Flow Meter Alarm Answer from CC

[chas]

Here's what Jason at Chris Coffee told me about not being able to use the Flow Meter Alarm on the Mini to sense choking:

The flowmeter alarm will not go off during backflushing or the case of a grind being too fine or coarse. It will only go off if the flowmeter cable is not attached or if there is a blockage preventing the impeller inside the flowmeter from moving. The reason is that since the Mini has vibratory pump it needs an expansion valve to regulate the pump pressure. When the valve opens to regulate the pump pressure the water is being re circulated through the system so the flow meter’s impeller keeps moving/counting.

I'm not sure whether this means that the flowmeter is in the feedback loop, which seems unlikely, or whether the pressure pulsations that are obvious on the manometer also make the flowmeter move slightly at all times. Since the Mini is not in the parts catalog, the closest thing is the Rossini. However, the Rossini doesn't appear to have a flowmeter.

[Endo]

The reason is that since the Mini has vibratory pump it needs an expansion valve to regulate the pump pressure. When the valve opens to regulate the pump pressure the water is being re circulated through the system so the flow meter’s impeller keeps moving/counting.[/i]

Sorry Jason. That's wrong.

On page 37, you'll see a tee fitting (part 7641). On the Mini, this is actually 4 way fitting. The input is from the pump (on the bottom), the outputs are:

1. brew boiler feed (past the flowmeter)
2. OPV (and then back to the pump inlet)
3. steam boiler feed (controlled by a solenoid valve and low water sensor in the boiler).

The flowmeter is not in the OPV loop (output 2).

I'm not sure whether this means that the flowmeter is in the feedback loop, which seems unlikely, or whether the pressure pulsations that are obvious on the manometer also make the flowmeter move slightly at all times. Since the Mini is not in the parts catalog, the closest thing is the Rossini. However, the Rossini doesn't appear to have a flowmeter.

Chas, the flow meter is in the catalog on page 37 (upper right corner, item 2498 referred to as "Contatore Volumetrico" in the parts list).

There are only 2 possibilities for why this happens:

A- The flowmeter is seeing vibe pump pulses and indicating minute flow (it works with a small impeller spinning past a magnetic sensor).

and/or

B- The fault logic has been disabled.

Since I saw the lights come on in the video from Zoey (where his pump stalled), I assume it's option A. I could test this by closing my OPV all the way until I stall my pump. But I don't really feel like doing that to my pump. It could also be both A and B. They had option A problems and so they simply disabled it (Option B) on newer models.

But like I said, for whatever the reason, it's no big deal, as long as you are not waiting for them to come on during backflushing.