with a flow meter would be the best at giving a accurate transfer rate.

I guess what I was trying to convey was the subtle adjustments in the TXV and refrigerant (r290) charge that really improved the performance in the air-condition mode also extended its charm when the lever was flipped to heating.

I really wasn't expecting that the machine would have overpowered the air-handler at such a lower power setting via the VFD.

The photo is the first build attempt which provided a better measurement of efficiency using the known volume of water for COP calculations

Randen

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Old 10-22-15, 10:35 PM   #132
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on one phase

ok, 3 phase vfd, 3.5 T guess vs. 4 T in original guess

(11.7/3)*(3.5/4) = COP of 3.4, THAT number I can believe.
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Old 10-22-15, 10:37 PM   #133
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maybe as much as COP of 4, if power factor of 0.85 assumed
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Old 10-22-15, 11:43 PM   #134
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Quote:
Originally Posted by randen View Post
The photo is the first build attempt which provided a better measurement of efficiency using the known volume of water for COP calculations
Randen
Your photo is a good way to do a more precise test with a stop-watch. I like it.


Perhaps adding an insulated water tank into your system would allow you to gain even more efficiency?

My reasoning for that statement is the following:

Up to a certain point, I would imagine running the compressor closer to it's design RPM at 60 Hz would get more efficiency out of your system. My reasoning is that you would have a larger delta-T across the heat exchangers which would result in a larger heat energy transfer given the same water flow rates. This would allow you to move all your BTUs in a shorter time, thus you run your circulator pump for a shorter amount of time per given quantity of heat energy.

I plumbed a 52 gallon clean/good/used water heater into my system for this purpose. I haven't run the system for more than 2 minutes at a time yet, so I have no data to back up my hypothesis.
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Old 02-13-16, 09:12 AM   #135
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Today or rather last night temperatures dipped to a low of -21 Deg C. And the snow is piling up. The DIY Geothermal shop heat-pump is operating so well keeping me comfortable during the work day while I toil away. But I was curious and had to go to the shop this morn to check on what the situation may be for the shop at these low temps. It is the weekend so the set back is 16 Deg. C. for the shop and 20 Deg. C. for the heated office floor. Well the temps were held and the HP was off so it seems its able to maintain even at these extreme temps.

For all accounts the system is performing exceedingly well even in the extreme temps. The HP is cycling keeping the shop warm. Looking at the electric bill the cost are still pleasingly low for operating the system. The variable frequency drive VFD is still set at 40 Hz from air-conditioning season. The HP is actually in a closet next to my office. During the day while I'm at my computer I hear it cycle. The fan on the VFD is noisier than the compressor. HMM I need to do something about that.

Randen
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Old 11-23-16, 08:24 PM   #136
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Can you please tell me the name and model off your heat exchangers because I did not seen it anywhere, I want to see the specs because as you know I have my own project that fallows your foot steeps


Quote:
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AC_Hacker

Thanks for the heads up. Didn't think of the possible resulting fatigue of the copper tube. I felt the generous loops in the first iteration would have been OK as the scroll compressor runs very smooth and with the VFD. The ramp to start/stop eliminates a lot of the torque rotation normally seen with a contactor closing/opening the circuit.

But the thought of a heads up and a fatigue crack happening without due diligence would be upsetting to say the least. I really do appreciate the input!!

It only took a few extra minuets to make the change. The vacuum is holding again so I will proceed again with the water circuit. All the copper is cut and fit.

Still some cold nights so we should get a good idea to what the heat-pump will be capable of.

Randen



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Old 02-09-17, 08:53 AM   #137
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Its been a year since my last report. The DIY heat-pump is still purring away in the shop warming nicely. It has been maintenance free just keeps moving the BTUs. In the summer months it air-conditions like a rock star!! Even with the machines kicking out humidity from the coolant and heat from the motors the heat-pump handles it without breaking a sweat.

The slight down side is our electrical costs have risen sharply 20% gulp! December proved to be very cold and very windy, my Kwh's usages were up therefore a electric bill like I haven't seen before.

Randen
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Old 02-09-17, 02:42 PM   #138
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Quote:
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The slight down side is our electrical costs have risen sharply 20% gulp! December proved to be very cold and very windy, my Kwh's usages were up therefore a electric bill like I haven't seen before.
Randen
...and if you had been heating with oil?

-AC
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I'm not an HVAC technician. In fact, I'm barely even a hacker...
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Old 02-09-17, 04:31 PM   #139
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...and if you had been heating with oil?

-AC
Its been about 4 yrs but probably more than double and north of $3k. for the season

I checked the loop temp and incoming 5 Deg. C. and return 2 Deg. C

Randen
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Old 06-13-17, 10:12 AM   #140
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Here we are the weather has warmed and yesterday's temp hit 33Deg C. and humid. The DIY heat pump was switched from heat to cool and kept the shop at 21Deg C. The DIY HP has been working very well.

Now if I could just pump a little solar PV into the mix to reduce the cost of electricity.

Randen

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