Coordinating VSP Filter Pump with Heat Pump Heater
- Thread starter burgerchef
- Start date
If the heat exchanger temp is 40 degrees above the pool water temperature, then a 1 degree difference in pool water temperature is only 2.5%.
The cost in power to go above 40 GPM is more than the cost of running the heat pump slightly longer.
The cost in power to go above 40 GPM is more than the cost of running the heat pump slightly longer.
There is a lot to unpack here for me. I appreciate it. I'll proceed a little at a time.
7 PSI @ 2,400
10 PSI @ 2,800
11 PSI @ 3,000
15 PSI @ 3,400
I have a very accurate darkroom thermometer (dial with a 6" probe) and a readout on the heater. Whenever I check them they are within a half degree of each other. For the test I mentioned above, I connected a short length of hose to a return, ran it into a bucket, used my thermometer and compared it to heater readout (3 degrees diff that test). Another similar test recently, after reading the return water, I moved well away from the return and did another thermometer reading directly in the pool (2 degrees diff that test). How should I do this test moving forward?
About two weeks ago I backwashed and immediately recorded that:
7 PSI @ 2,400
10 PSI @ 2,800
11 PSI @ 3,000
15 PSI @ 3,400
I will do that today or tomorrow.
I have a very accurate darkroom thermometer (dial with a 6" probe) and a readout on the heater. Whenever I check them they are within a half degree of each other. For the test I mentioned above, I connected a short length of hose to a return, ran it into a bucket, used my thermometer and compared it to heater readout (3 degrees diff that test). Another similar test recently, after reading the return water, I moved well away from the return and did another thermometer reading directly in the pool (2 degrees diff that test). How should I do this test moving forward?
Your system curve seems to be between C and D, which is pretty good.
In my opinion, 2,000 RPM should be sufficient.
You can get a flowmeter if you really want a better idea.
You can use the Pump Performance Curve along with suction and discharge pressure, you can use temperature differential and you can use a flowmeter to get measurements of the flow and then compare and contrast the readings.
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In my opinion, 2,000 RPM should be sufficient.
You can get a flowmeter if you really want a better idea.
You can use the Pump Performance Curve along with suction and discharge pressure, you can use temperature differential and you can use a flowmeter to get measurements of the flow and then compare and contrast the readings.
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- May 3, 2007
- 18,097
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
If the filter pressure is correct, then the plumbing curve is nearly on top of Curve C. 0.0082 vs 0.008.
54 GPM would be 2328 GPM
40 GPM would be 1724 GPM
54 GPM would be 2328 GPM
40 GPM would be 1724 GPM
Assuming a little bit of margin, I would go for about 1,900 to 2,000 RPM.
- May 3, 2007
- 18,097
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
If the reason the manufacture suggests a minimum flow of 0.45 GPM/kBTU is to keep the refrigerant temperature below the alarm level, then the RPM may need to be in the 2300 range. Experimentation could determine the threshold although it may not be good for the HP to trigger that alarm.
I tried my hand at a feet of head calculation. Data called for and my input was:
Water level to pump (I used water to gauge): 4 actual feet
All straight runs both suction and pressure sides: 260 actual feet
All fittings: 30 = 97 factor /100 = .97 x 7.7 = 7' head - I think this fits a 70gpm scenario. Pipe underground is flex so I used 45 not 90 for sweeping turns.
Filter: estimated 6' head
Heater: estimated 9' head
Results:
GPM 40 - 48'
GPM 50 - 61'
GPM 60 - 75'
I looked at the directions on another website and my results would be 2 to 3' less, primarily due to differences in straight run calculation.
I'm really beyond my knowledge here, so not much confidence in what I arrive at.
Water level to pump (I used water to gauge): 4 actual feet
All straight runs both suction and pressure sides: 260 actual feet
All fittings: 30 = 97 factor /100 = .97 x 7.7 = 7' head - I think this fits a 70gpm scenario. Pipe underground is flex so I used 45 not 90 for sweeping turns.
Filter: estimated 6' head
Heater: estimated 9' head
Results:
GPM 40 - 48'
GPM 50 - 61'
GPM 60 - 75'
I looked at the directions on another website and my results would be 2 to 3' less, primarily due to differences in straight run calculation.
I'm really beyond my knowledge here, so not much confidence in what I arrive at.
Attachments
I think that it is just to find the optimum efficiency.
The error probably happens at 20 GPM.
