Pool Main Pump Motor

The main pool pump motor at the facility (as of August 2021) is a Leeson Model C254T17DK13A (catalog #199987.00). It is rated for 15 HP (11 kW), 37 FLA @ 230 VAC. It is inverter duty rated (confirmed by the local manufacturer's rep) with a 10:1 PWM ratio (60 Hz, 1770 RPM down to 6 Hz, 177 RPM).
It has a month/year manufacturing designation of "H2016" - presumably corresponding with August (H=8) 2016. This makes sense, as the pump was noted to have been replaced in early 2017.
Operation
Starting and Stopping
Prior to the spring of 2022, this was performed via pushbuttons on the motor starter.
Further details will be posted once the VFD is brought up.
Flow Adjustment
Prior to the spring of 2022, pump flow was manually adjusted via the butterfly valve on the output side of the pump.
Flow adjustment will be automatic with the VFD (details to follow).
Maintenance
Lubrication
Use Mobil Polyrex EM (or equivalent Polyurea grease for electric motors), 3-4 pumps per port (i.e. front and rear of the motor). Lubrication should be performed twice per season.
Wiring and Fuse Protection
The motor is supplied 3-phase "high-leg delta" 240 VAC. This is an asymmetrical supply (relative to earth ground); see measurements in the appendix. There are two disconnects: one in the basement of the clubhouse (fused at 100 A) and one in the pump house (fused at 60 A). See the Electrical System diagram for details.
The existing motor is fed by 3 x TBD (#10 AWG GND). Fused with 3 x FRN-R-60 (60 A) fuses.
Thermal Monitoring
At this time, no thermal monitoring is performed on the motor. It does not appear the motor has any embedded temperature sensors. The possibility of adding thermocouples is being investigated.
Variable Frequency Drive
Background
Prior to the spring of 2022, the main pump motor was controlled by a Square D 8536 latching motor starter (relay). Start and stop operations were manually performed by pushbuttons. Adjustment of the flow rate was only possible by positioning the butterfly valve on the output side of the pump.
Benefits to changing to the VFD include:
- The main pump motor speed can be automatically adjusted (via the automation system) to compensate for changes in flow rate due to the state of the strainer basket and sand filters. A constant flow rate can be assured until the strainer basket or filters become too clogged. The automation system is NOT required to operate the drive. In the event that the automation system is not operational (or remote VFD control is disabled), the VFD can be operated with start and stop pushbuttons in a manner very similar to that of the motor starter.
- No need for the operator (the pool manager or B&G personnel) to regularly adjust the flow rate due to changing conditions. An improper flow rate:
- Violates best practices and/or health department requirements if it is too low (there is a required minimum number of complete water turn-over cycles per 24 hour period).
- Causes channeling in the sand filters due if it is too high. This can lead to incomplete filtration (cloudy water) and requires opening and manually stirring tank sand to resolve.
- Utility incentives will pay for a significant portion of the material cost. At the time of the project, DTE reimbursed up to $900 for a 15 HP VFD.
- Enhanced safety with the addition of two emergency stop buttons, including one at the gallery level (near the pump).
- Reduced stress on the mechanical system during startup as the motor speed can be ramped up rather than instant-on. This prevents "hammering" that can occur from an abrupt start.
- Improved fault detection. The drive can detect shorts, over-current events, low voltage, phase loss, etc. The existing configuration relies solely upon fuses, which may not offer the same level of protection.
- Improved power factor. An improved power factor reduces losses in the cabling between the distribution panel in the clubhouse basement and the pump house.
There are some downsides, too:
- The material cost (see the bill of materials). This is managed by creative purchasing - utilizing refurbished and surplus materials where possible.
- Some added complexity.
- Added failure points - including the addition of sensitive electronics in a harsh environment (corrosive vapors and dust).
An improvement in energy efficiency may be possible. However, it is not confirmed. Restricting the output flow on a centrifugal pump reduces the amount of work (pushing a lower volume weight of water). Data in the appendix below confirms this to a point.
Theory of Operation
NOTE: The sections that follow are still under development.
Reset
The state of "reset" refers to the operating state of the safety relay. In order to operate the VFD, the safety relay must be reset by pressing the reset pushbutton. The safety relay cannot be reset if an Emergency Stop switch is tripped.
Power failure will cause a loss of reset. Unfortunately, this is required for safety, as an electromechanical interlock ensures the motor will not start automatically (without explicit operator intervention). Even with a safety module, the electrical disconnect should still be used when maintaining the motor or pump.
