A10VO 52/53 Controls: DRF, DRS, LA and EP Explained
On a medium-pressure mobile pump, the control is often the part that gets ordered wrong. Two pumps can share the same size and the same pressure rating and still behave completely differently, because the control decides how the pump reacts to the machine: pressure only, pressure and flow, or pressure, flow and power. The A10VO Series 52 and Series 53 use two closely related control families with two different naming systems, and a few controls that exist on one series only. This guide sets out what each control does, where the names differ, and which controls are actually available on which size.
The short version
- Series 52 sizes: 10, 28, 45, 60, 85. Series 53 sizes: 18, 28, 45, 63, 72, 85, 100. Both run at 250 bar nominal and 315 bar maximum, open circuit.
- The same load-sensing function carries two names: Series 52 orders as DFR / DFR1, Series 53 as DRF / DRS — the catalogue itself writes them as DRF (DFR) and DRS (DFR1).
- X–T open or plugged is the real difference between DFR/DRF and DFR1/DRS, and only the plugged versions offer a flushing function.
- ED is negative, ER is positive — both are electro-hydraulic pressure controls, in 12 V and 24 V versions.
- Constant-power LA and electro-proportional EP / EK exist on Series 53 only.
- Not every control is available on every size — a size 10 Series 52 pump, for example, cannot be ordered with DRSC, ED or ER.
Two naming systems, not two functions
| Function | Series 52 order code | Series 53 order code |
|---|---|---|
| Pressure controller | DR | DR |
| Pressure controller, remotely controlled | DRG | DRG |
| Pressure and flow control, X–T open | DFR | DRF |
| Pressure and flow control, X–T plugged, with flushing | DFR1 | DRS |
| Pressure and flow control, X–T plugged, without flushing | DRSC | DRSC |
The catalogue lists this family as DRF (DFR) / DRS (DFR1) / DRSC: the DRF/DRS spellings and the DFR/DFR1 spellings describe the same controls. What changes between the two series is the order code you will find on the nameplate. That matters when you quote a replacement — a Series 52 pump carries DFR or DFR1, a Series 53 pump carries DRF or DRS, and mixing the two spellings in an enquiry is the fastest way to get the wrong drain arrangement.
Load sensing: X–T open or plugged
All three load-sensing versions use an adjustable orifice to set the differential pressure, and the pump then delivers the flow the consumer actually asks for instead of the full displacement. The difference is what happens to the X–T connection inside the control:
- X–T open (DFR / DRF) — the control is open towards the tank line; this is the version used with an open X–T connection.
- X–T plugged, with flushing (DFR1 / DRS) — the connection is plugged and the control includes a flushing function; the LS line has to be unloaded in the system.
- X–T plugged, without flushing (DRSC) — plugged, without the flushing function; again the LS line must be unloaded in the system.
In practice: copy the letters from your own nameplate. A pump ordered with the wrong variant has the right flange, the right pressure setting and the wrong internal drain path, and the symptoms show up as heat, noise or a slow circuit rather than as an obvious failure.
Electro-hydraulic pressure control: ED or ER
| Control | Characteristic | Voltage |
|---|---|---|
| ED71 | Negative control | 12 V |
| ED72 | Negative control | 24 V |
| ER71 | Positive control | 12 V |
| ER72 | Positive control | 24 V |
ED and ER are electrically commanded hydraulic pressure controls: the machine’s electric signal sets the pressure level, and the pump regulates its swivel angle to hold it. The letters separate the control characteristic — ED is the negative version, ER the positive one — and the number separates the voltage (71 for 12 V, 72 for 24 V). Both exist through the Series 52 range above size 10 and across the whole Series 53 range. Before ordering, check the old pump’s control code and the machine’s supply voltage: an ER where the machine expects ED is a functioning pump that regulates in the wrong direction.
Constant power: the LA family (Series 53 only)
The LA controls add a power limit to the pressure and flow functions, which is what keeps a mobile machine from stalling when several functions are used at once. They are ordered by the beginning of the pressure cut-off, from 10 bar up to 230 bar:
| Control | Beginning of pressure cut-off |
|---|---|
| LA5D | 10 to 35 bar (145 to 510 psi) |
| LA6D | 36 to 70 bar (520 to 1015 psi) |
| LA7D | 71 to 105 bar (1030 to 1520 psi) |
| LA8D | 106 to 140 bar (1535 to 2030 psi) |
| LA9D | 141 to 230 bar (2045 to 3335 psi) |
The family also includes the remotely controlled version (LA.DG) and the version with flow control, X–T plugged and a flushing function (LA.DS). All of these are available across the full Series 53 size range, and none of them on Series 52 — if your machine is a size 45 or 60 and needs a power limit, that requirement has to be solved another way or the pump changed to a Series 53 size.
Electro-proportional: EP and EK (Series 53 only)
EP and EK control the swivel angle directly by a proportional solenoid, so displacement follows a control current rather than a pressure signal. They come in three functional variants:
- EP1D / EP2D and EK1D / EK2D — with pressure control (12 V / 24 V).
- EP1DF / EP2DF and EK1DF / EK2DF — with pressure and flow control, X–T open (load sensing).
- EP1DS / EP2DS and EK1DS / EK2DS — with pressure and flow control, X–T plugged.
The difference between the EP and EK families is the last letter of the pair: EK adds a controller cut-off in the control characteristic, EP does not. Like the LA family, EP and EK are Series 53 controls and are available through the whole Series 53 size range.
Availability by size
The two series overlap at sizes 28, 45 and 85, which is where the confusion usually starts. Availability is not uniform even inside one series:
| Control | Series 52 (10 / 28 / 45 / 60 / 85) | Series 53 (18 / 28 / 45 / 63 / 72 / 85 / 100) |
|---|---|---|
| DR, DRG | All sizes | All sizes |
| DFR / DFR1 / DRSC | DFR and DFR1 on all sizes; DRSC not on size 10 | DRF, DRS and DRSC on all sizes |
| ED71 / ED72 / ER71 / ER72 | Not on size 10; all other sizes | All sizes |
| LA (constant power) | Not available | All sizes |
| EP / EK (electro-proportional) | Not available | All sizes |
| EC4 electro-hydraulic control valve | Size 28 | Size 63, on request |
Five checks before you order
- The control code from the nameplate — DR, DFR/DFR1, DRSC, DRG, ED, ER, EP, EK or LA, exactly as printed.
- Which series it belongs to — DFR/DFR1 means Series 52, DRF/DRS means Series 53.
- X–T open or plugged — and whether the machine’s LS line is unloaded, which decides whether you need the flushing version.
- Voltage — 12 V or 24 V for ED, ER, EP and EK.
- Whether the control exists on your size — size 10 Series 52 has no DRSC, ED or ER; constant-power LA and electro-proportional EP/EK are Series 53 only.
You can browse the two series here: A10VO Series 52 and A10VO Series 53. For the wider picture, our earlier guides cover how the two series differ and the control options on the industrial Series 31 and 32.
Send us the control code
Tell us the complete code from the nameplate — the control position is what we check first, together with the size, the series index and the direction of rotation. Send us the code and we will confirm that the replacement carries the same control family, the same X–T arrangement and the same voltage before you order.