The transition from mostly horizontal to mostly vertical (45 degrees) happens at about 25 GPM.
So, that is what I would use as an absolute minimum.
In my opinion, 40 GPM is well within the safe and efficient range.
The Minimum Flow Rate for the UltraTemp is 30 GPM and it will be similar to other heat pumps.
Maximum 120 gpm [456 lpm] - If system flow rate exceeds 120 gpm, a bypass valve is required.
Minimum 30 gpm [110 lpm]
Maximum Working Water Pressure 50 psi
Attachments
- May 3, 2007
- 18,097
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Here are my calculations:
This sheet, columns L & M are based upon filter pressure.
Pool Pump Tools v030 - burgerchef
This sheet Column V, is a full head calculation based upon the plumbing layout. However, I do not have accurate numbers for the filter and the HP so I would go by filter pressure instead although both are fairly close anyway:
Pool Pump Tools v030 - burgerchef
Mark, trying to compare our head calcs - is there a big difference between our numbers for pipe length?
- May 3, 2007
- 18,097
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
I used 3 parallel lines of 45' each which has the same head loss as the actual lines with different line lengths.
Equivalence principle:
Equivalent length = n^2 / (1 / L1^1/2 + 1 / L2^1/2 + 1 / L3^1/2 + ... )^2
Parallel lines have the same pressure loss but differing flow rates if lengths are different. This method results in the same answer and easier to implement.
Equivalence principle:
Equivalent length = n^2 / (1 / L1^1/2 + 1 / L2^1/2 + 1 / L3^1/2 + ... )^2
Parallel lines have the same pressure loss but differing flow rates if lengths are different. This method results in the same answer and easier to implement.
You do not add parallel lengths.
The flow is divided for parallel lengths such that the head loss for each pipe is equal.
Near skimmer - 30'. H = 0.001667F1^2
Bottom Drain - 40' (depth factored in). H = 0.002222F2^2
Far skimmer - 88'. H = 0.004888F3^2.
F1 + F2 + F3 = FT
F1 = A
F2 = B
F3 = C
FT = Flow Total.
0.001667F1^2 = 0.002222F2^2 = 0.004888F3^2.
0.002222F2^2 = 0.001667F1^2
F2^2 = 0.7502F1^2
B = F2 = sqrt(0.7502F1^2)
0.004888F3^2 = 0.001667F1^2
F3^2 = 0.3410 F1^2
F3 = sqrt(0.3410 F1^2)
F1 + F2 + F3 = 60 GPM.
A + sqrt(0.7502A^2) + sqrt(0.3410A^2) = 60
A = 24.4889 GPM. 40.815%
B = 21.2108 GPM. 35.351%
C = 14.3003 GPM. 23.833%
Each line has 1 foot of head loss at 60 GPM.
So, the equation for the suction is H= 0.00027778FT^2
The flow is divided for parallel lengths such that the head loss for each pipe is equal.
Near skimmer - 30'. H = 0.001667F1^2
Bottom Drain - 40' (depth factored in). H = 0.002222F2^2
Far skimmer - 88'. H = 0.004888F3^2.
F1 + F2 + F3 = FT
F1 = A
F2 = B
F3 = C
FT = Flow Total.
0.001667F1^2 = 0.002222F2^2 = 0.004888F3^2.
0.002222F2^2 = 0.001667F1^2
F2^2 = 0.7502F1^2
B = F2 = sqrt(0.7502F1^2)
0.004888F3^2 = 0.001667F1^2
F3^2 = 0.3410 F1^2
F3 = sqrt(0.3410 F1^2)
F1 + F2 + F3 = 60 GPM.
A + sqrt(0.7502A^2) + sqrt(0.3410A^2) = 60
A = 24.4889 GPM. 40.815%
B = 21.2108 GPM. 35.351%
C = 14.3003 GPM. 23.833%
Each line has 1 foot of head loss at 60 GPM.
So, the equation for the suction is H= 0.00027778FT^2
- May 3, 2007
- 18,097
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Yes, return lines start.on line 114. I used the same length as I did not have actuals. Guessed on the number of returns and eyeball diameter as well.
