Title: Openai/6944401e-07c8-800d-9890-76b35b1d919d - freem URL Source: https://freemwiki.com/index.php?mobileaction=toggle_view_mobile&title=Openai%2F6944401e-07c8-800d-9890-76b35b1d919d Markdown Content: ### User: Do duplex septic pumps require both pumps to be operational?[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=2 "Edit section: User: Do duplex septic pumps require both pumps to be operational?") Do duplex septic pumps require both pumps to be operational? ### Assistant: Short answer: no—both pumps do not have to be operational for a duplex septic system to function, but it depends on how…[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=3 "Edit section: Assistant: Short answer: no—both pumps do not have to be operational for a duplex septic system to function, but it depends on how…") Short answer: no—_both_ pumps do not have to be operational for a duplex septic system to function, but it depends on how the system is intended to operate. Here’s how duplex septic pump systems are typically set up: #### ###[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=4 "Edit section: ###") * Only one pump runs at a time * Pumps alternate each cycle to equalize wear * If one pump fails, the other can usually: - Keep the system operating on its own - Trigger an alarm indicating a pump failure Result: ✔ System still works with one pump operational ⚠ Reduced redundancy until repaired ##### - One pump is the primary[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=5 "Edit section: - One pump is the primary") * The second pump: - Starts only if liquid level rises unusually high - Or if the first pump can’t keep up Result: ✔ Normal conditions: one pump is sufficient ✔ Peak flow: both pumps may be required ##### - Both pumps are designed to run together every cycle[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=6 "Edit section: - Both pumps are designed to run together every cycle") * Used in: - Commercial systems - Large or high-head applications Result: ❌ One pump alone may not meet design flow ⚠ System may alarm or fail to dose properly #### - Alternating systems: usually no immediate failure, just loss of redundancy[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=7 "Edit section: - Alternating systems: usually no immediate failure, just loss of redundancy") * Lead/lag systems: alarms during heavy usage * Simultaneous systems: potential overflow or inadequate dosing Most systems will: * Activate a high-water alarm * Continue operating (if possible) until serviced #### Look for:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=8 "Edit section: Look for:") * Control panel labels (alternating vs lead/lag) * Float arrangement (separate lead/lag floats vs shared) * Pump specs (flow/head requirements) * Local code or engineer’s design documents If you want, you can describe: * The number of floats * Whether the pumps run together or alternate * Residential vs commercial system and I can help you identify which configuration you have and whether one pump alone is acceptable. ### User: there is an issue with this system overloading a generator on startup, we are trying to find a startup procedure that w…[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=9 "Edit section: User: there is an issue with this system overloading a generator on startup, we are trying to find a startup procedure that w…") there is an issue with this system overloading a generator on startup, we are trying to find a startup procedure that will let it run ### Assistant: Got it — this helps a lot.[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=10 "Edit section: Assistant: Got it — this helps a lot.") Got it — this helps a lot. Based on the panel photo and what you’re describing, this looks very much like a duplex pump system that _can_ start both pumps together, which is exactly the kind of thing that will slam a generator on startup. I’ll walk through what’s likely happening, then give you a practical startup procedure that usually works in the field. #### ![https://www\.wholesalesepticsupply\.com/cdn/shop/products/ALT\-DM2HP\-DV\_Control\_Panel\-01\-02\_4119aab6\-8464\-4f01\-94d5\-4babc36a0c59\_1200x1200\.jpg?v=1560439732&utm\_source=chatgpt\.com](https://www%5C.wholesalesepticsupply%5C.com/cdn/shop/products/ALT%5C-DM2HP%5C-DV%5C_Control%5C_Panel%5C-01%5C-02%5C_4119aab6%5C-8464%5C-4f01%5C-94d5%5C-4babc36a0c59%5C_1200x1200%5C.jpg?v=1560439732&utm%5C_source=chatgpt%5C.com)[[2]](https://freemwiki.com/index.php?mobileaction=toggle_view_mobile&title=Openai%2F6944401e-07c8-800d-9890-76b35b1d919d#cite_note-2)[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=11 "Edit section: !https://www\.wholesalesepticsupply\.com/cdn/shop/products/ALT\-DM2HP\-DV\_Control\_Panel\-01\-02\_4119aab6\-8464\-4f01\-94d5\-4babc36a0c59\_1200x1200\.jpg?v=1560439732&utm\_source=chatgpt\.com[2]") ![https://www\.wholesalesepticsupply\.com/cdn/shop/products/LPD\-G3E\_Control\_Panel\-01\-01\_fa4ea7b3\-345f\-4fba\-baa7\-024a8da034d2\_512x512\.jpg?v=1559762128&utm\_source=chatgpt\.com](https://www%5C.wholesalesepticsupply%5C.com/cdn/shop/products/LPD%5C-G3E%5C_Control%5C_Panel%5C-01%5C-01%5C_fa4ea7b3%5C-345f%5C-4fba%5C-baa7%5C-024a8da034d2%5C_512x512%5C.jpg?v=1559762128&utm%5C_source=chatgpt%5C.com)[[3]](https://freemwiki.com/index.php?mobileaction=toggle_view_mobile&title=Openai%2F6944401e-07c8-800d-9890-76b35b1d919d#cite_note-3) ![https://www\.wholesalesepticsupply\.com/cdn/shop/products/ALT\-DM2HP\-DV\_Control\_Panel\-01\-02\_62957531\-0012\-4143\-887a\-13b702549023\.jpg?v=1559758508&width=480&utm\_source=chatgpt\.com](https://www%5C.wholesalesepticsupply%5C.com/cdn/shop/products/ALT%5C-DM2HP%5C-DV%5C_Control%5C_Panel%5C-01%5C-02%5C_62957531%5C-0012%5C-4143%5C-887a%5C-13b702549023%5C.jpg?v=1559758508&width=480&utm%5C_source=chatgpt%5C.com)[[4]](https://freemwiki.com/index.php?mobileaction=toggle_view_mobile&title=Openai%2F6944401e-07c8-800d-9890-76b35b1d919d#cite_note-4) Key