Run
Pressing the Run pushbutton causes the VFD digital input (FWD/DI1) to go HIGH (+24V). Assuming the safety module is reset, the VFD will ramp up to full speed (60 Hz). The speed may be reduced via closed-loop control from the automation system (based upon flow meter feedback). By defaulting to 60 Hz, the motor can be operated normally without the automation system, using the butterfly valve on the output side of the pump to adjust flow.
A VFD digital output (DO1) illuminates the green LED embedded in the Run pushbutton.
Stop
Pressing the Stop pushbutton causes the VFD digital input (DI3) to go LOW (no longer connected to +24V). The VFD will ramp down to zero speed.
A switch guard (cover) may be placed on the stop button to deter its use (in favor of Programmed Stop). In an emergency, the Emergency Stop pushbutton can still be easily accessed.
Programmed Stop
Pressing the Programmed Stop pushbutton notifies the PLC (automation system) that a pump stop is requested. The pump may not stop immediately; this pushbutton is not connected to the VFD. Instead, if the boiler is operating, it is disabled and allowed to cool. Once the boiler has cooled sufficiently, the pump is stopped.
An indicator in the Programmed Stop pushbutton blinks periodically during the period between when the button is pushed and the pump motor is stopped. Pressing the button repeatedly has no effect; the programmed stop cannot be canceled. When desired, the user may press the Run pushbutton to resume pump motor operation.
The term "Programmed Stop" may be changed to something better or more descriptive.
NOTE: Existing blue control wires 20080, 20090, 21071 and 22131 could be re-used for this pushbutton. At present, these wires are used to force-stop the motor starter and provide feedback. Refer to FFSC-001 Pg 41 - Pump House Motor.png.
Emergency Stop
VFD Unit
This section has been updated to alter its context from research to implementation. A majority of the data for "other" VFD units has been removed.
Yaskawa GA50U2042ABA:
- The 2042 model sized for "normal duty" (ND) 15 HP which is appropriate for variable torque (VT) applications (i.e. centrifugal pumps).
- Internal PCBs are conformally coated (IEC 60721-3-3, Class 3C2 for chemical gasses). This is a huge plus!
- Rated for -10 °C to +50 °C (122 °F).
- 42 A current rating. Exceeds the FLA of the motor (37 A) with a 14% margin.
- No built-in DC link reactor (can be added externally between terminals +1 and +2).
- No built-in EMC filter (desirable for non-symmetric 3-phase supply).
- Frame 5 is 10.24" H x 5.51" W x 5.51" D
- Required vertical-installation clearance is 3.94" top/bottom, 1.18" sides.
- 391 W total loss @ 2 kHz, 42 A output.
Drive Catalog Code | Description | Comment | |
---|---|---|---|
Product Series | GA50 | ||
Region Code | U | Americas | |
Input Power Supply Voltage | 2 | Three-Phase AC 200 V Class | |
Rated Output Current | 42 | 42 A | |
EMC Noise Filter | A | No Internal EMC Filter | |
Enclosure Protection Design | B | IP20/UL Open Type | |
Environmental Specification | A | Standard |
Prior Considerations
VFDs from various manufacturers were considered during the evaluation process. In particular, the following other drives were evaluated:
- ABB ACS310-03U-50A8-2+J400
- Automation Direct GS23-2015
- Automation Direct GS4-2015
Line Reactor
This section is currently being revised.
A 3% impedance reactor absorbs transients and prevents nuisance tripping of drives in most applications and is typical for the line side. A 5% impedance reactor can be used if the harmonic content is severe or if IEEE519 recommendations should be met. The reactor impedance magnitude is said to be equal to the voltage drop.
For 37 FLA (motor rating). Assume the VFD has about 97% efficiency (given loss is 391 W @ 42 A).
Manufacturer | Part Number | Dimensions | Rated Voltage |
Rated Current |
Impedance | Estimated Cost |
Comment(s) |
---|---|---|---|---|---|---|---|
Automation Direct | LR-2015 | 4.25" H x 7.2" W x 4.75" D | 208/240 V | 46.2 A | 0.22 mH (rated) |
$179 | Recommended for the LR-2015. |
MTE | RL-04501 | 4.60" H x 8.91" W x 7.13" D | 45 A | 0.300 mH (rated) |
$289.31 (Galco) | Very large physical dimensions. | |
TCI | KDRD2L | 40 A | |||||
TCI | KDRULD42L | 600 V | 32 A | 0.861 mH (calculated) |
3% @ 575/600V | ||
TCI | KLR35BTB | 480 V | 35 A | 0.315 mH (calculated) |
1.5% @ 480V (0.315 mH), 3% @ 240V | ||
TCI | KLR45BTB | 480 V | 45 A | 0.490 mH (calculated) |
3% @ 480V | ||
TCI | KDRULD2L |
- MTE RLW-004601 (42 A, 3.68" H x 6.00" W x 5.76" D). Not readily available.