At 45 gpm, the flow will be:
18.3663 GPM. Near skimmer - 30'. H = 0.001667F1^2
15.9081 GPM. Bottom Drain - 40' (depth factored in). H = 0.002222F2^2
10.7257 GPM. Far skimmer - 88'. H = 0.004888F3^2.
18.3663 GPM. Near skimmer - 30'. H = 0.001667F1^2
15.9081 GPM. Bottom Drain - 40' (depth factored in). H = 0.002222F2^2
10.7257 GPM. Far skimmer - 88'. H = 0.004888F3^2.
Last edited:
At 80 GPM.
Near skimmer = 32.65 GPM.
Bottom Drain = 28.28 GPM.
Far skimmer = 19.07 GPM.
Head loss = 1.8 feet.
Maybe between Curve D at H = 0.0044F^2 and H = 0.005F^2
Near skimmer = 32.65 GPM.
Bottom Drain = 28.28 GPM.
Far skimmer = 19.07 GPM.
Head loss = 1.8 feet.
The System Curve might be closer to about H = 0.005F2.
Maybe between Curve D at H = 0.0044F^2 and H = 0.005F^2
Last edited:
A + sqrt(0.7502A^2) + sqrt(0.3410A^2) = 100
A + 0.8661A + 0.5839A = 100
2.45A = 100
A = 40.8163 GPM.
A + 0.8661A + 0.5839A = 100
2.45A = 100
A = 40.8163 GPM.
- May 3, 2007
- 18,097
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
I didn't see this before but it looks like you are putting the pipes in series and not parallel. As I showed above, it is a different calculation. You can't just add the lengths of each pipe. It is a more complicated calculation:
Equivalent length of parallel pipes = n^2 / (1 / L1^1/2 + 1 / L2^1/2 + 1 / L3^1/2 + ... )^2
The equivalent length of the 3 pipes (30', 40' & 88') are either 3x45' parallel pipes or 1x5'. The all will have approximately the same head loss at the same total flow rate.
I made some modifications to the pad plumbing since that appears to be mostly ridged rather than flex. For flex, I use an ID of 1.5" because it tends to a little smaller than ridged at 1.61".
Here are the individual plumbing curve components that I get using the filter pressure:
3 Suction lines in parallel: 0.00049
Suction pad combine into pump: 0.00055
Return pad between pump and filter: 0.00027
16.5 PSI elevated at 43": 0.00634
Total Suction Side plumbing curve: 0.00104
Total Return Side plumbing curve: 0.00661
Total plumbing curve: 0.00765
Another way to look at this is that we know from the filter pressure, that portion has a head loss of:
16.5 * 3.21 + 43/12 = 41.7'
Plotting an offset plumbing curve over the pump curve:
Plumbing Head (ft) = 41.7' + 0.00131*GPM^2
Which results in an operating point of 81 GPM @ 50' of head.
Last edited:
Mark, stumbling through my edit attempt on your doc, I see very little difference regarding what I thought was a big one.
I was just trying to factor in my estimation of pipe lengths and fittings, I did not understand how that was notated.
Thanks for the "live" lesson!
Your calculations for Prepanel Total Dynamic Head Loss (ft) - 18.06
Your calculations for Postpanel Total Dynamic Head Loss (ft) - 33.3
With my edit calculations for Prepanel Total Dynamic Head Loss (ft) - 23.11
With my edit calculations for Postpanel Total Dynamic Head Loss (ft) - 30.4
Total difference is only 2.05, but I don't know if that means anything.
Worse yet, I now know that at one point I'm looking at the term "Total Dynamic Head In Feet", then later see "Total Dynamic Head Loss" and equate the two. I'm now assuming they are not the same. I have learned a few things from you and James and will absorb more as I continue to review it all. However I am far too ignorant in this to grasp the majority of it.
I was just trying to factor in my estimation of pipe lengths and fittings, I did not understand how that was notated.
Thanks for the "live" lesson!
Your calculations for Prepanel Total Dynamic Head Loss (ft) - 18.06
Your calculations for Postpanel Total Dynamic Head Loss (ft) - 33.3
With my edit calculations for Prepanel Total Dynamic Head Loss (ft) - 23.11
With my edit calculations for Postpanel Total Dynamic Head Loss (ft) - 30.4
Total difference is only 2.05, but I don't know if that means anything.
Worse yet, I now know that at one point I'm looking at the term "Total Dynamic Head In Feet", then later see "Total Dynamic Head Loss" and equate the two. I'm now assuming they are not the same. I have learned a few things from you and James and will absorb more as I continue to review it all. However I am far too ignorant in this to grasp the majority of it.