How to Adjust a Solenoid Dosing Pump: NEWDOSE DFD Manual vs DP Pulse Control

Short answer first. If the dose is basically fixed, choose the DFD. If the dose has to follow incoming flow and you have a water meter or flowmeter with pulse output, choose the DP. What's left is understanding how to adjust a solenoid dosing pump of each type, and where the two really differ once you are standing in front of them.

What the Two Solenoid Dosing Pump Models Share

DFD and DP are both built the same way: inside each solenoid dosing pump, a solenoid pushes a PTFE diaphragm, each stroke delivers a roughly fixed volume, and you change flow by changing stroke rate. Pump head materials, power options and check valve sizes are common to both, so spares are interchangeable. Every DP has a level switch input. On the DFD only the NX, GX and X frames do, which matters if you want dry-run protection when the tank empties.

Most flow steps overlap as well. The classic X frame exists in both, from the DFD-02-16-X to the DFD-50-02-X, with a matching DP model for each, 2 m suction lift and 65 W.

DFD Manual Model: How to Adjust This Solenoid Dosing Pump

The DFD panel has three keys: down, start/stop and up. Power on and the power light comes on. Press start/stop to run the pump, then use the arrow keys to set stroke rate. You can adjust it running or stopped. The red light blinks at the current stroke rate.

Estimating flow on a manual solenoid dosing pump is simple: rated flow divided by maximum stroke rate, multiplied by the current rate. Take the DFD-09-07-NX, rated 9 L/h at a maximum of 160 strokes per minute. At 80 strokes you get about 4.5 L/h.

That number is a theoretical value with clean water at rated pressure. Real back pressure shifts it, and the manual says accurate dosing needs calibration on site. Use a graduated cylinder, run for at least 5 minutes, work out the real flow, then back-calculate the setting.

People often ask how to make a solenoid dosing pump accurate. The answer isn't on the panel, it's in that step. Our habit is to calibrate a new pump once after installation, again whenever chemical concentration or piping changes, and spot-check now and then. Write the result on a tag next to the pump so the next shift can set it the same way.

Some DFD models have a remote input on the solenoid dosing pump housing that takes a dry-contact signal. It only handles start/stop, not flow. It's fine for a level switch or timer to switch the pump on and off, but it can't make flow follow a signal.

DP Pulse Model: Getting a Solenoid Dosing Pump Onto Automatic

The DP range adds a small LM frame that the DFD doesn't have, from DP-02-07-LM to DP-09-03-LM, drawing only 30 W with 2 m suction lift. It suits small doses that still need a signal. There are also GX models up to 55 L/h.

On this solenoid dosing pump, the panel adds an A/M key for manual/auto and an ADJ function key. In manual mode it behaves exactly like a DFD. Switch to auto and the pump decides its speed from the external pulses.

One thing to remember: you can only switch between manual and auto with the pump stopped. It won't switch while running. Press start/stop first, then switch.

Divide or multiply?

Auto mode has two control methods.

When external pulses are dense, faster than the pump's maximum rate, use divide mode. Set it to one stroke for every 6 pulses, for example, and the pump won't be chasing the signal.

When pulses are sparse, much slower than the pump's maximum, use multiply mode, so one pulse triggers several strokes.

Multiply mode has a behavior that catches people out. If pulses arrive faster than the pump can finish its strokes, the extra signals are stored. Even after the pulses stop, the pump keeps running until the stored count is used up. If you see the meter stopped and the pump still stroking, don't call for service yet.

Get the wiring right

The DP pulse input accepts pulse signals or voltage-free contacts, and signal voltage must not exceed 24 V. Reversed polarity can burn the board, so check terminal numbers against the manual before connecting.

Which Solenoid Dosing Pump Should You Pick?

A few typical calls from the field:

• Cooling towers, pools and small pure water units with a steady daily dose: a DFD is enough and costs less.
• Wastewater plants dosing flocculant or disinfectant in proportion to inflow, with big swings in flow: choose the DP pulse solenoid dosing pump and pair it with a pulse-output water meter.
• Only a 4–20 mA signal on site and no pulses: neither DFD nor DP is the answer. Look at the DM.

If there is a PLC on site, it can generate pulses at a calculated rate for the DP. The calculation then lives in the control panel and the pump just strokes on each pulse. When the chemical concentration changes, edit a parameter in the program instead of walking out to the pump panel, which is one less job for the night shift.

There is also a middle path: install a DFD now, leave room, and swap to a DP when a flowmeter arrives. If the mounting codes match, the base stays as it is.

Conclusion

How you adjust a NEWDOSE solenoid dosing pump depends on which one you bought. The DFD is set only from the panel keys, and flow scales with stroke rate as a share of maximum, which suits steady doses. The DP adds a pulse-driven auto mode, using divide for dense signals and multiply for sparse ones, which suits flow-proportional dosing. With either solenoid dosing pump, calibrate after installation. Only then does the number on the display mean anything.

FAQ

Can pulse control be added to a DFD later?

Not according to current literature. The DFD only has a start/stop remote input and no pulse input. If you need pulse dosing, you need a DP, so think about future flowmeters before ordering.

How is adjusting stroke rate different from adjusting stroke length?

A NEWDOSE solenoid dosing pump changes stroke rate while stroke volume stays roughly constant. Mechanical diaphragm pumps change stroke length. The two are adjusted differently.

Why do two pumps at the same setting give different flows?

Back pressure, suction lift and chemical viscosity all affect real output. Calibrate each pump on its own and set it from measured values rather than copying another pump's numbers.

Can the DP divide ratio be changed?

Yes. In auto mode, hold the ADJ key to enter setup, change the output pulse count and the control pulse count, then press ADJ to return.

Can a DP take a 4–20 mA signal directly?

No. The DP reads only pulses and voltage-free contacts. For a current signal choose the DM series, which lets you set two points between 4 and 20 mA for proportional or inverse-proportional dosing.

Not sure whether DFD or DP fits? Tell us your signal type and dose through our contact page and we'll match the model with you.