Iwaki EHN Pump Settings: Getting the Digital Controller Right

The pump is plumbed in, the power is on, there's a number glowing on the display, and now you need to know which key to press. Setting up an Iwaki EHN pump is one of the questions customers ask us most. The good news is there isn't much to adjust. Once you understand the stroke knob, the keypad and a handful of modes, it doesn't take long.

One caveat up front: this covers the logic of each setting and what each mode does. For the exact key sequence, follow the manual shipped with your pump.

Two Things Set the Flow on an Iwaki EHN Pump

The Iwaki EHN pump is a solenoid metering pump, and its output is set by stroke rate and stroke length together.

Stroke rate is set on the digital controller from 1 to 360 spm in steps of 1 spm. Stroke length is set with the knob on the pump: 50–100% on BN models and 40–100% on CN models. Between the two, you can adjust precisely from minimum to maximum flow.

Set stroke length first, then fine-tune with rate

When commissioning, we usually set stroke length fairly high and then use stroke rate to hit the target. Rate is a digital setting, easy to change and very repeatable. Stroke length is a mechanical knob, and turning it back and forth invites drift. The output per stroke in the brochure is a range too, 0.05–0.11 mL/shot on the BN11 for example, which roughly tracks stroke length from low to high.

Always measure the Iwaki EHN pump afterwards. Draw down from a graduated cylinder on the suction side for a set time, work out the real flow, then trim the rate. The brochure figure is measured on clean water at maximum discharge pressure, and your chemical and back pressure will be different.

Choose the Right Mode on the Iwaki EHN Pump

Manual mode

The simplest option. The keys start and stop the pump and set the stroke rate. You can change the rate whether the pump is running or stopped. For fixed dosing with no interlocks, manual is all you need.

EXT mode: follow an external pulse

Use EXT when the Iwaki EHN pump has to dose in proportion to flow. It offers two calculations:

Pulse multiply 1:n: one pulse in, n strokes out, with n from 1 to 999. Pulses that arrive during a multiply run are stored, not lost.
Pulse divide n:1: n pulses in, one stroke out, again with n from 1 to 999.

Set n to 1 and the pump runs in sync. Iwaki gives an example: a pulse flow meter on a purified water line drives the pump to inject disinfectant, so the mix stays at the same concentration however the water flow changes.

Choosing multiply or divide depends on how dense the meter's pulses are. Sparse pulses, say one per large slug of water, call for multiply. Dense pulses call for divide, or the pump won't keep up.

STOP Function and Key Lock

STOP is an external contact that halts the pump. When the signal arrives the pump stops, and it resumes when the signal clears. The usual setup is a level sensor in the chemical tank that stops the pump at low level to prevent dry running. Whether the pump stops on that signal can be switched ON/OFF in the controller settings. The STOP input can also be reassigned from the keypad, after which a pump in EXT mode runs in sync with that signal.

Once the Iwaki EHN pump is set, turn on the key lock. Both the R standard and YN advanced controllers have it, and it stops a passer-by from changing the rate without anyone noticing.

Extra Settings on the YN Advanced Iwaki EHN Pump

YN uses four keys where R uses three, and both have a 4-digit LCD. YN adds analog input, an FCM input and an alarm output.

Two-point 0–20 mA setup

Set two points anywhere in 0–20 mA to map current to stroke rate. Iwaki shows two examples. In one, 4 mA gives 270 spm and 16 mA gives 90 spm, so the pump slows as current rises. In the other, 8 mA gives 90 spm and 16 mA gives 270 spm, so the pump speeds up. Direct or reverse action comes entirely from those two points, so agree on signal direction with the control system team before connecting.

FCM flow check and alarm modes

The FCM flow checker is an Iwaki EHN pump option mounted below the inlet, monitoring flow in the suction line. If it sees no flow, the pump alarms and runs at full speed, 360 spm, to clear air or a blockage. Choose between three behaviors:

PA: run at full speed when no flow is detected;
PA+AL: run at full speed for the AL time, then stop if still abnormal;
PA+AL+RE: after the full-speed run, return to the set speed if flow is detected continuously during the RE time.

With an FCM fitted, the pump must run at 100% stroke and minimum discharge pressure must be 0.2 MPa or more. Miss either condition and detection becomes unreliable, so false alarms are possible whatever you set.

Start operation

YN also has a helper function: hold the up and down keys together for maximum-stroke operation. It's handy when priming a new Iwaki EHN pump or bleeding air after a tank change.

Iwaki EHN Pump Settings That Never Seem Right? Check These

First, no back pressure. Below 0.12 MPa discharge pressure (0.05 MPa for BN31 and CN36), the pump over-feeds, and flow reads high however you adjust it. Fit a check valve or back pressure valve first. Second, swapping multiply and divide in EXT mode, which throws the dose off many times over. Third, forgetting the key lock and finding a few days later that someone has changed the settings.

Conclusion

The order to remember: set stroke length, then stroke rate, then choose manual or EXT, wire up STOP, and finally lock the keypad. If a YN Iwaki EHN pump takes a current signal, agree the two-point mapping with the control system in advance. If an FCM is fitted, pick the alarm mode that suits the site.

FAQ

Can stroke length go to zero?

No. BN models bottom out at 50% and CN models at 40%. Lower flows come from reducing stroke rate.

Do I have to stop the Iwaki EHN pump to change the rate?

No. In manual mode the stroke rate can be set while running or stopped.

Can the R standard controller take 4–20 mA?

No. R only has pulse and stop inputs. Analog input is on the YN advanced controller only, set by two points within 0–20 mA.

Will pulses get lost if they arrive too fast in EXT mode?

Pulses arriving during a multiply run are stored rather than dropped. But if they consistently arrive faster than the Iwaki EHN pump can stroke, switch to divide mode or recheck the flow size.

The level switch is wired but the pump won't stop. Why?

Check the STOP signal type first: the input needs a voltage-free contact or open collector. Then check whether the stop ON/OFF setting in the controller has been switched.

If setup still isn't behaving, send us the model, mode and a photo of the wiring through our contact page and we'll go through it with you.