Editing Openai/6944401e-07c8-800d-9890-76b35b1d919d (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 =====

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 ====

Looking closely at the photo:

===== 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” =====

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 =====

A LOGO! PLC is commonly used in:
* Sand filter backwash systems
* Timed dosing
* Flush cycles

Not just simple alternation.

===== 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 ====

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 ====

Likely startup sequence on power restore:
# PLC boots
# Detects system not at setpoint
# Commands: - Sand filter pump ON - Dosing pump ON (or flush cycle)
# Both contactors pull in within milliseconds
# Generator sees 10–14× FLA equivalent
# 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) ====

===== Correct field workaround =====

====== 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 ======
* 1–2 minutes, no load

====== 3. Bring loads online one at a time ======
# SAND FILTER → MAN - Let motor fully start and stabilize
# DOSING TANK → MAN
# Return both to AUTO

This prevents coincident inrush.

==== If you want a permanent solution ====

In order of effectiveness:

===== 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 =====
* Cheap
* Very effective
* Common retrofit for generator compatibility

===== 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 =====
* When on generator, disable non-critical pump cycles

==== 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.