- TCI KDRD24L (208/240 VAC 48 A 15 HP, 3-phase, 3% - Low Z, 3.82" H x 6.95" W x 5.57" D). $195.94 on Galco (eBay TBD).
- Hammond CRX0046AC (46 A, 0.21 mH, 15 HP, 3-phase, 3%, 5.00" L x 6.13" H x 4.38" D, 40 Watts). Not readily available on eBay.
To evaluate further:
- Baldor LRAC04501 (45 A, 0.3 mH).
- For the Yaskawa GA50...2042 Normal Duty (ND) 15 HP, an Yaskawa open frame 3% URX000323 (35 A, 0.35 mH) or 5 % URX00324 (35 A, 0.71 mH) reactor is recommended.
Drawings
The Line Reactor Placement Study sheet has been created to help evaluate the physical fit of multiple line reactors. To keep the cost low, multiple options are being considered.
Additionally, concurrent designs for the GS23-2015 and GA50U2042ABA are in development.
Bill of Materials
The list below is updated as of 5-Jan-2022. Some items have been pre-emptively purchased (anticipating board approval; can be re-sold otherwise).
The list below does not include parts for "Programmed Stop", nor does it include cooling fans and filters. The VFD motor cable (if used) is also not included.
Quantity | Description | Cost Each | Total Cost | Comment |
---|---|---|---|---|
1 | DURApulse GS23-2015 | $614 | $614 | In stock as of January 2022. |
1 | Line Reactor (see section below) | $50 | $50 | eBay estimate (deal pending). |
2 | Hoffman Q403018PCICC Enclosure | $150 | $300 | Based on $206.25/ea @ Zoro w/ 20% discount. Alternate: Q403018PCI (listed at $80 on eBay, 7-Feb-2022). |
2 | Hoffman Q4030PI Panel | $26 | $52 | Searching eBay, etc. |
2 | Hoffman Q4030EXTI Extension Ring | $42.40 | $84.80 | Purchased on eBay 8-Dec-2021. |
3 | Edison TJN110 110 A Class T Fuse | $28 | $83 | 110 A for the GS-2015; 150 A for the GA50U2042ABA. |
1 | Marathon T200A3B Class T Fuse Block Holder | $50 | $50 | Estimated eBay cost. To confirm fit with TJN110. |
1 | Pilz PNOZ X3 Safety Module 774316 (120 VAC) | $37.10 | $37.10 | Purchased on eBay 6-Dec-2021. |
1 | Marathon 1423570 Power Dist Block | $23 | $23 | Purchased on eBay 12-Jan-2022. |
1 | White LED Pushbutton GCX3206-24L w/ "Reset" Plate | $24 | $24 | |
1 | Green LED Pushbutton GCX3202-24L w/ "Run" Plate | $23 | $23 | |
1 | Red Pushbutton GCX3101 w/ "Stop" Plate | $9 | $9 | |
2 | E-Stop Pushbutton GCX3136 w/ Ring & Extra Contact | $19 | $38 |
Total: $1494 (estimated)
Not Included: DIN rail, terminals, small fuse terminal(s), control wire, etc.
Motor Cable
Distance from the presumed origin to the motor terminals is estimated at 28 ft (55" mid motor starter to floor, 102" to north wall, 74" to motor horizontal, 92" pit ceiling to floor, 16" wall to motor junction box).
Shielded VFD cabling may be required to contain high-frequency emissions.
Assume use of non-metallic conduit (ENT); Table 1, Chapter 9 applies. Cross-sectional fill of 53% is permitted. So, for a 1-1/4" ID conduit, cable may have up to a 0.66" diameter. For a 1-1/2" ID conduit, cable may have up to a 0.80" diameter. VFD cable counts as a single conductor for conduit fill.
- The Yaskawa GA50U2042ABA accepts up to (and recommends) #6 AWG on U/T1, V/T2 and W/T3 terminals.