observations: * Two motor contactors labeled M1 and M2 - These are full-voltage across-the-line starters (no soft start, no VFD) * Two pump breakers labeled PUMP 1 (20A) and PUMP 2 (20A) * Siemens LOGO! PLC - Almost certainly doing alternation, interlocks, and alarms * Hand/Off/Auto selector switches for multiple subsystems * No visible: - Soft starter - VFD - Reduced-voltage starter ##### Each pump likely pulls:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=12 "Edit section: Each pump likely pulls:") * 5–7× FLA on startup * If both contactors close together (even briefly), the generator sees a huge inrush spike On utility power you’d never notice. On a generator → instant overload / stall / breaker trip. #### One (or more) of these is happening:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=13 "Edit section: One (or more) of these is happening:") ##### This can happen if:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=14 "Edit section: This can happen if:") * PLC boots and initializes outputs simultaneously * Lead/lag logic doesn’t delay the lag pump * High-level float is already made at startup ##### - Generator struggles[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=15 "Edit section: - Generator struggles") * PLC browns out momentarily * Outputs re-assert → both contactors pull in again ##### Even if:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=16 "Edit section: Even if:") * Running load is fine * Starting load is not #### This is the part you asked for directly.[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=17 "Edit section: This is the part you asked for directly.") ##### Start only ONE pump, let the generator stabilize, then return to automatic control.[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=18 "Edit section: Start only ONE pump, let the generator stabilize, then return to automatic control.") ##### ####[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=19 "Edit section: ####") * Put both Pump selectors to OFF (or MAN → OFF if that’s how they’re wired) * Leave generator running unloaded for ~30–60 seconds ###### - Select Pump 1 → MAN[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=20 "Edit section: - Select Pump 1 → MAN") * Verify: - Generator does not bog - Voltage and frequency stabilize * Let it run 30–60 seconds ###### Choose ONE:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=21 "Edit section: Choose ONE:") * Leave Pump 2 selector in OFF * Or trip Pump 2 breaker (preferred if selector logic is unclear) This guarantees no simultaneous start. ###### - Generator is already under load[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=22 "Edit section: - Generator is already under load") * PLC sees an already-running system, not a cold start ###### - Put selector back to AUTO[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=23 "Edit section: - Put selector back to AUTO") * Reset breaker if opened At this point: * Alternation will resume * Generator will not see a double inrush #### Then one of these is true:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=24 "Edit section: Then one of these is true:") ##### Rule of thumb:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=25 "Edit section: Rule of thumb:") * Generator kVA should be ≥ 3–4× largest motor HP * Duplex systems often need 5–6× if simultaneous start is possible ##### Common fix:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=26 "Edit section: Common fix:") * Add time-delay relay on M2 * Or program PLC to: - Enforce 10–30s delay between pump starts ##### If the wet well is already high:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=27 "Edit section: If the wet well is already high:") * PLC may intentionally start both pumps * That’s fatal on a small generator #### From simplest to best:[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=28 "Edit section: From simplest to best:") 1. Disable lag pump on generator power - Manual procedure or selector switch 2. Add a start-delay relay to Pump 2 3. Add a soft starter to at least one pump 4. Reprogram PLC to enforce staggered starts 5. Larger generator #### - No, both pumps do not need to run for the system to function[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=29 "Edit section: - No, both pumps do not need to run for the system to function") * Yes, this panel is capable of starting both, which explains the generator overload * Manual single-pump startup is the correct workaround * This is a starting kVA problem, not a running load problem If you want, tell me: * Generator kW/kVA rating * Pump HP (or model numbers) * Whether this only happens after total power loss I can sanity-check whether the generator is even theoretically capable of this setup. ### User: the user suspects that the pumps are for the sand and dosing pumps[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=30 "Edit section: User: the user suspects that the pumps are for the sand and dosing pumps") the user suspects that the pumps are for the sand and dosing pumps ### Assistant: That suspicion actually makes a lot of sense — and it changes the interpretation of the panel in an important way.