Ebara BEST 4 Submersible Sump Pump

The Ebara BEST 4 is a stainless steel sump pump for clean and dirty water, in portable or fixed installation. Ebara puts the range on seepage water, on emptying basements, garages and cellars, and on draining small and medium-sized construction sites. It is built entirely in AISI 304 with a double mechanical seal. At 13.8 kg it is the heaviest frame in the range, 0.3 kg above the BEST 5, and it is still a one-person lift.

Read the range headline carefully, because not one of the limits in it is set by this pump. Ebara publishes BEST 2-5 as one range, and the figures on its own product page cover all four frames together, 1.2–21.6 m³/h and 2.9–18.4 m of head. Those are not the BEST 4's numbers. The 21.6 m³/h ceiling is the BEST 5's, so is the 18.4 m, and the 2.9 m is the BEST 2 running out at the end of its curve. The BEST 4's own curve stops at 19.8 m³/h and works between 18 m at shutoff and 4.6 m at maximum capacity. Both of those sit inside the headline where you cannot see them, and the 18 m in particular is close enough to the published 18.4 m to be read as the same figure. It is not.

Selected points off Ebara's selection chart, for the BEST 4 alone:

The supply is the real reason to stop at this frame rather than take the one above. Ebara rates the single-phase motor from 0.55 kW to 1.1 kW, so the BEST 4M is the biggest pump in the range you can plug into 230 V, and the biggest one that comes with a float switch and overload protection built into the motor. Step up to a BEST 5 and you lose all three: three-phase only, no float, and motor protection moves into the starter or the board. That is worth real money on a site with no three-phase supply and no control panel.

What it costs you is current. The single-phase BEST 4M draws 7.3 A at full load and 25 A locked rotor, against 3.0 A and 16.5 A on the three-phase build. Check the circuit and the protective device before you commit, particularly if the pump is going on an extension reel in a basement. Where three-phase is already on site, take the three-phase build and put the level control in the panel. You will have an easier time of it.

Measure the chamber too. The BEST 4 stands 377 mm tall against 352 mm for a BEST 2 or BEST 3, so a shallow sump or a tight inspection cover that took the smaller frame will not automatically take this one.

A 10 mm solids passage is what it says. Suspended particles up to 10 mm go through the impeller. Rag, wipes and fibre will still wrap it, because an open centrifugal impeller has no cutter and nothing to clear itself with. If the sump takes anything off a WC or a macerator, this is the wrong pump and we will tell you so rather than sell you one.

The temperature limit is +35°C across the range. Warm process water, boiler blowdown or anything coming off a wash plant will take you past it. Send us the liquid temperature with the duty and we will check it before you buy.

Water enters through a stainless strainer in the base and leaves through a G 1½ connection to UNI ISO 228, driven by an open centrifugal impeller of 125 mm diameter. Behind it sits a submersible dry-type motor, two pole, rated 1.1 kW and turning at about 2,800 rpm on a 50 Hz supply. Ebara measures the curves to ISO 9906:2012 Grade 3B, on clean water at 20°C and a kinematic viscosity of 1 cSt. Anything thicker than that will not follow the chart.

Two seals and an oil chamber

The shaft passes through two mechanical seals with an oil chamber between them. The pump-side seal runs silicon carbide against silicon carbide with NBR elastomers, the motor-side seal carbon against ceramic with NBR. Between them sits 180 cc of white mineral oil, Esso Marcol 172, which lubricates and cools both sets of faces.

Two seals in series is not the same thing as one seal and a lip, and the difference shows in a gritty sump. Wear the pump-side face and the oil chamber is still between the water and the windings. Milky oil in that chamber is the warning you get, and it arrives before the motor does anything expensive, so check it at service rather than waiting for a trip. The one thing that kills the arrangement quickly is dry running: a mechanical seal needs liquid to lubricate it, and the faces go as soon as the film does.

What the extra power buys over a BEST 3

The step from BEST 3 to BEST 4 is a bigger impeller as well as a bigger motor, 125 mm against 120 mm, and it shows up everywhere on the curve. Ebara's selection chart puts the BEST 3 at 11.1 m and the BEST 4 at 15 m at 4.8 m³/h, then 6.4 m against 10 m at 12 m³/h. Maximum capacity goes from 16.8 to 19.8 m³/h.

The step from BEST 4 to BEST 5 is smaller and different in kind. Both run the same 125 mm impeller, so the BEST 5's extra 0.4 kW buys about a metre of head across the curve and takes maximum capacity to 21.6 m³/h. If the duty point sits comfortably inside the BEST 4's curve, buy the BEST 4 and keep the single-phase option.

Ebara also sets a floor on flow. It says the pumps should not be run below 10% of the best efficiency point, because they overheat. Throttling a BEST 4 down to suit a small sump is not the way to correct an oversized selection.

The electrical side

The single-phase build runs on 1230 V ±10% and draws 7.3 A at full load, with a 30 µF 450 V capacitor and overload protection built into the motor. Locked rotor current is 25 A. The three-phase build runs on 3400 V ±10%, draws 3.0 A at full load and 16.5 A locked rotor, and has neither the capacitor nor the built-in protector. Input power is 1.7 kW single-phase and 1.6 kW three-phase, which is the figure to size the supply against rather than the 1.1 kW shaft rating.

Both builds ship with 10 m of H07RN-F cable, 3G1.5 single-phase and 4G1 three-phase. Maximum immersion is 7 m on that cable.

Reading the type key

Ebara's own worked example in the data book is BEST 3 M A. The model number gives the frame, 2 to 5. M means single phase only, and A means the pump is supplied with a float switch. So a BEST 4M A is a single-phase 1.1 kW pump with a float, and a plain BEST 4 is the three-phase build. If you are matching an existing unit, send us that designation and the serial number off the nameplate.

Certification

TÜV SÜD Product Service GmbH issued GS mark certificate Z1A 015912 0052 to Ebara Pumps Europe S.p.A. for the range. The certificate lists three BEST 4 builds: BEST/A 4 H07RN8-F, code 1731154604A, at 400-415 V three-phase with 1.6 kW rated input and 3.0 A rated current; and BEST/A 4M H07RN8-F, code 1731154721A, with BEST/A 4M A H07RN8-F, code 1731154621A, at 230-240 V. All three carry a maximum head of 18 m, a minimum head of 4.6 m and a maximum submersion depth of 7 m. Testing was to EN 60335-1:2012/A15:2021, EN 60335-2-41:2021/A11:2021, EN 62233:2008 and AfPS GS 2019:01 PAK, and the certificate runs to 6 February 2029. The motor is IP68 with class F insulation.