Options under investigation:
- Automation Direct has #8 AWG 4-conductor XLPE insulated shielded cable, rated for 50 A at 75 °C (NEC 310.15 (B), assumes 30 °C ambient) for $8.08/ft (August 2021 pricing). The cable is made in USA by Southwire. This cable has an OD of 0.87 inches and minimum bend radius of 10 inches. Calculations suggest a 1-1/4" conduit may be necessary to pull a cable of this diameter with adequate fill margin. The existing PVC conduit appears to be about 3/4" (to confirm), which would need to be replaced.
- In January 2022, there appears to be a low-cost option (on eBay, Michigan-based seller) to purchase Lapp Kabel #760604 (4 x #6 AWG) VFD cable for less than $6/ft. This cable has an OD of 25.5 mm (1.00 inches).
- SAB Cable 08610804 8/4 THHN VFD Cable (eBay option).
Thermal Considerations
According to the datasheet, the Yaskawa GA50U2042ABA dissipates 391 W @ 42 A. Assuming operation at 37 A, and an approximately linear decrease is power dissipation, up to 344 W of power dissipation is expected. The drive is specified to operate (without de-rating) at up to 50 °C (122 °F). Assuming that the pump house may reach temperatures exceeding 90 °F, thermal rise must be kept to a minimum. Assume that no more than 10 °F of temperature rise is allowed (112 °F ambient).
Using the formula: CFM = (3.17 * P) / dT (where dT is in °F), CFM = 3.17 * 344 W / 10 °F; 109 CFM.
The line reactor dissipates considerably less. Exact dissipation is TBD; conservatively assume 67 W (KDRD24L value @ 48 A = 85 W; 85 W * 38 A / 48 A = 67 W). CFM = 3.17 * 67 W / 10 °F; 21 CFM.
Bypass
A bypass mechanism can be used to operate a motor in the event of VFD failure. No wired bypass will be implemented due to cost/space. However, the component/wire layout will be such that bypass should be possible with minimal effort.
Prior Modifications Evaluated
Power Factor Correction Capacitor
At present (as of August 2021), no power factor correction capacitor (PFCC) is in use. It was decided that given cost priorities, a PFCC would not offer sufficient payback to justify its purchase.
Myron Zucker was contacted in August 2020 and provided two options, both rated for 240 VAC, 5 kVAr, 3-phase, 60 Hz:
- KNM23005-3 (NEMA 12 for indoor use, 14" H x 9.25" W x 5.25" D)
- KNM23005-3N3 (NEMA 3R suitable for outdoor use, 16" H x 12" W x 6" D)
Applying a 5 kVAr PFCC would reduce the FLA from 37 A to 31 A. This would reduce i-squared-R losses by 6 A. Actual losses are then based upon the cable run.
Appendix
Measurement Data
Measurements made on a Fluke 322 meter in September 2021.
Line to Ground Voltage:
L1 to GND | 117 VAC |
---|---|
L2 to GND | 211 VAC |
L3 to GND | 120 VAC |
Line to Line Voltage:
L1 to L2 | 240 VAC |
---|---|
L2 to L3 | 240 VAC |
L3 to L1 | 238 VAC |
Current Consumption:
Trial #1 | Trial #2 | Trial #3 | Trial #4 | |
---|---|---|---|---|
L1 | 34.3 A | 35.2 A | 27.8 A | 32.5 A |
L2 | 35.5 A | 36.0 A | 29.2 A | 33.6 A |
L3 | 32.2 A | 33.2 A | 26.2 A | 30.4 A |
Tank Pressures | 9-10 psi | 11-12 psi | 0-1 psi | 5-6 psi |
Flow Rate | 617 GPM | 694 GPM | 248 GPM | 476 GPM |
Total Power (See Note 1) |
14.133 kVA | 14.466 kVA | 11.529 kVA | 13.371 kVA |
- Trial #1: The output flow valve is cut back to just shy of 45° (half closed). The input flow valve is fully open.
- Trial #2: The output and input flow valves are fully open.
- Trial #3: The output flow valve is cut back far (very restricted). The input flow valve is fully open.
- Trial #4: The output flow valve is fully open. The input flow valve is very restricted.
Notes:
- Note 1: The total power calculation is based on the average current of all three phases, multiplied by 240 V, multiplied by the square root of 3.
- The power factor (PF) according to the motor plate is 0.81, but it's not known how this applies to the particular loads in each trial.