Ebara BEST 5 Submersible Sump Pump

The Ebara BEST 5 is a stainless steel sump pump for clean and dirty water, for 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, and at 13.5 kg one person still carries it.

Read the range headline carefully before you order. 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. Half of that belongs to this pump and half does not. The BEST 5 is the frame that sets the top of the flow spread, so 21.6 m³/h is its own maximum capacity. The head spread is a different story. The 2.9 m is the BEST 2 running out at the end of its curve, and the BEST 5 never goes near it. This pump works between 19 m at shutoff and 5 m at maximum capacity, and the 18.4 m in the headline is its own head at the 1.2 m³/h minimum rated flow.

Each frame against its own curve, from Ebara's selection chart:

The supply is the other thing to settle early, because on the BEST 5 you have no choice. Ebara offers single-phase up to 1.1 kW, which stops at the BEST 4M. The BEST 5 is 3~400 V ±10% only. That costs you two things a single-phase frame gives you for nothing: the float switch, which Ebara lists as a single-phase option, and the built-in overload protection, which the three-phase motor does not have. Level control and motor protection both move into the starter or the board. Price that in rather than discovering it on site.

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, and it catches people out on warm process water and anything coming off a wash plant. Send us the liquid temperature with the duty and we will check it before you buy.

The BEST 5 pulls water through a stainless strainer in the base, throws it out through an open centrifugal impeller of 125 mm diameter, and discharges through a G 1½ connection to UNI ISO 228. The motor is a submersible dry type, two pole, running at about 2,800 rpm at 50 Hz and rated 1.5 kW. Ebara measures the curves to ISO 9906:2012 Grade 3B with clean water at 20°C and a kinematic viscosity of 1 cSt.

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.

That is a genuine double seal, and it matters in a sump full of grit. If the pump-side face wears, the oil chamber gives you a second barrier before water reaches the windings, and oil in the chamber going milky is the early warning you get before a motor failure. Run the pump dry and you lose the lubricating film on the faces, which is the fastest way to kill it.

What the extra power actually buys

The BEST 4 and the BEST 5 run the same 125 mm impeller. The difference is 1.1 kW against 1.5 kW, and it shows up as head at every point on the curve rather than as a bigger wet end. Ebara's selection chart puts the BEST 4 at 15 m and the BEST 5 at 16.1 m at 4.8 m³/h, then 10 m against 11.4 m at 12 m³/h. The BEST 5 also carries on to 21.6 m³/h where the BEST 4 stops at 19.8.

So the reason to step up is a metre or so of static lift you cannot design out, or a long discharge run. If the duty point sits comfortably inside the BEST 4's curve, buy the BEST 4. The BEST 5 draws 1.7 kW at the input against the BEST 4's 1.6 kW, and that difference runs for the life of the installation.

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 5 down to suit a small sump is not the way to correct an oversized selection.

Reading the type key

Ebara's own worked example 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. Neither letter appears on a BEST 5, because the frame is three-phase and the float is a single-phase option. If you are matching an existing unit, send us the full 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 this frame as BEST/A 5 H07RN8-F, code 1731204604A, at 400-415 V three-phase, 1.7 kW rated input and 3.3 A rated current, with a maximum head of 19 m, a minimum head of 5 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.