[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=31 "Edit section: Assistant: That suspicion actually makes a lot of sense — and it changes the interpretation of the panel in an important way.") That suspicion actually makes a lot of sense — and it changes the interpretation of the panel in an important way. ##### Short answer[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=32 "Edit section: Short answer") Those two pumps are very likely _sand filter_ and _dosing_ pumps, not a duplex “same-job” pump pair. If that’s the case, they are not redundant, and the control logic may legitimately start both at the same time, which explains the generator overload. #### Evidence from the panel that supports this[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=33 "Edit section: Evidence from the panel that supports this") Looking closely at the photo: ##### 1. The right-hand selector switches are labeled by process, not pump number[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=34 "Edit section: 1. The right-hand selector switches are labeled by process, not pump number") You have switches labeled: * SAND FILTER * DOSING TANK * SPIN FILTER * SYSTEM FLUSH That’s already a strong hint this is a treatment train, not a lift station with two identical pumps. ##### 2. The contactors are labeled generically (M1 / M2), not “Lead / Lag”[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=35 "Edit section: 2. The contactors are labeled generically (M1 / M2), not “Lead / Lag”") In true duplex lift stations you usually see: * “Pump A / Pump B” * “Lead / Lag” * Or alternating relays Here, M1 and M2 are just motors — the PLC decides when each runs. ##### 3. The PLC (Siemens LOGO!) strongly implies sequenced process control[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=36 "Edit section: 3. The PLC (Siemens LOGO!) strongly implies sequenced process control") A LOGO! PLC is commonly used in: * Sand filter backwash systems * Timed dosing * Flush cycles Not just simple alternation. ##### 4. Handwritten conduit labels[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=37 "Edit section: 4. Handwritten conduit labels") At the bottom you have handwritten labels such as: * Pump (dose) * Pump discharge * Controls That lines up with different functional pumps, not two doing the same job. #### What that means operationally[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=38 "Edit section: What that means operationally") If one pump is: * Sand filter feed / backwash and the other is: * Dosing pump to the drainfield Then: * ❌ You cannot just disable one indefinitely * ✅ The system expects both to run during certain cycles * ⚠️ Startup may intentionally energize both motors On utility power → fine On generator → inrush disaster #### Why the generator is getting hit so hard[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=39 "Edit section: Why the generator is getting hit so hard") Likely startup sequence on power restore: 1. PLC boots 2. Detects system not at setpoint 3. Commands: - Sand filter pump ON - Dosing pump ON (or flush cycle) 4. Both contactors pull in within milliseconds 5. Generator sees 10–14× FLA equivalent 6. Voltage collapses or breaker trips This is normal behavior for a treatment system — just not generator-friendly. #### Safer generator startup procedure (updated, given this new understanding)[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=40 "Edit section: Safer generator startup procedure (updated, given this new understanding)") ##### Correct field workaround[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=41 "Edit section: Correct field workaround") ###### 1. Before starting the generator[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=42 "Edit section: 1. Before starting the generator") * Put SAND FILTER → OFF * Put DOSING TANK → OFF * Leave others OFF as well ###### 2. Start generator and let it stabilize[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=43 "Edit section: 2. Start generator and let it stabilize") * 1–2 minutes, no load ###### 3. Bring loads online one at a time[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=44 "Edit section: 3. Bring loads online one at a time") 1. SAND FILTER → MAN - Let motor fully start and stabilize 2. DOSING TANK → MAN 3. Return both to AUTO This prevents coincident inrush. #### If you want a permanent solution[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=45 "Edit section: If you want a permanent solution") In order of effectiveness: ##### Option 1: PLC interlock (best)[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=46 "Edit section: Option 1: PLC interlock (best)") Program logic such that: * Only one motor may start at a time * Enforce 10–30 second delay between starts * Especially on power-up ##### Option 2: Time-delay relay on one contactor[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=47 "Edit section: Option 2: Time-delay relay on one contactor") * Cheap * Very effective * Common retrofit for generator compatibility ##### Option 3: Soft starter on the larger motor[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=48 "Edit section: Option 3: Soft starter on the larger motor") * Reduces inrush by 50–70% * Often enough to make small generators happy ##### Option 4: Generator load-shed contact[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=49 "Edit section: Option 4: Generator load-shed contact") * When on generator, disable non-critical pump cycles #### Key takeaway[edit](https://freemwiki.com/index.php?title=Openai/6944401e-07c8-800d-9890-76b35b1d919d&action=edit§ion=50 "Edit section: Key takeaway") This is not a duplex redundancy problem — it’s a process sequencing problem. The system is doing what it was designed to do, but: * Utility power masked the issue * Generator power exposes it If you can provide: * Pump HP or nameplates * Generator kW/kVA * Whether this is septic → sand filter → drainfield I can tell you exactly which pump should get the delay or soft start.